Last Mile QoS WAS: RE: QOS or more bandwidth

Rafi Sadowsky rafi-nanog at
Tue May 29 20:26:17 UTC 2001


 Sorry about the previous  (content free :-( ) Email
May I suggest reading (and following links from)


(Scanning for "cRTP" & "Interleaving" should be useful)

 Also you could follow some interesting links from the above URL
For Example:



On Tue, 29 May 2001, Nathan Stratton wrote:

> On Tue, 29 May 2001, Pete Kruckenberg wrote:
> > A 1536-byte frame has a fairly significant impact (~8ms) at
> > 1.5Mb/s. QoS appears to have diminishing return as you move
> > beyond 45Mbps, at least as far as multi-service networks go.
> > Maybe QoS isn't necessary or useful in the core if you have
> > line-speed switching and no congestion on an OC-X/DWDM
> > network.
> It has even a larger impact on a 128K frac T1 (~93ms). QoS is a big help,
> but at slower speeds you also need to deal with fragmentation and the
> layer 2 transport. I am surprised that there has been so little movement
> as far as QoS and efficiency in regards to VoIP. Take a standard voice call
> using G.726 at 32 kbps, you get 40 bytes of voice every 10 ms. Now add on
> your 20 byte IP header, 8 bytes UDP, and 12 byte RTP header. So now we are
> at 80 bytes and most of the time we are shoving this on ATM so our 32K
> voice stream now sucks 84.8 kbps.
> If you are interested in more info on QoS and Voice/Data over last mine
> networks check out my website:
> ><>
> Nathan Stratton				CTO, Exario Networks, Inc.
> nathan at                     nathan at

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