[j-nsp] juniper router reccomendations

[Adam Vitkovsky]

> From: Saku Ytti [mailto:saku at ytti.fi]
> Sent: Friday, July 29, 2016 1:58 PM
>
> On 29 July 2016 at 15:00, Adam Vitkovsky <Adam.Vitkovsky at gamma.co.uk>
> wrote:
>
> Hey,
>
> > Ok that makes sense, but I have read somewhere that on MX80 (not sure
> > about MX104), only MICs have H-QOS (but I'd expect the H-QOS to be
> > available in the WAN out rather than Fabric out direction).
> > So I probably remember it the other way around it's the integrated
> > ports that only support H-QOS then?
>
> You remember correctly.
>
> It's not HW restriction, QX does not care where the packets came in.
> Problem is QX is isn't fast enough to do deal with 40Gbps OUT. Then they
> added IN support. So It would need to support 40+40+40+40, to do
> in+out on all ports, when it can't support 40.
Yeah nowhere close to that.
Now that I think about it I agree that it doesn't matter whether the traffic comes to LU from WAN or Fabric resulting in LU classifying the packet and sending chunk pointers to QX to maintain queues, so in this sense QX couldn't care less where the traffic came from.
It's just if QX has to maintain queues for both Fab-to-WAN as well as WAN-to-Fab the available delay buffer memory would have to be divided to two and the QX would have to process twice the amount of chunk pointers per second.
So yeah all in all probably not a good idea to enable it in both directions.

> I guess they just wanted to avoid people oversubscribing QX too much,
> probably had to add code to create the limit.
>
Yeah that's definitely it.
Though on Gen2 Trio you could select which ports will use QX (rich queuing) so it's not all or nothing anymore and you can carefully chose how much traffic does the QX have to deal with.


adam








        Adam Vitkovsky
        IP Engineer

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