From: Shine Joseph (shinepjoseph@iprimus.com.au)
Date: Thu Aug 30 2007 - 20:37:50 ART
Oops!!
Sorry Wink, I misspelled your name.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Shine Joseph
Sent: Friday, 31 August 2007 9:12 AM
To: 'Wink'; 'eicc tester'; 'Scott Smith'; 'groupstudy'
Subject: RE: frame-relay traffic shaping, fragmentation, port speed
Wunk,
I think he was referring to Traffic Shaping (TS) :)
Regards,
Shine
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Wink
Sent: Friday, 31 August 2007 8:50 AM
To: eicc tester; Scott Smith; groupstudy
Subject: Re: frame-relay traffic shaping, fragmentation, port speed
Eric:
What is TS? Do you mean Tc?
----- Original Message -----
From: "eicc tester" <reto_ccie@yahoo.com>
To: "Scott Smith" <hioctane@gmail.com>; "groupstudy"
<ccielab@groupstudy.com>
Sent: Thursday, August 30, 2007 10:35 AM
Subject: Re: frame-relay traffic shaping, fragmentation, port speed
> Hi,
>
> The issue with fragmentation is related with the TS , the time that you
> use for shaping, in order to keep the CIR rate in the TS. The
> fragmentation have to be small enough in order to fill completely between
> the TS time-space.
>
> For example a 512K CIR using a TS of 10 ms, implied a BC of 5120 bits,
> which correspond with a maximum of 640 bytes fragment. You transmit rate
> are T1 , then you are able to transmit 5120 bits in less of 10 ms (aprox
> 4ms) the rest 6 ms are idle (no transmit) for that pvc.
>
> The fragmentation to 640 is used to cut big data packet (1500 bytes) in
> fragments in order to match the shapping. voice packet with less of 640
> will not be fragmented.
>
> reto
>
>
>
> Scott Smith <hioctane@gmail.com> wrote:
> I'm hoping someone can shed some light on why my thinking is wrong on
> this.
>
> Config example: 2 512k PVCs on a T1 port. Each PVC is shaped via FRTS
> to 512k with no burst and the physical interface can run at T1 speed.
>
> Cisco says "you do not need fragmentation because the port speed is
> T1, irregardless of the shaping."
>
> I know all the in and outs of fragmentation/interleaving,
> serialization delay, etc and how this impacts voice traffic. Where
> I've got a problem is the seeming disregard for the amount of traffic
> that will actually pass through the interface. T1 port or not a single
> PVC cannot send more than 512k since it is shaped to that rate.
> Granted, once the traffic passes through shaper and its time to place
> the bits on the wire it'll be serialized at T1 rate (512k of traffic
> will be serialized at T1 rate) . Since a single PVC can only place
> 512k on the T1 port how is it that we completely ignore this fact when
> deciding to frag or not frag? It seems to me, in this case, the port
> speed is irrelevant because we can only send at 512k... OK, I could go
> on and on but I'll spare you all :-)
>
> So, obviously I'm wrong and or confused... lord knows it isn't the
> first time and will not be the last but I'd really like to know why my
> logic is flawed. Thus far no one who says I'm confused (including
> Cisco) has been able to explain why.
>
> TIA!
>
> --
> Scott
> CCIE #17040 (R&S)
>
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This archive was generated by hypermail 2.1.4 : Sat Sep 01 2007 - 11:32:14 ART