Appendix VInterconnected rings example
V.1 Configuration for interconnected rings
主子环的2种组合，需要注意的是3环，即2个主环中间用一个子环连接
The Sub-Ring is composed of at least one Sub-Ring link and one R-APS Virtual Channel in order toallocate the RPL on a Sub-Ring ---不知道什么意思 V.2 Topology examples for interconnected Ethernet rings a-g多种互联拓扑模型，写cases有用(P69) a. Location of the RPL for a sub-ring
b. Intermediate Ethernet ring node(s) between interconnection nodes c. Multiple sub-rings connected to a major ring d. Sub-ring(s) interconnection
e. A sub-ring connected to multiple Ethernet rings f. A sub-ring attached to multiple major rings
g. A sub-ring connected to a network that supports any technology network
Appendix VIProtection switching for multiple ERP instances
VI.1 Multiple ERP instances
同一个物理环可以创建多个ERP实例，每个实例相互独立，并各自维护一个映射到traffic channel的VLAN的子集
目的：提高链路利用率，RPL链路可以被利用起来；
注意：各实例的VLAN子集互斥，neighbor配合保证链路带宽利用率
VI.2 Applying protection mechanisms to multiple ERP instances 如1.1各实例单独配，RPL一般要配在不同的link上
VI.2.1 Addressing of multiple ERP instances
01-19-A7-00-00-01，其中01是ring-id, 同一个物理环中，ring-id一样，不同实例用不同的R-APS vlan区分
R-APS messages of different ERP instances are differentiated by the use of different R-APS VIDs.
VI.2.2 Protection switching – Signal failure
各实例独立响应SF
VI.2.3 Protection switching – Revertive and non-revertive
各实例re,non-re可能不一致，独立处理
VI.2.4 Protection switching – Manual switch and forced switch
各实例独立处理
VI.3 Protection switching model for multiple ERP instances
所谓Protection switching model for multiple ERP instances是指，各ERP实例独立运行，但故障通告是共享的
The MEP adaptation function is de-multiplexed VI.4 Multiple instances of interconnected rings
互联环多实例vlan定义 1.vlan限制在一个环
2.vlan跨环，多环多实例 图中G2是主环
Appendix VIIGuidelines for the configuration of VIDs and Ring-IDs of R-APS channels
VII.1 Sub-ring with R-APS virtual channel
VII.1.1 Example 1: R-APS channel with different VIDs, and R-APS channel of sub-ringand R-APS virtual channel having different VIDs
主子环，不同实例各用不同的VID区分，虚通道也另用一和子环不同的VID。 缺点：需要的VID多
优点：子环的VID可重用，主环，或不共互联节点的子环【with virtual channel, 互联节点存在vlan转换，共存则产生歧义,例如sub1, 2-21, sub2 2-31, vid 2不可在同一互联节点共用】
注意：VID重用应只考虑已作为RAPS VLAN的VID，如果某VID已在某环中做RAPS-VLAN 还考虑作为Traffic channel则往往带来SPAN的问题，意义不大。
注意2：子环with virtual channel，主子环之间是有消息交互的，子环收到的RAPS消息会通过RAPS-2-FF转给主环，内容包含在ETH_C里，例如2->21, 再由主环转发。P75，参考图Figure 9-8
VII.1.2 Example 2: R-APS channel with different VIDs, and R-APS channel of sub-ringand R-APS virtual channel having the same VID
虚通道和子环RAPS channel共用一个VID 优点：管理简单
缺点：VID不能被其它环重用，总消耗的VID和example 1是一样的
VII.2 Example 3: Sub-ring without R-APS virtual channel model; each R-APS channel withdifferent VIDs
w/o虚通道的场景，主子环各实例vid，ring id独立配置，互不相干 模型参考figure 9-10, 子环erp不会借助主环erpforward raps消息 问题1：ring id有什么用 问题2：为何vid不能重用？
However, the same number of VIDs as in Example 2 is used, and cannot be reassigned. P77
VII.3 Example 4: Co-existence on an Ethernet ring of Ethernet ring nodes which support this Recommendation (v2) and the previous version (v1) of this Recommendation
v1,v2对接 v2做互联节点，ring-id必须设为1，只支持单实例，子环要用with virtual channel方式
On the other hand, when a subring without R-APS virtual channel is used, the behaviour of the blocked ring port is different between ITU-T G.8032v1 and ITU-T G.8032v2 as specified in clause 10.1.14. Therefore, when Ethernet ring nodes running ITU-T G.8032v1 and ITU-T G.8032v2 co-exist on an Ethernet ring, the sub-ring should be deployed with the R-APS virtual channel. P77
--如果子环不用neighbor port功能,则所有子环节点可以正确地响应任何protection switchingevent, 所以不存在上述限制。
Appendix VIIIFlush optimization
VIII.1 Flushing FDB consideration
发生倒换就得FLUSH,但某些情况下逻辑拓扑未变化，则不必flush，flush有潜在风暴的可能，这就是为什么考虑避免不必要的flush。
VIII.2 Scenarios of unnecessary FDB flushing a) Do not flush when RPL fails or recovers.
