Alcatel-Lucent 7750 SR OS, Руководство по настройке интерфейса

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Configuration Overview
Page 22 7750 SR OS Interface Configuration Guide
• If the service QoS policy for the SAP specifies IP or MAC filters for forwarding class
identification, then traffic will be treated as Best Effort. Full MAC or IP classification is
not possible on the MDA (but is possible on the IOM).
• The packet is classified into 16 classes. Typically, these are the eight forwarding classes
and each packet is assigned one priority per forwarding class. After classification, the
packet is offered to the MDA queuing model. This queuing model is limited to three
queues each having four thresholds. These thresholds define whether an incoming packet,
after classification, is accepted in the queue or not.
Table 2 displays typical mapping of
classes onto queues/threshold.
A counter is associated with each mapping. Note that the above is an example and is dependent on
the type of classification (such as dscp-exp, dot1p, etc.). When the threshold of a particular class is
reached, packets belonging to that class will not be accepted in the queue. The packets will be
dropped and the associated counter will be incremented.
The scheduling of the three queues is done in a strict priority, highest priority basis is associated
with queue 0. This means that scheduling is done at queue level, not on the class that resulted from
the classification. As soon as a packet has been accepted by the queue there is no way to
differentiate it from other packets in the same queue (for example, another classification result not
exceeding its threshold). All packets queued in the same queue will have the same priority from a
scheduling point of view.
Table 2: Typical Mapping Of Classes Onto Queues/Threshold
Counter {Queue Threshold Traffic Class }
0 {2 3 "fc-nc / in-profile"}
1 {2 2 "fc-nc / out-profile"}
2 {2 1 "fc-h1 / in-profile"}
3 {2 0 "fc-h1 / out-profile"}
4 {1 3 "fc-ef / in-profile"}
5 {1 2 "fc-ef / out-profile"}
6 {1 1 "fc-h2 / in-profile"}
7 {1 0 "fc-h2 / out-profile"}
8 {0 3 "fc-l1 / in-profile"}
9 {0 3 "fc-l1 / out-profile"}
10 {0 2 "fc-af / in-profile"}
11 {0 2 "fc-af / out-profile"}
12 {0 1 "fc-l2 / in-profile"}
13 {0 1 "fc-l2 / out-profile"}
14 {0 0 "fc-be / in-profile"}
15 {0 0 "fc-be / out-profile"}