Network Working Group G. Armitage
Request for Comments: 2269 Lucent Technologies
Category: Informational January 1998
Network Working Group G. Armitage
Request for Comments: 2269 Lucent Technologies
Category: Informational January 1998
Using the MARS Model in non-ATM NBMA Networks
在非ATM NBMA网络中使用MARS模型
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 (1998). All Rights Reserved.
版权所有（C）互联网协会（1998年）。版权所有。
Abstract
摘要
Initially developed for IP over ATM, the RFC 2022 (MARS) model is also applicable to other NBMA networks that provide the equivalent of switched, point to multipoint connections. This short document is intended to state the obvious equivalences, and explain the less obvious implications. No changes to the MARS model per se are suggested or required. RFC 2022 is not required over NBMA networks that offer Ethernet-like group addressing functionality.
RFC 2022（MARS）模型最初是为ATM上的IP而开发的，它也适用于提供交换式点对多点连接的其他NBMA网络。本简短文件旨在说明明显的等效性，并解释不太明显的含义。不建议或不需要对火星模型本身进行任何更改。在提供类似以太网的组寻址功能的NBMA网络上不需要RFC 2022。
Most network layer models, like the one described in STD 5, RFC 1112 [1] for IP multicasting, assume sources may send their packets to an abstract 'multicast group addresses'. Link layer support for such an abstraction is assumed to exist, and is provided by technologies such as Ethernet.
大多数网络层模型，如STD 5、RFC 1112[1]中描述的IP多播模型，都假设源可以将其数据包发送到抽象的“多播组地址”。假定存在对这种抽象的链路层支持，并由以太网等技术提供。
Some NBMA networks (e.g. ATM using UNI3.0 or UNI3.1 signaling [4,5]) do not support a multicast (or group) address abstraction. In these environments multicasting is typically supported through point to multipoint calls (or emulated with multiple point to point calls). The MARS model (RFC 2022) [2] was originally developed by the IP over ATM working group, and so uses ATM-centric descriptive language. For completeness this memo explains how RFC 2022 can be applied to other NBMA technologies.
一些NBMA网络（例如，使用UNI3.0或UNI3.1信令的ATM[4,5]）不支持多播（或组）地址抽象。在这些环境中，通常通过点对多点调用（或通过多个点对点调用模拟）支持多播。MARS模型（RFC 2022）[2]最初由IP over ATM工作组开发，因此使用以ATM为中心的描述语言。为完整起见，本备忘录解释了RFC 2022如何应用于其他NBMA技术。
2. RFC 2022's basic assumptions.
2. RFC 2022的基本假设。
Section 3 of [2] describes the basic assumptions that the MARS model makes about the services available from the link layer network (using ATM as the specific case). In summary these are:
[2]的第3节描述了MARS模型对链路层网络可用服务的基本假设（使用ATM作为具体情况）。总之，这些是：
The ATM model broadly describes an 'AAL User' as any entity that establishes and manages VCs and underlying AAL services to exchange data. An IP over ATM interface is a form of 'AAL User'
ATM模型广泛地将“AAL用户”描述为建立和管理VCs和底层AAL服务以交换数据的任何实体。ATM上的IP接口是“AAL用户”的一种形式
The most fundamental limitations of UNI 3.0/3.1's multicast support are:
UNI 3.0/3.1的多播支持的最基本限制是：
Only point to multipoint, unidirectional VCs may be established.
只能建立点对多点、单向VCs。
Only the root (source) node of a given VC may add or remove leaf nodes.
只有给定VC的根（源）节点可以添加或删除叶节点。
Leaf nodes are identified by their unicast ATM addresses.
叶节点由其单播ATM地址标识。
Given this point to multipoint call service, the MARS document goes on to describe two architectures for emulating multipoint to multipoint IP multicasting - the VC Mesh, and the Multicast Server. In either case it was assumed that IP/ATM interfaces (whether in routers or hosts) are allowed to originate and manage outgoing point to multipoint calls without network operator intervention or manual provisioning.
鉴于此点对多点呼叫服务，MARS文档继续描述两种用于模拟多点对多点IP多播的体系结构—VC Mesh和多播服务器。在这两种情况下，都假定IP/ATM接口（无论是在路由器还是主机中）允许发起和管理传出点对多点呼叫，而无需网络运营商干预或手动配置。
The MARS document also specifies that AAL5 be used for all SVCs, implying a requirement that the underlying link service supports the atomic exchange of PDUs.
MARS文件还规定AAL5可用于所有SVC，这意味着要求底层链路服务支持PDU的原子交换。
3. Generalising the MARS model.
3. 推广火星模型。
Any NBMA service that offers an equivalent to (or superset of) the ATM point to multipoint call service can use the MARS model directly. It must be possible to transmit atomic data units bi-directionally with point to point calls, and unidirectionally (from root to leaves) on point to multipoint calls.
任何提供与ATM点对多点呼叫服务等价（或超集）的NBMA服务都可以直接使用MARS模型。必须能够通过点对点调用双向传输原子数据单元，并通过点对多点调用单向（从根到叶）传输原子数据单元。
A MARS is an entity known by its NBMA address.
