Riverstone Networks WICT1-12 - Manual (Page 144)

8-10 Riverstone Networks RS Switch Router User Guide Release 8.0
Traffic Management ATM Configuration Guide
This feature is advantageous in the case where different priority traffic needs to travel between two end devices. The
end devices can essentially share one logical connection (through the VC group) while still prioritizing data up to four
different levels. If a connection becomes oversubscribed and packets start dropping, using a VC group ensures that the
data traffic passing between the two end devices are ranked by importance.
Creating a Virtual Channel Group
To configure a VC group, you should:
1. Create the VCs using the
atm create vcl
command.
2. Create the VC group using the
atm create vcgroup
command.
3. Add up to four separate virtual channels to the group using the atm add vcl command. You can also
set a priority level for each VC within the VC group, as well as designate one of the VCs to handle
broadcast-multicast traffic.
If you add less than four virtual channels to a VC group, the next lower priority virtual channel will handle the
traffic that lacks a particular VC for its priority. For example, you add two VCs (one low priority and one high
priority) to a VC group. If a medium priority packet comes in, then the next lower priority VC, the VC low, will
handle the packet.
Note You cannot add a virtual channel with forced-bridged enabled to a VC group.
Applying Service Profiles to VC Groups
Either the virtual channel or the VC group may have a service profile applied, but not both. You must first negate the
separate service profiles from each virtual channel before trying to apply a service profile to the whole VC group, and
vice versa.
It is recommended that you pay special attention when selecting the ATM service parameters for the VCs with different
IP priorities. For example, control priority needs to have some dedicated bandwidth allocated while the low priority
VC could have UBR defined with no dedicated bandwidth.
8.4.3 Traffic Management Configuration Example
The examples in this section show how you can manage traffic using QoS policies on the ATM multi-rate line card,
and using VC groups on the ATM OC-12 line card.
Suppose you are a network administrator in charge of managing a network with three Client workstations (Client1,
Client2, Client3) and a server. You are using two RS’s to connect and manage traffic between the server and the clients.
Your network requirements are as follows:
• Traffic from the Server heading to Client1 is assigned high priority in the event that the connection
becomes oversubscribed.
• Traffic from the Server heading to Client2 is assigned medium priority in the event that the
connection becomes oversubscribed.
• Traffic from the Server heading to Client3 is assigned low priority in the event that the connection
becomes oversubscribed.