Subject: [NSIS] on-path versus off-path discussion

From: Marcus Brunner <[email-masked]>
Date: Fri, 18 Oct 2002 10:44:15 +0200

The issue about on-path signaling versus off-path signaling raises quite a 
bit of traffic on the NSIS WG mailing list. You can call it also in-band or 
out-of-band signaling. There still not a clear definition of what on and 
what off-path is. E.g. you could call RSVPv1 RSRV message off-path because 
it does not follow the path base on IP routing.

There definitely are some pro and cons for both approaches. See "On path 
and off path signaling for NSIS", draft-schelen-nsis-opopsig-00.txt for a 
discussion on some of them. Furthermore, there are some implementations 
(experimentqal and products) available for centralized QoS provisioning.

We need to clarify what the way forward is concerning off-path signaling. 
On-path is in the charter of the NSIS WG. Additionally, there are a number 
of issues for clarifying what on-path includes. In certain cases the 
boundary is not straight forward.

Currently, there seam to be 3 positions in the community:
1) Forget about off-path, nobody will use it and it is architecturally 
problematic in IP networks
2) Form a new WG taking care of the off-path issue completely independent 
of NSIS.
3) Require NSIS to work for on- and off-path signaling, because data 
objects to be carried by the protocol should basically be the same in both 
cases, and a soft-state approach is worth for off-path as well.

Current draft dealing with some of the issues
"On path and off path signaling for NSIS", draft-schelen-nsis-opopsig-00.txt

Discussion list:
mailing list is called "nsobs", which stands for "Next Steps in Out-of-Band 
Signaling" is Majordomo list at ccrle.nec.de

To subscribe send e-mail to [email-masked] with subscribe in 
the body.

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--------------------------------------
Marcus Brunner
Network Laboratories
NEC Europe Ltd.

E-Mail: [email-masked]
WWW:    http://www.ccrle.nec.de/
Phone: +49 (0) 6221 905 11 29
personal home page: http://www.brubers.org/marcus

--------------------------------------
Dr. Marcus Brunner
Network Laboratories
NEC Europe Ltd.

E-Mail: [email-masked]
WWW:    http://www.ccrle.nec.de/
Phone: +49 (0) 6221 905 11 29
personal home page: http://www.brubers.org/marcus

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---

From: Roland Bless <[email-masked]>
Date: Fri, 18 Oct 2002 11:45:57 +0200

Hi Marcus,

> out-of-band signaling. There still not a clear definition of what on and 

I disagree here: in-band/out-of-band is another distinction:
a typical case of in-band signaling is DTMF tone in-band signaling within
the telephone system, so I would say that in-band signaling would mean to
place the signaling data into the header or user data part of an IP datagram
which is part of the user data flow.
I like the proposed term from Robert Hancock path-coupled/path-decoupled.

> it does not follow the path base on IP routing.

Right RESV not, PATH yes. I thought that on-path signaling messages simply
have the same source and destination address as the data flow which is true
for PATH messages. Off-path signaling may use different addresses. However,
you gain flexibility when using off-path signaling while you can let the
signaling messages still follow the same data path as corresponding on-path 
message would.
 
> (experimentqal and products) available for centralized QoS provisioning.

If we meet the I-D deadline there should be a new draft revision before 
the next meeting.
 
> problematic in IP networks

I don't see that it's problematic.

> 2) Form a new WG taking care of the off-path issue completely independent 

I don't think that this makes sense.

> cases, and a soft-state approach is worth for off-path as well.

Right. It is absolutely no problem to define a protocol that supports
both variants at the same time.

> "On path and off path signaling for NSIS", draft-schelen-nsis-opopsig-00.txt

We will try to write a new revision with a more clear structure and distinction
between properties and examples for advantages/disadvantages.
 
> To send E-Mail to the list use [email-masked]

Best regards,
 Roland

-- 
Roland Bless -- e-Mail: [email-masked]
Institute of Telematics, University of Karlsruhe, Germany  
Zirkel 2, D-76128 Karlsruhe -- Office: Bld. 20.20, 3rd floor, R 358
Phone: +49 721 608-6413 Fax: +49 721 388097

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From: Melinda Shore <[email-masked]>
Date: Fri, 18 Oct 2002 09:10:02 -0400

At 10:44 AM 10/18/02 +0200, Marcus Brunner wrote:
>1) Forget about off-path, nobody will use it and it is architecturally problematic in IP networks

I think that's not exactly what's been said.  There are
ways of doing off-path signaling that will work and ways of
doing off-path signaling that are "architecturally problematic."

Melinda