User guide

156 CHAPTER 8: PRIORITIZING NETWORK TRAFFIC
As these standards each define a single field in which to store the
marking, it means that simple classification devices can still be used as
part of a network-wide traffic prioritization solution provided that the
following conditions are met:
■ Simple classification devices must be able to classify on the user
priority field, the DiffServ field or both.
■ Complex classification devices must be able to mark packets
appropriately based upon their traffic type. This must be done using a
marking mechanism that the simple classification devices are able to
classify. Whilst it is possible to use different marking schemes at
different locations in the network 3Com recommends that, if possible,
one is selected and used throughout the network.
■ Packets sent across the network must first pass through a complex
classification device (such as a 3Com SuperStack 3 Switch 4400) so
that they can be marked appropriately. This enables simple
classification devices to prioritize packets.
For traffic prioritization to work on an end-to-end basis in your network it
is recommended that you structure your network as shown in Figure 72
.
Figure 72 Network Topology
Boundary Nodes
Interior Nodes
Device Capable of
Complex Classification
Device Capable of
Complex Classification
Device Capable of
Complex Classification
W
A
N
L
i
n
k
Device Capable of
Complex Classification
3Com Network Administrator for HP OpenView.book Page 156 Wednesday, November 12, 2003 2:33 PM