b) Do not flush when the RPL owner node or the RPL neighbour node fails or recovers. c) Do not flush when the currently blocked ring port fails or recovers in non-revertive mode. d) Do not flush when a request that results in blocking an already blocked ring link is issued (e.g., MS on RPL owner node).
VIII.3 Example of FDB flush optimization 引入了2个新概念
1. RPL next-neighbour node连接owner或neighbor的node
2. RPL next-neighbourportsRPL next-neighbour node和owner或neighbor的端口 Rule 1: If detecting RPL link failure in [idle state], transmit R-APS (SF, DNF).
Rule 2: When detecting a failure from an RPL next-neighbour port, in idle state, transmit R-APS (SF) message only on the RPL next-neighbour port and do not transmit R-APS messages on the other ring port.
Rule 3: If the RPL recovers, transmit R_APS (NR, RB, DNF) message from the RPL owner node
Rule 4: If the RPL owner node detects ring recovery in the R-APS (SF, DNF) condition, transmit R_APS (NR, RB, DNF) after the WTR timer expires.
VIII.4 Additional definition for ERP control process model and state machine 上述规则1,3基本ERP逻辑已实现，2,4需要修改ERP状态机 1. 加DNF的状态，供查询 2. 加next-neighbour port VIII.5 DNF status
Appendix IXGuidelines for management procedures
IX.1 An example procedure for removing an Ethernet ring node 在待移除节点的邻接节点用FS或MS
IX.2 Management procedures to exit the FS state in case of failure of an Ethernet ring node under an FS condition
描述了一种如果直接在待移除节点执行FS，移除节点，导致的异常情况，和恢复办法，邻接节点执行FS,clear
IX.3 Replacing a v1 Ethernet ring node with a v2 Ethernet ring node Owner要先升级，否则有如下问题
unidirectional failure on the non-RPL ring link attachedto the RPL owner node
Appendix XMinimizing segmentation in interconnected rings
X.1 Characterization of the segmentation issue
Dualfailures in one of the rings
不可避免，但可规避 X.1.1 Problem statement
X.1.2 Relationship to interconnection models
上述segmentation无论有否virtual channel都会存在
X.2 Class of double faults addressed
X.2.1 Detection of interconnection segmentation 用up mep
X.3 Procedure for minimization of segmentation
X.3.1 Management configuration
为了实现避免网络隔离的目标，需要额外的管理配置信息于子环ERP进程的互联节点上
– ETH_C_MI_RAPS_Interconnection_Node ? Values: \ ? Default value: \
标示是否是互联节点,pri或sec都可以，如果配为互联节点，则需要配a tandem connection，即2个互联节点之间的up mep.
– ETH_C_MI_RAPS_Multiple_Failure
? Values: \. ? Default value: \
X.3.2 Block indication logic procedure
从过程看不是很清楚
故障时比较上面设定的两个值是否一致，即ETH_C_MI_RAPS_Interconnection_Node和 ETH_C_MI_RAPS_Multiple_Failure，如果相同则执行一个MS,锁sub-ring port. 这里有2个疑问：
1. 两个参数到底代表什么含义，该怎么设，为什么他们一致就认为双断
a) 推测就是给两个节点指定一个角色，pri或sec,其实是随意指定的，某个端口侦测
到双断时，SSF消息和设定的端口角色消息进行比对，一致，则认为双断了
2. 如果双断两个端口那个端口执行MS
a) 协议中未明确说明，700中可能是先发NS比较，node id小的端口阻断？
Appendix XIEnd-to-end service resilience
XI.1 Generic end-to-end service resilience
端到端保护，可以在access link上用8031,中间用8032
XI.2 Layering ITU-T G.8031 protection over ITU-T G.8032
假定端到端保护用的是8031
XI.2.1 Basic guidelines for the layering of ITU-T G.8031 over ITU-T G.8032 Rule：
Working/protection每个路径Node2个，一进一出 ERP部分视为一条Link，具体路径由ERP决定 8031的hold off要设置足够大
Working/protection使用的vid要被ERP保护
XI.3 End-to-end service that traverses interconnected rings
规则类似单环
V2 neighbor, block RPL at both end It totally isolates RPL from the traffic channel