From: Nauman Khan (mustafa@247emails.com)
Date: Mon Jan 26 2004 - 22:26:14 GMT-3
>--- "kasturi cisco" <kasturi_cisco@hotmail.com> wrote:
>Nauman or anyone,
>Can u please explain or elaborate on what u mean here:
>- Can use any physical interface queuing (FIFO, PQ, CQ or WFQ)
>- Only uses WFQ as the shaping queue (that is, on the input of the
>shaper)
Hi Kasturi,
-Traffic Policing typically "drops" excess traffic to stay within the
limit.....alternatively it can remark excess traffic.
-Traffic Shaping "delays" excess packets to stay within the rate
limit....using a "queuing mechanism"
Packet flow through GTS is implemented using three queues. The first, the "shaping queue", is WFQ-based and shapes traffic according to the specified/configured rate using a token bucket model. This queue dispatches packets to the "software queue", which may be configured with other queuing mechanisms (PQ, CQ, WFQ or FIFO).This software queue dispatches packets at line rate and if the software queue is empty, traffic is forwarded directly to the output hardware queue(which is always FIFO...and dispatches packets at line rate)
In GTS, WFQ is used as the shaping delay queue, providing fair scheduling within a traffic class. Other queuing strategies (FIFO, PQ, CQ and WFQ) may be employed "after GTS" to provide traffic scheduling on the shaped traffic.
Now unlike GTS, which performs a WFQ-based scheduling on the entry of the shaper with an arbitrary scheduling mechanism on the physical interface, FRTS performs its operations the other way around.
FRTS can use priority queuing, custom queuing, or weighed fair queuing as the scheduling method on the entry of the shaper. This allows for finer granularity in the prioritization and queuing of traffic and provides more control over the traffic flow on an individual VC.
For e.g , If CQ is combined with the per-VC queuing and rate
enforcement capabilities, Frame Relay VCs are enabled to carry multiple traffic types, with bandwidth guaranteed for each traffic type.
For example, if CQ is combined with the per-VC queuing and rate enforcement capabilities, FR VCbs can be enabled to carry IP, SNA and IPX traffic, with bandwidth guaranteed for each.
At the physical interface itself (after the packet has been fancy queued and shaped) WFQ needs to be enabled in conjunction with FRTS. WFQ is currently the only supported interface scheduling method.
I hope this clarifies.
Best Regards,
Nauman
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