[xcp] Embedding XCP signalling in IP header

[Henderson, Thomas R]

Marko,
Interesting proposal.  My thoughts are:
i) it seems like it will be difficult to support the dynamic
range and precision necessary with the fewer bits allotted.
We experienced some problems with XCP convergence when
fractions were being rounded. (we were using 16 bits
for the feedback field, also with mantissa-exponent format).

ii) given that a router has agreed to do XCP computations
on your packets, wouldn't it be better to make its
life easier by simplifying the arithmetic as much as
possible?  I don't know whether heavy compression of the
XCP fields is the right design trade to make.

iii) shouldn't we be worrying about IPv6 anyway, by the
time XCP is matured?  

iv) Yongguang and I discussed previously the potential
for reducing the frequency of packets that carry XCP-FWD,
specifically to reduce the overhead consumed by XCP and
to reduce the router operations, and I think it would
be interesting to examine that angle from a sensitivity 
standpoint, although we did not look at it.

Tom

> -----Original Message-----
> From: Marko Zec [mailto:zec at icir.org]
> Sent: Wednesday, August 18, 2004 5:36 AM
> To: xcp at mailman.isi.edu
> Subject: [xcp] Embedding XCP signalling in IP header
> 
> 
> Here's just a thought - perhaps XCP signalling could be 
> embedded directly into 
> the IP header, by reusing the existing fragmentation fields?  
> The obvious 
> benefit from such a scheme would be transparent compatibility 
> with existing 
> TCP implementations, which could make quite a difference for 
> any real-world 
> deployment scenario.
> 
> http://tel.fer.hr/zec/xcp-hdr-encoding.txt
> 
> Would this make any sense?
> 
> Marko
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