Provisioning the rate control mode
The desired rate control mode can be chosen by enabling/disabling oversubscription
support (QoS_osub = enabled/disabled), and by setting the CIR and PIR values.CIR
and PIR values can be set by means of QoS profiles (see “Quality of Service
provisioning” (p. 8-94)).
The setting of the QoS_osub configuration parameter in combination with the
relationship between CIR and PIR determines which rate control mode becomes
effective. If, for example, oversubscription support is enabled, and the relationship
between CIR and PIR is CIR = PIR ≤ MAX, then the rate controller is operated in
strict policing mode.
Important!
1. Which of the rate control modes can actually be configured depends on the
mode of operation (see “Quality of Service configuration options” (p. 8-82)).
2. As a general rule it is recommended to use the oversubscription mode for
TCP/IP applications, especially in case of meshed or ring network topologies
where multiple end-users share the available bandwidth.
Dropper / Marker
Based on the indication of the rate controller, and the rate control mode for the flow,
the dropper/marker will do the following:
No rate control Oversubscription mode Strict policing mode
Incoming rate < CIR mark “green” mark “green” mark “green”
Incoming rate > CIR mark “green” mark “yellow” drop
In the dropper function a decision is made whether to drop or forward a packet. On a
TransLAN
®
card a deterministic dropping from tail when the queue is full is
implemented. Packets that are marked red are always dropped. If WAN Ethernet link
congestion occurs, frames are dropped. Yellow packets are always dropped before any
of the green packets are dropped. This is the only dependency on queue occupation
and packet color that is currently present in the dropper function. No provisioning is
needed.
Information
rate
0 kbit/s PIR
yellow red
0 = CIR < PIR < MAX
(CIR)
Traffic provisioning
Classification, queueing, and scheduling
....................................................................................................................................................................................................................................
8-88
Alcatel-Lucent - Proprietary
See notice on first page
365-312-807R7.2
Issue 4, May 2007
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