Subject: Reservation style

From: John Sparr <[email-masked]>
Date: Fri, 15 Dec 2000 12:51:55 -0800 (PST)

Hello,

I have a question about reservation style in RSVP:

How does the receiver decide the reservation style?
Since the sender has no effect for the style.

Thanks,

John

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From: David Charlap <[email-masked]>
Date: Mon, 18 Dec 2000 10:57:32 -0500

> Since the sender has no effect for the style.

There is a flag in the SESSION_ATTRIBUTES object which an ingress node
can use to request SE style of an egress node.  But the choice of style
is advisory, not mandatory (note the use of SHOULD in the draft, not
MUST).

If an egress node only supports one style, then it just uses that style
- this is legal.  If both FF and SE are used, then the choice should be
based on the SESSION_ATTRIBUTES flag.

The reason for requesting SE style is for doing make-before-break
rerouting.  It is more efficient when done with SE style vs. FF style. 
While make-before-break rerouting with FF is possible, it requires that
extra resources (double the amount required by the LSP) be available on
nodes that are shared between the original and new LSPs.  When done with
SE style, the two LSPs share resources and the problem is avoided.

-- David

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From: Jie Zou <[email-masked]>
Date: Tue, 19 Dec 2000 09:50:40 -0500

Hi David,

You are right for the SESSION_ATTRIBUTES flag. But I have another
question: what happened if there is no SESSION_ATTRIBUTES object in the
Path message? since it is optional in Path message. 

For example, when an egress node suppport both FF and SE style, and there
is no SESSION_ATTRIBUTES in Path message, how the egress node decide use
which style?

Thanks in advance

--Jie

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From: David Charlap <[email-masked]>
Date: Tue, 19 Dec 2000 09:58:16 -0500

Jie Zou wrote:
> question: what happened if there is no SESSION_ATTRIBUTES object in
> the Path message? since it is optional in Path message.
> 
> For example, when an egress node suppport both FF and SE style, and
> there is no SESSION_ATTRIBUTES in Path message, how the egress node
> decide use which style?

Then it doesn't matter.  Pick whichever one you like.  If you want to be
nice to your customers, allow the operator to choose which style is used
by default.

-- David