Network Working Group P. Christian
Request for Comments: 3147 Nortel Networks
Category: Informational July 2001
Network Working Group P. Christian
Request for Comments: 3147 Nortel Networks
Category: Informational July 2001
Generic Routing Encapsulation over CLNS Networks
CLNS网络上的通用路由封装
Status of this Memo
本备忘录的状况
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2001). All Rights Reserved.
版权所有（C）互联网协会（2001年）。版权所有。
Abstract
摘要
This document proposes a method for transporting an arbitrary protocol over a CLNS (Connectionless Network Service) network using GRE (Generic Routing Encapsulation). This may then be used as a method to tunnel IPv4 or IPv6 over CLNS.
本文档提出了一种使用GRE（通用路由封装）在CLNS（无连接网络服务）网络上传输任意协议的方法。然后，这可以用作通过CLN对IPv4或IPv6进行隧道传输的方法。
RFC 2784 Generic Routing Encapsulation (GRE) [1] provides a standard method for transporting one arbitrary network layer protocol over another arbitrary network layer protocol.
RFC 2784通用路由封装（GRE）[1]提供了在另一个任意网络层协议上传输一个任意网络层协议的标准方法。
RFC 1702 Generic Routing Encapsulation over IPv4 networks [2] provides a standard method for transporting an arbitrary network layer protocol over IPv4 using GRE.
RFC 1702 IPv4网络上的通用路由封装[2]提供了使用GRE通过IPv4传输任意网络层协议的标准方法。
However no standard method exists for transporting other network layer protocols over CLNS. This causes lack of interoperability between different vendors' products as they provide solutions to migrate from CLNS networks to IP networks. This is a problem specifically in, but not limited to, the context of management networks for SONET and SDH networks elements.
但是，不存在通过CLN传输其他网络层协议的标准方法。这导致不同供应商的产品之间缺乏互操作性，因为它们提供了从CLNS网络迁移到IP网络的解决方案。这是SONET和SDH网络元件管理网络环境中的一个具体问题，但不限于此。
Large networks exist for the purpose of providing management communications for SONET and SDH network elements. Standards Bellcore GR-253-CORE [3] and ITU-T G.784 [4] mandate that these networks are based on CLNS.
大型网络用于为SONET和SDH网元提供管理通信。标准Bellcore GR-253-CORE[3]和ITU-T G.784[4]要求这些网络基于CLN。
Many vendors have already started to offer SONET and SDH products that are managed by IP instead of CLNS and a general migration from CLNS towards IP is anticipated within the industry.
许多供应商已经开始提供由IP而不是CLN管理的SONET和SDH产品，预计业界将从CLN向IP进行全面迁移。
Part of any migration strategy from CLNS to IP should provide for the co-existence of both CLNS managed and IP managed network elements in the same network.
从CLN迁移到IP的任何迁移策略的一部分都应保证CLN管理的和IP管理的网元在同一网络中共存。
Such a migration strategy should foresee the need to manage existing CLNS managed network elements that become isolated by a new IP network. Such a scenario may be tackled by tunnelling CLNP PDUs over IP using the existing GRE standard RFC 2784 [1] and informational RFC 1702 [2]. Networks have already been deployed that use this method.
这种迁移策略应该预见到需要管理由新IP网络隔离的现有CLN管理的网络元素。通过使用现有GRE标准RFC 2784[1]和信息RFC 1702[2]在IP上隧道CLNP PDU，可以解决这种情况。已经部署了使用此方法的网络。
Such a migration strategy should also foresee the need to manage new IP managed network elements that are installed on the far side of existing CLNS managed network. Such a scenario requires a method for tunnelling IP over CLNS.
这种迁移策略还应预见到需要管理安装在现有CLNS管理网络远端的新IP管理网络元素。这种情况需要一种通过CLN对IP进行隧道传输的方法。
Using GRE to tunnel IP over CLNS offers some advantages.
使用GRE在CLN上隧道IP提供了一些优势。
In the absence of a standard for tunnelling IP over CLNS, GRE as specified in RFC 2784 [1] is the most applicable standard that exists.
