The bottom line is you fragment data packets, never voice, so that a
voice packets, which are small, never get queued behind a 1500 byte
packet. The rule of thumb I think is you don't want more than 150ms
delay in any voice packets or you may as well dump it.
dave
Stephen Skinner wrote:
>
> the only thing i could find was this
>
> http://www.cisco.com/warp/public/788/voice-qos/voip-ov-fr-qos.pdf
>
> which says
>
> "Turn on fragmentation for low speed links (less than 1.5Mbps).
> Set the fragment size so voice packets are not fragmented and do not
> experience a serialization delay greater than 20 ms.
>
> Lowest Link Speed in Path Recommended Fragmentation Size
>
> 56Kbps 70 bytes
> 64Kbps 80 bytes
> 128Kbps 160 bytes
> 256Kbps 320 bytes
> 512Kbps 640 bytes
> 768Kbps 1000 bytes
> 1536Kbps 1600 bytes
>
> Note: For 1536 Kbps, no fragmentation is technically needed, but
> fragmentation is needed to enable the dual first-in, first-out
> (FIFO) queueing system to ensure voice quality. A fragment size of 1600
> bytes enables the dual FIFO, but since 1600 bytes is
> higher than the typical serial interface maximum transmission unit (MTU),
> large data packets are not fragmented.
>
> from what it says it`s just multple "stack" queue
>
> sorry i can`t be of more help..
>
> Cheers
>
> steve
> >From: "John Neiberger"
> >Reply-To: "John Neiberger"
> >To: [EMAIL PROTECTED]
> >Subject: Dual FIFO? [7:19691]
> >Date: Wed, 12 Sep 2001 18:34:53 -0400
> >
> >When configuring VoIP on T-1 links, I see that CCO suggests turning on
> >frame relay fragmentation with a fragment size of 1600 simply to turn on
> >the dual fifo queue. What is that? I'm familiar with the single fifo
> >but what is dual fifo and how does it work?
> >
> >I've searched CCO and all I can find is how to turn it on. I have yet
> >to find any sort of explanation.
> >
> >thanks!
> >
> >John
> _________________________________________________________________
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--
David Madland
Sr. Network Engineer
CCIE# 2016
Qwest Communications Int. Inc.
[EMAIL PROTECTED]
612-664-3367
"Emotion should reflect reason not guide it"
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=19779&t=19691
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