Subject: Re: [Ipsec] Next Layer Protocol (Ref: 2401-bis draft)

From: Subha Venkataramanan <[email-masked]>
Date: Thu, 17 Mar 2005 18:33:02 -0800 (PST)

Hi , 

I have a follow-up question. 

If an implementation understands says hop-to-hop,
routing, fragmentation and Destination Options, it
can parse these extension headers and look for the
next protocol information. When it parses each
extension header, it knows the length of bytes it
needs to skip to reach the next extension header.

If there are any new extension headers and the
implemenation cannot interpret these extension
headers, it cannot process the packet. In which
case, it may choose to send an ICMP Error message.

What additional help is given to the implementation,
by configuring the extension headers that it needs
to ignore while parsing the IPv6 header.

1) Does this kind of configuration in the
implementation advise the user, that it has
capabilities skip A,B,C extension headers ? 

2) Does this kind of configuration mean, that if the
implementation comes across any other extension
headers which it can interpret but is not in the
configured list, it should drop the packet ?

3) Does this kind of configuration mean, that when the
user tries to add some extension header values, that
the implementation does not support, it can throw an
error indicating the same ?

Can someone please clarify ?

Thanks,
Subha
--- Stephen Kent <[email-masked]> wrote:
> At 3:51 PM -0800 1/13/05, Subha Venkataramanan
> wrote:
> >Hi List-members,
> >
> >In Section 4.4.4.1 (Selectors) under Next- Layer
> >Protocols, it is mentioned that "to simplify
> locating
> >the next header protocol, there SHOULD be a
> mechanism
> >for configuring which IPv6 extension headers to
> SKIP"
> >
> >Could someone indicate to me what was the intent
> >behind this kind of configuration ?
> >
> >Thanks,
> >Subha
> 
> In IPv6, the use of hop-by-hop and destination
> extension headers can 
> make it harder than in Ipv4 to locate the next layer
> protocol. This 
> text suggests that it would be useful to be able to
> configure an 
> IPsec implementation with a list of which of these
> extension headers 
> can safely be ignored when parsing the IPv6 header
> to locate the next 
> protocol.
> 
> Steve
> 

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