Network Working Group                                       G. Fairhurst
Request for Comments: 4947                        University of Aberdeen
Category: Informational                                  M.-J. Montpetit
                                       Motorola Connected Home Solutions
                                                               July 2007
Network Working Group                                       G. Fairhurst
Request for Comments: 4947                        University of Aberdeen
Category: Informational                                  M.-J. Montpetit
                                       Motorola Connected Home Solutions
                                                               July 2007

Address Resolution Mechanisms for IP Datagrams over MPEG-2 Networks


Status of This Memo


This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.


Copyright Notice


Copyright (C) The IETF Trust (2007).




This document describes the process of binding/associating IPv4/IPv6 addresses with MPEG-2 Transport Streams (TS). This procedure is known as Address Resolution (AR) or Neighbor Discovery (ND). Such address resolution complements the higher-layer resource discovery tools that are used to advertise IP sessions.


In MPEG-2 Networks, an IP address must be associated with a Packet ID (PID) value and a specific Transmission Multiplex. This document reviews current methods appropriate to a range of technologies (such as DVB (Digital Video Broadcasting), ATSC (Advanced Television Systems Committee), DOCSIS (Data-Over-Cable Service Interface Specifications), and variants). It also describes the interaction with well-known protocols for address management including DHCP, ARP, and the ND protocol.


Table of Contents


   1. Introduction ....................................................3
      1.1. Bridging and Routing .......................................4
   2. Conventions Used in This Document ...............................7
   3. Address Resolution Requirements ................................10
      3.1. Unicast Support ...........................................12
      3.2. Multicast Support .........................................12
   4. MPEG-2 Address Resolution ......................................14
      4.1. Static Configuration ......................................15
           4.1.1. MPEG-2 Cable Networks ..............................15
      4.2. MPEG-2 Table-Based Address Resolution .....................16
           4.2.1. IP/MAC Notification Table (INT) and Its Usage ......17
           4.2.2. Multicast Mapping Table (MMT) and Its Usage ........18
           4.2.3. Application Information Table (AIT) and Its Usage ..18
           4.2.4. Address Resolution in ATSC .........................19
           4.2.5. Comparison of SI/PSI Table Approaches ..............19
      4.3. IP-Based Address Resolution for TS Logical Channels .......19
   5. Mapping IP Addresses to MAC/NPA Addresses ......................21
      5.1. Unidirectional Links Supporting Unidirectional
           Connectivity ..............................................22
      5.2. Unidirectional Links with Bidirectional Connectivity ......23
      5.3. Bidirectional Links .......................................25
      5.4. AR Server .................................................26
      5.5. DHCP Tuning ...............................................27
      5.6. IP Multicast AR ...........................................27
           5.6.1. Multicast/Broadcast Addressing for UDLR ............28
   6. Link Layer Support .............................................29
      6.1. ULE without a Destination MAC/NPA Address (D=1) ...........30
      6.2. ULE with a Destination MAC/NPA Address (D=0) ..............31
      6.3. MPE without LLC/SNAP Encapsulation ........................31
      6.4. MPE with LLC/SNAP Encapsulation ...........................31
      6.5. ULE with Bridging Header Extension (D=1) ..................32
      6.6. ULE with Bridging Header Extension and NPA Address (D=0) ..32
      6.7. MPE with LLC/SNAP & Bridging ..............................33
   7. Conclusions ....................................................33
   8. Security Considerations ........................................34
   9. Acknowledgments ................................................35
   10. References ....................................................35
      10.1. Normative References .....................................35
      10.2. Informative References ...................................36
   1. Introduction ....................................................3
      1.1. Bridging and Routing .......................................4
   2. Conventions Used in This Document ...............................7
   3. Address Resolution Requirements ................................10
      3.1. Unicast Support ...........................................12
      3.2. Multicast Support .........................................12
   4. MPEG-2 Address Resolution ......................................14
      4.1. Static Configuration ......................................15
           4.1.1. MPEG-2 Cable Networks ..............................15
      4.2. MPEG-2 Table-Based Address Resolution .....................16
           4.2.1. IP/MAC Notification Table (INT) and Its Usage ......17
           4.2.2. Multicast Mapping Table (MMT) and Its Usage ........18
           4.2.3. Application Information Table (AIT) and Its Usage ..18
           4.2.4. Address Resolution in ATSC .........................19
           4.2.5. Comparison of SI/PSI Table Approaches ..............19
      4.3. IP-Based Address Resolution for TS Logical Channels .......19
   5. Mapping IP Addresses to MAC/NPA Addresses ......................21
      5.1. Unidirectional Links Supporting Unidirectional
           Connectivity ..............................................22
      5.2. Unidirectional Links with Bidirectional Connectivity ......23
      5.3. Bidirectional Links .......................................25
      5.4. AR Server .................................................26
      5.5. DHCP Tuning ...............................................27
      5.6. IP Multicast AR ...........................................27
           5.6.1. Multicast/Broadcast Addressing for UDLR ............28
   6. Link Layer Support .............................................29
      6.1. ULE without a Destination MAC/NPA Address (D=1) ...........30
      6.2. ULE with a Destination MAC/NPA Address (D=0) ..............31
      6.3. MPE without LLC/SNAP Encapsulation ........................31
      6.4. MPE with LLC/SNAP Encapsulation ...........................31
      6.5. ULE with Bridging Header Extension (D=1) ..................32
      6.6. ULE with Bridging Header Extension and NPA Address (D=0) ..32
      6.7. MPE with LLC/SNAP & Bridging ..............................33
   7. Conclusions ....................................................33
   8. Security Considerations ........................................34
   9. Acknowledgments ................................................35
   10. References ....................................................35
      10.1. Normative References .....................................35
      10.2. Informative References ...................................36
1. Introduction
1. 介绍

This document describes the process of binding/associating IPv4/IPv6 addresses with MPEG-2 Transport Streams (TS). This procedure is known as Address Resolution (AR), or Neighbor Discovery (ND). Such address resolution complements the higher layer resource discovery tools that are used to advertise IP sessions. The document reviews current methods appropriate to a range of technologies (DVB, ATSC, DOCSIS, and variants). It also describes the interaction with well-known protocols for address management including DHCP, ARP, and the ND protocol.


The MPEG-2 TS provides a time-division multiplexed (TDM) stream that may contain audio, video, and data information, including encapsulated IP Datagrams [RFC4259], defined in specification ISO/IEC 138181 [ISO-MPEG2]. Each Layer 2 (L2) frame, known as a TS Packet, contains a 4 byte header and a 184 byte payload. Each TS Packet is associated with a single TS Logical Channel, identified by a 13-bit Packet ID (PID) value that is carried in the MPEG-2 TS Packet header.

MPEG-2 TS提供可包含音频、视频和数据信息的时分复用(TDM)流,包括规范ISO/IEC 13818[ISO-MPEG2]中定义的封装IP数据报[RFC4259]。每个第2层(L2)帧称为TS数据包,包含一个4字节的报头和一个184字节的有效负载。每个TS分组与单个TS逻辑信道相关联,由MPEG-2ts分组报头中携带的13位分组ID(PID)值标识。

The MPEG-2 standard also defines a control plane that may be used to transmit control information to Receivers in the form of System Information (SI) Tables [ETSI-SI], [ETSI-SI1], or Program Specific Information (PSI) Tables.


To utilize the MPEG-2 TS as a L2 link supporting IP, a sender must associate an IP address with a particular Transmission Multiplex, and within the multiplex, identify the specific PID to be used. This document calls this mapping an AR function. In some AR schemes, the MPEG-2 TS address space is subdivided into logical contexts known as Platforms [ETSI-DAT]. Each Platform associates an IP service provider with a separate context that shares a common MPEG-2 TS (i.e., uses the same PID value).

为了将MPEG-2 TS用作支持IP的L2链路,发送方必须将IP地址与特定的传输多路复用相关联,并且在多路复用内标识要使用的特定PID。本文档将此映射称为AR函数。在一些AR方案中,MPEG-2 TS地址空间被细分为称为平台[ETSI-DAT]的逻辑上下文。每个平台将IP服务提供商与共享公共MPEG-2 TS的单独上下文相关联(即,使用相同的PID值)。

MPEG-2 Receivers may use a Network Point of Attachment (NPA) [RFC4259] to uniquely identify a L2 node within an MPEG-2 transmission network. An example of an NPA is the IEEE Medium Access Control (MAC) address. Where such addresses are used, these must also be signalled by the AR procedure. Finally, address resolution could signal the format of the data being transmitted, for example, the encapsulation, with any L2 encryption method and any compression scheme [RFC4259].


The numbers of Receivers connected via a single MPEG-2 link may be much larger than found in other common LAN technologies (e.g., Ethernet). This has implications on design/configuration of the address resolution mechanisms. Current routing protocols and some multicast application protocols also do not scale to arbitrarily


large numbers of participants. Such networks do not by themselves introduce an appreciable subnetwork round trip delay, however many practical MPEG-2 transmission networks are built using links that may introduce a significant path delay (satellite links, use of dial-up modem return, cellular return, etc.). This higher delay may need to be accommodated by address resolution protocols that use this service.


1.1. Bridging and Routing
1.1. 桥接和路由

The following two figures illustrate the use of AR for a routed and a bridged subnetwork. Various other combinations of L2 and L3 forwarding may also be used over MPEG-2 links (including Receivers that are IP end hosts and end hosts directly connected to bridged LAN segments).


                           Broadcast Link AR
                           - - - - - - - - -
                           |               |
                            1a            2b        2a
                   +--------+              +--------+
               ----+   R1   +----------+---+   R2   +----
                   +--------+ MPEG-2   |   +--------+
                              Link     |
                                       |   +--------+
                                       +---+   R3   +----
                                       |   +--------+
                                       |   +--------+
                                       +---+   R4   +----
                                       |   +--------+
                           Broadcast Link AR
                           - - - - - - - - -
                           |               |
                            1a            2b        2a
                   +--------+              +--------+
               ----+   R1   +----------+---+   R2   +----
                   +--------+ MPEG-2   |   +--------+
                              Link     |
                                       |   +--------+
                                       +---+   R3   +----
                                       |   +--------+
                                       |   +--------+
                                       +---+   R4   +----
                                       |   +--------+

Figure 1: A routed MPEG-2 link


Figure 1 shows a routed MPEG-2 link feeding three downstream routers (R2-R4). AR takes place at the Encapsulator (R1) to identify each Receiver at Layer 2 within the IP subnetwork (R2, etc.).


When considering unicast communication from R1 to R2, several L2 addresses are involved:


1a is the L2 (sending) interface address of R1 on the MPEG-2 link. 2b is the L2 (receiving) interface address of R2 on the MPEG-2 link. 2a is the L2 (sending) interface address of R2 on the next hop link.


AR for the MPEG-2 link allows R1 to determine the L2 address (2b) corresponding to the next hop Receiver, router R2.


Figure 2 shows a bridged MPEG-2 link feeding three downstream bridges (B2-B4). AR takes place at the Encapsulator (B1) to identify each Receiver at L2 (B2-B4). AR also takes place across the IP subnetwork allowing the Feed router (R1) to identify the downstream Routers at Layer 2 (R2, etc.). The Encapsulator associates a destination MAC/NPA address with each bridged PDU sent on an MPEG-2 link. Two methods are defined by ULE (Unidirectional Lightweight Encapsulation) [RFC4326]:


The simplest method uses the L2 address of the transmitted frame. This is the MAC address corresponding to the destination within the L2 subnetwork (the next hop router, 2b of R2). This requires each Receiver (B2-B4) to associate the receiving MPEG-2 interface with the set of MAC addresses that exist on the L2 subnetworks that it feeds. Similar considerations apply when IP-based tunnels support L2 services (including the use of UDLR (Unidirectional Links) [RFC3077]).


It is also possible for a bridging Encapsulator (B1) to encapsulate a PDU with a link-specific header that also contains the MAC/NPA address associated with a Receiver L2 interface on the MPEG-2 link (Figure 2). In this case, the destination MAC/NPA address of the encapsulated frame is set to the Receiver MAC/NPA address (y), rather than the address of the final L2 destination. At a different level, an AR binding is also required for R1 to associate the destination L2 address 2b with R2. In a subnetwork using bridging, the systems R1 and R2 will normally use standard IETF-defined AR mechanisms (e.g., IPv4 Address Resolution Protocol (ARP) [RFC826] and the IPv6 Neighbor Discovery Protocol (ND) [RFC2461]) edge-to-edge across the IP subnetwork.


