Chapter 10Chapter 10 QoS Configuration GuideQoS and L2/L3/L4 flow OverviewThe SSR allows network managers to identify traffic and set Quality of Service (QoS)policies without compromising wire speed performance. The SSR can guaranteebandwidth on an application by application basis, thus accommodating high-prioritytraffic even during peak periods of usage. QoS policies can be broad enough toencompass all the applications in the network, or relate specifically to a single host-to-host application flow.Within the SSR, QoS policies are used to classify Layer-2, Layer-3, and Layer-4 trafficinto the following priorities:• Control• High• Medium• LowBy assigning priorities to network traffic, you can ensure that critical traffic will reachits destination even if the exit ports for the traffic are experiencing greater-than-maximum utilization.Layer-2, 3, 4 Flow SpecificationFor Layer-2 traffic, you can define a flow based on the MAC packet headers.• The MAC fields are source MAC address, destination MAC address and VLAN IDs.A list of incoming ports can also be specifiedFor Layer-3 (IP and IPX) traffic, you can define “flows”, blueprints or templates of IPand IPX packet headers.• The IP fields are source IP address, destination IP address, UDP/TCP source port,UDP/TCP destination port, TOS (Type of Service), transport protocol (TCP orUDP), and a list of incoming interfaces• The IPX fields are source network, source node, destination network, destinationnode, source port, destination port, and a list of incoming interfacesThe flows specify the contents of these fields. If you do not enter a value for a field, awildcard value (all values acceptable) is assumed for the field.
