5 SSM - Core Network

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■视频名称：

    《5 SSM - Core Network》

■所属专辑：

    《Developing Interdomain Multicast Networks》（跨域组播）

■视频时长：

    6分47秒

■内容简介：

    部署了PIM-SM的组播网，可以支持PIM-SSM。PIM-SSM也可以独立部署，不必与PIM-SM共存，所以SSM不依赖MSDP、Auto-RP或BSR。但是，SSM可能需要部署组播BGP，以满足某些特殊需求。

    如果组播网已经部署了PIM-SM，那么只有最后一跳路由器才需要升级支持SSM，没有直连接受者的路由器不必升级。通常没有直连接受者的路由器需要特殊的访问控制，以抑制MSDP信令、Source Registration过程或其他PIM-SM的行为。

    命令ip pim ssm可以全局开启SSM功能，对组播网有以下影响：对于工作在SSM状态的组播地址，路由器会接收相应IGMPv3 INCLUDE模式成员通告、IGMPv3 Lite或URD，这些功能配置在接口模式下。SSM范围外的IGMPv3 Lite或URD被忽略。

    在PIM-SSM模式下，路由器只产生（S，G）join和prune。接收到与RPT相关的消息或执行RPT相关的操作，都被忽略。接收到Source Registration时马上回复Register-stop消息。部署SSM的时候，只有最后一跳路由器必须支持SSM，其他路由器可以运行PIM-SM或PIM-SSM。

■Abstract：

    An established network in which IP multicast service is based on PIM-SM can support SSM services. You can also deploy SSM alone in a network without the full range of protocols that are required for interdomain PIM-SM (for example, MSDP, Auto-RP, or bootstrap router [BSR]) if only SSM service is needed. However, multiprotocol BGP might be required to maintain IP multicast connectivity if multiple autonomous systems are deployed in a network.

    If SSM is deployed in a network already configured for PIM-SM, only the last hop routers must be upgraded to supports SSM. In general, non-last hop routers must run only PIM-SM in the SSM range and might need additional access control configuration to suppress MSDP signalling, registering, or PIM-SM shared tree operations from occurring within the SSM range.

    You enable the SSM operation mode by configuring the SSM range through the ip pim ssm global configuration command. This configuration has the following effects: For groups within the SSM range, (S, G) channel subscriptions are accepted through IGMPv3 INCLUDE mode membership reports, IGMP v3lite, or URD. Each of these methods must be configured on a per-interface basis. IGMP v3lite and URD (S, G) channel subscriptions are ignored for groups outside the SSM range.

    In PIM-SSM mode, only PIM (S, G) join and prune messages are generated by the router, and no (S, G) rendezvous point tree (RPT) or (*, G) RPT messages are generated. Incoming messages related to RPT operations are ignored or rejected, and incoming PIM register messages are immediately answered with register-stop messages. PIM-SSM is backward-compatible with PIM-SM, unless the router is a last hop router. Routers that are not last hop routers can run PIM-SM for SSM groups (for example, if they do not yet support SSM).