Dei Egress Remarking - Alcatel-Lucent 7950 Quality Of Service Manual

DEI Egress Remarking

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 (emission 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 (emission priorities) that could be
indicated using the 3 802.1p 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 in/out profile information.
The following commands can be used to remark the DE values at a SAP egress:
CLI Syntax: sap-egress <policy-id> create
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 de-mark-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.
Note that the egress remarking occurs after any egress classification.
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fc <fc-name> create
exit
exit
de-mark-outer used for outer tag markings
de-mark-inner used for inner tag markings
existing de-mark used for marking both tags
markings taken from packet received at ingress
de-mark [force <de-value>]
de-mark-inner [force <de-value>]
de-mark-outer [force <de-value>]
7950 XRS Quality of Service Guide