Congestion/latency-aware routing for MPLS?

[Adam Thompson <athompson () merlin mb ca>]

Using a mix of Juniper hardware...

Network provides VPLS to customer, over MPLS (obviously) in a dual-redundant-ring radio topology.  Each site is 
connected to one or more neighbors, generally with two radios, in two different bands, to *each* neighbor.  So an 
ordinary node might have 4 radios, 2 pointing in each direction.

Every single radio link has different bandwidth, different latency, and different interference characteristics.

These radio links do run at 100% capacity at least some of the time.

It's possible to set each link's relative cost in OSPF or IS-IS, of course, but I haven't found a way to make the 
router react to latency changes on one link or the other.  (Right now, I think costs are set equal so traffic will use 
both links.)  This means interference in one band invisibly diminishes the Ethernet bandwidth available and silently 
increases the latency on that link, sometimes dramatically.  This seems to do interestingly unpleasant things to the 
client's flows.

It's generally true that one band will be much more severely affected than the other, in any interference event.  
Before anyone asks, I'm told the network is a mixture of licensed and unlicensed bands, that's not changing anytime 
soon.

In a perfect world, I'd like the routers to dynamically adjust traffic balance, but even just temporarily halting use 
of the impaired link would be helpful (or so I believe right now, at least).

Is this a pipe dream?  I'm not seeing anything in JunOS that could accomplish this...  I'm not even sure if a mesh 
protocol could handle dual active links like this?

Ideas, comments, etc. all appreciated.

Also, I'm not the direct operator of use network. I'm involved, but mostly just trying to help them find better 
solutions.  Nor am I an MPLS expert, as is obvious here.

Thanks,
-Adam


Adam Thompson

Consultant, Infrastructure Services

MERLIN

100 - 135 Innovation Drive

Winnipeg, MB R3T 6A8

(204) 977-6824 or 1-800-430-6404 (MB only)

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