Subject: RSVP: Using AdSpec with Sender TSpec of type CoS

From: Rohit Chhapolia <[email-masked]>
Date: Wed, 03 Nov 1999 10:38:52 -0500

RSVP Authors,

from rsvp-lsp-tunnel-04 (section 4.8):
      M
         The maximum packet size parameter [M]  SHOULD  be  set  to  the
         value  of the smallest path MTU.  This parameter is set in Resv
         messages by the reliever based on information in arriving  RSVP
         ADSPEC  objects.   This parameter is ignored when the object is
         contained in Path messages.

   There is no Adspec associated with the Class-of-Service SENDER_TSPEC.
   Either the Adspec is omitted or an int-serv adspec with only the
   Default General Characterization Parameters is used.

These two paragraphs provide some non-consistent usage of AdSpec object in
PATH messages. If AdSpec object is omitted from the PATH message, it is not
possible for receiver to determine the value of M. Should we have a value
say 0 to indicate that this field should be ignored in RESV messages also?

Rohit

-- 
Rohit Chhapolia
Ficon Technology, Inc.
mailto:[email-masked]
http://www.ficon-tech.com

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From: Lou Berger <[email-masked]>
Date: Wed, 03 Nov 1999 11:24:17 -0500

Thanks for pointing this out.  It's a bad cut and paste job. (I borrowed 
the text from one of the int-serv documents.)   The text should read:

"This parameter is set in Resv messages by the receiver based on 
information in arriving RSVP SENDER_TSPEC objects.  For shared 
reservations, the smallest value received across all associated senders is 
used.  When the object is contained in Path messages, this parameter is 
updated at each hop with the lesser of the received value and the MTU of 
the outgoing interface."

Lou

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From: Rohit Chhapolia <[email-masked]>
Date: Wed, 03 Nov 1999 11:47:10 -0500

Lou,

Sorry for the previous message, wrongly pressed send.

> > updated at each hop with the lesser of the received value and the MTU of

It is not clear from the draft that how the MTU field is used. Can you please
provide some clarifications?

Thanks,
Rohit

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From: Rohit Chhapolia <[email-masked]>
Date: Wed, 03 Nov 1999 11:43:52 -0500

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From: Lou Berger <[email-masked]>
Date: Wed, 03 Nov 1999 12:02:01 -0500

Ahh.  sorry I didn't get the nature of your question.  This parameter is 
used to collect path MTU.  (which is needed by the LSP ingress)  The 
parameter performs the same functions as the [M] parameter in int-serv, see 
rfc 2210.

Lou

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From: Rohit Chhapolia <[email-masked]>
Date: Wed, 03 Nov 1999 12:35:40 -0500

Lou,

One small point:
You are suggesting that the MTU size should be updated in Sender TSpec
object. However, it contradicts with RFC 2210 which says that (page 3,
3rd para) RSVP SENDER_TSPEC is transported unchanged through the network.

Rohit

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From: Lou Berger <[email-masked]>
Date: Wed, 03 Nov 1999 12:48:28 -0500

I don't see this as a conflict.  The CoS Objects use a different c-type 
than int-serv objects, i.e., RFC2210 doesn't apply to them.

Lou