Precedence For Layer-3 Flows; Ssr Queuing Policies; Configure Layer-2 Qos - Cabletron Systems SmartSwitch 8-slot User's Reference Manual

Chapter 10: QoS Configuration Guide

Precedence for Layer-3 Flows

A precedence from 1 - 7 is associated with each field in a flow. The SSR uses the
precedence value associated with the fields to break ties if packets match more than
one flow. The highest precedence is 1 and the lowest is 7. Here is the default
precedence of the fields:
• IP - destination port (1), destination address (2), source port (3), source IP address
(4), TOS (5), interface (6), protocol (7)
• IPX - destination network (1), source network (2), destination node (3), source node
(4), destination port (5), source port (6), interface (7)
Use the
default precedence.

SSR Queuing Policies

You can use one of two queuing policies on the SSR:
• strict priority – assures the higher priorities of throughput but at the expense of
lower priorities. For example, during heavy loads, low-priority traffic can be
dropped to preserve throughput of control-priority traffic, and so on.
• weighted fair queuing – distributes priority throughput among the four priorities
(control, high, medium, and low) based on percentages.
The SSR can use only one queuing policy at a time. The policy is used on the entire
SSR. The default queuing policy is strict priority.

Configure Layer-2 QoS

QoS policies applied to layer-2 flows allow you to assign priorities based on source
and destination MAC addresses. A QoS policy set for a layer-2 flow allows you to
classify the priority of traffic from:
• A specific source MAC address to a specific destination MAC address (use only
when the port is in flow bridging mode)
• Any source MAC address to a specific destination MAC address
Before applying a QoS policy to a layer-2 flow, you must first determine whether a port
is in address-bridging mode or flow-bridging mode. If a port operates in address-
bridging mode (default) then you can specify the priority based on the destination
MAC address and a VLAN ID. You can also specify a list of ports to apply the policy.
10 - 2
qos precedence ip
and
qos precedence ipx
SSR User Reference Manual
commands to change the