                                Subnetwork AR
                      - - - - - - - - - - - - - - - -
                      |                             |
                                Subnetwork AR
                      - - - - - - - - - - - - - - - -
                      |                             |
                      |        MPEG-2 Link AR       |
                             - - - - - - - - -
                      |      |               |      |
                      \/     \/
                      1a      x              y      2b        2a
             +--------+  +----+              +----+  +--------+
         ----+   R1   +--| B1 +----------+---+ B2 +--+   R2   +----
             +--------+  +----+ MPEG-2   |   +----+  +--------+
                                Link     |
                                         |   +----+
                                         +---+ B3 +--
                                         |   +----+
                                         |   +----+
                                         +---+ B4 +--
                                         |   +----+
                      |        MPEG-2 Link AR       |
                             - - - - - - - - -
                      |      |               |      |
                      \/     \/
                      1a      x              y      2b        2a
             +--------+  +----+              +----+  +--------+
         ----+   R1   +--| B1 +----------+---+ B2 +--+   R2   +----
             +--------+  +----+ MPEG-2   |   +----+  +--------+
                                Link     |
                                         |   +----+
                                         +---+ B3 +--
                                         |   +----+
                                         |   +----+
                                         +---+ B4 +--
                                         |   +----+

Figure 2: A bridged MPEG-2 link


Methods also exist to assign IP addresses to Receivers within a network (e.g., stateless autoconfiguration [RFC2461], DHCP [RFC2131], DHCPv6 [RFC3315], and stateless DHCPv6 [RFC3736]). Receivers may also participate in the remote configuration of the L3 IP addresses used in connected equipment (e.g., using DHCP-Relay [RFC3046]).

还存在将IP地址分配给网络内接收器的方法(例如,无状态自动配置[RFC2461]、DHCP[RFC2131]、DHCPv6[RFC3315]和无状态DHCPv6[RFC3736])。接收器还可以参与连接设备中使用的L3 IP地址的远程配置(例如,使用DHCP中继[RFC3046])。

The remainder of this document describes current mechanisms and their use to associate an IP address with the corresponding TS Multiplex, PID value, the MAC/NPA address and/or Platform ID. A range of approaches is described, including Layer 2 mechanisms (using MPEG-2 SI tables), and protocols at the IP level (including ARP [RFC826] and ND [RFC2461]). Interactions and dependencies between these mechanisms and the encapsulation methods are described. The document does not propose or define a new protocol, but does provide guidance on issues that would need to be considered to supply IP-based address resolution.

本文档的其余部分描述了将IP地址与相应的TS多路复用、PID值、MAC/NPA地址和/或平台ID关联的当前机制及其使用。描述了一系列方法,包括第2层机制(使用MPEG-2 SI表)和IP级协议(包括ARP[RFC826]和ND[RFC2461]).描述了这些机制和封装方法之间的交互和依赖关系。该文件没有提出或定义新的协议,但就提供基于IP的地址解析所需考虑的问题提供了指导。

2. Conventions Used in This Document
2. 本文件中使用的公约

AIT: Application Information Table specified by the Multimedia Home Platform (MHP) specifications [ETSI-MHP]. This table may carry IPv4/IPv6 to MPEG-2 TS address resolution information.

AIT:多媒体家庭平台(MHP)规范[ETSI-MHP]规定的应用信息表。此表可能包含IPv4/IPv6到MPEG-2 TS地址解析信息。

ATSC: Advanced Television Systems Committee [ATSC]. A framework and a set of associated standards for the transmission of video, audio, and data using the ISO MPEG-2 standard [ISO-MPEG2].

先进电视系统委员会(ATSC)。使用ISO MPEG-2标准[ISO-MPEG2]传输视频、音频和数据的框架和一组相关标准。

b: bit. For example, one byte consists of 8-bits.


B: Byte. Groups of bytes are represented in Internet byte order.


DSM-CC: Digital Storage Media Command and Control [ISO-DSMCC]. A format for the transmission of data and control information carried in an MPEG-2 Private Section, defined by the ISO MPEG-2 standard.

DSM-CC:数字存储媒体命令和控制[ISO-DSMCC]。一种用于传输MPEG-2专用部分中所载数据和控制信息的格式,由ISO MPEG-2标准定义。

DVB: Digital Video Broadcasting [DVB]. A framework and set of associated standards published by the European Telecommunications Standards Institute (ETSI) for the transmission of video, audio, and data, using the ISO MPEG-2 Standard.

DVB:数字视频广播[DVB]。欧洲电信标准协会(ETSI)发布的一个框架和一组相关标准,用于使用ISO MPEG-2标准传输视频、音频和数据。

DVB-RCS: Digital Video Broadcast Return Channel via Satellite. A bidirectional IPv4/IPv6 service employing low-cost Receivers [ETSI-RCS].


DVB-S: Digital Video Broadcast for Satellite [ETSI-DVBS].


Encapsulator: A network device that receives PDUs and formats these into Payload Units (known here as SNDUs) for output as a stream of TS Packets.


Feed Router: The router delivering the IP service over a Unidirectional Link.


INT: Internet/MAC Notification Table. A unidirectional address resolution mechanism using SI and/or PSI Tables.


L2: Layer 2, the link layer.


L3: Layer 3, the IP network layer.


MAC: Medium Access Control [IEEE-802.3]. A link layer protocol defined by the IEEE 802.3 standard (or by Ethernet v2).

MAC:媒体访问控制[IEEE-802.3]。由IEEE 802.3标准(或以太网v2)定义的链路层协议。

MAC Address: A 6-byte link layer address of the format described by the Ethernet IEEE 802 standard (see also NPA).

MAC地址:以太网IEEE 802标准所述格式的6字节链路层地址(另见NPA)。

MAC Header: The link layer header of the IEEE 802.3 standard [IEEE-802.3] or Ethernet v2. It consists of a 6-byte destination address, 6-byte source address, and 2 byte type field (see also NPA, LLC (Logical Link Control)).

MAC头:IEEE 802.3标准[IEEE-802.3]或Ethernet v2的链路层头。它由6字节的目标地址、6字节的源地址和2字节类型的字段组成(另请参见NPA,LLC(逻辑链路控制))。

MHP: Multimedia Home Platform. An integrated MPEG-2 multimedia Receiver, that may (in some cases) support IPv4/IPv6 services [ETSI-MHP].


MMT: Multicast Mapping Table (proprietary extension to DVB-RCS [ETSI-RCS] defining an AR table that maps IPv4 multicast addresses to PID values).


MPE: Multiprotocol Encapsulation [ETSI-DAT], [ATSC-A90]. A method that encapsulates PDUs, forming a DSM-CC Table Section. Each Section is sent in a series of TS Packets using a single Stream (TS Logical Channel).


MPEG-2: A set of standards specified by the Motion Picture Experts Group (MPEG), and standardized by the International Standards Organization (ISO/IEC 113818-1) [ISO-MPEG2], and ITU-T (in H.220).

MPEG-2:由电影专家组(MPEG)规定并由国际标准组织(ISO/IEC 113818-1)[ISO-MPEG2]和ITU-T(H.220)标准化的一组标准。

NPA: Network Point of Attachment. A 6-byte destination address (resembling an IEEE MAC address) within the MPEG-2 transmission network that is used to identify individual Receivers or groups of Receivers [RFC4259].

NPA:网络连接点。MPEG-2传输网络内的6字节目的地址(类似于IEEE MAC地址),用于识别单个接收机或接收机组[RFC4259]。

PAT: Program Association Table. An MPEG-2 PSI control table. It associates each program with the PID value that is used to send the associated PMT (Program Map Table). The table is sent using the well-known PID value of 0x000, and is required for an MPEG-2 compliant Transport Stream.


PDU: Protocol Data Unit. Examples of a PDU include Ethernet frames, IPv4 or IPv6 Datagrams, and other network packets.


PID: Packet Identifier [ISO-MPEG2]. A 13 bit field carried in the header of each TS Packet. This identifies the TS Logical Channel to which a TS Packet belongs [ISO-MPEG2]. The TS Packets that form the parts of a Table Section, or other Payload Unit must all carry the same PID value. A PID value of all ones indicates a Null TS Packet introduced to maintain a constant bit rate of a TS Multiplex. There is no required relationship between the PID values used for TS Logical Channels transmitted using different TS Multiplexes.


PMT: Program Map Table. An MPEG-2 PSI control table that associates the PID values used by the set of TS Logical Channels/ Streams that comprise a program [ISO-MPEG2]. The PID value used to send the PMT for a specific program is defined by an entry in the PAT.

PMT:程序映射表。一种MPEG-2 PSI控制表,用于关联组成程序[ISO-MPEG2]的TS逻辑通道/流集合使用的PID值。用于发送特定程序的PMT的PID值由PAT中的条目定义。

Private Section: A syntactic structure constructed according to Table 2-30 of [ISO-MPEG2]. The structure may be used to identify private information (i.e., not defined by [ISO-MPEG2]) relating to one or more elementary streams, or a specific MPEG-2 program, or the entire Transport Stream. Other Standards bodies, e.g., ETSI and ATSC, have defined sets of table structures using the private_section structure. A Private Section is transmitted as a sequence of TS Packets using a TS Logical Channel. A TS Logical Channel may carry sections from more than one set of tables.


PSI: Program Specific Information [ISO-MPEG2]. PSI is used to convey information about services carried in a TS Multiplex. It is carried in one of four specifically identified Table Section constructs [ISO-MPEG2], see also SI Table.


Receiver: Equipment that processes the signal from a TS Multiplex and performs filtering and forwarding of encapsulated PDUs to the network-layer service (or bridging module when operating at the link layer).


SI Table: Service Information Table [ISO-MPEG2]. In this document, this term describes a table that is been defined by another standards body to convey information about the services carried in a TS Multiplex. A Table may consist of one or more Table Sections, however, all sections of a particular SI Table must be carried over a single TS Logical Channel [ISO-MPEG2].


SNDU: Subnetwork Data Unit. An encapsulated PDU sent as an MPEG-2 Payload Unit.


Table Section: A Payload Unit carrying all or a part of an SI or PSI Table [ISO-MPEG2].


TS: Transport Stream [ISO-MPEG2], a method of transmission at the MPEG-2 level using TS Packets; it represents Layer 2 of the ISO/OSI reference model. See also TS Logical Channel and TS Multiplex.


TS Logical Channel: Transport Stream Logical Channel. In this document, this term identifies a channel at the MPEG-2 level [ISO-MPEG2]. This exists at level 2 of the ISO/OSI reference model. All packets sent over a TS Logical Channel carry the same PID value (this value is unique within a specific TS Multiplex). The term "Stream" is defined in MPEG-2 [ISO-MPEG2]. This describes the


content carried by a specific TS Logical Channel (see ULE Stream). Some PID values are reserved (by MPEG-2) for specific signaling. Other standards (e.g., ATSC and DVB) also reserve specific PID values.


TS Multiplex: In this document, this term defines a set of MPEG-2 TS Logical Channels sent over a single lower layer connection. This may be a common physical link (i.e., a transmission at a specified symbol rate, FEC setting, and transmission frequency) or an encapsulation provided by another protocol layer (e.g., Ethernet, or RTP over IP). The same TS Logical Channel may be repeated over more than one TS Multiplex (possibly associated with a different PID value) [RFC4259], for example, to redistribute the same multicast content to two terrestrial TV transmission cells.

TS多路复用:在本文档中,该术语定义了通过单个较低层连接发送的一组MPEG-2 TS逻辑通道。这可以是公共物理链路(即,以指定符号速率、FEC设置和传输频率的传输)或由另一协议层(例如,以太网或RTP over IP)提供的封装。相同的TS逻辑信道可以在多个TS多路复用上重复(可能与不同的PID值相关联)[RFC4259],例如,将相同的多播内容重新分发到两个地面TV传输小区。

TS Packet: A fixed-length 188B unit of data sent over a TS Multiplex [ISO-MPEG2]. Each TS Packet carries a 4B header.


UDL: Unidirectional link: A one-way transmission link. For example, and IP over DVB link using a broadcast satellite link.

单向链路:单向传输链路。例如,使用广播卫星链路的IP over DVB链路。

ULE: Unidirectional Lightweight Encapsulation. A scheme that encapsulates PDUs, into SNDUs that are sent in a series of TS Packets using a single TS Logical Channel [RFC4326].

ULE: Unidirectional Lightweight Encapsulation. A scheme that encapsulates PDUs, into SNDUs that are sent in a series of TS Packets using a single TS Logical Channel [RFC4326].translate error, please retry

ULE Stream: An MPEG-2 TS Logical Channel that carries only ULE encapsulated PDUs. ULE Streams may be identified by definition of a stream_type in SI/PSI [RFC4326, ISO-MPEG2].

ULE流:仅承载ULE封装PDU的MPEG-2 TS逻辑通道。ULE流可通过SI/PSI[RFC4326,ISO-MPEG2]中的流类型定义来识别。

3. Address Resolution Requirements
3. 解决解决方案要求

The MPEG IP address resolution process is independent of the choice of encapsulation and needs to support a set of IP over MPEG-2 encapsulation formats, including Multi-Protocol Encapsulation (MPE) ([ETSI-DAT], [ATSC-A90]) and the IETF-defined Unidirectional Lightweight Encapsulation (ULE) [RFC4326].

MPEG IP地址解析过程独立于封装的选择,需要支持一组IP over MPEG-2封装格式,包括多协议封装(MPE)([ETSI-DAT],[ATSC-A90])和IETF定义的单向轻量封装(ULE)[RFC4326]。

The general IP over MPEG-2 AR requirements are summarized below:

MPEG-2 AR的一般IP要求总结如下:

- A scalable architecture that may support large numbers of systems within the MPEG-2 Network [RFC4259].

