110 Quality of Service
CoS Mapping Table for Trusted Ports
Mapping is from the designated field values on trusted ports’ incoming packets to a traffic class priority
(actually a CoS traffic queue). The trusted port field-to-traffic class configuration entries form the
Mapping Table the switch uses to direct ingress packets from trusted ports to egress queues.
Egress Port Configuration—Traffic Shaping
For unit/slot/port interfaces, you can specify the shaping rate for the port, which is an upper limit of the
transmission bandwidth used, specified as a percentage of the maximum link speed.
Queue configuration
For each queue, you can specify:
• Minimum bandwidth guarantee
• Scheduler type – strict/weighted: Strict priority scheduling gives an absolute priority, with highest
priority queues always sent first, and lowest priority queues always sent last. Weighted scheduling
requires a specification of priority for each queue relative to the other queues, based on their minimum
bandwidth values.
• Queue management – tail drop
Queue Management Type
The switch supports the tail drop method of queue management. This means that any packet forwarded
to a full queue is dropped regardless of its importance.
CLI Examples
Figure 7-1 illustrates the network operation as it relates to CoS mapping and queue configuration.
Four packets arrive at the ingress port 1/g10 in the order A, B, C, and D. You’ve configured port 1/g10 to
trust the 802.1p field of the packet, which serves to direct packets A, B, and D to their respective queues
on the egress port. These three packets utilize port 1/g10’s 802.1p to COS Mapping Table. In this case,
the 802.1p user priority 3 was set up to send the packet to queue 5 instead of the default queue 3. Since
packet C does not contain a VLAN tag, the 802.1p user priority does not exist, so Port 1/g10 relies on its
default port priority (2) to direct packet C to egress queue 1.
To Next Page
Loading...
