Congestion/latency-aware routing for MPLS?

Thu Oct 19 03:02:27 UTC 2023

I remember some time back Juniper had a feature that would listen to snmp? from the radios and adjust ospf cost. My search foo is failing right now but I think they had a paper on the topic also.

On Oct 18, 2023, at 6:13 AM, Adam Thompson <athompson at merlin.mb.ca> wrote:

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) 
https://www.merlin.mb.ca <https://www.merlin.mb.ca/> 
Chat with me on Teams <https://teams.microsoft.com/l/chat/0/[email protected]> 

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