- 可扩展架构,可支持MPEG-2网络内的大量系统[RFC4259]。

- A protocol version, to indicate the specific AR protocol in use and which may include the supported encapsulation method.

- 协议版本,用于指示正在使用的特定AR协议,可能包括支持的封装方法。

- A method (e.g., well-known L2/L3 address/addresses) to identify the AR Server sourcing the AR information.

- 一种方法(例如,众所周知的L2/L3地址),用于识别获取AR信息的AR服务器。

- A method to represent IPv4/IPv6 AR information (including security mechanisms to authenticate the AR information to protect against address masquerading [RFC3756]).

- 表示IPv4/IPv6 AR信息的方法(包括验证AR信息以防止地址伪装的安全机制[RFC3756])。

- A method to install AR information associated with clients at the AR Server (registration).

- 在AR服务器上安装与客户端关联的AR信息的方法(注册)。

- A method for transmission of AR information from an AR Server to clients that minimize the transmission cost (link-local multicast is preferable to subnet broadcast).

- 一种用于将AR信息从AR服务器传输到客户端的方法,该方法使传输成本最小化(链路本地多播比子网广播更可取)。

- Incremental update of the AR information held by clients.

- 客户持有的AR信息的增量更新。

- Procedures for purging clients of stale AR information.

- 清除客户端过时应收账款信息的过程。

An MPEG-2 transmission network may support multiple IP networks. If this is the case, it is important to recognize the scope within which an address is resolved to prevent packets from one addressed scope leaking into other scopes [RFC4259]. Examples of overlapping IP address assignments include:


(i) Private unicast addresses (e.g., in IPv4, 10/8 prefix; 172.16/12 prefix; and 192.168/16 prefix). Packets with these addresses should be confined to one addressed area. IPv6 also defines link-local addresses that must not be forwarded beyond the link on which they were first sent.

(i) 专用单播地址(例如,在IPv4中,10/8前缀;172.16/12前缀;和192.168/16前缀)。具有这些地址的数据包应限制在一个寻址区域内。IPv6还定义了链路本地地址,这些地址不得转发到第一次发送它们的链路之外。

(ii) Local scope multicast addresses. These are only valid within the local area (examples for IPv4 include: 224.0.0/24; 224.0.1/24). Similar cases exist for some IPv6 multicast addresses [RFC2375].


(iii) Scoped multicast addresses [RFC2365] and [RFC2375]. Forwarding of these addresses is controlled by the scope associated with the address. The addresses are only valid within an addressed area (e.g., the 239/8 [RFC2365]).


Overlapping address assignments may also occur at L2, where the same MAC/NPA address is used to identify multiple Receivers [RFC4259]:


(i) An MAC/NPA unicast address must be unique within the addressed area. The IEEE-assigned MAC addresses used in Ethernet LANs are globally unique. If the addresses are not globally unique, an address must only be re-used by Receivers in different addressed (scoped) areas.

(i) MAC/NPA单播地址在寻址区域内必须是唯一的。以太网LAN中使用的IEEE分配的MAC地址是全局唯一的。如果地址不是全局唯一的,则地址只能由不同寻址(作用域)区域中的接收者重新使用。

(ii) The MAC/NPA address broadcast address (a L2 address of all ones). Traffic with this address should be confined to one addressed area.


(iii) IP and other protocols may view sets of L3 multicast addresses as link-local. This may produce unexpected results if frames with the corresponding multicast L2 addresses are distributed to systems in a different L3 network or multicast scope (Sections 3.2 and 5.6).


Reception of unicast packets destined for another addressed area will lead to an increase in the rate of received packets by systems connected via the network. Reception of the additional network traffic may contribute to processing load, but should not lead to unexpected protocol behaviour, providing that systems can be uniquely addressed at L2. It does however introduce a potential Denial of Service (DoS) opportunity. When the Receiver operates as an IP router, the receipt of such a packet can lead to unexpected protocol behaviour.


3.1. Unicast Support
3.1. 单播支持

Unicast address resolution is required at two levels.


At the lower level, the IP (or MAC) address needs to be associated with a specific TS Logical Channel (PID value) and the corresponding TS Multiplex (Section 4). Each Encapsulator within an MPEG-2 Network is associated with a set of unique TS Logical Channels (PID values) that it sources [ETSI-DAT, RFC4259]. Within a specific scope, the same unicast IP address may therefore be associated with more than one Stream, and each Stream contributes different content (e.g., when several different IP Encapsulators contribute IP flows destined to the same Receiver). MPEG-2 Networks may also replicate IP packets to send the same content (Simulcast) to different Receivers or via different TS Multiplexes. The configuration of the MPEG-2 Network must prevent a Receiver accepting duplicated copies of the same IP packet.


At the upper level, the AR procedure needs to associate an IP address with a specific MAC/NPA address (Section 5).


3.2. Multicast Support
3.2. 多播支持

Multicast is an important application for MPEG-2 transmission networks, since it exploits the advantages of native support for link broadcast. Multicast address resolution occurs at the network-level in associating a specific L2 address with an IP Group Destination Address (Section 5.6). In IPv4 and IPv6 over Ethernet, this


association is normally a direct mapping, and this is the default method also specified in both ULE [RFC4326] and MPE [ETSI-DAT].


Address resolution must also occur at the MPEG-2 level (Section 4). The goal of this multicast address resolution is to allow a Receiver to associate an IPv4 or IPv6 multicast address with a specific TS Logical Channel and the corresponding TS Multiplex [RFC4259]. This association needs to permit a large number of active multicast groups, and should minimize the processing load at the Receiver when filtering and forwarding IP multicast packets (e.g., by distributing the multicast traffic over a number of TS Logical Channels). Schemes that allow hardware filtering can be beneficial, since these may relieve the drivers and operating systems from discarding unwanted multicast traffic.


There are two specific functions required for address resolution in IP multicast over MPEG-2 Networks:


(i) Mapping IP multicast groups to the underlying MPEG-2 TS Logical Channel (PID) and the MPEG-2 TS Multiplex at the Encapsulator.

(i) 将IP多播组映射到封装器处的底层MPEG-2 TS逻辑通道(PID)和MPEG-2 TS多路复用。

(ii) Provide signalling information to allow a Receiver to locate an IP multicast flow within an MPEG-2 TS Multiplex.

(ii)提供信令信息以允许接收器在MPEG-2 TS多路复用内定位IP多播流。

Methods are required to identify the scope of an address when an MPEG-2 Network supports several logical IP networks and carries groups within different multicast scopes [RFC4259].


Appropriate procedures need to specify the correct action when the same multicast group is available on separate TS Logical Channels. This could arise when different Encapsulators contribute IP packets with the same IP Group Destination Address in the ASM (Any-Source Multicast) address range. Another case arises when a Receiver could receive more than one copy of the same packet (e.g., when packets are replicated across different TS Logical Channels or even different TS Multiplexes, a method known as Simulcasting [ETSI-DAT]). At the IP level, the host/router may be unaware of this duplication and this needs to be detected by other means.


When the MPEG-2 Network is peered to the multicast-enabled Internet, an arbitrarily large number of IP multicast group destination addresses may be in use, and the set forwarded on the transmission network may be expected to vary significantly with time. Some uses of IP multicast employ a range of addresses to support a single application (e.g., ND [RFC2461], Layered Coding Transport (LCT) [RFC3451], and Wave and Equation Based Rate Control (WEBRC) [RFC3738]). The current set of active addresses may be determined dynamically via a multicast group membership protocol (e.g., Internet


Group Management Protocol (IGMP) [RFC3376] and Multicast Listener Discovery (MLD) [RFC3810]), via multicast routing (e.g., Protocol Independent Multicast (PIM) [RFC4601]) and/or other means (e.g., [RFC3819] and [RFC4605]), however each active address requires a binding by the AR method. Therefore, there are advantages in using a method that does not need to explicitly advertise an AR binding for each IP traffic flow, but is able to distribute traffic across a number of L2 TS Logical Channels (e.g., using a hash/mapping that resembles the mapping from IP addresses to MAC addresses [RFC1112, RFC2464]). Such methods can reduce the volume of AR information that needs to be distributed, and reduce the AR processing.


Section 5.6 describes the binding of IP multicast addresses to MAC/NPA addresses.


4. MPEG-2 Address Resolution
4. MPEG-2地址解析

The first part of this section describes the role of MPEG-2 signalling to identify streams (TS Logical Channels [RFC4259]) within the L2 infrastructure.


At L2, the MPEG-2 Transport Stream [ISO-MPEG2] identifies the existence and format of a Stream, using a combination of two PSI tables: the Program Association Table (PAT) and entries in the program element loop of a Program Map Table (PMT). PMT Tables are sent infrequently and are typically small in size. The PAT is sent using the well-known PID value of 0X000. This table provides the correspondence between a program_number and a PID value. (The program_number is the numeric label associated with a program). Each program in the Table is associated with a specific PID value, used to identify a TS Logical Channel (i.e., a TS). The identified TS is used to send the PMT, which associates a set of PID values with the individual components of the program. This approach de-references the PID values when the MPEG-2 Network includes multiplexors or re-multiplexors that renumber the PID values of the TS Logical Channels that they process.


In addition to signalling the Receiver with the PID value assigned to a Stream, PMT entries indicate the presence of Streams using ULE and MPE to the variety of devices that may operate in the MPEG-2 transmission network (multiplexors, remultiplexors, rate shapers, advertisement insertion equipment, etc.).


A multiplexor or remultiplexor may change the PID values associated with a Stream during the multiplexing process, the new value being reflected in an updated PMT. TS Packets that carry a PID value that is not associated with a PMT entry (an orphan PID), may, and usually will be dropped by ISO 13818-1 compliant L2 equipment, resulting in

多路复用器或再多路复用器可以在多路复用过程中改变与流相关联的PID值,新值反映在更新的PMT中。带有与PMT条目(孤立PID)不相关的PID值的TS数据包可能,并且通常会被符合ISO 13818-1的L2设备丢弃,从而导致

the Stream not being forwarded across the transmission network. In networks that do not employ any intermediate devices (e.g., scenarios C,E,F of [RFC4259]), or where devices have other means to determine the set of PID values in use, the PMT table may still be sent (but is not required for this purpose).


Although the basic PMT information may be used to identify the existence of IP traffic, it does not associate a Stream with an IP prefix/address. The remainder of the section describes IP addresses resolution mechanisms relating to MPEG-2.


4.1. Static Configuration
4.1. 静态配置

The static mapping option, where IP addresses or flows are statically mapped to specific PIDs is the equivalent to signalling "out-of-band". The application programmer, installing engineer, or user receives the mapping via some outside means, not in the MPEG-2 TS. This is useful for testing, experimental networks, small subnetworks and closed domains.

静态映射选项(其中IP地址或流静态映射到特定PID)相当于发送“带外”信号。应用程序程序员、安装工程师或用户通过某种外部方式(而不是MPEG-2 TS)接收映射。这对于测试、实验网络、小型子网和封闭域非常有用。

A pre-defined set of IP addresses may be used within an MPEG-2 transmission network. Prior knowledge of the active set of addresses allows appropriate AR records to be constructed for each address, and to pre-assign the corresponding PID value (e.g., selected to optimize Receiver processing; to group related addresses to the same PID value; and/or to reflect a policy for usage of specific ranges of PID values). This presumes that the PID mappings are not modified during transmission (Section 4).


A single "well-known" PID is a specialization of this. This scheme is used by current DOCSIS cable modems [DOCSIS], where all IP traffic is placed into the specified TS stream. MAC filtering (and/or Section filtering in MPE) may be used to differentiate subnetworks.


4.1.1. MPEG-2 Cable Networks
4.1.1. MPEG-2有线网络

Cable networks use a different transmission scheme for downstream (head-end to cable modem) and upstream (cable modem to head-end) transmissions.


IP/Ethernet packets are sent (on the downstream) to the cable modem(s) encapsulated in MPEG-2 TS Packets sent on a single well-known TS Logical Channel (PID). There is no use of in-band signalling tables. On the upstream, the common approach is to use Ethernet framing, rather than IP/Ethernet over MPEG-2, although other proprietary schemes also continue to be used.

IP/以太网数据包被发送(在下游)到封装在MPEG-2 TS数据包中的电缆调制解调器,该数据包在单个已知TS逻辑通道(PID)上发送。不使用带内信令表。在上游,常用的方法是使用以太网帧,而不是MPEG-2上的IP/以太网,尽管也继续使用其他专有方案。

Until the deployment of DOCSIS and EuroDOCSIS, most address resolution schemes for IP traffic in cable networks were proprietary, and did not usually employ a table-based address resolution method. Proprietary methods continue to be used in some cases where cable modems require interaction. In this case, equipment at the head-end may act as gateways between the cable modem and the Internet. These gateways receive L2 information and allocate an IP address.


DOCSIS uses DHCP for IP client configuration. The Cable Modem Terminal System (CMTS) provides a DHCP Server that allocates IP addresses to DOCSIS cable modems. The MPEG-2 transmission network provides a L2 bridged network to the cable modem (Section 1). This usually acts as a DHCP Relay for IP devices [RFC2131], [RFC3046], and [RFC3256]. Issues in deployment of IPv6 are described in [RFC4779].


