Subject: Reg. MPLS-RSVP LSP Tunnels...

From: Pramoda Nallur <[email-masked]>
Date: Tue, 25 Jul 2000 17:23:12 +0530

Hi,

I have a query on setting up RSVP MPLS LSPs in an ATM network.
[ Topology Driven LSP Setup Scenario ]

Suppose the network configuration is as follows :

    S--A--LER1---LSR---LER2--B--R

where,
    S                   --> Sender(RSVP aware)
    R                   --> Receiver(RSVP aware)
    A, B                --> Legacy IP Routers
    LER1, LER2 and LSR  --> MPLS-RSVP ATM switches.

An LSP setup is initiated from LER1 with FEC=(S,R).

The RSVP-TE PATH msg (with Sender=S, Session = Sess_R) creates an
RSVP Session, Sess_R at LER1, LSR and LER2. The Egress LER2 responds with a

RSVP-TE RESV msg reserving resources and sets up an LSP via LSR to LER1.

After the LSP is setup, the RSVP-TE PATH msgs from LER1 and RSVP-TE RESV
msgs
from LER2 periodically refresh the RSVP reservation state on all nodes
along the LSP.

Suppose, Sender S sends an RSVP PATH msg to R (with Session = Sess_R).

 1. Will this PATH msg take the unlabelled path OR will it get switched
onto the LSP at LER1 ?

 2. Also, how are the resulting RESV msgs from R propagated back to S ?

 3. If these PATH and RESV msgs take the unlabelled path, will this result
in
    resource allocation again along all nodes traversed by the LSP ?

The "RSVP-TE: Extensions to RSVP for LSP Tunnels"
(draft-ietf-mpls-rsvp-lsp-tunnel-06.txt)
does not mention how the above should be handled.

Any comments on this ?

- Pramoda Nallur

---

From: Jie Zou <[email-masked]>
Date: Tue, 25 Jul 2000 09:19:08 -0400

I hope the following can answer a part of questions.

According the darft, if A or B is a non-RSVP router, it can't convey
labels via RSVP path. And it's neighber who knows it's non-RSVP 
router should send a PathErr back to the sender.

If A or B is an RSVP router but doesn't recognize the LRO, it should
send a PathErr toward the sender.

If A or B is an RSVP router and recognize the LRO but not C_TYPE also
sends a PathErr toward the sender.

Else the Path msg should pass A and B toward the receiver and 
vice verse the Resv msg should pass the B and A toward the sender.

Regards,

-----------------------------------------------------
Jie Zou				(603)862-4212(Office)
MPLS Consortium		
IOL, UNH			(603)868-2983(Home)
-----------------------------------------------------