在没有CLN上的IP隧道标准的情况下，RFC 2784[1]中规定的GRE是现有的最适用标准。
The move from CLNS to IP comes at a time when IP is itself migrating from IPv4 to IPv6. GRE defines a method to tunnel any protocol that has an Ethernet Protocol Type. Therefore by defining a method for CLNS to transport GRE, a method will then exist for CLNS to transport any other protocol that has an Ethernet Protocol Type defined in RFC 1700 [5]. Thus GRE over CLNS can be used to tunnel both IPv4 and IPv6.
从CLN到IP的迁移发生在IP本身正在从IPv4迁移到IPv6的时候。GRE定义了一种方法来隧道任何具有以太网协议类型的协议。因此，通过定义CLN传输GRE的方法，CLN将有一种方法来传输任何其他具有RFC 1700[5]中定义的以太网协议类型的协议。因此，CLN上的GRE可用于对IPv4和IPv6进行隧道传输。
GRE is already commonly used to tunnel CLNP PDUs over IP and so using GRE to tunnel IP over CLNS gives a common approach to tunnelling and may simplify software within network elements that initiate and terminate tunnels.
GRE已经常用于通过IP隧道CLNP PDU，因此使用GRE通过CLNS隧道IP提供了一种隧道的通用方法，并可简化网络元件中启动和终止隧道的软件。
The only disadvantage of using GRE is the extra minimum of four bytes that will be used between CLNP header and IP payload packet. Given the large size of CLNP headers this will not make a significant difference to the performance of any network that has IP over CLNP PDUs present on it.
使用GRE的唯一缺点是在CLNP报头和IP有效负载数据包之间使用额外的最少四个字节。考虑到CLNP报头的大容量，这不会对任何存在IP over CLNP PDU的网络的性能产生显著影响。
3. Transporting GRE packets over CLNS.
3. 通过CLN传输GRE数据包。
It is suggested that GRE should be transported over CLNS at the lowest layer possible, which is as a transport layer protocol over the network layer. This can be achieved by placing the entire GRE packet inside a CLNP Data Type PDU (DT PDU) as data payload.
建议GRE应尽可能在最低层通过CLN传输，这是网络层上的传输层协议。这可以通过将整个GRE数据包作为数据有效负载放置在CLNP数据类型PDU（DT PDU）中来实现。
The GRE packet is a GRE packet as defined in RFC 2784 [1], in other words GRE header plus payload packet.
GRE数据包是RFC 2784[1]中定义的GRE数据包，换句话说，GRE报头加上有效载荷数据包。
Data payload is the part of a Data PDU that is described as "Data" in the structure of a Data PDU in ISO/IEC 8473-1 [6].
数据有效载荷是数据PDU的一部分，在ISO/IEC 8473-1[6]的数据PDU结构中被描述为“数据”。
For convenience the structure of a Data PDU is reproduced from ISO/IEC 8473-1 [6] below:
