Subject: Re: Two signalling protocols (LDP & RSVP)

From: [email-masked]
Date: Fri, 27 Apr 2001 15:07:20 +0530

> Hi,
>
> Is there any practical reason that the signalling protocols (LDP & RSVP) is
> supported on the same interface?
>

Although both CR-LDP and RSVP-TE provides similar functionalities, but one
significant reason why we would like to run both the protocols on the same
interface can be that TE-RSVP supports IP record route option using its record
route objects.But CR-LDP doesn't support IP record route option.

Regards
Mohit Goel

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From: Kireeti Kompella <[email-masked]>
Date: Fri, 27 Apr 2001 02:56:36 -0700 (PDT)

> route objects.But CR-LDP doesn't support IP record route option.

The above seems to be an excellent argument for running RSVP-TE.
It is not (as it stands) a justification for running *both* RSVP
and CR-LDP.

Kireeti.

---

From: Ajay Simha <[email-masked]>
Date: Fri, 27 Apr 2001 10:09:59 -0400 (Eastern Daylight Time)

> It is not (as it stands) a justification for running *both* RSVP

Kireeti,

Do you think the original question used "LDP" to mean "CR-LDP"?  I just
assumed they were talking about RFC3036.

It would make more sense for folks to have LDP and RSVP on the same
interface but may not make much sense to have CR-LDP and RSVP on the same
interface.

-ajay

-- 
Ajay Simha
MPLS Deployment Engineer
IOS Technology Division
(919) 392-3141

"Study as if you were to live forever
 Live as if you were to die tomorrow"

 - Mahatma Gandhi

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From: Kireeti Kompella <[email-masked]>
Date: Fri, 27 Apr 2001 09:13:06 -0700 (PDT)

> Do you think the original question used "LDP" to mean "CR-LDP"?

I don't think so, but the previous poster switched subjects.  I
agree completely, it makes perfect sense to run LDP and RSVP-TE
on the same interfaces (depending on your applications), whereas
running RSVP-TE and CR-LDP in the same network, let alone on the
same interfaces, seems to be inviting gratuitous complexity.

Kireeti.

---

From: Eric Osborne <[email-masked]>
Date: Fri, 27 Apr 2001 16:47:56 -0400

> same interfaces, seems to be inviting gratuitous complexity.

Except in multi-vendor networks, where one vendor does RSVP and the
other does CR-LDP:

      C
     /
A---B 
     \
      D

If C does only CR-LDP and D does only RSVP, then A may need to do both 
RSVP and CR-LDP on the A<->B link.  This would not be the case if B
instead did some sort of RSVP<->CR-LDP translation, however.

eric

---

From: David Charlap <[email-masked]>
Date: Mon, 30 Apr 2001 11:02:35 -0400

[email-masked] wrote:
> 
> Although both CR-LDP and RSVP-TE provides similar functionalities,
> but one significant reason why we would like to run both the
> protocols on the same interface can be that TE-RSVP supports IP
> record route option using its record route objects.But CR-LDP
> doesn't support IP record route option.

CR-LDP has the Path-Vector TLV, which works almost identically to the
RSVP RECORD_ROUTE object.

-- David

---

From: Ajay Simha <[email-masked]>
Date: Mon, 30 Apr 2001 11:17:14 -0400 (Eastern Daylight Time)

> RSVP RECORD_ROUTE object.

Good point.  But is it of consequence when one is not using Ordered/DoD?

-ajay

-- 
Ajay Simha
MPLS Deployment Engineer
IOS Technology Division
(919) 392-3141

 - Mahatma Gandhi

---

From: David Charlap <[email-masked]>
Date: Mon, 30 Apr 2001 11:26:56 -0400

Ajay Simha wrote:
>> 
>> CR-LDP has the Path-Vector TLV, which works almost identically to
>> the RSVP RECORD_ROUTE object.
> 

Other modes are only for LDP, not CR-LDP.

But, since you ask, they are also useful in LDP in those modes, but
Path-Vector must now be used in conjunction with hop-count.  Hop-count
will only be non-zero for messages that come from, or are propagated
from, the egress node.  So...

If an ingress node receives a Label Mapping where the hop-count is zero
(unknown), then it the Path-Vector is not a complete path to the
egress.  It represents a partial path through the MPLS cloud, and may
change as the LSP setup is completed.

If it receives a Label Mapping where the hop-count is non-zero, then it
knows that there is a path all the way to the egress, and the
Path-Vector should be an accurate trace of what that path is.

-- David