The MPLS WG Archive

["Peter Ashwood-Smith" <petera@nortelnetworks.com>]

Title: RE: IP Source Route Option

I assume it would be placed on the appropriate LSP as normal. Then, when it popped off the LSP it would route again, as usual. So, if the source route were not carefully structured to take the LSP into account it could take you all the way back to say the second router along the LSP, which would then put you on possibly the same LSP. You would then pop off the end of the LSP and be returned by normal routing to possibly the third router along the LSP ... kind of neat but undesirable behaviour.

Anyway, source routing and MPLS LSP's are somewhat orthogonal but source routing would I presume work if you did not specify any of the routers along which the LSP already flowed in the source route, otherwise it would loop around a bit before getting to its destination.

Cheers,

Peter Ashwood-Smith

-----Original Message-----
From:   mgoel@hss.hns.com [SMTP:mgoel@hss.hns.com]
Sent:   Thursday, April 26, 2001 6:50 AM
To:     mpls@UU.NET
Subject:        IP Source Route Option





Hi All,

I have a small doubt. Let an unlabelled IP packet with IP source route option
enabled comes in MPLS domain. Let the packet is assigned to a LSP (say numbered
1). While traversing the MPLS domain, packet will not go to the Network layer,
thus the LSR in between the ingress LSR and egress LSR cannot insert their IP
addresses in the datagram. So does MPLS supports IP source route option or it
does not support it?

Thanks
Mohit Goel