CoS Marking for Self-generated Traffic

The 7705 SAR is the source of some types of traffic; for example, a link state PDU for sending IS-IS topology updates or an SNMP trap sent to indicate that an event has happened. This type of traffic that is created by the 7705 SAR is considered to be self-generated traffic (SGT). Another example of self-generated traffic is Telnet, but in that application, user commands initiate the sending of the Telnet traffic.

Network operators often have different QoS models throughout their networks and apply different QoS schemes to portions of the networks in order to better accommodate delay, jitter, and loss requirements of different applications. The class of service (DSCP or dot1p) bits of self-generated traffic can be marked on a per-application basis to match the network operator’s QoS scheme. This marking option enhances the ability of the 7705 SAR to match the various requirements of these applications.

The 7705 SAR supports marking self-generated traffic for the base routers and for virtual routers. Refer to ‟QoS Policies” in the 7705 SAR Services Guide for information on SGT QoS as applied to virtual routers (for VPRN services).

The DSCP and dot1p values of the self-generated traffic, where applicable, are marked in accordance with the values that are configured under the sgt-qos command. In the egress direction, self-generated traffic is forwarded using the egress control queue to ensure premium treatment, unless SGT redirection is configured (see SGT Redirection). PTP (IEEE 1588v2) and SAA-enabled ICMP traffic is forwarded using the CoS queue. The next-hop router uses the DSCP values to classify the traffic accordingly.

Table: Applications and Support for Configurable DSCP or dot1p Markings lists various applications and indicates whether they have configurable DSCP or dot1p markings.