H3C Technologies H3C S7500E Series Switches - Manual (Page 78)

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nodes of Ring 2 and Ring 3 will open their respective secondary ports, and thus a loop among
Device B, Device C, Device E, and Device F is generated. As a result, broadcast storm occurs.
In this case, to prevent generating this loop, the edge node will block the edge port temporarily.
The blocked edge port is activated only when the edge node is sure that no loop will be brought
forth when the edge port is activated.
Load balancing
In a ring network, maybe traffic of multiple VLANs is transmitted at the same time. RRPP can
implement load balancing for the traffic by transmitting traffic of different VLANs along different
paths.
By configuring an individual RRPP domain for transmitting the traffic of the specified VLANs
(referred to as protected VLANs) in a ring network, traffic of different VLANs can be transmitted
according to different topologies in the ring network. In this way, load balancing is achieved.
As shown in Figure 7-6 , Ring 1 is configured as the primary ring of Domain 1 and Domain 2,
which are configured with different protected VLANs. Device A is the master node of Ring 1 in
Domain 1; Device B is the master node of Ring 1 in Domain 2. With such configurations, traffic
of different VLANs can be transmitted on different links, and thus, load balancing is achieved in
a single-ring network.
RRPP ring group
In an edge node RRPP ring group, only an activated subring with the lowest domain ID and ring
ID can send Edge-Hello packets. In an assistant-edge node RRPP ring group, any activated
subring that has received Edge-Hello packets will forward these packets to the other activated
subrings. With an edge node RRPP ring group and an assistant-edge node RRPP ring group
configured, only one subring sends Edge-Hello packets on the edge node, and only one subring
receives Edge-Hello packets on the assistant-edge node, thus reducing CPU workload.
As shown in Figure 7-5 , 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:
z 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