Allocating Bandwidth - Lenovo Flex System Fabric CN4093 Application Manual

Allocating Bandwidth

Allocated Bandwidth for PGID 0 Through 7
Unlimited Bandwidth for PGID 15
© Copyright Lenovo 2015
The administrator may allocate a portion of the switch's available bandwidth to
PGIDs 0 through 7. Available bandwidth is defined as the amount of link
bandwidth that remains after priorities within PGID 15 are serviced (see
"Unlimited Bandwidth for PGID 15" on page
are fully subscribed. If any PGID does not fully consume its allocated bandwidth,
the unused portion is made available to the other priority groups.
Priority group bandwidth allocation can be configured using the following
command:
CN4093(config)# cee global ets priority­group pgid <priority group number>
bandwidth <bandwidth allocation> pgid <priority group number> bandwidth
<bandwidth allocation>
where bandwidth allocation represents the percentage of link bandwidth, specified
as a number between 0 and 100, in 1% increments.
The following bandwidth allocation rules apply:
Bandwidth allocation must be 0% for any PGID that has no assigned 802.1p pri‐

ority values.
 Any PGID assigned one or more priority values must have a bandwidth allocation
greater than 0%.
 Total bandwidth allocation for groups 0 through 7 must equal exactly 100%.
Increasing or reducing the bandwidth allocation of any PGID also requires
adjusting the allocation of other PGIDs to compensate.
If these conditions are not met, the switch will report an error when applying the
configuration.
To achieve a balanced bandwidth allocation among the various priority groups,
packets are scheduled according to a weighted deficit round‐robin (WDRR)
algorithm. WDRR is aware of packet sizes, which can vary significantly in a CEE
environment, making WDRR more suitable than a regular weighted round‐robin
(WRR) method, which selects groups based only on packet counts.
Note: Actual bandwidth used by any specific PGID may vary from configured
values by up to 10% of the available bandwidth in accordance with 802.1Qaz ETS
standard. For example, a setting of 10% may be served anywhere from 0% to 20%
of the available bandwidth at any given time.
PGID 15 is permitted unlimited bandwidth and is generally intended for critical
traffic (such as switch management). Traffic in this group is given highest priority
and is served before the traffic in any other priority group.
If PGID 15 has low traffic levels, most of the switch's bandwidth will be available to
serve priority groups 0 through 7. However, if PGID 15 consumes a larger part of
the switch's total bandwidth, the amount available to the other groups is reduced.
Note: Consider traffic load when assigning priority values to PGID 15. Heavy traffic
in this group may restrict the bandwidth available to other groups.
281), and assuming that all PGIDs
Chapter 18: FCoE and CEE
281