Patton electronic 2800 Configuring quality of service QoS, Applying scheduling at the bottleneck

OnSite 2800 Series User Manual 8 • Link scheduler configuration

NAPT

Profile

Context		IP
	use command	router
Interfaces	ACL
	Profile
	bind command

Circuit
Ports	Ethernet

Service

Policy

Profile

use command

bind command

PVC

Serial

Figure 17. IP context and related elements

Configuring quality of service (QoS)

In the OnSite 2800, the link scheduler enables the definition of QoS profiles for network traffic on a certain interface, as shown in figure 17. QoS refers to the ability of a network to provide improved service to selected network traffic over various underlying technologies including Frame Relay, Ethernet and 802.x type net- works, and IP-routed networks. In particular, QoS features provide improved and more predictable network service by providing the following services:

•Supporting dedicated bandwidth

•Improving loss characteristics

•Avoiding and managing network congestion

•Shaping network traffic

•Setting traffic priorities across the network

Applying scheduling at the bottleneck

When an OnSite acts as an access router, the access link is the point where intelligent use of scarce resources really makes a difference. Frequently, the access link modem is outside of the OnSite and the queueing would happen in the modem, which does not distinguish between packet types. To improve QoS, you can configure the OnSite to send no more data to the Internet than the modem can carry. This keeps the modem’s queue empty and gives the OnSite control over which packet is sent over the access link at what time.

Using traffic classes

The 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 OnSite has a tag attached to it on which the classification can be noted. The access control list “stage” (ACL) can be used to apply such a traffic-class name to some type of packet based on its IP-header filtering capabilities. The traffic-class tags exist only inside the OnSite router, but layer 2 priority bits (802.1pq class-of-service) and IP header type-of-service bits (TOS field)

Configuring quality of service (QoS) 95