4.2. MPEG-2 Table-Based Address Resolution
4.2. 基于MPEG-2表的地址解析

The information about the set of MPEG-2 Transport Streams carried over a TS Multiplex can be distributed via SI/PSI Tables. These tables are usually sent periodically (Section 4). This design requires access to and processing of the SI Table information by each Receiver [ETSI-SI], [ETSI-SI1]. This scheme reflects the complexity of delivering and coordinating the various Transport Streams associated with multimedia TV. A TS Multiplex may provide AR information for IP services by integrating additional information into the existing control tables or by transmitting additional SI Tables that are specific to the IP service.


Examples of MPEG-2 Table usage that allows an MPEG-2 Receiver to identify the appropriate PID and the multiplex associated with a specific IP address include:


(i) IP/MAC Notification Table (INT) in the DVB Data standard [ETSI-DAT]. This provides unidirectional address resolution of IPv4/IPv6 multicast addresses to an MPEG-2 TS.

(i) DVB数据标准[ETSI-DAT]中的IP/MAC通知表(INT)。这为MPEG-2 TS提供IPv4/IPv6多播地址的单向地址解析。

(ii) Application Information Table (AIT) in the Multimedia Home Platform (MHP) specifications [ETSI-MHP].


(iii) Multicast Mapping Table (MMT) is an MPEG-2 Table employed by some DVB-RCS systems to provide unidirectional address resolution of IPv4 multicast addresses to an MPEG-2 TS.

(iii)多播映射表(MMT)是一些DVB-RCS系统使用的MPEG-2表,用于向MPEG-2 TS提供IPv4多播地址的单向地址解析。

The MMT and AIT are used for specific applications, whereas the INT [ETSI-DAT] is a more general DVB method that supports MAC, IPv4, and IPv6 AR when used in combination with the other MPEG-2 tables (Section 4).

MMT和AIT用于特定应用,而INT[ETSI-DAT]是一种更通用的DVB方法,当与其他MPEG-2表结合使用时,它支持MAC、IPv4和IPv6 AR(第4节)。

4.2.1. IP/MAC Notification Table (INT) and Its Usage
4.2.1. IP/MAC通知表(INT)及其使用

The INT provides a set of descriptors to specify addressing in a DVB network. The use of this method is specified for Multiprotocol Encapsulation (MPE) [ETSI-DAT]. It provides a method for carrying information about the location of IP/L2 flows within a DVB network. A Platform_ID identifies the addressing scope for a set of IP/L2 streams and/or Receivers. A Platform may span several Transport Streams carried by one or multiple TS Multiplexes and represents a single IP network with a harmonized address space (scope). This allows for the coexistence of several independent IP/MAC address scopes within an MPEG-2 Network.


The INT allows both fully-specified IP addresses and prefix matching to reduce the size of the table (and hence enhance signalling efficiency). An IPv4/IPv6 "subnet mask" may be specified in full form or by using a slash notation (e.g., /127). IP multicast addresses can be specified with or without a source (address or range), although if a source address is specified, then only the slash notation may be used for prefixes.


In addition, for identification and security descriptors, the following descriptors are defined for address binding in INT tables:


(i) target_MAC_address_descriptor: A descriptor to describe a single or set of MAC addresses (and their mask).

(i) 目标MAC地址描述符:描述单个或一组MAC地址(及其掩码)的描述符。

(ii) target_MAC_address_range_descriptor: A descriptor that may be used to set filters.

(ii)目标\ MAC\地址\范围\描述符:可用于设置过滤器的描述符。

(iii) target_IP_address_descriptor: A descriptor describing a single or set of IPv4 unicast or multicast addresses (and their mask).


(iv) target_IP_slash_descriptor: Allows definition and announcement of an IPv4 prefix.


(v) target_IP_source_slash_descriptor: Uses source and destination addresses to target a single or set of systems.

(v) 目标\ IP \源\斜杠\描述符:使用源地址和目标地址以单个或一组系统为目标。

(vi) IP/MAC stream_location_descriptor: A descriptor that locates an IP/MAC stream in a DVB network.


The following descriptors provide corresponding functions for IPv6 addresses:


target_IPv6_address_descriptor target_IPv6_slash_descriptor and target_IPv6_source_slash_descriptor

目标\u IPv6\u地址\u描述符目标\u IPv6\u斜杠\u描述符和目标\u IPv6\u源\u斜杠\u描述符

The ISP_access_mode_descriptor allows specification of a second address descriptor to access an ISP via an alternative non-DVB (possibly non-IP) network.


One key benefit is that the approach employs MPEG-2 signalling (Section 4) and is integrated with other signalling information. This allows the INT to operate in the presence of (re)multiplexors [RFC4259] and to refer to PID values that are carried in different TS Multiplexes. This makes it well-suited to a Broadcast TV Scenario [RFC4259].


The principal drawback is a need for an Encapsulator to introduce associated PSI/SI MPEG-2 control information. This control information needs to be processed at a Receiver. This requires access to information below the IP layer. The position of this processing within the protocol stack makes it hard to associate the results with IP Policy, management, and security functions. The use of centralized management prevents the implementation of a more dynamic scheme.

主要缺点是需要封装器引入相关的PSI/SI MPEG-2控制信息。此控制信息需要在接收器处处理。这需要访问IP层下的信息。此处理在协议栈中的位置使得很难将结果与IP策略、管理和安全功能相关联。集中管理的使用阻止了更动态方案的实施。

4.2.2. Multicast Mapping Table (MMT) and Its Usage
4.2.2. 多播映射表(MMT)及其使用

In DVB-RCS, unicast AR is seen as a part of a wider configuration and control function and does not employ a specific protocol.


A Multicast Mapping Table (MMT) may be carried in an MPEG-2 control table that associates a set of multicast addresses with the corresponding PID values [MMT]. This table allows a DVB-RCS Forward Link Subsystem (FLSS) to specify the mapping of IPv4 and IPv6 multicast addresses to PID values within a specific TS Multiplex. Receivers (DVB-RCS Return Channel Satellite Terminals (RCSTs)) may use this table to determine the PID values associated with an IP multicast flow that it requires to receive. The MMT is specified by the SatLabs Forum [MMT] and is not currently a part of the DVB-RCS specification.


4.2.3. Application Information Table (AIT) and Its Usage
4.2.3. 应用程序信息表(AIT)及其用法

The DVB Multimedia Home Platform (MHP) specification [ETSI-MHP] does not define a specific AR function. However, an Application Information Table (AIT) is defined that allows MHP Receivers to receive a variety of control information. The AIT uses an MPEG-2 signalling table, providing information about data broadcasts, the required activation state of applications carried by a broadcast stream, etc. This information allows a broadcaster to request that a Receiver change the activation state of an application, and to direct


applications to receive specific multicast packet flows (using IPv4 or IPv6 descriptors). In MHP, AR is not seen as a specific function, but as a part of a wider configuration and control function.


4.2.4. Address Resolution in ATSC
4.2.4. ATSC中的地址解析

ATSC [ATSC-A54A] defines a system that allows transmission of IP packets within an MPEG-2 Network. An MPEG-2 Program (defined by the PMT) may contain one or more applications [ATSC-A90] that include IP multicast streams [ATSC-A92]. IP multicast data are signalled in the PMT using a stream_type indicator of value 0x0D. A MAC address list descriptor [SCTE-1] may also be included in the PMT.


The approach focuses on applications that serve the transmission network. A method is defined that uses MPEG-2 SI Tables to bind the IP multicast media streams and the corresponding Session Description Protocol (SDP) announcement streams to particular MPEG-2 Program Elements. Each application constitutes an independent network. The MPEG-2 Network boundaries establish the IP addressing scope.

该方法侧重于服务于传输网络的应用程序。定义了一种使用MPEG-2 SI表将IP多播媒体流和相应的会话描述协议(SDP)公告流绑定到特定MPEG-2节目元素的方法。每个应用程序构成一个独立的网络。MPEG-2网络边界确定了IP寻址范围。

4.2.5. Comparison of SI/PSI Table Approaches
4.2.5. SI/PSI表格方法的比较

The MPEG-2 methods based on SI/PSI meet the specified requirements of the groups that created them and each has their strength: the INT in terms of flexibility and extensibility, the MMT in its simplicity, and the AIT in its extensibility. However, they exhibit scalability constraints, represent technology specific solutions, and do not fully adopt IP-centric approaches that would enable easier use of the MPEG-2 bearer as a link technology within the wider Internet.


4.3. IP-Based Address Resolution for TS Logical Channels
4.3. TS逻辑通道基于IP的地址解析

As MPEG-2 Networks evolve to become multi-service networks, the use of IP protocols is becoming more prevalent. Most MPEG-2 Networks now use some IP protocols for operations and control and data delivery. Address resolution information could also be sent using IP transport. At the time of writing there is no standards-based IP-level AR protocol that supports the MPEG-2 TS.

随着MPEG-2网络向多业务网络的发展,IP协议的使用变得越来越普遍。大多数MPEG-2网络现在使用一些IP协议进行操作、控制和数据传输。地址解析信息也可以使用IP传输发送。在撰写本文时,还没有支持MPEG-2 TS的基于标准的IP级AR协议。

There is an opportunity to define an IP-level method that could use an IP multicast protocol over a well-known IP multicast address to resolve an IP address to a TS Logical Channel (i.e., a Transport Stream). The advantages of using an IP-based address resolution include:


(i) Simplicity: The AR mechanism does not require interpretation of L2 tables; this is an advantage especially in the growing market share for home network and audio/video networked entities.

(i) 简单性:AR机制不需要解释L2表;这是一个优势,尤其是在家庭网络和音频/视频网络实体的市场份额不断增长的情况下。

(ii) Uniformity: An IP-based protocol can provide a common method across different network scenarios for both IP to MAC address mappings and mapping to TS Logical Channels (PID value associated with a Stream).


(iii) Extensibility: IP-based AR mechanisms allow an independent evolution of the AR protocol. This includes dynamic methods to request address resolution and the ability to include other L2 information (e.g., encryption keys).


(iv) Integration: The information exchanged by IP-based AR protocols can easily be integrated as a part of the IP network layer, simplifying support for AAA, policy, Operations and Management (OAM), mobility, configuration control, etc., that combine AR with security.


The drawbacks of an IP-based method include:


(i) It can not operate over an MPEG-2 Network that uses MPEG-2 remultiplexors [RFC4259] that modify the PID values associated with the TS Logical Channels during the multiplexing operation (Section 4). This makes the method unsuitable for use in deployed broadcast TV networks [RFC4259].

(i) 它不能在使用MPEG-2复用器[RFC4259]的MPEG-2网络上运行,该复用器在复用操作期间修改与TS逻辑信道相关联的PID值(第4节)。这使得该方法不适用于已部署的广播电视网络[RFC4259]。

(ii) IP-based methods can introduce concerns about the integrity of the information and authentication of the sender [RFC4259]. (These concerns are also applicable to MPEG-2 Table methods, but in this case the information is confined to the L2 network, or parts of the network where gateway devices isolate the MPEG-2 devices from the larger Internet creating virtual MPEG-2 private networks.) IP-based solutions should therefore implement security mechanisms that may be used to authenticate the sender and verify the integrity of the AR information as a part of a larger security framework.


An IP-level method could use an IP multicast protocol running an AR Server (see also Section 5.4) over a well-known (or discovered) IP multicast address. To satisfy the requirement for scalability to networks with a large number of systems (Section 1), a single packet needs to transport multiple AR records and define the intended scope


for each address. Methods that employ prefix matching are desirable (e.g., where a range of source/destination addresses are matched to a single entry). It can also be beneficial to use methods that permit a range of IP addresses to be mapped to a set of TS Logical Channels (e.g., a hashing technique similar to the mapping of IP Group Destination Addresses to Ethernet MAC addresses [RFC1112] [RFC2464]).


5. Mapping IP Addresses to MAC/NPA Addresses
5. 将IP地址映射到MAC/NPA地址

This section reviews IETF protocols that may be used to assign and manage the mapping of IP addresses to/from MAC/NPA addresses over MPEG-2 Networks.


An IP Encapsulator requires AR information to select an appropriate MAC/NPA address in the SNDU header [RFC4259] (Section 6). The information to complete this header may be taken directly from a neighbor/ARP cache, or may require the Encapsulator to retrieve the information using an AR protocol. The way in which this information is collected will depend upon whether the Encapsulator functions as a Router (at L3) or a Bridge (at L2) (Section 1.1).


Two IETF-defined protocols for mapping IP addresses to MAC/NPA addresses are the Address Resolution Protocol, ARP [RFC826], and the Neighbor Discovery protocol, ND [RFC2461], respectively for IPv4 and IPv6. Both protocols are normally used in a bidirectional mode, although both also permit unsolicited transmission of mappings. The IPv6 mapping defined in [RFC2464] can result in a large number of active MAC multicast addresses (e.g., one for each end host).


