根据需要，在项目符号z重新刻字后立即插入以下文字和项目符号: 本标准规定了协议、程序和受管对象，允许网络运营商为管理选择的VLAN标识符禁用未知目标地址转发、源地址学习和生成树协议，从而支持在提供商主干桥接网络内显式选择流量工程路径的供应系统，同时允许其他网络控制协议动态确定其他服务的活动拓扑。这些可互操作的功能是 通过使用SMIv2 MIB的SNMP管理单个网桥，通过扩展本标准中规定的其他控制协议，通过使用指定流量工程连接的地址和VLAN标识符的CFM，以及通过1: 1路保护开关，能够分担负载。为此，它: a） 通过负责设置以太网交换路径（ESP）的外部代理，通过在分布式生成树协议和供应控制之间拆分B-VID空间，实现主动拓扑的构建。 b） 支持在配置控制下丢弃具有未知目标地址的b-vid帧。 c） 支持在配置的流量工程路径上运行连续性检查、环回和链接跟踪协议。 d） 支持1:1保护切换，能够为流量工程服务实例分担负载。 e） 通过SMIv2 MIB模块提供SNMP管理所需的扩展。 本标准未规定通过多提供商主干网桥流量工程（PBB）的以太网交换路径（ESP）的操作- （e）区域。指定用于PBB-TE区域的所有主干边缘网桥都是IB-BEB。

Insert the following text and bullets immediately after bullet z re-lettering as needed: This standard specifies protocols, procedures, and managed objects to allow support of provisioning systems that explicitly select traffic engineered paths within Provider Backbone Bridged Networks by allowing a network operator to disable unknown destination address forwarding, source address learning and spanning tree protocols for administratively selected VLAN Identifiers, while allowing other network control protocols to dynamically determine active topologies for other services. These interoperable capabilities are supported by management of individual bridges by SNMP using an SMIv2 MIB, by extensions to the other control protocols specified in this standard, by the use of CFM with the addresses and VLAN Identifiers that specify traffic engineered connections, and by 1:1 path protection switching capable of load sharing. To this end, it: a) Enables construction of active topologies by an external agent that is responsible for setting up Ethernet Switched Paths (ESPs) by splitting the B-VID space between distributed spanning tree protocols and provisioned control. b) Supports discard of frames with unknown destination addresses for B-VIDs under provisioned control. c) Supports the operation of Continuity Check, Loopback, and Linktrace protocols on provisioned traffic engineered paths. d) Supports 1:1 protection switching capable of load sharing for Traffic Engineered service instances. e) Provides required extension to SNMP management by SMIv2 MIB modules. This standard does not specify operation of Ethernet Switched Paths (ESPs) through multiple Provider Backbone Bridge Traffic Engineered (PBB-TE) Regions. All the Backbone Edge Bridges specified for use in a PBB-TE Region are IB-BEBs.