Bandwidth calculation during failover, Figure 463 – Brocade Network Advisor SAN + IP User Manual v12.1.0 User Manual
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Brocade Network Advisor SAN + IP User Manual
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FCIP trunking
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FIGURE 463
Link loss and retransmission over peer lowest metric circuit
In
, circuit 1 is assigned a metric of 0, and circuit 2 is assigned a metric of 1. In this
case, circuit 2 is a standby that is not used unless there are no lowest metric circuits available. If all
lowest metric circuits fail, then the pending send traffic is retransmitted over any available circuits
with the higher metric,
FIGURE 464
Failover to a higher metric standby circuit
You can configure a tunnel with standby metric 1 circuits that operate when all circuits configured
with metric 0 fail. However, these configurations can lead to condition where the tunnel is active,
but operating in a degraded mode because all metric 1 circuits (and failed metric 0 circuits) will not
be transferring tunnel data until all metric 0 circuits fail. Only at the point when all metric 0 circuits
fail, do available metric 1 circuits over data transfer. Consider configuring
to avoid this problem.
Bandwidth calculation during failover
The bandwidth of higher-metric circuits is not calculated as available bandwidth on an FCIP tunnel
until all lowest metric circuits have failed. Following is an example.
Assume the following configurations for circuits 0 through 3:
•
Circuits 0 and 1 are created with a metric of 0. Circuit 0 is created with a maximum
transmission rate of 1 Gbps, and circuit 1 is created with a maximum transmission rate of 500
Mbps. Together, circuits 0 and 1 provide an available bandwidth of 1.5 Gbps.
•
Circuits 2 and 3 are created with a metric of 1. Both are created with a maximum transmission
rate of 1 Gbps, for a total of 2 Gbps. This bandwidth is held in reserve.
The following actions occur during circuit failures:
•
If either circuit 0 or circuit 1 fails, traffic flows over the remaining circuit while the failed circuit
is being recovered. The available bandwidth is still considered to be 1.5 Gbps.
•
If both circuit 0 and circuit 1 fail, there is a failover to circuits 2 and 3, and the available
bandwidth is updated as 2 Gbps.