【正文】 tter state machine to time out the expected transmission of LTRs. CCIwhile Timer counter for transmitting CCMs. CCIwhile has a granularity finer than or equal to 1/4 of the time represented by the CCMinterval variable. errorCCMwhile Timer counter for timing out invalid CCMs. errorCCMwhile has a granularity finer than or equal to 1 ms. xconCCMwhile Timer counter for timing out cross connect CCMs. xconCCMwhile has a granularity finer than or equal to 1 ms. Timer (2) LBIwhile A timer variable used by the MEP Loopback Initiator transmit state machine to time out the expected reception of LBRs. FNGwhile A timer variable used by the MEP Fault Notification Generator state machine to wait for defects to stabilize and disappear. rMEPwhile Timer counter for timing out CCMs. rMEPwhile has a granularity finer than or equal to 1/4 of the time represented by the CCMinterval variable. A Bridge shall not set rMEPCCMdefect within ( ?CCMtime(CCMinterval)) seconds of the receipt of a CCM, and shall set rMEPCCMdefect within ( ? CCMtime(CCMinterval)) seconds after the receipt of the last CCM. CFM and STP/EAPS In the MP architecture figure, all those CFM entities are located between port filtering entity and the LAN while STP/EAPS work on Filtering entity. So CFM will not be influenced by STP/EAPS configured on the same MP. Individual and shared MP address a) Individual MP address model The Individual MAC address assigned to an MP associated with a particular MA, and hence that MA’s MD Level and set of VIDs, is unique over all service instances associated with that same set of VIDs, such that those service instances’ CFM PDUs can be distinguished only by their MD Levels that can pass through that MP’s Bridge Port. b) Shared MP address model The same as the Individual MP address model, except that Up MPs (but not Down) in the same MA and in the same Bridge can share a (., can all have the same) MAC address. Down MPs in different Bridge Ports have different MAC addresses. If two Bridge Ports are connected to the same LAN, but have the same MAC address, then both would respond to an LBM sent to that MAC address. This is true, even though one of those two Bridge Ports would be Blocked (it would be either a Backup or an Alternate Port, see ), because Down MEPs are between the LAN and the Port filtering entities (, , ) that enforce the blocking. This placement allows Down MEPs to test their service instances even when their Port is blocked, so that the system administrator knows that the failover links will be ready to carry data when a work event causes the Port to bee Forwarding. A Bridge can use the Shared MP address model, or the Individual MP address model, on any given Bridge Port. This is an implementation decision。 no managed objects are provided to select one or the other model of operation. A Bridge using either of these two models can also make use of a third scheme for configuring MPs: c) Management Port MEPs Up MEPs (not Up MHFs, not Down MPs) are configured on a Management Port, a Bridge Port that does not connect to any LAN exterior to the Bridge. (See and Figure 87.) Typically, this would be the same MAC address, and the same Bridge Port, that used for the Bridge’s Management Port (see Figure 87). When CCM es into the bridge ports which are not enabled any MEP, the CCM will be forwarded other ports which also are not enabled MEP. APS APS Overview APS (Automatic Protection Switch) is a service protection technology, derived from the legacy technology SDH, even the detailed method is the same. It is always used together with some connection fault detection mechanism, like , . Once the fault is detected, APS module will be notified. It will switch the traffic from the broken path to another backup path immediately. Generally, less than 50ms fault detection amp。 protection switch time is required. amp。 ITU defines ether linear APS ITU defines ether ring APS (1) 1+1 protection Both Bidirectional and unidirectional Source: bridge, dual feed Sink: selector, initiate the switch 1:1 protection Only bidirectional Source bridge, single feed, initiate the switch Both Revertive and nonrevertive switch are configurable Generally, 1+1 will be nonrevertive while 1:1 will be revertive since most of time, working path will be more optimized. UP/Down MEP 一個(gè) vlan對(duì)應(yīng)多個(gè) MA 多個(gè) vlan對(duì)應(yīng)一個(gè) MA 什么時(shí)候 untagged LTM用 individual mac address? Configuration remendation in practice Firstly, create a MD with MD level and name Secondly, in the MD, create MA, with MA name and vlanId Thirdly, under port interface, create MEP, with down/up property and MA 從實(shí)際組網(wǎng)的角度看 CCM使用 multicast的好處 Compared with unicast CCM, using multicast CCM has the following benefits: Minimize bandwidth usage Can detect some cross connect fault() Don’t need to learn Rmep firstly