Subject: RE: Label Stacking !!

From: "Vijayanand C - CTD, Chennai." <[email-masked]>
Date: Thu, 4 Apr 2002 15:10:11 +0530

Hi amar,
Yes the signalling protocols have a role in label stacking if the labels
stack is installed by them.

CR LDP and RSVP-TE support multiple levels of tunnels. CR-LDP allows the use
of LSPID TLV in label request message to acheive this,the remote peering
feature of LDP helps in this. In RSVP-TE tunnels are used as Forwarding
adjacencies to acheive label stacking/multiple levels of tunneling.

Regards,
Vijay

-----Original Message-----
From: Amarendra [mailto:[email-masked]]
Sent: Thursday, April 04, 2002 3:04 PM
To: [email-masked]
Subject: Label Stacking !!

Hi all,
I am very much aware of Label Stack Encoding, but I have a few basic related
queries:
1. How do we achieve label stacking using the Signalling protocols like LDP,
CR-LDP or RSVP-TE ?
2. Do these protocols really play a role in Label Stacking ? I couldn't find
anything specifically related to this in these specs. Has the Extended
Discovery mechanism of LDP anything to do with this ? I guess I am missing
something here.
Could anyone please provide pointers to this ?

Regards,
Amarendra.

---

From: "Amarendra" <[email-masked]>
Date: Thu, 4 Apr 2002 15:45:17 +0530

Hi Vijay,
 Are u talking Forwarding Adjacencies discussed in
draft-ietf-mpls-lsp-hierarchy-04.txt, If yes then in this case CR-LDP or LDP
can also use the same. Am I right? And does that mean OSPF or IS-IS instance
running should also be MPLS aware ?

Amarendra

---

From: Eric Gray <[email-masked]>
Date: Thu, 04 Apr 2002 15:46:23 -0500

Amarendra,

    It isn't actually necessary for a signaling protocol to explicitly
support stacking for the signaling protocol to be useful in signaling
stacked labels.

    Consider the case where an LSP is established bi-directionally
by two LSR implementations that are (most likely) not adjacent.
Now imagine that the implementations allow the combination of
these two LSPs to appear as a single link between the LSRs - now
making them adjacent via that link.  

    From the implementation's perspective, this looks the same as
if a new physical link has been established between the two LSRs.
Protocol entities at each LSR can now treat each other as directly
adjacent peers.  For example, LDP peers could discover each other
via this new logical link and signal labels.  These labels would be
stacked labels.

    Of course, it's not exactly as simple as that, but you can figure it
out if you start there...

You wrote:

>>CR LDP and RSVP-TE support multiple levels of tunnels. CR-LDP allows the
>>
>use
>
>>I am very much aware of Label Stack Encoding, but I have a few basic
>>
>related
>
>>queries:
>>1. How do we achieve label stacking using the Signalling protocols like
>>
>LDP,
>
>>CR-LDP or RSVP-TE ?
>>2. Do these protocols really play a role in Label Stacking ? I couldn't
>>
>find
>

-- 
--
Eric Gray (mailto:[email-masked])
http://www.mindspring.com/~ewgray

---

From: "Amarendra" <[email-masked]>
Date: Fri, 5 Apr 2002 10:05:51 +0530

Eric,
I am agree with you. But, how can I allow the combination of these two LSPs
to be used as a single link? I mean to say, How can I inform LDP about this
link, so that  it can use the new logical link as an actual link to discover
its new peer. I think I am missing somthing.

Amarendra

---

From: "Amarendra" <[email-masked]>
Date: Fri, 5 Apr 2002 13:37:44 +0530

Eric,