Subject: LSP ID

From: Yuan Gu <[email-masked]>
Date: Thu, 19 Apr 2001 16:18:07 -0400

Hello:

I have some questions about LSP ID of  rsvp-tunnel comparing the one
defined in cr-ldp:

In draft-ietf-mpls-cr-ldp-05.txt  section 4.5 LSP ID TLV:

"LSPID is a unique identifier of a CR-LSP within an MPLS network.
The LSPID is composed of the ingress LSR Router ID (or any of its own
Ipv4 addresses) and a Locally unique CR-LSP ID to that LSR."

It's very clear. I have no doubt.

But In draft-ietf-mpls-rsvp-lsp-tunnel-08.txt section: 4.6.2.1:

"LSP ID

         A  16-bit  identifier  used  in  the  SENDER_TEMPLATE  and  the

         FILTER_SPEC  that  can  be  changed  to allow a sender to share

         resources with itself."

My question are:
Is this LSP ID Locally unique?
What's mean of  "it can be changed to allow a sender to share resources
with itself"?
In RSVP-LSP-tunnel, how can we unique identify a LSP within an MPLS
network? Is it enough to use  "LSP ID + sender node address" to identify
it? Is there any specification about it?

Best Regards!
Yuan

---

From: David Charlap <[email-masked]>
Date: Thu, 19 Apr 2001 19:41:36 -0400

> Is this LSP ID Locally unique?

Yes.  It is only meaningful when used in conjunction with the rest of
the SENDER_TEMPLATE or FILTER_SPEC object.  Since the only other field
in the LSP-CType of these objects is the sender IP address, you may
safely think of the SENDER_TEMPLATE/FITER_SPEC objects as functionally
identical to the CR-LDP LSPDI.

> What's mean of "it can be changed to allow a sender to share
> resources with itself"?

In RSVP, two LSPs that belong to the same tunnel (which is defined by
the tunnel-endpoint/tunnel-ID/extended-tunnel-ID triple) will share
resources if SE-style reservations are used.

A single sender can signal two LSPs in the same session by using
identical SESSION objects but different LSPID values in the
SENDER_TEMPLATE/FILTER_SPEC objects.  If the egress router uses SE
style, these two LSPs will share resources wherever possible.

> network? Is it enough to use "LSP ID + sender node address" to
> identify it? Is there any specification about it?

The combination of SESSION object and SENDER_TEMPLATE uniquely
identifies a single LSP in Path messages.  The combination of SESSION
object and FILTER_SPEC uniquely identifies a single LSP in Resv
messages.

In both cases, this is a 5-tuple consisting of tunnel-endpoint address,
tunnel-ID, extended tunnel-ID, sender address, and LSP ID.

-- David

---

From: David Charlap <[email-masked]>
Date: Fri, 20 Apr 2001 13:30:49 -0400

Yuan Gu wrote:
> 
> CR-LDP LSPID is Locally unique to that LSR(please see the definition
> above).
> That means LSPID in RSVP-TE is unique within same node i.s.o same
> session.

No.  In RSVP, the same LSPID can be used by multiple LSPs, as long as
those LSPs are all in different sessions.

I do not know if CR-LDP's LSPID must be unique for the entire LSR or if
they are only unique on a per-FEC basis.

-- David

---

From: Yuan Gu <[email-masked]>
Date: Fri, 20 Apr 2001 12:11:58 -0400

Hello, David:

Thanks for your answer.

Please see my reply in line:

CR-LDP LSPID is Locally unique to that LSR(please see the definition
above).
That means LSPID in RSVP-TE is unique within same node i.s.o same session.
Do you agree?