Riverstone Networks WICT1-12 - Manual (Page 564)

26-2 Riverstone Networks RS Switch Router User Guide Release 8.0
Layer-2, Layer-3 and Layer-4 Flow Specification QoS Configuration
Separate buffer space is allocated to each of these four priority queues. By default, buffered traffic in higher priority
queues is forwarded ahead of pending traffic in lower priority queues. This is the strict priority queuing policy. During
heavy loads, low-priority traffic can be dropped to preserve the throughput of the higher-priority traffic. This ensures
that critical traffic will reach its destination even if the exit ports for the traffic are experiencing greater-than-maximum
utilization. To prevent low-priority traffic from waiting indefinitely as higher-priority traffic is sent, you can apply the
Weighted Fair Queuing (WFQ) queuing policy to set a minimum bandwidth for each class. You can also apply WRED
to keep the congestion of TCP traffic under control.
26.1 LAYER-2, LAYER-3 AND LAYER-4 FLOW
SPECIFICATION
In the RS, traffic classification is accomplished by mapping Layer-2, -3, or -4 traffic to one of the four priorities. Each
traffic classification is treated as an individual traffic flow in the RS.
For Layer-2 traffic, you can define a flow based on MAC packet header fields, including source MAC address,
destination MAC address, and VLAN IDs. A list of incoming ports can also be specified.
For Layer-3 (IP and IPX) traffic, you can define flows, blueprints or templates of IP and IPX packet headers:
Ip Fields – The source IP address, destination IP address, UDP/TCP source port, UDP/TCP destination port, TOS
(Type of Service), transport protocol (TCP or UDP), and a list of incoming interfaces.
Ipx Fields – The source network, source node, destination network, destination node, source port, destination port,
and a list of incoming interfaces.
For Layer-4 traffic, you can define a flow based on source/destination TCP/UDP port number in addition to the Layer-3
source/destination IP address.
The flows specify the contents of these fields. If you do not enter a value for a field, a wildcard value (all values
acceptable) is assumed for the field.
26.2 PRECEDENCE FOR LAYER-3 FLOWS
A precedence from 1 to 7 is associated with each field in a flow. The RS uses the precedence value associated with the
fields to break ties if packets match more than one flow. The highest precedence is 1 and the lowest is 7. Here is the
default precedence of the fields:
• IP
- Destination port – 1
- Destination IP address – 2
- Source port – 3
- Source IP address – 4
- ToS – 5
- Interface – 6
- Protocol – 7