Hey all,

I've seen some forum posts saying that it wasn't possible to match on the MPLS EXP bit when in the middle of a label switched path (so only ingress and egress would ever use it due to the value being copied into the IP header). However these posts are a couple of years old, and I haven't seen any mention of it since.

Is this something that has changed in the past couple of years, or is it still not something that can be done? There are ways round this, but I'd prefer to not have to match upon source MACs and the like, given the MPLS EXP field is already there and set.

Thanks in advance for your help!

Stuart

I'll take the views without any reply to mean either no-one knows, or nothing has changed. No worries, I'll just try and find a hack to get round it....

Thanks all!

Stuart

Nothing is changed. Please describe in more details what you want to atchieve maybe it is possible.

Not a problem, a quick view of the problem I have



The above is an overview of the design I'm looking at. Nothing particularly special, but anyway. The outline is

1) The links between R1 to R2, R2 to R3, and R3 to R4 are leased lines
2) The link between R1 and R4 goes out via the public internet. Currently I'm using PPTP to establish this, partly for getting around MTU issues (using MRRU)
3) In the Primary and Secondary VLANs, there are switches, with IP phones in the primary, and standard data in the secondary
4) Leased lines are to be used when they are up, in the event of failure, traffic should reroute via the PPTP link between R1 and R4
5) The bandwidth available via the internet is much less than via leased line (down from around 100mb to less than 10mb)
6) Control traffic needs to be prioritised (already done with matching on DSCP 48)
7) Voice traffic needs prioritising over data

To take care of the tunnel only being used as a backup, I am using OSPF costs on the PPTP interface. This works well, no issues there. Also control traffic is being prioritised so no issues with that either.

The problem is I cannot separate out the voice from the data traffic when it is to go over the tunnel. To make things a little more difficult, the only place where QoS should be applied is over the tunnel, as the leased lines have more than enough bandwidth for the traffic used over it.

I have tried using a second PPTP interface solely for data traffic (and then rate limit this so that there is always free bandwidth for voice traffic), but I cannot establish a second VPLS session to a different loopback address on each router due to LDP only establishing to one address, which makes sense.

I have done a Wireshark trace to see whether there is anything different in the traffic that I could match based upon, but so far I am seeing nothing.

Let me know if you need any further info to look at this

Thanks!