The MPLS WG Archive

[Jeff Bush <jbush@mitre.org>]

Hello:

My colleagues and I have some questions on on MPLS that are more of a
generic nature - as we are getting more knowledgeable about the
subject.  Your comments would be most appreciated. We apologize if some
topics have already been discussed on the list.

1.  Is there any issue with MTU conflicts as shims are added to the
original packet?

2.  Is it true (as some ISP folks have stated) that MPLS VPNs are not
scalable?

3.  Is MPLS currently providing traffic engineering only - using TOS
bits.  Are there deployments out there that provide QoS (voice over
data) using MPLS (without ATM, say)?

4. Does LDP create a huge state machine and potentially clog the network
(especially if the one or more LSPs are disturbed or disconnected)? 

5. If there are more than one LDP used in a hybrid environment, could
there be conflicts regarding LSPs? 

6. Does variable length header processing cause high latency?

7. How does MPLS gets deployed in the "last mile" - between the egress
router and the end-system - say on the LAN?

8. What are the overhead issues of MPLS with respect to path computation
as against node processing?

9. Say you have a path (LSP) established between four LSRs, A, B, C, and
D.  Then when packets are being transmitted on this LSP, C fails.  What
happens then?  We would be trying to establish another LSP by sending
LDP packets to D from B.  Or should this be A which established the LSP
first?  And, what happens to the packets in transit?

10. Is it true that MPLS is good for the network backbone only?