Cabletron Systems SMARTSWITCH ROUTER 9032578-05 - Manual (Page 317)

SmartSwitch Router User Reference Manual 291
Chapter 21
QoS Configuration
Guide
QoS & Layer-2/Layer-3/Layer-4 Flow Overview
The SSR allows network managers to identify traffic and set Quality of Service (QoS)
policies without compromising wire speed performance. The SSR can guarantee
bandwidth on an application by application basis, thus accommodating high-priority
traffic even during peak periods of usage. QoS policies can be broad enough to encompass
all the applications in the network, or relate specifically to a single host-to-host application
flow.
The SSR provides four different features to satisfy QoS requirements:
• Traffic prioritization allows network administrators to identify and segregate mission-
critical network traffic into different priority queues from non-critical network traffic.
Once a packet has been identified, it can be assigned into any one of four priority
queues in order to ensure delivery. Priority can be allocated based on any combination
of Layer-2, Layer-3, or Layer-4 traffic.
• Weighted Random Early Detection (WRED) alleviates traffic congestion by randomly
dropping packets before the queue becomes completely flooded. WRED should only
be applied to TCP traffic.
• Type of Service (ToS) rewrite provides network administrators access to the ToS octet in
an IP packet. The ToS octet is designed to provide feedback to the upper layer
application. The administrator can “mark” packets using the ToS rewrite feature so
that the application (a routing protocol, for example) can handle the packet based on a
predefined mechanism.
• Traffic rate limiting provides network administrators with tools to manage bandwidth
resources. The administrator can create an upper limit for a traffic profile, which is
based on Layer-3 or Layer-4 information. Traffic that exceeds the upper limit of the
profile can either be dropped or re prioritized into another priority queue.