Dei Egress Remarking - Alcatel-Lucent 7450 Quality Of Service Manual

Service Egress QoS Policy
The precedence of the above commands is summarized as, from highest to lowest
precedence:
The configuration of qinq-mark-top-only under the SAP egress takes precedence over the use
of the dot1p-inner in the policy, i.e. the inner VLAN tag is not remarked when qinq-mark-
top-only is configured (the marking used for the inner VLAN tag is based on the current
default which is governed by the marking of the packet received at the ingress to the system).
If qinq-mark-top-only is omitted, both the inner and outer VLAN tags are remarked.
Remarking the inner dot1p is not supported based on the profile result of egress policing.
The egress remarking occurs after any egress classification.

DEI Egress Remarking

It is often desirable to meter traffic from different users to ensure fairness or to meet
bandwidth guarantees. Dropping all traffic in excess of a committed rate is likely to result in
severe under-utilization of the networks, since most traffic sources are bursty in nature. It is
burdensome to meter traffic at all points in the network where bandwidth contention occurs.
One solution is to mark those frames in excess of the committed rate as drop eligible on
admission to the network.
Previously, the discard eligibility was marked / determined using existing QoS fields: for
example, the three MPLS EXP and Ethernet dot1p bits. Using certain combination(s) of these
bits to indicate both forwarding class (priority) and discard eligibility meant decreasing the
number of Forwarding Classes that can be differentiated in the network.
IEEE 802.1ad-2005 and IEEE 802.1ah standards allow drop eligibility to be conveyed
separately from priority, preserving all the eight forwarding classes (priorities) that could be
indicated using the three 802.1p bits. Now all the previously introduced traffic types will be
marked as drop eligible. Customers can continue to use the dot1p markings with the
enhancement of changing the dot1p value used, in access, based on the profile information.
The following commands can be used to remark the DE values at a SAP egress:
CLI Syntax:
200
exit
exit
• dot1p-outer used for outer tag markings
• dot1p-inner used for inner tag markings
• existing dot1p used for marking both tags
• markings taken from packet received at ingress
sap-egress <policy-id> create
Quality of Service Guide