火星是由其NBMA地址所知的实体。
A MARS Client is an entity known by its NBMA address.
MARS客户端是一个通过其NBMA地址知道的实体。
An MCS (where needed) is an entity known by its NBMA address.
MCS（如果需要）是一个通过其NBMA地址知道的实体。
The MARS control messages defined in sections 4 onwards of the MARS document are shown carrying ATM addresses. Using different mar$afn (Address Family) values in the fixed header of MARS control messages allows MARS entities to indicate they are carrying other types of NBMA addresses (as done in NHRP [3]). As for NHRP, the interpretation of the 'sub-address' fields shall be in the context of the address family selected (which means it will often simply be null).
MARS文件第4节及以后定义的MARS控制消息显示带有ATM地址。在MARS控制消息的固定报头中使用不同的mar$afn（地址系列）值允许MARS实体指示它们携带其他类型的NBMA地址（如NHRP[3]中所做的）。对于NHRP，“子地址”字段的解释应在所选地址系列的上下文中进行（这意味着它通常为空）。
In all cases where {IP, ATM.1, ATM.2, ...} mappings are referred to, they may be interpreted as {IP, NBMA.1, NBMA.2, ...} in the context of whatever NBMA network you are deploying MARS.
在所有引用{IP，ATM.1，ATM.2，…}映射的情况下，在您正在部署的任何NBMA网络的上下文中，它们可能被解释为{IP，NBMA.1，NBMA.2，…}。
The MARS Cluster is defined in [2] as:
火星星团在[2]中定义为：
The set of ATM interfaces chosing to participate in direct ATM connections to achieve multicasting of AAL_SDUs between themselves.
选择参与直接ATM连接的一组ATM接口，以在它们之间实现AAL_SDU的多播。
It is trivial to observe that the cluster definition is independent of the underlying link layer technology. A revised definition becomes:
观察到集群定义独立于底层链路层技术是很容易的。修订后的定义为：
The set of NBMA interfaces chosing to participate in direct NBMA connections to achieve multicasting of packets between themselves.
选择参与直接NBMA连接的一组NBMA接口，以在它们之间实现数据包的多播。
The term 'Cluster Member' continues to refer to an endpoint that is currently using a specific MARS for multicast support. The potential scope of a cluster may be the entire membership of a LIS, while the actual scope of a cluster depends on which LIS members are actually registered with the cluster's MARS at any given time.
术语“集群成员”继续指当前正在使用特定MARS进行多播支持的端点。集群的潜在范围可能是LIS的全部成员，而集群的实际范围取决于在任何给定时间哪些LIS成员实际注册到集群的MARS。
Section 3.4 of [2] provided a set of mneumonics for the signalling functions available to AAL Users. These mneumonics are then used in the remainder of [2] to indicate link layer events to which MARS entities might react. Recast from the perspective of an NBMA based MARS entity, the descriptions would now read:
[2]第3.4节为AAL用户可用的信令功能提供了一套助记符。然后在[2]的其余部分中使用这些助记符来指示MARS实体可能对其作出反应的链路层事件。从基于NBMA的火星实体的角度重铸，描述内容如下：
The following generic signalling functions are presumed to be available to local MARS entities:
假定本地MARS实体可使用以下通用信令功能：
L_CALL_RQ Establish a pt-pt call to a specific endpoint. L_MULTI_RQ Establish pt-mpt call to a specific endpoint. L_MULTI_ADD Add new leaf node to previously established pt-mpt call. L_MULTI_DROP Remove specific leaf node from established pt-mpt call. L_RELEASE Release pt-pt call, or all Leaves of a pt-mpt call.
L_CALL_RQ建立对特定端点的pt调用。L_MULTI_RQ建立对特定端点的pt mpt调用。L_MULTI_将新叶节点添加到先前建立的pt mpt调用。L_MULTI_DROP从已建立的pt mpt调用中删除特定叶节点。L_释放pt呼叫，或pt mpt呼叫的所有叶子。
The signalling exchanges and local information passed between MARS entity and NBMA signalling entity with these functions are outside the scope of this document.
具有这些功能的MARS实体和NBMA信令实体之间传递的信令交换和本地信息不在本文件范围内。
The following indications are assumed to be available to MARS entities, generated by by the local NBMA signalling entity:
假设本地NBMA信令实体生成的MARS实体可使用以下指示：
L_ACK Succesful completion of a local request. L_REMOTE_CALL A new call has been established to the MARS entity. ERR_L_RQFAILED A remote NBMA endpoint rejected an L_CALL_RQ, L_MULTI_RQ, or L_MULTI_ADD. ERR_L_DROP A remote NBMA endpoint dropped off an existing call. ERR_L_RELEASE An existing call was terminated.
确认成功完成本地请求。远程呼叫一个新的呼叫已经建立到火星实体。ERR_L_RQ失败远程NBMA端点拒绝了L_调用、L_多_RQ或L_多_添加。ERR_L_DROP远程NBMA端点从现有呼叫中断开。ERR_L_RELEASE现有呼叫已终止。
The signalling exchanges and local information passed between MARS entity and NBMA signalling entity with these functions are outside the scope of this document.
