Re: New draft on IPv6 extension headers

[Su Thunder <sujiang at huawei-3com.com>]

I don't think your comment is a problem.Whether a block of memory is payload or an extension header is determined by the Next Header value of the immediately preceding header, not whether the extension header is known or unknown.A node should pass an unknown extension header to the next header immediately following it, why it regards something unknown as something else?
----- Original Message ----- 
From: "Stig Venaas" <stig.venaas at uninett.no>
To: "Rémi Denis-Courmont" <rdenis at simphalempin.com>
Cc: <ipv6 at ietf.org>; "Suresh Krishnan" <suresh.krishnan at ericsson.com>
Sent: Thursday, October 19, 2006 3:48 PM
Subject: Re: New draft on IPv6 extension headers


Rémi Denis-Courmont wrote:
> Hello,
> 
> On Wed, Oct 18, 2006 at 04:07:15PM -0400, Suresh Krishnan wrote :
> 
>>  I have submitted a draft requesting a standard format for IPv6 
>>extension headers. I would appreciate any comments on it.
> 
> 
> I think I don't understand why one would need new extension headers,
> instead of adding options to the existing ones (plus depleting the IP
> protocols number might not be such a godd idea). But I guess I'm missing
> something.

I hope we can avoid that as well. I see one problem with creating new 
extension headers, which this draft won't solve.

End hosts and some other systems (e.g. firewalls) need to locate the IP 
payload for various reasons. The only way to locate the payload, is to 
pass through the known extension headers one by one, until you find a 
next header value that is not a known extension header. If a new 
extension header is created, then such equipment will need to be 
updated, else they will treat the new extension header as being
the payload and not locate the real payload.

Stig

> 
> Regards,
> 



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