Overview
726 Quality of Service Guide
port named pools are created, the XMA or MDA weight should be set to ‘0’. Setting the
default weight to ‘0’ should be done with care as any queues without named pool definitions
or queues with non-existent pool names use the default pools. The weights are summed and
then each individual weight is divided by the sum. The result is multiplied by the buffer space
managed by port to determine the amount of buffer space given to each category.
The portion of buffering set aside for default pools is applied to the default network and
access pools based solely on the amount of bandwidth in network and access modes on the
physical port. Combining the default pool buffering chunks from all ports result in the
aggregate size of the default pools. For Ethernet ports, all the bandwidth is either network or
access (there is never both). For channelized ports, the amount given to network and access
default pools is based on the ratio between access and network bandwidth and not based on
weights defined within the pools. The default pool configuration is not changed when named
pool mode is enabled.
The portion of buffering managed by the port relative to the ports XMA or MDA weight
parameter is separated into two sub-portions based on the ratio between network and access
bandwidth on port. If the port is all network or access bandwidth, that opposite sub-portion
will be empty. The sub-portion associated with network bandwidth on the port and the sub-
portion associated with access bandwidth on the port are individually summed with the
network and access XMA or MDA named pool bandwidth set aside by the other ports on the
XMA or MDA. The outcome is a total amount of access and a total amount of network
bandwidth that will be given to XMA or MDA named pools based on each pools network and
access weights.
The portion of buffering assigned to port named pools based on the port weight is also
separated into two sub-portions in the same manner as step 4 above. The network and access
bandwidth defines the ratio of bandwidth population between the network and access sub-
portions. If the port is all network or access bandwidth, that opposite sub-portion will be
empty. Each sub-portion is divided between the port named pools based on each pools
network and access defined weights.
On the ingress side, network queues may only be associated with the default ingress network
pool or one of the XMA or MDA named pools. Because ingress network queues may not use
ingress port based pools, the port’s network sub-portion is added to the ports XMA or MDA
named pool network sub-portion to be distributed to the named XMA or MDA pools based
on each pools network weight.
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