H3C Technologies H3C S10500 Series Switches - Manual (Page 64)

55
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 (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
18 , 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, and
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 to achieve load balancing in the 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, reducing CPU workload.
As shown in
Figure
17 , 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 must send or receive Edge-Hello
packets frequently. If more subrings are configured or if load balancing is configured for 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, some devices on an RRPP ring may not support RRPP. 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:
• 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 the Health state; otherwise, the ring transits into
the Disconnect state.
• 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
14 , 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, implementing link status fast detection.
NOTE:
•
The timer resolution refers to the shortest-period timer provided on an RRPP node.
• 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.