IBM 8260 manual Address-to-Port Mapping for Module Switching Modules

Monitor is attached. Once the Recovery ASIC is inserted into that ring, the DRA will be placed downstream of the last port of the module on the beaconing ring. Also, the URA will be inserted into the backup path if ports 17 and 18 are configured as trunk ports.

Similar to the beacon recovery on the module switching module, the DRA will start transmitting Beacon type 1 MAC frames when it sees a Beacon MAC frame. But the difference is that the Recovery ASIC will use the ring monitors to establish the fault domain.

There is a ring monitor associated with each port and each of them is polled by the Recovery ASIC to find the last one to see the beacon type 1 MAC frame that was sent by DRA. The fault domain is the port downstream from the ring monitor.

Once the fault domain is established, the faulty port will be wrapped.

8.10 Address-to-Port Mapping for Module Switching Modules

To discuss the address-to-port mapping on the module switching module, we will use Figure 97 on page 159 as an example.

Note that the same Recovery ASIC that is used for beacon recovery is used to provide the address-to-port mapping facility on the 8260.

As mentioned in 8.1.2.1, ªActive Monitorº on page 130, every seven seconds the active monitor starts a neighbor notification process. All the stations attached to the ring will take part in the neighbor notification, enabling each station to learn its NAUN.

Note

Although the URA and DRA have a MAC address, they do not participate in the neighbor notification process. In other words, they do not issue AMP or SMP MAC frames and do not copy them either.

One of the functions of the Recovery ASIC is to monitor for AMP and SMP MAC frames and use this process to build its address-to-port map.

To build the address-to-port map, URA/DRA listen to the AMP and SMP MAC frames looking for the address-recognized and frame-copied bits on these frames. On each module, URA will be the first to see these frames enter the module and DRA will be the last to see these frames leave the module.

URA ignores all the AMP/SMP MAC frames which have the A and C bits set to B′1′, because these are the frames which have been recognized and copied by the stations which are located upstream of URA such as stations attached to other token-ring modules on this 8260. In our example, the URA in ″TR Module 2″ will ignore the AMP/SMP MAC frames issued by station ″ A″, ″ B″ and ″C″, as they will have A/C bits set to B′1′ by the time they have been seen by URA in

″TR Module 2″. But, as soon as the URA sees an AMP/SMP MAC frame with the A/C bits set to B′0′, it realizes that this frame has been issued by its NAUN. In this example, it would be the AMP/SMP MAC frame issued by station ″D″.

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