ARP requires support for L2 broadcast packets. A large number of Receivers can lead to a proportional increase in ARP traffic, a concern for bandwidth-limited networks. Transmission delay can also impact protocol performance.


ARP also has a number of security vulnerabilities. ARP spoofing is where a system can be fooled by a rogue device that sends a fictitious ARP RESPONSE that includes the IP address of a legitimate network system and the MAC of a rogue system. This causes legitimate systems on the network to update their ARP tables with the false mapping and then send future packets to the rogue system instead of the legitimate system. Using this method, a rogue system can see (and modify) packets sent through the network.


Secure ARP (SARP) uses a secure tunnel (e.g., between each client and a server at a wireless access point or router) [RFC4346]. The router ignores any ARP RESPONSEs not associated with clients using the secure tunnels. Therefore, only legitimate ARP RESPONSEs are used


for updating ARP tables. SARP requires the installation of software at each client. It suffers from the same scalability issues as the standard ARP.


The ND protocol uses a set of IP multicast addresses. In large networks, many multicast addresses are used, but each client typically only listens to a restricted set of group destination addresses and little traffic is usually sent in each group. Therefore, Layer 2 AR for MPEG-2 Networks must support this in a scalable manner.


A large number of ND messages may cause a large demand for performing asymmetric operations. The base ND protocol limits the rate at which multicast responses to solicitations can be sent. Configurations may need to be tuned when operating with large numbers of Receivers.


The default parameters specified in the ND protocol [RFC2461] can introduce interoperability problems (e.g., a failure to resolve when the link RTT (round-trip time) exceed 3 seconds) and performance degradation (duplicate ND messages with a link RTT > 1 second) when used in networks where the link RTT is significantly larger than experienced by Ethernet LANs. Tuning of the protocol parameters (e.g., RTR_SOLICITATION_INTERVAL) is therefore recommended when using network links with appreciable delay (Section 6.3.2 of [RFC2461]).


ND has similar security vulnerabilities to ARP. The Secure Neighbor Discovery (SEND) [RFC3971] was developed to address known security vulnerabilities in ND [RFC3756]. It can also reduce the AR traffic compared to ND. In addition, SEND does not require the configuration of per-host keys and can coexist with the use of both SEND and insecure ND on the same link.


The ND Protocol is also used by IPv6 systems to perform other functions beyond address resolution, including Router Solicitation / Advertisement, Duplicate Address Detection (DAD), Neighbor Unreachability Detection (NUD), and Redirect. These functions are useful for hosts, even when address resolution is not required.


5.1. Unidirectional Links Supporting Unidirectional Connectivity
5.1. 支持单向连接的单向链路

MPEG-2 Networks may provide a Unidirectional Broadcast Link (UDL), with no return path. Such links may be used for unicast applications that do not require a return path (e.g., based on UDP), but commonly are used for IP multicast content distribution.


                         MPEG-2 Uplink    /MPEG-2 \
                      ###################( Network )
                      #                   \       /
                 +----#------+             \--.--/
                 |  Network  |                |
                 |  Provider +                v MPEG-2 Downlink
                 +-----------+                |
                                        |   MPEG-2   |
                                        |  Receiver  |
                         MPEG-2 Uplink    /MPEG-2 \
                      ###################( Network )
                      #                   \       /
                 +----#------+             \--.--/
                 |  Network  |                |
                 |  Provider +                v MPEG-2 Downlink
                 +-----------+                |
                                        |   MPEG-2   |
                                        |  Receiver  |

Figure 3: Unidirectional connectivity


The ARP and ND protocols require bidirectional L2/L3 connectivity. They do not provide an appropriate method to resolve the remote (destination) address in a unidirectional environment.


Unidirectional links therefore require a separate out-of-band configuration method to establish the appropriate AR information at the Encapsulator and Receivers. ULE [RFC4326] defines a mode in which the MAC/NPA address is omitted from the SNDU. In some scenarios, this may relieve an Encapsulator of the need for L2 AR.

因此,单向链路需要单独的带外配置方法,以在封装器和接收器处建立适当的AR信息。ULE[RFC4326]定义了一种模式,在该模式下,从SNDU中省略MAC/NPA地址。在某些情况下,这可能会减轻封装器对L2 AR的需求。

5.2. Unidirectional Links with Bidirectional Connectivity
5.2. 具有双向连接的单向链路

Bidirectional connectivity may be realized using a unidirectional link in combination with another network path. Common combinations are a Feed link using MPEG-2 satellite transmission and a return link using terrestrial network infrastructure. This topology is often known as a Hybrid network and has asymmetric network routing.


                         MPEG-2 uplink    /MPEG-2 \
                      ###################( Network )
                      #                   \       /
                 +----#------+             \--.--/
                 |  Network  |                |
                 |  Provider +-<-+            v MPEG-2 downlink
                 +-----------+   |            |
                                 |      +-----v------+
                                 +--<<--+   MPEG-2   |
                               Return   |  Receiver  |
                               Path     +------------+
                         MPEG-2 uplink    /MPEG-2 \
                      ###################( Network )
                      #                   \       /
                 +----#------+             \--.--/
                 |  Network  |                |
                 |  Provider +-<-+            v MPEG-2 downlink
                 +-----------+   |            |
                                 |      +-----v------+
                                 +--<<--+   MPEG-2   |
                               Return   |  Receiver  |
                               Path     +------------+

Figure 4: Bidirectional connectivity


The Unidirectional Link Routing (UDLR) [RFC3077] protocol may be used to overcome issues associated with asymmetric routing. The Dynamic Tunnel Configuration Protocol (DTCP) enables automatic configuration of the return path. UDLR hides the unidirectional routing from the IP and upper layer protocols by providing a L2 tunnelling mechanism that emulates a bidirectional broadcast link at L2. A network using UDLR has a topology where a Feed Router and all Receivers form a logical Local Area Network. Encapsulating L2 frames allows them to be sent through an Internet Path (i.e., bridging).


Since many unidirectional links employ wireless technology for the forward (Feed) link, there may be an appreciable cost associated with forwarding traffic on the Feed link. Therefore, it is often desirable to prevent forwarding unnecessary traffic (e.g., for multicast this implies control of which groups are forwarded). The implications of forwarding in the return direction must also be considered (e.g., asymmetric capacity and loss [RFC3449]). This suggests a need to minimize the volume and frequency of control messages.


Three different AR cases may be identified (each considers sending an IP packet to a next-hop IP address that is not currently cached by the sender):


(i) A Feed Router needs a Receiver MAC/NPA address.

(i) 馈送路由器需要一个接收器MAC/NPA地址。

This occurs when a Feed Router sends an IP packet using the Feed UDL to a Receiver whose MAC/NPA address is unknown. In IPv4, the Feed Router sends an ARP REQUEST with the IP address of the Receiver. The Receiver that recognizes its IP address replies with an ARP RESPONSE to the MAC/NPA address of the Feed Router (e.g., using a UDLR tunnel). The Feed Router may then address IP packets to the unicast MAC/NPA address associated with the Receiver. The ULE encapsulation format also permits packets to be sent without specifying a MAC/NPA address, where this is desirable (Section 6.1 and 6.5).

当Feed路由器使用Feed UDL向MAC/NPA地址未知的接收器发送IP包时,就会发生这种情况。在IPv4中,馈送路由器发送带有接收器IP地址的ARP请求。识别其IP地址的接收器用ARP响应回复馈送路由器的MAC/NPA地址(例如,使用UDLR隧道)。然后,馈送路由器可将IP分组寻址到与接收器相关联的单播MAC/NPA地址。ULE封装格式还允许在不指定MAC/NPA地址的情况下发送数据包,这是需要的(第6.1和6.5节)。

(ii) A Receiver needs the Feed Router MAC/NPA address.


This occurs when a Receiver sends an IP packet to a Feed Router whose MAC/NPA address is unknown. In IPv4, the Receiver sends an ARP REQUEST with the IP address of the Feed Router (e.g., using a UDLR tunnel). The Feed Router replies with an ARP RESPONSE using the Feed UDL. The Receiver may then address IP packets to the MAC/NPA address of the recipient.

当接收器向MAC/NPA地址未知的馈送路由器发送IP数据包时,就会发生这种情况。在IPv4中,接收方发送一个带有馈送路由器IP地址的ARP请求(例如,使用UDLR隧道)。Feed路由器使用Feed UDL以ARP响应进行响应。然后,接收机可以将IP分组寻址到接收机的MAC/NPA地址。

(iii) A Receiver needs another Receiver MAC/NPA address.


This occurs when a Receiver sends an IP packet to another Receiver whose MAC/NPA address is unknown. In IPv4, the Receiver sends an ARP REQUEST with the IP address of the remote Receiver (e.g., using a UDLR tunnel to the Feed Router). The request is forwarded over the Feed UDL. The target Receiver replies with an ARP RESPONSE (e.g., using a UDLR tunnel). The Feed Router forwards the response on the UDL. The Receiver may then address IP packets to the MAC/NPA address of the recipient.


These 3 cases allow any system connected to the UDL to obtain the MAC/NPA address of any other system. Similar exchanges may be performed using the ND protocol for IPv6.


A long round trip delay (via the UDL and UDLR tunnel) impacts the performance of the reactive address resolution procedures provided by ARP, ND, and SEND. In contrast to Ethernet, during the interval when resolution is taking place, many IP packets may be received that are addressed to the AR Target address. The ARP specification allows an interface to discard these packets while awaiting the response to the resolution request. An appropriately sized buffer would however prevent this loss.


In case (iii), the time to complete address resolution may be reduced by the use of an AR Server at the Feed (Section 5.4).


Using DHCP requires prior establishment of the L2 connectivity to a DHCP Server. The delay in establishing return connectivity in UDLR networks that use DHCP, may make it beneficial to increase the frequency of the DTCP HELLO message. Further information about tuning DHCP is provided in Section 5.5.

使用DHCP需要事先建立到DHCP服务器的L2连接。在使用DHCP的UDLR网络中建立返回连接的延迟可能有助于增加DTCP HELLO消息的频率。第5.5节提供了有关调整DHCP的更多信息。

5.3. Bidirectional Links
5.3. 双向链路

Bidirectional IP networks can be and are constructed by a combination of two MPEG-2 transmission links. One link is usually a broadcast link that feeds a set of remote Receivers. Links are also provided from Receivers so that the combined link functions as a full duplex interface. Examples of this use include two-way DVB-S satellite links and the DVB-RCS system.


5.4. AR Server
5.4. AR服务器

An AR Server can be used to distribute AR information to Receivers in an MPEG-2 Network. In some topologies, this may significantly reduce the time taken for Receivers to discover AR information.


The AR Server can operate as a proxy responding on behalf of Receivers to received AR requests. When an IPv4 AR request is received (e.g., Receiver ARP REQUEST), an AR Server responds by (proxy) sending an AR response, providing the appropriate IP to MAC/NPA binding (mapping the IP address to the L2 address).

AR服务器可以作为代理,代表接收者响应接收到的AR请求。当接收到IPv4 AR请求(例如,接收器ARP请求)时,AR服务器通过(代理)发送AR响应进行响应,提供适当的IP到MAC/NPA绑定(将IP地址映射到L2地址)。

Information may also be sent unsolicited by the AR Server using multicast/broadcast to update the ARP/neighbor cache at the Receivers without the need for explicit requests. The unsolicited method can improve scaling in large networks. Scaling could be further improved by distributing a single broadcast/multicast AR message that binds multiple IP and MAC/NPA addresses. This reduces the network capacity consumed and simplifies client/server processing in networks with large numbers of clients.


An AR Server can be implemented using IETF-defined Protocols by configuring the subnetwork so that AR Requests from Receivers are intercepted rather than forwarded to the Feed/broadcast link. The intercepted messages are sent to an AR Server. The AR Server maintains a set of MAC/NPA address bindings. These may be configured or may learned by monitoring ARP messages sent by Receivers. Currently defined IETF protocols only allow one binding per message (i.e., there is no optimization to conserve L2 bandwidth).


Equivalent methods could provide IPv6 AR. Procedures for intercepting ND messages are defined in [RFC4389]. To perform an AR Server function, the AR information must also be cached. A caching AR proxy stores the system state within a middle-box device. This resembles a classic man-in-the-middle security attack; interactions with SEND are described in [SP-ND].

等效方法可以提供IPv6 AR。拦截ND消息的过程在[RFC4389]中定义。要执行AR服务器功能,还必须缓存AR信息。缓存AR代理将系统状态存储在中间盒设备中。这类似于典型的中间人安全攻击;[SP-ND]中描述了与SEND的交互。

Methods are needed to purge stale AR data from the cache. The consistency of the cache must also be considered when the Receiver bindings can change (e.g., IP mobility, network topology changes, or intermittent Receiver connectivity). In these cases, the use of old (stale) information can result in IP packets being directed to an inappropriate L2 address, with consequent packet loss.


Current IETF-defined methods provide bindings of IP addresses to MAC/NPA, but do not allow the bindings to other L2 information pertinent to MPEG-2 Networks, requiring the use of other methods for


this function (Section 4). AR Servers can also be implemented using non-IETF AR protocols to provide the AR information required by Receivers.

