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Date:      Tue, 19 Dec 2006 08:26:01 -0500
From:      Randall Stewart <rrs@cisco.com>
To:        "Bruce M. Simpson" <bms@freebsd.org>
Cc:        freebsd-net@freebsd.org, dave jones <s.dave.jones@gmail.com>
Subject:   Re: UDP lite for FreeBSD
Message-ID:  <4587E869.90108@cisco.com>
In-Reply-To: <458745F8.4090707@FreeBSD.org>
References:  <5628d8010612160452y5c562757h8ef8ed0776c5525d@mail.gmail.com> <458745F8.4090707@FreeBSD.org>

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Bruce M. Simpson wrote:
> dave jones wrote:
> 
>> Hi,
>>
>> Is anyone working on implementing UDP lite in FreeBSD? If not,
>> I'd like to work on it.
> 
> Nope. I just skimmed the RFC and it sounds like a bit of a hack, though 
> I am sure it can be done cleanly in the source tree without unnecessary 
> code duplication or interference at the user-kernel boundary.
> 
> I look forward to seeing patches for this. It would be interesting to 
> see if hardware checksum offloading can be taught to do it, cleanly, 
> though I imagine that is something much further down the line.
> 
> Regards,
> BMS
> 
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> 
Bruce:

I have always thought of it as a bit of a hack as well... and
there is one really big problem with it.. It has no value
unless you can tell your network-interface card to deliver
damaged packets. I don't know if some cards have this option
now or not.. nor if an API in any driver exists for it... without this
you will find very very few packets that are "damaged" that
do get through.. since generally the link layer checksum
is a MUCH better CRC vs the very weak IP/UDP checksum :-0

If you get the driver mods.. then codecs like (... if my
grey cells remember right..) AMR will be able to use
the information.. of course that assumes you have something
that can do the AMR codec... not sure what media uses this :-)

There may be other codecs as well now too... I don't keep up
with that side of the IETF :-)


R

-- 
Randall Stewart
NSSTG - Cisco Systems Inc.
803-345-0369 <or> 803-317-4952 (cell)



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