[e2e] Re: crippled Internet

David P. Reed dpreed at reed.com
Fri Apr 27 14:13:18 PDT 2001

At 09:16 AM 4/27/01 -0600, Vernon Schryver wrote:
>In my view, a reasonable PPP implementation honors the IP TOS bits as
>well as optionally watching for interesting UDP and TCP port number
>and might even move small packets to the front of the transmit queue,
>and so gives low-latency traffic delays as good as possible.

PPP's lack of implementing such features introduces unnecessary jitter, and 
this why my point.  And if done properly, PPP on a bottleneck link (like a 
56 Kb modem's 33 Kb uplink) would chop elephants into link-level fragments, 
so priority datagrams would preempt FTP packets of 500 bytes or so (a 
significant jitter can be induced at today's access link speeds).
What PPP implementations honor TOS bits today, and what VoIP sources 
actually set the TOS bits?  I'm much more dubious that PPP should read 
magic port numbers (especially since RTP can't be identified by port 
numbers in packets).

- David
WWW Page: http://www.reed.com/dpr.html

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