此功能(第4节)。AR服务器也可以使用非IETF AR协议来实现,以提供接收机所需的AR信息。

5.5. DHCP Tuning
5.5. DHCP调优

DHCP [RFC2131] and DHCPv6 [RFC3315] may be used over MPEG-2 Networks with bidirectional connectivity. DHCP consists of two components: a protocol for delivering system-specific configuration parameters from a DHCP Server to a DHCP Client (e.g., default router, DNS server) and a mechanism for the allocation of network addresses to systems.


The configuration of DHCP Servers and DHCP Clients should take into account the local link round trip delay (possibly including the additional delay from bridging, e.g., using UDLR). A large number of clients can make it desirable to tune the DHCP lease duration and the size of the address pool. Appropriate timer values should also be selected: the DHCP messages retransmission timeout, and the maximum delay that a DHCP Server waits before deciding that the absence of an ICMP echo response indicates that the relevant address is free.


DHCP Clients may retransmit DHCP messages if they do not receive a response. Some client implementations specify a timeout for the DHCPDISCOVER message that is small (e.g., suited to Ethernet delay, rather than appropriate to an MPEG-2 Network) providing insufficient time for a DHCP Server to respond to a DHCPDISCOVER retransmission before expiry of the check on the lease availability (by an ICMP Echo Request), resulting in potential address conflict. This value may need to be tuned for MPEG-2 Networks.


5.6. IP Multicast AR
5.6. IP多播AR

Section 3.2 describes the multicast address resolution requirements. This section describes L3 address bindings when the destination network-layer address is an IP multicast Group Destination Address.


In MPE [ETSI-DAT], a mapping is specified for the MAC Address based on the IP multicast address for IPv4 [RFC1112] and IPv6 [RFC2464]. (A variant of DVB (DVB-H) uses a modified MAC header [ETSI-DAT]).


In ULE [RFC4326], the L2 NPA address is optional, and is not necessarily required when the Receiver is able to perform efficient L3 multicast address filtering. When present, a mapping is defined based on the IP multicast address for IPv4 [RFC1112] and IPv6 [RFC2464].

在ULE[RFC4326]中,L2 NPA地址是可选的,并且在接收器能够执行有效的L3多播地址过滤时不一定需要。存在时,将根据IPv4[RFC1112]和IPv6[RFC2464]的IP多播地址定义映射。

The L2 group addressing method specified in [RFC1112] and [RFC2464] can result in more than one IP destination address being mapped to the same L2 address. In Source-Specific Multicast, SSM [RFC3569], multicast groups are identified by the combination of the IP source and IP destination addresses. Therefore, senders may independently select an IP group destination address that could map to the same L2 address if forwarded onto the same L2 link. The resulting addressing overlap at L2 can increase the volume of traffic forwarded to L3, where it then needs to be filtered.


These considerations are the same as for Ethernet LANs, and may not be of concern to Receivers that can perform efficient L3 filtering. Section 3 noted that an MPEG-2 Network may need to support multiple addressing scopes at the network and link layers. Separation of the different groups into different Transport Streams is one remedy (with signalling of IP to PID value mappings). Another approach is to employ alternate MAC/NPA mappings to those defined in [RFC1112] and [RFC2464], but such mappings need to be consistently bound at the Encapsulator and Receiver, using AR procedures in a scalable manner.


5.6.1. Multicast/Broadcast Addressing for UDLR
5.6.1. UDLR的多播/广播寻址

UDLR is a Layer 2 solution, in which a Receiver may send multicast/broadcast frames that are subsequently forwarded natively by a Feed Router (using the topology in Figure 2), and are finally received at the Feed interface of the originating Receiver. This multicast forwarding does not include the normal L3 Reverse Path Forwarding (RPF) check or L2 spanning tree checks, the processing of the IP Time To Live (TTL) field or the filtering of administratively scoped multicast addresses. This raises a need to carefully consider multicast support. To avoid forwarding loops, RFC 3077 notes that a Receiver needs to be configured with appropriate filter rules to ensure that it discards packets that originate from an attached network and are later received over the Feed link.

UDLR是一种第2层解决方案,在该解决方案中,接收器可以发送多播/广播帧,这些帧随后由馈送路由器(使用图2中的拓扑)本地转发,并最终在发起接收器的馈送接口处接收。此多播转发不包括正常的L3反向路径转发(RPF)检查或L2生成树检查、IP生存时间(TTL)字段的处理或管理范围多播地址的过滤。这就需要仔细考虑多播支持。为了避免转发循环,RFC 3077注意到接收机需要配置适当的过滤规则,以确保其丢弃源自连接网络且随后通过馈送链路接收的数据包。

When the encapsulation includes an MAC/NPA source address, re-broadcast packets may be filtered at the link layer using a filter that discards L2 addresses that are local to the Receiver. In some circumstances, systems can send packets with an unknown (all-zero) MAC source address (e.g., IGMP Proxy Queriers [RFC4605]), where the source at L2 can not be determined at the Receiver. These packets need to be silently discarded, which may prevent running the associated services on the Receiver.


Some encapsulation formats also do not include an MAC/NPA source address (Table 1). Multicast packets may therefore alternatively be discarded at the IP layer if their IP source address matches a local IP address (or address range). Systems can send packets with an


all-zero IP source address (e.g., BOOTP (bootstrap protocol) [RFC951], DHCP [RFC2131] and ND [RFC2461]), where the source at L3 can not be determined at the Receiver these packets need to be silently discarded. This may prevent running the associated services at a Receiver, e.g., participation in IPv6 Duplicate Address Detection or running a DHCP server.


6. Link Layer Support
6. 链路层支持

This section considers link layer (L2) support for address resolution in MPEG-2 Networks. It considers two issues: The code-point used at L2 and the efficiency of encapsulation for transmission required to support the AR method. The table below summarizes the options for both MPE ([ETSI-DAT], [ATSC-A90]) and ULE [RFC4326] encapsulations.


[RFC4840] describes issues and concerns that may arise when a link can support multiple encapsulations. In particular, it identifies problems that arise when end hosts that belong to the same IP network employ different incompatible encapsulation methods. An Encapsulator must therefore use only one method (e.g., ULE or MPE) to support a single IP network (i.e., set of IPv4 systems sharing the same subnet broadcast address or same IPv6 prefix). All Receivers in an IP network must receive all IP packets that use a broadcast (directed to all systems in the IP network) or a local-scope multicast address (Section 3). Packets with these addresses are used by many IP-based protocols including service discovery, IP AR, and routing protocols. Systems that fail to receive these packets can suffer connectivity failure or incorrect behaviour (e.g., they may be unable to participate in IP-based discovery, configuration, routing, and announcement protocols). Consistent delivery can be ensured by transmitting link-local multicast or broadcast packets using the same Stream that is used for unicast packets directed to this network. A Receiver could simultaneously use more than one L2 AR mechanism. This presents a potential conflict when the Receiver receives two different bindings for the same identifier. When multiple systems advertise AR bindings for the same identifiers (e.g., Encapsulators), they must ensure that the advertised information is consistent. Conflicts may also arise when L2 protocols duplicate the functions of IP-based AR mechanisms.

[RFC4840]描述了当链路支持多个封装时可能出现的问题和担忧。特别是,它确定了当属于同一IP网络的终端主机采用不同的不兼容封装方法时出现的问题。因此,封装器必须仅使用一种方法(例如,ULE或MPE)来支持单个IP网络(即,共享相同子网广播地址或相同IPv6前缀的一组IPv4系统)。IP网络中的所有接收器必须接收使用广播(指向IP网络中的所有系统)或本地范围多播地址(第3节)的所有IP数据包。具有这些地址的数据包被许多基于IP的协议使用,包括服务发现、IP AR和路由协议。无法接收这些数据包的系统可能会出现连接故障或错误行为(例如,它们可能无法参与基于IP的发现、配置、路由和公告协议)。通过使用用于定向到此网络的单播数据包的相同流传输链路本地多播或广播数据包,可以确保一致的传输。接收机可以同时使用多个L2 AR机制。当接收者接收到同一标识符的两个不同绑定时,这就产生了潜在的冲突。当多个系统为相同的标识符(例如,封装器)发布AR绑定时,它们必须确保发布的信息是一致的。当L2协议重复基于IP的AR机制的功能时,也可能出现冲突。

In ULE, the bridging format may be used in combination with the normal mode to address packets to a Receiver (all ULE Receivers are required to implement both methods). Frames carrying IP packets using the ULE Bridging mode, that have a destination address corresponding to the MAC address of the Receiver and have an IP address corresponding to a Receiver interface, will be delivered to the IP stack of the Receiver. All bridged IP multicast and broadcast frames will also be copied to the IP stack of the Receiver.


Receivers must filter (discard) frames that are received with a source address that matches an address of the Receiver itself [802.1D]. It must also prevent forwarding frames already sent on a connected network. For each network interface, it must therefore filter received frames where the frame source address matches a unicast destination address associated with a different network interface [802.1D].


   |                               | PDU    |L2 Frame Header Fields|
   | L2 Encapsulation              |overhead+----------------------+
   |                               |[bytes] |src mac|dst mac| type |
   |6.1 ULE without dst MAC address| 8      |   -   |  -    | x    |
   |6.2 ULE with dst MAC address   | 14     |   -   |  x    | x    |
   |6.3 MPE without LLC/SNAP       | 16     |   -   |  x    | -    |
   |6.4 MPE with LLC/SNAP          | 24     |   -   |  x    | x    |
   |6.5 ULE with Bridging extension| 22     |   x   |  x    | x    |
   |6.6 ULE with Bridging & NPA    | 28     |   x   |  x    | x    |
   |6.7 MPE with LLC/SNAP&Bridging | 38     |   x   |  x    | x    |
   |                               | PDU    |L2 Frame Header Fields|
   | L2 Encapsulation              |overhead+----------------------+
   |                               |[bytes] |src mac|dst mac| type |
   |6.1 ULE without dst MAC address| 8      |   -   |  -    | x    |
   |6.2 ULE with dst MAC address   | 14     |   -   |  x    | x    |
   |6.3 MPE without LLC/SNAP       | 16     |   -   |  x    | -    |
   |6.4 MPE with LLC/SNAP          | 24     |   -   |  x    | x    |
   |6.5 ULE with Bridging extension| 22     |   x   |  x    | x    |
   |6.6 ULE with Bridging & NPA    | 28     |   x   |  x    | x    |
   |6.7 MPE with LLC/SNAP&Bridging | 38     |   x   |  x    | x    |
   Table 1: L2 Support and Overhead (x =supported, - =not supported)
   Table 1: L2 Support and Overhead (x =supported, - =not supported)

The remainder of the section describes IETF-specified AR methods for use with these encapsulation formats. Most of these methods rely on bidirectional communications (see Sections 5.1, 5.2, and 5.3 for a discussion of this).


6.1. ULE without a Destination MAC/NPA Address (D=1)
6.1. 没有目标MAC/NPA地址的ULE(D=1)

The ULE encapsulation supports a mode (D=1) where the MAC/NPA address is not present in the encapsulated frame. This mode may be used with both IPv4 and IPv6. When used, the Receiver is expected to perform L3 filtering of packets based on their IP destination address [RFC4326]. This requires careful consideration of the network topology when a Receiver is an IP router, or delivers data to an IP router (a simple case where this is permitted arises in the connection of stub networks at a Receiver that have no connectivity to other networks). Since there is no MAC/NPA address in the SNDU, ARP and the ND protocol are not required for AR.


IPv6 systems can automatically configure their IPv6 network address based upon a local MAC address [RFC2462]. To use auto-configuration, the IP driver at the Receiver may need to access the MAC/NPA address of the receiving interface, even though this value is not being used to filter received SNDUs.


Even when not used for AR, the ND protocol may still be required to support DAD, and other IPv6 network-layer functions. This protocol uses a block of IPv6 multicast addresses, which need to be carried by the L2 network. However, since this encapsulation format does not provide a MAC source address, there are topologies (e.g., Section 5.6.1) where a system can not differentiate DAD packets that were originally sent by itself and were re-broadcast, from those that may have been sent by another system with the same L3 address. Therefore, DAD can not be used with this encapsulation format in topologies where this L2 forwarding may occur.


6.2. ULE with a Destination MAC/NPA Address (D=0)
6.2. 具有目标MAC/NPA地址(D=0)的ULE

The IPv4 Address Resolution Protocol (ARP) [RFC826] is identified by an IEEE EtherType and may be used over ULE [RFC4326]. Although no MAC source address is present in the ULE SNDU, the ARP protocol still communicates the source MAC (hardware) address in the ARP record payload of any query messages that it generates.

