[j-nsp] A conceptual advice on QoS is needed

[Adam Vitkovsky]

> Victor Sudakov [mailto:vas at mpeks.tomsk.su]
> Sent: Wednesday, February 17, 2016 12:32 PM
>
> Adam Vitkovsky wrote:
> > >
> > > We have Juniper switches interconnected by a transport network (NEC
> > > equipment mostly). The nodes of the transport network are Ethernet
> > > switches in their own right, they have 4 or 8 interface queues and
> > > can do priority queueing and/or WRR queueing based on 802.1p
> > > codepoints in received frames.
> > >
> > > Now if you had to implement QoS policies, where would you do the
> > > actual
> > > prioritization:
> > >
> > > 1. Classify the frames on the Juniper switches, but do the actual
> > > queueing/prioritization in the transport network.
> > >
> > > 2. Configure one FIFO queue on the transport network nodes and do
> > > both classification and prioritization on the switches.
> > >
> > > It may be important to know that most switches are connected to the
> > > transport network by Gigabit interfaces, but the real throughtput of
> > > the transport network itself is about 150 Mbit/s.
> > >
> > > But there is another branch of the transport network where all
> > > interfaces on the nodes are 100BaseT, so the switches are connected
> > > at
> > > 100 Mbit/s.
> > >
> > > Thanks in advance for any opinions.
> > >
> > Victor,
> >
> > If your network carries traffic of higher priority that is interleaved with
> traffic of lower priority then the below questions are relevant:
> >
> > 1) Can it happen on Juniper switches that BW on input > BW on output
> > (e.g. traffic incoming on multiple ports will be transmitted out one
> > port)?
>
> Very unlikely.
You mentioned that the Juniper switches are going to be connected to the transport network via 1GE interface(s)
Is the sum of inputs(edge links) less than 1Gbps(core link) please?

>
> >
> > 2) Can it happen on NEC transport switches that BW on input > BW on
> output?
>
> Most likely.
>
>
> > If yes then you need QOS (classification and scheduling)
>
> The question is, where I need QoS: before the traffic enters the transport
> switches or inside them.
>
If contention is most likely to happen on NEC transport switches then you need QOS on NEC transport switches.

adam


        Adam Vitkovsky
        IP Engineer

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