为方便起见，数据PDU的结构根据ISO/IEC 8473-1[6]复制如下：
Octet
----------------------------------------
| Network Layer Protocol Identifier | 1
----------------------------------------
| Length Indicator | 2
----------------------------------------
| Version/Protocol Id Extension | 3
----------------------------------------
| Lifetime | 4
----------------------------------------
| SP | MS | E/R | Type | 5
----------------------------------------
| Segment Length | 6,7
----------------------------------------
| Checksum | 8,9
----------------------------------------
| Destination Address Length Indicator | 10
----------------------------------------
| | 11
| Destination Address |
| | m-1
----------------------------------------
| Source Address Length Indicator | m
----------------------------------------
| | m+1
| Source Address |
| | n-1
----------------------------------------
| Data Unit Identifier | n,n+1
----------------------------------------
| Segment Offset | n+2,n+3
----------------------------------------
| Total Length | n+4,n+5
----------------------------------------
| | n+6
| Options |
| | p
----------------------------------------
| | p+1
| Data ( GRE packet ) |
| | z
----------------------------------------
Octet
----------------------------------------
| Network Layer Protocol Identifier | 1
----------------------------------------
| Length Indicator | 2
----------------------------------------
| Version/Protocol Id Extension | 3
----------------------------------------
| Lifetime | 4
----------------------------------------
| SP | MS | E/R | Type | 5
----------------------------------------
| Segment Length | 6,7
----------------------------------------
| Checksum | 8,9
----------------------------------------
| Destination Address Length Indicator | 10
----------------------------------------
| | 11
| Destination Address |
| | m-1
----------------------------------------
| Source Address Length Indicator | m
----------------------------------------
| | m+1
| Source Address |
| | n-1
----------------------------------------
| Data Unit Identifier | n,n+1
----------------------------------------
| Segment Offset | n+2,n+3
----------------------------------------
| Total Length | n+4,n+5
----------------------------------------
| | n+6
| Options |
| | p
----------------------------------------
| | p+1
| Data ( GRE packet ) |
| | z
----------------------------------------
4. NSAP selector (N-SEL) value.
4. NSAP选择器（N-SEL）值。
Transport of GRE packets is a new type of Network Service (NS) user. Different Network Service users are identified by using different NSAP selector bytes also known as N-SEL bytes.
GRE数据包传输是一种新型的网络服务（NS）用户。通过使用不同的NSAP选择器字节（也称为N-SEL字节）来识别不同的网络服务用户。
This is a similar concept to the use of the IP Protocol Type used in IP packets.
这是一个类似于在IP数据包中使用IP协议类型的概念。
Whilst it is not strictly necessary for all vendors to use the same N-SEL values, they must use the same N-SEL value for it to be possible for one vendor's CLNS device or network element to initiate a GRE tunnel which is then terminated on a different vendor's CLNS device.
虽然并非严格要求所有供应商使用相同的N-SEL值，但他们必须使用相同的N-SEL值，以便一个供应商的CLNS设备或网络元件能够启动GRE隧道，然后在另一个供应商的CLNS设备上终止。
Although N-SEL values (other than zero) are not defined in CLNS/CLNP standards, some are defined when CLNS is used in SONET networks by Bellcore GR-253-CORE [3] whilst others are in common use.
尽管CLNS/CLNP标准中未定义N-SEL值（除零外），但当Bellcore GR-253-CORE[3]在SONET网络中使用CLNS时，定义了一些值，而其他值则常用。
As the IP protocol number for GRE is 47, as defined in RFC 1702 [2], and as 47 is not commonly used as an N-SEL value, it is suggested that 47 (decimal) should be used as an N-SEL value to indicate to the CLNS stack that the Data portion of the Data Type PDU contains a GRE packet.
由于GRE的IP协议号为47，如RFC 1702[2]中所定义，并且由于47通常不用作N-SEL值，因此建议将47（十进制）用作N-SEL值，以向CLNS堆栈指示数据类型PDU的数据部分包含GRE分组。
The N-SEL byte should be set to 47 (decimal) in both the source address and the destination address of the CLNP PDU.
CLNP PDU的源地址和目标地址中的N-SEL字节应设置为47（十进制）。
The N-SEL value of 47 should indicate only that the payload is GRE, and the device or network element that transmits the PDU should use the GRE header to indicate what protocol (for example IPv4 or IPv6) is encapsulated within the GRE packet in conformance with RFC 2784 [1]. Similarly the device or network element that receives the PDU should then inspect the GRE header to ascertain what protocol is contained within the GRE packet in conformance with RFC 2784 [1].
N-SEL值47应仅指示有效负载为GRE，并且传输PDU的设备或网元应使用GRE报头指示根据RFC 2784[1]在GRE数据包中封装的协议（例如IPv4或IPv6）。类似地，接收PDU的设备或网元随后应检查GRE报头，以确定GRE分组中包含的协议符合RFC 2784[1]。
5. Segmentation Permitted (SP) value.
5. 分段允许（SP）值。
It is recommended that the SP flag in all CLNP PDUs containing GRE packets should be set.
