3Com S7902E, Руководство по настройке

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node RRPP ring group and an assistant-edge node RRPP ring group configured, only one subring
sends and receives Edge-Hello packets, thus reducing CPU workload.
As shown in Figure 1-5 , Device B is the edge node of Ring 2 and Ring 3, and Device C is the
assistant-edge node of Ring 2 and Ring 3. Device B and Device C need to send or receive Edge-Hello
packets frequently. If more subrings are configured or load balancing is configured for more multiple
domains, Device B and Device C will send or receive a mass of Edge-Hello packets.
To reduce Edge-Hello traffic, you can assign Ring 2 and Ring 3 to an RRPP ring group configured on the
edge node Device B, and assign Ring 2 and Ring 3 to an RRPP ring group configured on Device C.
After such configurations, if all rings are activated, only Ring 2 on Device B sends Edge-Hello packets.
Fast detection mechanism
Ideally, an RRPP ring can fast converge because the transit nodes on it can detect link failures fast and
send out notifications immediately. In practice, however, some devices on an RRPP ring may not
support RRPP and thus RRPP can detect link failures between these devices only through the timeout
mechanism. This results in long-time traffic interruption and failure to implement millisecond-level
convergence.
To address this problem, a fast detection mechanism was introduced. The mechanism works as follows:
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The master node sends Fast-Hello packets out its primary port at the interval specified by the
Fast-Hello timer. If the secondary port receives the Fast-Hello packets sent by the local master
node before the Fast-Fail timer expires, the entire ring is in Health state; otherwise, the ring transits
into Disconnect state.
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The edge node sends Fast-Edge-Hello packets out its common ports at the interval specified by
the timer resolution. If the assistant-edge node fails to receive the Fast-Edge-Hello packets within
three times the timer resolution, the SRPTs transit to Disconnect state.
As shown in Figure 1-2 , with fast detection enabled for RRPP domain 1, Device A, the master node of
Ring 1, sends out Fast-Hello packets periodically and determines the ring status according to whether
Fast-Hello packets are received before the Fast-Fail timer expires, thus implementing link status fast
detection.
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The timer resolution refers to the shortest-period timer provided on an RRPP node.
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To implement fast detection on an RRPP ring, enable fast detection on the master node, edge
node, and assistant-edge node of the RRPP ring.
Typical RRPP Networking
Here are several typical networking applications.
Single ring
As shown in Figure 1-2 , there is only a single ring in the network topology. In this case, you only need to
define an RRPP domain.