From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Sun May 23 2004 - 17:30:43 GMT-3
Joe,
I think you know what's going on... there is a lot more than docs talk
about, as is the case in many areas.
Yes, once you start queuing, you keep queueing (you are not supposed to
reorder traffic in traffic shapping) and then transmit from the queue to
the tx-ring as much as Bc per Tc. Eventually you either empty the queue
and fall back to initial strategy or you start tail-dropping excess
traffic that does not fit your shapping buffer.
All shapping metrics are done based on Tc. Tc is calculated from rate
and Bc. Then there is that shape to average or peak. I don't really know
what the difference between shaping to average with be = 0 and shapping
to peak would be though, but it comes handy to easily define different
shapping schemes. (AFAIK, shaping to peak with given (Bc,Be) is the same
as shapping to average with (Bc+Be,0).
One thing that seems not clear is that Be does not apply to a Tc, but
instead is the size of your "overrun" quota. That quota is
"rechargeable" so to speak, as long and you drop under cir.
Does that make sense ?
Joe Chang wrote:
> That's right. The buffer is a queue, the style of which can be specified in
> the configuration. But at what point can this buffer be emptied onto the I/O
> transmit ring of the interface? I guess there's a lot more to the algorithm
> than the texts are letting on.
>
>
> ----- Original Message -----
> From: "Brian McGahan" <bmcgahan@internetworkexpert.com>
> To: "Joe Chang" <changjoe@earthlink.net>; <ccielab@groupstudy.com>
> Sent: Sunday, May 23, 2004 10:33 AM
> Subject: RE: Traffic Shaping question
>
>
> Hi Joe,
>
> Traffic shaping uses a buffer to hold packets that cannot be
> transmitted due to lack of Bc or Be credit. This buffer is defined in
> legacy FRTS by the "frame-relay holdq" map-class subcommand, and the
> "queue-limit" policy-map/class-map subcommand for MQC FRTS.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
>
>
>
>>-----Original Message-----
>>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>
> Of
>
>>Joe Chang
>>Sent: Saturday, May 22, 2004 6:35 PM
>>To: ccielab@groupstudy.com
>>Subject: Traffic Shaping question
>>
>>QoS is a real popular topic here!
>>
>>Does anyone know what happens to packets that are queued as a result
>
> of
>
>>being
>>rejected by the token bucket algorithm? At what point are these
>
> packets
>
>>forwarded onto the transmit ring? Two streams result from the token
>
> bucket
>
>>function - one that conforms and one that doesn't. How and when can
>
> the
>
>>unconforming stream be sent without defeating the objective of traffic
>>shaping
>>- keeping the average rate under the CIR?
>>
>>TIA
>>
>>
>
> _______________________________________________________________________
>
>>Please help support GroupStudy by purchasing your study materials
>
> from:
>
>>http://shop.groupstudy.com
>>
>>Subscription information may be found at:
>>http://www.groupstudy.com/list/CCIELab.html
>
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
This archive was generated by hypermail 2.1.4 : Wed Jun 02 2004 - 11:12:15 GMT-3