建议在所有包含GRE数据包的CLNP PDU中设置SP标志。
If the SP flag is not set, and a CLNP PDU is too large for a particular link, then a CLNS device or network element will drop the PDU. The originator of the packet that is inside the GRE packet will not have visibility of the packet loss or the reason for the packet loss, and a black hole may form.
如果未设置SP标志，并且CLNP PDU对于特定链路太大，则CLNS设备或网元将丢弃该PDU。GRE数据包内数据包的发起人将无法看到数据包丢失或数据包丢失的原因，并且可能会形成黑洞。
6. Interaction with Path MTU Discovery (PMTU), RFC 1191 [7].
6. 与路径MTU发现（PMTU）的交互，RFC 1191[7]。
A tunnel entry point for a GRE tunnel should treat IP packets that are bigger than the MTU size of the GRE tunnel as per RFC 1191 [7]. If the oversize IP packet that is about to enter the GRE tunnel does not have its Don't Fragment (DF) bit set then it should be fragmented before entering the tunnel.
GRE隧道的隧道入口点应根据RFC 1191[7]处理大于GRE隧道MTU大小的IP数据包。如果即将进入GRE隧道的超大IP数据包未设置其不分段（DF）位，则应在进入隧道之前对其进行分段。
If the oversize IP packet that is about to enter the GRE tunnel has its DF bit set then the packet should be discarded, and an ICMP unreachable error message (in particular the "fragmentation needed and DF set" code) should be sent back to the originator of the packet as described in RFC 1191 [7].
如果即将进入GRE隧道的超大IP数据包设置了DF位，则应丢弃该数据包，并应将ICMP无法访问的错误消息（尤其是“所需碎片和DF设置”代码）发送回数据包的发起人，如RFC 1191[7]所述。
CLNS and GRE do not provide any security when employed in the way recommended in this document.
CLNS和GRE在按照本文件建议的方式使用时不提供任何担保。
If security is required, then it must be provided by other methods and applied to the payload protocol before it is transported by GRE over CLNS.
如果需要安全性，则必须通过其他方法提供安全性，并在GRE通过CLN传输有效负载协议之前将其应用于有效负载协议。
[1] Farinacci, D., Li, T., Hanks, S., Meyer, D. and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000.
[1] Farinaci，D.，Li，T.，Hanks，S.，Meyer，D.和P.Traina，“通用路由封装（GRE）”，RFC 27842000年3月。
[2] Hanks, S., Li, T., Farinacci, D. and P. Traina, "Generic Routing Encapsulation over IPv4", RFC 1702, October 1994.
[2] Hanks，S.，Li，T.，Farinaci，D.和P.Traina，“IPv4上的通用路由封装”，RFC 1702，1994年10月。
[3] Bellcore Publication GR-253-Core "Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria", January 1999
[3] Bellcore出版物GR-253-Core“同步光网络（SONET）传输系统：通用通用标准”，1999年1月
[4] ITU-T Recommendation G.784 "Synchronous Digital Hierarchy (SDH) management", June 1999
[4] ITU-T建议G.784“同步数字体系（SDH）管理”，1999年6月
[5] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC 1700, October 1994.
[5] Reynolds，J.和J.Postel，“分配的数字”，标准2，RFC 1700，1994年10月。
[6] "Information technology - Protocol for providing the connectionless-mode network service", ISO/IEC 8473-1, 1994
[6] “信息技术.提供无连接模式网络服务的协议”，ISO/IEC 8473-11994
[7] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191, November 1990.
[7] Mogul，J.和S.Deering，“MTU发现路径”，RFC191990年11月。
Chris Murton, Paul Fee, Mike Tate for their contribution in writing this document.
Chris Murton、Paul Fee、Mike Tate感谢他们在撰写本文件中的贡献。
Philip Christian Nortel Networks Harlow Laboratories London Road, Harlow, Essex, CM17 9NA UK
菲利普克里斯蒂安北电网络哈洛实验室伦敦路，哈洛，埃塞克斯，CM17 9NA英国
EMail: christi@nortelnetworks.com
EMail: christi@nortelnetworks.com
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Acknowledgement
确认
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