[c-nsp] ASR9k Bundle QoS in 6.0.1

Adam Vitkovsky Adam.Vitkovsky at gamma.co.uk
Thu Jun 16 14:37:49 EDT 2016

> Robert Williams
> Sent: Thursday, June 16, 2016 5:18 PM
> > Your customers are running MPLS between their sites - across L2 MPLS
> provider Links?
> > This is something that I also want to do as an enterprise man, but was
> always worried about MTU etc.
> > Just so I understand - this also causes a hashing issue for the ISP's as the
> sources and destinations are many labels deep - and you only see the /30 IP's
> I have chosen for the links across your backbone?
> Yes that's correct. The 9K goes into the frame until the src/dst/ip/port then
> hashes based on that. However, it's actually unknowingly using the
> 'customer' MPLS adjacencies, not the underlying real 'end-user' data (for
> want of a better term). So the match is always the same.
> The most interesting effect we see from this is after a port flap or
> configuration change as the MPLS-TE tunnels optimise without being aware
> of the bandwidth within them which can or cannot be etherchannel balanced
> successfully. Thus, we have some 10G tunnels that traverse 4 x 10G physicals,
> but sometimes the whole 'tunnel' containing one customer adjacency may
> land on just one physical member of a 10G bundle.
> Alternatively, you can try to 'motivate' the customer to build 2 or 4 (or more)
> adjacencies between their edge boxes and use ECMP. Giving you a
> reasonable variety of IPs to has with. However, you still can't guarantee that
> the 9K will balance these out nicely for you. They may still finish up with
> 3:1:0:0 when it gets to 4 x 10G the physical layer.
> As an aside, in one case we finished up mapping a customer 10G service
> (site-to-site) to it's own 10G port pair on our DWDM core, for this precise
> reason. Does seem a little crazy with technology today, but no crazier than
> my 'limit a bundle to a single total rate per class for all the member ports'
> original issue :)

Hi Robert,

Bundles are tricky. Have you considered separate IP links instead? Cause then you could do MPLS-TE/SR tunnel over each link and forcing PWs into tunnels to get proper PW-to-Link distribution.


        Adam Vitkovsky
        IP Engineer

T:      0333 006 5936
E:      Adam.Vitkovsky at gamma.co.uk
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