Subject: Conflicting Resernation Style

From: "chetan kumar s" <[email-masked]>
Date: Tue, 19 Nov 2002 18:45:49 +0530 (IST)

Hi All,
	The session attribute object as a flag 'SE Style desired', which
mandates the egress to respond the resv message with SE style. Now if the
Path refersh messages have conflicting flags, how is this handled. I was
looking at the classical RSVP mailing list archive, found an interesting
thread on this:
http://www.cs-ipv6.lancs.ac.uk/ipv6/mail-archive/rsvp/1996-04/0068.html

Any comments, especially comments on the response from Bob..

Thanks
Chetan S

-- 
------------
Thinking is progress, non thinking is destruction of individual, organization
and nation

-Abdul Kalam

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From: David Charlap <[email-masked]>
Date: Tue, 19 Nov 2002 10:42:40 -0500

> http://www.cs-ipv6.lancs.ac.uk/ipv6/mail-archive/rsvp/1996-04/0068.html

You have one critical mistaken assumption here.  The flags in 
SESSION_ATTRIBUTES are not mandatory.  They are advisory.  An egress 
node is free to ignore them if it wants to.

This should also answer your second question.  If the ingress signals a 
Path requesting SE style, and an SE style Resv is returned, and then the 
ingress refreshes that LSP (or perhaps creates another LSP in the same 
session) without the SE-style request, the egress node should simply 
ignore the change and continue sending back SE-style Resv messages.

Now, if the egress node sends back two different Resv messages with two 
different styles, then the node detecting that conflict should generate 
a ResvErr message.  But this shouldn't happen unless the egress node is 
broken.  A style-conflict error should only happen in a multicast 
situation, where two different egress nodes for the same session choose 
different styles.

-- David

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From: "chetan kumar s" <[email-masked]>
Date: Wed, 20 Nov 2002 09:08:46 +0530 (IST)

> SESSION_ATTRIBUTES are not mandatory.  They are advisory.  An egress

Yea, the session_attribute flags are not mandatory, but however, if the
flags are present(and set) the egress node SHOULD use SE style, the RFC
says. So it may not be good for egress to ignore.

The SE style desired flag is required in the session attribute so that
ingress can control the reservation style, since it is the ingress node
that decides if there is requirement for rerouting of tunnel without
tearing it down. Now if the egress node ignore any such request, one can
not expect consistent network operations..

Thanks
Chetan S