Patton electronic ONSITE 2800 - Manual (Page 95)

Configuring quality of service (QoS) 95
OnSite 2800 Series User Manual 8 • Link scheduler configuration
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)
Ser
ial
PVC
IP
router
bind command
Service
Policy
Profile
Ethe
rn
et
use command
bind command
use command
NAPT
Profile
ACL
Profile
Context
Interfaces
Circuit
Ports