Subject: RE: RSVPTE question

From: Vasanthi Thirumalai <[email-masked]>
Date: Thu, 20 Jun 2002 14:48:45 -0400

Julia,
I responded once before on this issue and my feeling is that it is Peak data
rate. But someone on the list disagreed. I guess it also depends to a large
extent on the type of the system. For instance on an optical system, you may
have a choice of dicrete bandwdths to choose from - say OC-12, OC-48 or
OC-192. In such a case the peak data rate seems more appropriate.

-Vasanthi

-----Original Message-----
From: Hong Liao [mailto:[email-masked]]
Sent: Thursday, June 20, 2002 12:25 PM
To: [email-masked]
Subject: RSVPTE question

Hi,

I want to know which field in the path msg is the one which requests for
the bandwidth.  (Is the TBS?)

Thanks,
Julia

---

From: David Charlap <[email-masked]>
Date: Thu, 20 Jun 2002 16:30:27 -0400

Vasanthi Thirumalai wrote:
> 
> I responded once before on this issue and my feeling is that it is
> Peak data rate. But someone on the list disagreed. I guess it also
> depends to a large extent on the type of the system. For instance
> on an optical system, you may have a choice of dicrete bandwdths
> to choose from - say OC-12, OC-48 or OC-192. In such a case the
> peak data rate seems more appropriate.

If you're on a network where there is no room for fuzziness in your
request, then it's not a big deal to generate a TSPEC where r == p.

As I wrote in response to Julia's message, IntServ objects do not define
a single "bandwidth" parameter.  Instead, they define 3 (5 for
guaranteed service) parameters which are used to define a specific
queueing algorithm.

If your hardware does not support this queueing model, then the
parameters must be massaged to fit what your hardware does support. 
There is no generalized way to do this.  The "right thing" will depend
on what your hardware's queueing model is.

-- David

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From: Curtis Villamizar <[email-masked]>
Date: Thu, 20 Jun 2002 17:13:22 -0400

> on what your hardware's queueing model is.

David,

Today's routers use "r" as the value that is credited against
"reservable bandwidth" on an interface and ignore "p" and "b" but it
wouldn't hurt to set "p" to be the same as "r".

It is probably best to set the value for "b" to a very large value
even though it is ignored.  I don't know of anything that does not
ignore "p" and "b" so the discussion of what others put in it and what
is best to put in it hasn't come up in a while.  Maybe someone else
knows of equipment that doesn't ignore "p" and "b" when using RSVP-TE.

Curtis

---

From: David Charlap <[email-masked]>
Date: Thu, 20 Jun 2002 17:27:56 -0400

> wouldn't hurt to set "p" to be the same as "r".

That's fine if all you're using the TSPEC/FLOWSPEC for is bookkeeping.

If your router actually performs traffic shaping/policing, then you need
the remaining values to properly program your queues.

-- David

---

From: Curtis Villamizar <[email-masked]>
Date: Fri, 21 Jun 2002 01:52:27 -0400

David,

If interoperability with major router vendors isn't important, then go
ahead and fill in and use "p" and "b" and use them.

Besides, there are technical problem.  I don't think there is a way to
signal "your 'r' value was just fine but 'b' was too big for the
buffering I have left".  Even if there was, there is just reservable
bandwidth in the flooded information so LSP path selection would
involve trial and error.

Curtis