Enterasys Networks X-PeditionTM manual Configuring Quality of Service

12

Configuring Quality of Service

Overview

In a typical network, there are often many users and applications competing for limited system and network resources. While resource sharing on a first-come, first-serve basis may suffice when your network load is light, access can freeze quickly when the network gets congested. Under these conditions, a bandwidth-hungry application (large file transfer files, emails) may devour most of the network bandwidth, depriving applications that send small-sized packets (voice, telnet and other interactive applications) of their fair share of bandwidth, and result in long delays causing applications to fail.

Quality of Service (QoS) cannot magically provide all applications their requested bandwidth, but it can help you identify your mission-critical, high priority application traffic and give it preferential treatment (higher priority, higher bandwidth or guaranteed bandwidth) relative to the rest of your network traffic. In this way, critical applications will work under both normal and congested conditions while less important and time-sensitive traffic will continue to flow, perhaps at a lower rate than expected.

Consider the following aspects of the XSR’s QoS implementation:

•QoS can be configured on LAN and/or WAN interfaces/sub-interfaces.

•QoS is implemented as a service which can be applied on any interface at will (intuitive configuration).

•Packet classification is based on source/destination address, source/destination port, IP precedence or DSCP value and is specified using ACLs, the IP precedence or DHCP fields.

•Class-Based queuing is provided for prioritization and bandwidth sharing.

•Up to four priority queues and 60 shared queues can be configured per policy-map.

•Link efficiency mechanisms with interleaving for real-time traffic: Multi Class MLPPP for PPP and FRF.12 for Frame Relay.

•Traffic policing using Single-color, Three-rate token bucket.

•Three buffer management strategies: tail drop, Weighted and Random Early Detection (WRED/ RED).

•Traffic shaping per class and per policy map on the output traffic.

•Marking the DSCP or IP precedence field of the packet.

•Marking the 802.1P info in VLAN header.

•Service policy can be applied on the input and/or output traffic.

•Automatic internal prioritization of the control packets locally generated by the XSR.

XSR User’s Guide 12-1