IPv4地址解析协议(ARP)[RFC826]由IEEE EtherType标识,可通过ULE[RFC4326]使用。尽管ULE SNDU中不存在MAC源地址,但ARP协议仍在其生成的任何查询消息的ARP记录有效负载中通信源MAC(硬件)地址。

The IPv6 ND protocol is supported. The protocol uses a block of IPv6 multicast addresses, which need to be carried by the L2 network. The protocol uses a block of IPv6 multicast addresses, which need to be carried by the L2 network. However, since this encapsulation format does not provide a MAC source address, there are topologies (e.g., Section 5.6.1) where a system can not differentiate DAD packets that were originally sent by itself and were re-broadcast, from those that may have been sent by another system with the same L3 address. Therefore, DAD can not be used with this encapsulation format in topologies where this L2 forwarding may occur.

支持IPv6 ND协议。该协议使用一组IPv6多播地址,这些地址需要由L2网络承载。该协议使用一组IPv6多播地址,这些地址需要由L2网络承载。然而,由于这种封装格式不提供MAC源地址,因此存在这样的拓扑(例如,第5.6.1节),系统无法区分最初由自身发送并重新广播的DAD数据包与可能由具有相同L3地址的另一系统发送的DAD数据包。因此,在可能发生L2转发的拓扑中,DAD不能与此封装格式一起使用。

6.3. MPE without LLC/SNAP Encapsulation
6.3. 不带LLC/SNAP封装的MPE

This is the default (and sometimes only) mode specified by most MPE Encapsulators. MPE does not provide an EtherType field and therefore can not support the Address Resolution Protocol (ARP) [RFC826].


IPv6 is not supported in this encapsulation format, and therefore it is not appropriate to consider the ND protocol.


6.4. MPE with LLC/SNAP Encapsulation
6.4. 带有LLC/SNAP封装的MPE

The LLC/SNAP (Sub-Network Access Protocol) format of MPE provides an EtherType field and therefore may support ARP [RFC826]. There is no specification to define how this is performed. No MAC source address is present in the SNDU, although the protocol communicates the source MAC address in the ARP record payload of any query messages that it generates.


The IPv6 ND protocol is supported using The LLC/SNAP format of MPE. This requires specific multicast addresses to be carried by the L2 network. The IPv6 ND protocol is supported. The protocol uses a block of IPv6 multicast addresses, which need to be carried by the L2 network. However, since this encapsulation format does not provide a MAC source address, there are topologies (e.g., Section 5.6.1) where a system can not differentiate DAD packets that were originally sent by itself and were re-broadcast, from those that may have been sent by another system with the same L3 address. Therefore, DAD can not be used with this encapsulation format in topologies where this L2 forwarding may occur.

使用MPE的LLC/SNAP格式支持IPv6 ND协议。这需要L2网络承载特定的多播地址。支持IPv6 ND协议。该协议使用一组IPv6多播地址,这些地址需要由L2网络承载。然而,由于这种封装格式不提供MAC源地址,因此存在这样的拓扑(例如,第5.6.1节),系统无法区分最初由自身发送并重新广播的DAD数据包与可能由具有相同L3地址的另一系统发送的DAD数据包。因此,在可能发生L2转发的拓扑中,DAD不能与此封装格式一起使用。

6.5. ULE with Bridging Header Extension (D=1)
6.5. 带桥接标头扩展的ULE(D=1)

The ULE encapsulation supports a bridging extension header that supplies both a source and destination MAC address. This can be used without an NPA address (D=1). When no other Extension Headers precede this Extension, the MAC destination address has the same position in the ULE SNDU as that used for an NPA destination address. The Receiver may optionally be configured so that the MAC destination address value is identical to a Receiver NPA address.

ULE封装支持同时提供源和目标MAC地址的桥接扩展头。这可以在没有NPA地址(D=1)的情况下使用。当此扩展之前没有其他扩展头时,MAC目标地址在ULE SNDU中的位置与用于NPA目标地址的位置相同。接收机可以可选地被配置为使得MAC目的地地址值与接收机NPA地址相同。

At the Encapsulator, the ULE MAC/NPA destination address is determined by a L2 forwarding decision. Received frames may be forwarded or may be addressed to the Receiver itself. As in other L2 LANs, the Receiver may choose to filter received frames based on a configured MAC destination address filter. ARP and ND messages may be carried within a PDU that is bridged by this encapsulation format. Where the topology may result in subsequent reception of re-broadcast copies of multicast frames that were originally sent by a Receiver (e.g., Section 5.6.1), the system must discard frames that are received with a source address that it used in frames sent from the same interface [802.1D]. This prevents duplication on the bridged network (e.g., this would otherwise invoke DAD).

在封装器处,ULE MAC/NPA目的地地址由L2转发决定确定。接收到的帧可以被转发或者可以被寻址到接收机本身。与在其他L2 LAN中一样,接收器可以选择基于配置的MAC目的地地址过滤器过滤接收到的帧。ARP和ND消息可以在通过这种封装格式桥接的PDU中传输。如果拓扑可能导致随后接收最初由接收器发送的多播帧的重新广播副本(例如,第5.6.1节),则系统必须丢弃其在从同一接口发送的帧中使用的源地址接收的帧[802.1D]。这可防止桥接网络上的重复(例如,否则将调用DAD)。

6.6. ULE with Bridging Header Extension and NPA Address (D=0)
6.6. 具有桥接头扩展和NPA地址(D=0)的ULE

The combination of an NPA address (D=0) and a bridging extension header are allowed in ULE. This SNDU format supplies both a source and destination MAC address and a NPA destination address (i.e., Receiver MAC/NPA address).


At the Encapsulator, the value of the ULE MAC/NPA destination address is determined by a L2 forwarding decision. At the Receiver, frames may be forwarded or may be addressed to the Receiver itself. As in other L2 LANs, the Receiver may choose to filter received frames based on a configured MAC destination address filter. ARP and ND messages may be carried within a PDU that is bridged by this

在封装器处,ULE MAC/NPA目的地地址的值由L2转发决定确定。在接收机处,帧可以被转发或被寻址到接收机本身。与在其他L2 LAN中一样,接收器可以选择基于配置的MAC目的地地址过滤器过滤接收到的帧。ARP和ND消息可以在通过该协议桥接的PDU内传送

encapsulation format. Where the topology may result in the subsequent reception of re-broadcast copies of multicast frames, that were originally sent by a Receiver (e.g., Section 5.6.1), the system must discard frames that are received with a source address that it used in frames sent from the same interface [802.1D]. This prevents duplication on the bridged network (e.g., this would otherwise invoke DAD).


6.7. MPE with LLC/SNAP & Bridging
6.7. MPE与LLC/SNAP和桥接

The LLC/SNAP format MPE frames may optionally support an IEEE bridging header [LLC]. This header supplies both a source and destination MAC address, at the expense of larger encapsulation overhead. The format defines two MAC destination addresses, one associated with the MPE SNDU (i.e., Receiver MAC address) and one with the bridged MAC frame (i.e., the MAC address of the intended recipient in the remote LAN).

LLC/SNAP格式MPE帧可以可选地支持IEEE桥接报头[LLC]。该报头同时提供源MAC地址和目标MAC地址,但以更大的封装开销为代价。该格式定义了两个MAC目的地地址,一个与MPE SNDU(即,接收器MAC地址)关联,另一个与桥接MAC帧(即,远程LAN中预期接收器的MAC地址)关联。

At the Encapsulator, the MPE MAC destination address is determined by a L2 forwarding decision. There is currently no formal description of the Receiver processing for this encapsulation format. A Receiver may forward frames or they may be addressed to the Receiver itself. As in other L2 LANs, the Receiver may choose to filter received frames based on a configured MAC destination address filter. ARP and ND messages may be carried within a PDU that is bridged by this encapsulation format. The MPE MAC destination address is determined by a L2 forwarding decision. Where the topology may result in a subsequent reception of re-broadcast copies of multicast frames, that were originally sent by a Receiver (e.g., Section 5.6.1), the system must discard frames that are received with a source address that it used in frames sent from the same interface [802.1D]. This prevents duplication on the bridged network (e.g., this would otherwise invoke DAD).

在封装器处,MPE MAC目的地地址由L2转发决定确定。目前没有关于这种封装格式的接收器处理的正式描述。接收机可以转发帧,也可以将帧寻址到接收机本身。与在其他L2 LAN中一样,接收器可以选择基于配置的MAC目的地地址过滤器过滤接收到的帧。ARP和ND消息可以在通过这种封装格式桥接的PDU中传输。MPE MAC目的地地址由L2转发决定确定。如果拓扑可能导致随后接收最初由接收器发送的多播帧的重新广播副本(例如,第5.6.1节),则系统必须丢弃其在从同一接口发送的帧中使用的源地址接收的帧[802.1D]。这可防止桥接网络上的重复(例如,否则将调用DAD)。

7. Conclusions
7. 结论

This document describes addressing and address resolution issues for IP protocols over MPEG-2 transmission networks using both wired and wireless technologies. A number of specific IETF protocols are discussed along with their expected behaviour over MPEG-2 transmission networks. Recommendations for their usage are provided.


There is no single common approach used in all MPEG-2 Networks. A static binding may be configured for IP addresses and PIDs (as in some cable networks). In broadcast networks, this information is normally provided by the Encapsulator/Multiplexor and carried in signalling tables (e.g., AIT in MHP, the IP Notification Table, INT,


of DVB and the DVB-RCS Multicast Mapping Table, and MMT). This document has reviewed the status of these current address resolution mechanisms in MPEG-2 transmission networks and defined their usage.


The document also considers a unified IP-based method for AR that could be independent of the physical layer, but does not define a new protocol. It examines the design criteria for a method, with recommendations to ensure scalability and improve support for the IP protocol stack.


8. Security Considerations
8. 安全考虑

The normal security issues relating to the use of wireless links for transmission of Internet traffic should be considered.


L2 signalling in MPEG-2 transmission networks is currently provided by (periodic) broadcasting of information in the control plane using PSI/SI tables (Section 4). A loss or modification of the SI information may result in an inability to identify the TS Logical Channel (PID) that is used for a service. This will prevent reception of the intended IP packet stream.


There are known security issues relating to the use of unsecured address resolution [RFC3756]. Readers are also referred to the known security issues when mapping IP addresses to MAC/NPA addresses using ARP [RFC826] and ND [RFC2461]. It is recommended that AR protocols support authentication of the source of AR messages and the integrity of the AR information, this avoids known security vulnerabilities resulting from insertion of unauthorized AR messages within a L2 infrastructure. For IPv6, the SEND protocol [RFC3971] may be used in place of ND. This defines security mechanisms that can protect AR.


AR protocols can also be protected by the use of L2 security methods (e.g., Encryption of the ULE SNDU [IPDVB-SEC]). When these methods are used, the security of ARP and ND can be comparable to that of a private LAN: A Receiver will only accept ARP or ND transmissions from the set of peer senders that share a common group encryption and common group authentication key provided by the L2 key management.

AR协议也可以通过使用L2安全方法(例如,加密ULE SNDU[IPDVB-SEC])进行保护。当使用这些方法时,ARP和ND的安全性可以与专用LAN的安全性相媲美:接收器将只接受来自对等发送者的ARP或ND传输,这些发送者共享L2密钥管理提供的公共组加密和公共组认证密钥。

AR Servers (Section 5.4) are susceptible to the same kind of security issues as end hosts using unsecured AR. These issues include hijacking traffic and denial-of-service within the subnet. Malicious nodes within the subnet can take advantage of this property, and hijack traffic. In addition, an AR Server is essentially a legitimate man-in-the-middle, which implies that there is a need to distinguish such proxies from unwanted man-in-the-middle attackers. This document does not introduce any new mechanisms for the


protection of these AR functions (e.g., authenticating servers, or defining AR Servers that interoperate with the SEND protocol [SP-ND]).


9. Acknowledgments
9. 致谢

The authors wish to thank the IPDVB WG members for their inputs and in particular, Rod Walsh, Jun Takei, and Michael Mercurio. The authors also acknowledge the support of the European Space Agency. Martin Stiemerling contributed descriptions of scenarios, configuration, and provided extensive proof reading. Hidetaka Izumiyama contributed on UDLR and IPv6 issues. A number of issues discussed in the UDLR working group have also provided valuable inputs to this document (summarized in "Experiments with RFC 3077", July 2003).

作者希望感谢IPDVB工作组成员的投入,特别是Rod Walsh、Jun Takei和Michael Mercurio。作者还感谢欧洲航天局的支持。Martin Stiemerling对场景、配置进行了描述,并提供了广泛的校对。Hidetaka Izumiyama对UDLR和IPv6问题做出了贡献。UDLR工作组讨论的一些问题也为本文件提供了宝贵的投入(总结于2003年7月的“RFC 3077实验”)。

10. References
10. 工具书类
10.1. Normative References
10.1. 规范性引用文件

[ETSI-DAT] EN 301 192, "Specifications for Data Broadcasting", v1.3.1, European Telecommunications Standards Institute (ETSI), May 2003.

[ETSI-DAT]EN 301 192,“数据广播规范”,v1.3.1,欧洲电信标准协会(ETSI),2003年5月。

[ETSI-MHP] TS 101 812, "Digital Video Broadcasting (DVB); Multimedia Home Platform (MHP) Specification", v1.2.1, European Telecommunications Standards Institute (ETSI), June 2002.

