RE: [Syslog] Discuss - UDP Checksum

["Anton Okmyanskiy \(aokmians\)" <aokmians at cisco.com>]

I agree with Juergen and Rainer that we could use less specification
here since it is a different layer.  How about we replace both
paragraphs with this:

"Syslog senders are RECOMMENDED to use UDP checksums when sending
messages over IPv4. Proper UDP checksum insertion and verification is
already required by IPv6 RFC 1883."

Let's be silent on what the receiver has to do since it may not have any
control.  I think if we put something like "Syslog receivers MAY accept
syslog message with invalid or zero checksums", it would directly
contradict IPv6 RFC, which says:

"IPv6 receivers must discard UDP packets containing a zero checksum, and
should log the error."

Anton.   

> -----Original Message-----
> From: Juergen Schoenwaelder 
> [mailto:j.schoenwaelder at jacobs-university.de] 
> Sent: Thursday, July 05, 2007 4:16 PM
> To: Chris Lonvick (clonvick)
> Cc: syslog at ietf.org
> Subject: Re: [Syslog] Discuss - UDP Checksum
> 
> On Thu, Jul 05, 2007 at 02:14:06PM -0700, Chris Lonvick wrote:
> 
> > How about the following:
> >
> >    syslog senders MUST NOT disable UDP checksums.  syslog 
> senders SHOULD
> >    use UDP checksums when sending messages over IPv4.  
> syslog senders MUST
> >    use UDP checksums when sending messages over IPv6.
> 
> The last sentence is a bit like requiring that the IPv6 
> implementation your code happens to run on MUST be correct 
> (and I have no clue how to turn this requirement into syslog code).
> 
> >    syslog receivers should be lenient in what they receive.  IPv4
> >    receivers SHOULD check the UDP checksums.  They SHOULD accept a
> >    syslog message with a zero checksum.  They MAY discard messages
> >    with invalid checksums, or they MAY accept them and 
> attempt to process
> >    them.  IPv6 receivers MUST check the UDP checksums and 
> MUST discard UDP
> >    packets containing a zero checksum.
> 
> I am not sure the MAY discard or MAY accept sentence is needed.
> 
> My proposal would be:
> 
>     syslog senders MUST NOT disable UDP checksums.  IPv4 syslog
>     senders SHOULD use UDP checksums when sending messages. Note that
>     RFC 2460 [RFC2460] mandates the use of UDP checksums when sending
>     UDP datagrams over IPv6.
> 
>     syslog receivers MUST NOT disable UDP checksum checks. IPv4 syslog
>     receivers SHOULD check UDP checksums and they SHOULD accept a
>     syslog message with a zero checksum. Note that RFC 2460 [RFC2460]
>     mandates the use of checksums for UDP over IPv6.
> 
> By simply refering to the IPv6 requirement for UDP checksums, 
> we avoid making this also a syslog requirement. I think we 
> should not use MUST language for something that can only be 
> implemented correctly below the syslog software layer.
> 
> [Enough hair splitting for today. ;-]
> 
> /js
> 
> -- 
> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
> Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>
> 
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