Configuring quality of service (QoS) 97IPLink 2800 Series Getting Started Guide 8 • Link scheduler configurationFigure 17. IP context and related elementsConfiguring quality of service (QoS)In the IPLink 2800, the link scheduler enables the definition of QoS profiles for network traffic on a certaininterface, as shown in figure 17. QoS refers to the ability of a network to provide improved service to selectednetwork traffic over various underlying technologies including Frame Relay, Ethernet and 802.x type networks,and IP-routed networks. In particular, QoS features provide improved and more predictable network service byproviding the following services:• Supporting dedicated bandwidth• Improving loss characteristics• Avoiding and managing network congestion• Shaping network traffic• Setting traffic priorities across the networkApplying scheduling at the bottleneckWhen an IPLink acts as an access router, the access link is the point where intelligent use of scarce resourcesreally makes a difference. Frequently, the access link modem is outside of the IPLink and the queueing wouldhappen in the modem, which does not distinguish between packet types. To improve QoS, you can configurethe IPLink to send no more data to the Internet than the modem can carry. This keeps the modem’s queueempty and gives the IPLink control over which packet is sent over the access link at what time.Using traffic classesThe link scheduler needs to distinguish between different types of packets. We refer to those types as “traffic-classes”. You can think of the traffic-class as if every packet in the IPLink has a tag attached to it on which theclassification can be noted. The access control list “stage” (ACL) can be used to apply such a traffic-class nameto some type of packet based on its IP-header filtering capabilities. The traffic-class tags exist only inside theIPLink router, but layer 2 priority bits (802.1pq class-of-service) and IP header type-of-service bits (TOS field)SerialPVCIProuterbind commandServicePolicyProfileEthernetuse commandbind commanduse commandNAPTProfileACLProfileContextInterfacesCircuitPorts