具有这些功能的MARS实体和NBMA信令实体之间传递的信令交换和本地信息不在本文件范围内。
4. Open Issues.
4. 未决问题。
The trade offs between VC Mesh and Multicast Server modes may look quite different for each NBMA technology. This will be especially true in the area of VC (or equivalent) resource consumption in the NICs of hosts, routers, and endpoints supporting MARSs or MCSs. The use of VC mesh mode is most vulnerable to NBMA technologies that are signalling intensive or resource challenged.
对于每种NBMA技术，VC Mesh和多播服务器模式之间的权衡可能会大不相同。在主机、路由器和支持MARS或MCSs的端点的NIC中的VC（或同等）资源消耗方面尤其如此。VC网状模式的使用最容易受到信号密集型或资源挑战型NBMA技术的影响。
Sizing of Clusters (and hence LISes) will also be affected by a given NBMA network's ability to support lots of pt-mpt calls. Additionally, you cannot have more members in a cluster than you can have leaf nodes on a pt-mpt call, without hacking the MARS model [6].
集群（以及LISE）的大小也将受到给定NBMA网络支持大量pt mpt呼叫的能力的影响。此外，集群中的成员数不能超过pt-mpt调用中的叶节点数，而无需黑客攻击MARS模型[6]。
On going developments in server synchronisation protocols for distributed RFC 2022 implementations are expected to be applicable to non-ATM NBMA networks.
用于分布式RFC 2022实现的服务器同步协议的持续发展预计将适用于非ATM NBMA网络。
Quality of service considerations are outside the scope of this document. They will be very specific to each NBMA technology's capabilities. Related work is being pursued outside the ION Working Group.
服务质量注意事项不在本文件范围内。它们将非常特定于每种NBMA技术的能力。相关工作正在离子工作组之外进行。
If the NBMA network offers some sort of native multipoint to multipoint service then use of the MARS model may not be optimal. Such situations require further analysis.
如果NBMA网络提供某种本地多点对多点服务，那么使用MARS模型可能不是最佳选择。这种情况需要进一步分析。
Security Considerations
安全考虑
This memo is informational, and specifies no protocol for deployment. No specific non-ATM NBMA network technologies or security characteristics are discussed. Should enhancements to security be required, they shall be added as an extension to the base architecture in RFC 2022, or described in documents explicitly proposing use of RFC 2022 over specific NBMA technologies.
此备忘录仅供参考，未指定部署协议。未讨论特定的非ATM NBMA网络技术或安全特性。如果需要增强安全性，则应将其作为RFC 2022中基础架构的扩展添加，或在明确建议在特定NBMA技术上使用RFC 2022的文件中进行描述。
Acknowledgments
致谢
This memo was substantially developed while the author was with Bell Communications Research (Bellcore).
本备忘录是作者在贝尔通信研究公司（Bellcore）任职期间编写的。
Author's Address
作者地址
Grenville Armitage Bell Laboratories, Lucent Technologies. 101 Crawfords Corner Rd, Holmdel, NJ, 07733 USA
朗讯科技公司格伦维尔·阿米蒂奇·贝尔实验室。美国新泽西州霍姆德尔克劳福德角路101号，邮编：07733
EMail: gja@lucent.com
EMail: gja@lucent.com
References
工具书类
[1] Deering, S., "Host Extensions for IP Multicasting", STD 5, RFC 1112, Stanford University, August 1989.
[1] Deering，S.，“IP多播的主机扩展”，STD 5，RFC 1112，斯坦福大学，1989年8月。
[2] Armitage, G., "Support for Multicast over UNI 3.0/3.1 based ATM Networks.", RFC 2022, November 1996.
[2] Armitage，G.“支持基于UNI 3.0/3.1的ATM网络上的多播”，RFC 2022，1996年11月。
[3] Luciani, J., et. al., "NBMA Next Hop Resolution Protocol (NHRP)", Work in Progress.
[3] Luciani，J.等人，“NBMA下一跳解析协议（NHRP）”，正在进行中。
[4] ATM Forum, "ATM User-Network Interface Specification Version 3.0", Englewood Cliffs, NJ: Prentice Hall, September 1993.
[4] ATM论坛，“ATM用户网络接口规范3.0版”，恩格尔伍德悬崖，新泽西州：普伦蒂斯大厅，1993年9月。
[5] ATM Forum, "ATM User Network Interface (UNI) Specification Version 3.1", ISBN 0-13-393828-X, Prentice Hall, Englewood Cliffs, NJ, June 1995.
[5] ATM论坛，“ATM用户网络接口（UNI）规范3.1版”，ISBN 0-13-393828-X，新泽西州恩格尔伍德悬崖普伦蒂斯大厅，1995年6月。
[6] Armitage, G., "Issues affecting MARS Cluster Size", RFC 2121, March 1997.
[6] Armitage，G.“影响火星团大小的问题”，RFC 21211997年3月。
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完整版权声明
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版权所有（C）互联网协会（1998年）。版权所有。
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