[ETSI-MHP]TS 101 812,“数字视频广播(DVB);多媒体家庭平台(MHP)规范”,v1.2.1,欧洲电信标准协会(ETSI),2002年6月。

[ETSI-SI] EN 300 468, "Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems", v1.7.1, European Telecommunications Standards Institute (ETSI), December 2005.

[ETSI-SI]EN 300 468,“数字视频广播(DVB);DVB系统中服务信息(SI)规范”,v1.7.1,欧洲电信标准协会(ETSI),2005年12月。

[ISO-MPEG2] ISO/IEC IS 13818-1, "Information technology -- Generic coding of moving pictures and associated audio information -- Part 1: Systems", International Standards Organization (ISO), 2000.

[ISO-MPEG2]ISO/IEC IS 13818-1,“信息技术——运动图像和相关音频信息的通用编码——第1部分:系统”,国际标准化组织(ISO),2000年。

[RFC826] Plummer, D., "Ethernet Address Resolution Protocol: Or Converting Network Protocol Addresses to 48.bit Ethernet Address for Transmission on Ethernet Hardware", STD 37, RFC 826, November 1982.

[RFC826]Plummer,D.,“以太网地址解析协议:或将网络协议地址转换为48位以太网地址,以便在以太网硬件上传输”,STD 37,RFC 826,1982年11月。

[RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989.

[RFC1112]Deering,S.,“IP多播的主机扩展”,STD 5,RFC11121989年8月。

[RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998.


[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, December 1998.


[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.


[RFC3077] Duros, E., Dabbous, W., Izumiyama, H., Fujii, N., and Y. Zhang, "A Link-Layer Tunneling Mechanism for Unidirectional Links", RFC 3077, March 2001.

[RFC3077]Duros,E.,Dabbous,W.,Izumiyama,H.,Fujii,N.,和Y.Zhang,“单向链路的链路层隧道机制”,RFC 3077,2001年3月。

[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.


[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6", RFC 3736, April 2004.

[RFC3736]Droms,R.,“IPv6的无状态动态主机配置协议(DHCP)服务”,RFC 3736,2004年4月。

[RFC4326] Fairhurst, G. and B. Collini-Nocker, "Unidirectional Lightweight Encapsulation (ULE) for Transmission of IP Datagrams over an MPEG-2 Transport Stream (TS)", RFC 4326, December 2005.

[RFC4326]Fairhurst,G.和B.Collini Nocker,“通过MPEG-2传输流(TS)传输IP数据报的单向轻量封装(ULE)”,RFC 4326,2005年12月。

10.2. Informative References
10.2. 资料性引用

[802.1D] IEEE 802.1D, "IEEE Standard for Local and Metropolitan Area Networks: Media Access Control (MAC) Bridges", IEEE, 2004.

[802.1D]IEEE 802.1D,“局域网和城域网的IEEE标准:媒体访问控制(MAC)网桥”,IEEE,2004年。

[802.3] IEEE 802.3, "Local and metropolitan area networks-Specific requirements Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications", IEEE Computer Society, (also ISO/IEC 8802-3), 2002.

[802.3]IEEE 802.3,“局域网和城域网特定要求第3部分:带冲突检测的载波侦听多址接入(CSMA/CD)接入方法和物理层规范”,IEEE计算机协会(也称ISO/IEC 8802-3),2002年。

[ATSC] A/53C, "ATSC Digital Television Standard", Advanced Television Systems Committee (ATSC), Doc. A/53C, 2004.


[ATSC-A54A] A/54A, "Guide to the use of the ATSC Digital Television Standard", Advanced Television Systems Committee (ATSC), Doc. A/54A, 2003.


[ATSC-A90] A/90, "ATSC Data Broadcast Standard", Advanced Television Systems Committee (ATSC), Doc. A/90, 2000.


[ATSC-A92] A/92, "Delivery of IP Multicast Sessions over ATSC Data Broadcast", Advanced Television Systems Committee (ATSC), Doc. A/92, 2002.


[DOCSIS] "Data-Over-Cable Service Interface Specifications, DOCSIS 2.0, Radio Frequency Interface Specification", CableLabs, document CM-SP-RFIv2.0-I10-051209, 2005.

[DOCSIS]“电缆数据服务接口规范,DOCSIS 2.0,射频接口规范”,电缆实验室,文件CM-SP-RFIv2.0-I10-0512092005。

[DVB] Digital Video Broadcasting (DVB) Project.


[ETSI-DVBS] EN 301 421,"Digital Video Broadcasting (DVB); Modulation and Coding for DBS satellite systems at 11/12 GHz", European Telecommunications Standards Institute (ETSI).

[ETSI-DVBS]EN 301 421,“数字视频广播(DVB);11/12 GHz下DBS卫星系统的调制和编码”,欧洲电信标准协会(ETSI)。

[ETSI-RCS] EN 301 790, "Digital Video Broadcasting (DVB); Interaction channel for satellite distribution Systems", European Telecommunications Standards Institute (ETSI).

[ETSI-RCS]EN 301 790,“数字视频广播(DVB);卫星分配系统的交互信道”,欧洲电信标准协会(ETSI)。

[ETSI-SI1] TR 101 162, "Digital Video Broadcasting (DVB); Allocation of Service Information (SI) codes for DVB systems", European Telecommunications Standards Institute (ETSI).

[ETSI-SI1]TR 101 162,“数字视频广播(DVB);DVB系统服务信息(SI)代码的分配”,欧洲电信标准协会(ETSI)。

[IPDVB-SEC] H. Cruickshank, S. Iyengar, L. Duquerroy, P. Pillai, "Security requirements for the Unidirectional Lightweight Encapsulation (ULE) protocol", Work in Progress, May 2007.


[ISO-DSMCC] ISO/IEC IS 13818-6, "Information technology -- Generic coding of moving pictures and associated audio information -- Part 6: Extensions for DSM-CC is a full software implementation", International Standards Organization (ISO), 2002.

[ISO-DSMCC]ISO/IEC IS 13818-6,“信息技术——运动图像和相关音频信息的通用编码——第6部分:DSM-CC的扩展是一个完整的软件实现”,国际标准化组织(ISO),2002年。

[LLC] ISO/IEC 8802.2, "Information technology; Telecommunications and information exchange between systems; Local and metropolitan area networks; Specific requirements; Part 2: Logical Link Control", International Standards Organization (ISO), 1998.

[LLC]ISO/IEC 8802.2,“信息技术;系统间的电信和信息交换;局域网和城域网;特殊要求;第2部分:逻辑链路控制”,国际标准组织(ISO),1998年。

[MMT] "SatLabs System Recommendations, Part 1, General Specifications", Version 2.0, SatLabs Forum, 2006. SatLabs_System_Recommendations_v2.0_general.pdf.

[MMT]“卫星实验室系统建议,第1部分,通用规范”,2.0版,卫星实验室论坛,2006年。 SatLabs_系统_建议_v2.0_general.pdf。

[RFC951] Croft, W. and J. Gilmore, "Bootstrap Protocol", RFC 951, September 1985.


[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, RFC 2365, July 1998.

[RFC2365]Meyer,D.,“管理范围的IP多播”,BCP 23,RFC 2365,1998年7月。

[RFC2375] Hinden, R. and S. Deering, "IPv6 Multicast Address Assignments", RFC 2375, July 1998.

[RFC2375]Hinden,R.和S.Deering,“IPv6多播地址分配”,RFC 23751998年7月。

[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998.


[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC 3046, January 2001.


[RFC3256] Jones, D. and R. Woundy, "The DOCSIS (Data-Over-Cable Service Interface Specifications) Device Class DHCP (Dynamic Host Configuration Protocol) Relay Agent Information Sub-option", RFC 3256, April 2002.

[RFC3256]Jones,D.和R.Woundy,“DOCSIS(有线数据服务接口规范)设备级DHCP(动态主机配置协议)中继代理信息子选项”,RFC 3256,2002年4月。

[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002.

[RFC3376]Cain,B.,Deering,S.,Kouvelas,I.,Fenner,B.,和A.Thyagarajan,“互联网组管理协议,第3版”,RFC 3376,2002年10月。

[RFC3449] Balakrishnan, H., Padmanabhan, V., Fairhurst, G., and M. Sooriyabandara, "TCP Performance Implications of Network Path Asymmetry", BCP 69, RFC 3449, December 2002.

[RFC3449]Balakrishnan,H.,Padmanabhan,V.,Fairhurst,G.,和M.Sooriyabandara,“网络路径不对称的TCP性能影响”,BCP 69,RFC 3449,2002年12月。

[RFC3451] Luby, M., Gemmell, J., Vicisano, L., Rizzo, L., Handley, M., and J. Crowcroft, "Layered Coding Transport (LCT) Building Block", RFC 3451, December 2002.

[RFC3451]Luby,M.,Gemmell,J.,Vicisano,L.,Rizzo,L.,Handley,M.,和J.Crowcroft,“分层编码传输(LCT)构建块”,RFC 34512002年12月。

[RFC3569] Bhattacharyya, S., "An Overview of Source-Specific Multicast (SSM)", RFC 3569, July 2003.

[RFC3569]Bhattacharyya,S.,“源特定多播(SSM)概述”,RFC 3569,2003年7月。

[RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor Discovery (ND) Trust Models and Threats", RFC 3756, May 2004.

[RFC3756]Nikander,P.,Kempf,J.,和E.Nordmark,“IPv6邻居发现(ND)信任模型和威胁”,RFC 37562004年5月。

[RFC3738] Luby, M. and V. Goyal, "Wave and Equation Based Rate Control (WEBRC) Building Block", RFC 3738, April 2004.

[RFC3738]Luby,M.和V.Goyal,“基于波动和方程的速率控制(WEBRC)构造块”,RFC 3738,2004年4月。

[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

[RFC3810]Vida,R.和L.Costa,“IPv6多播侦听器发现版本2(MLDv2)”,RFC 3810,2004年6月。

[RFC3819] Karn, P., Bormann, C., Fairhurst, G., Grossman, D., Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L. Wood, "Advice for Internet Subnetwork Designers", BCP 89, RFC 3819, July 2004.

[RFC3819]Karn,P.,Bormann,C.,Fairhurst,G.,Grossman,D.,路德维希,R.,Mahdavi,J.,黑山,G.,Touch,J.,和L.Wood,“互联网子网络设计师的建议”,BCP 89,RFC 3819,2004年7月。

[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

[RFC3971]Arkko,J.,Kempf,J.,Zill,B.,和P.Nikander,“安全邻居发现(SEND)”,RFC 39712005年3月。

[RFC4259] Weis, B., "The Use of RSA/SHA-1 Signatures within Encapsulating Security Payload (ESP) and Authentication Header (AH)", RFC 4359, January 2006.

[RFC4259]Weis,B.“在封装安全有效载荷(ESP)和身份验证头(AH)中使用RSA/SHA-1签名”,RFC 4359,2006年1月。

[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006.

[RFC4346]Dierks,T.和E.Rescorla,“传输层安全(TLS)协议版本1.1”,RFC 4346,2006年4月。

[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery Proxies (ND Proxy)", RFC 4389, April 2006.

[RFC4389]Thaler,D.,Talwar,M.,和C.Patel,“邻居发现代理(ND代理)”,RFC 4389,2006年4月。

[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006.

[RFC4601]Fenner,B.,Handley,M.,Holbrook,H.,和I.Kouvelas,“协议独立多播-稀疏模式(PIM-SM):协议规范(修订版)”,RFC 46012006年8月。

[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet Group Management Protocol (IGMP) / Multicast Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")", RFC 4605, August 2006.

[RFC4605]Fenner,B.,He,H.,Haberman,B.,和H.Sandick,“基于Internet组管理协议(IGMP)/多播侦听器发现(MLD)的多播转发(“IGMP/MLD代理”)”,RFC 4605,2006年8月。

[RFC4779] Asadullah, S., Ahmed, A., Popoviciu, C., Savola, P., and J. Palet, "ISP IPv6 Deployment Scenarios in Broadband Access Networks", RFC 4779, January 2007.

[RFC4779]Asadullah,S.,Ahmed,A.,Popoviciu,C.,Savola,P.,和J.Palet,“宽带接入网络中的ISP IPv6部署场景”,RFC 4779,2007年1月。

[RFC4840] Aboba, B., Davies, E., and D. Thaler, "Multiple Encapsulation Methods Considered Harmful", RFC 4840, April 2007.

[RFC4840]Aboba,B.,Davies,E.,和D.Thaler,“认为有害的多种封装方法”,RFC 4840,2007年4月。

[SCTE-1] "IP Multicast for Digital MPEG Networks", SCTE DVS 311r6, March 2002.

[SCTE-1]“数字MPEG网络的IP多播”,SCTE DVS 311r6,2002年3月。

[SP-ND] Daley, G., "Securing Proxy Neighbour Discovery Problem Statement", Work in Progress, February 2005.


Authors' Addresses


Godred Fairhurst Department of Engineering University of Aberdeen Aberdeen, AB24 3UE UK



Marie-Jose Montpetit Motorola Connected Home Solutions Advanced Technology 55 Hayden Avenue, 3rd Floor Lexington, Massachusetts 02421 USA



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