Re: Question on Software and hardware queue

Nick,
some of your questions are mixing router and switch architectures.
Routers are more homogeneous, switches are less so.

Nick Jay @ 26/7/2011 15:34 -0300 dixit:
> Hi All,
>
> I am trying to understand the difference between the terms
> software
> queue
> hardware queue
> ingress queue
> egress queue
>
> So far my understanding
> says:
> * When no congestion, the packets are directly copied into the hardware
> queue in a FIFO manner without taking it through the software queue. Only FIFO
> is possible in hardware queue and there is only 1 hardware queue. (Is this
> correct?)
This is the router way.
Switches do have many (hardware) TX queues.

> * Software queue are defined as per the number of classes you define
> manually. Are ingress queue and software queue one and the same?

Router way, you can define software queues to be used when congested.
Ingress queues, if memory serves, only happen on high end switches with
some kind of line interconnection bus that is not non-blocking.

> * Each
> physical port have a set of tx and rx queues depnding on the platform they
> could be 2Q2T or 1P2Q2T. Are these ingress and egress queues?

Usually egress, could be ingress (again, switches).

> * Is egress and
> hardware queue one and the same? I think they are not then what is the
> difference?

In routers, only one hardware (egress) queue.

> Can anyone help me to understand the clear distinction between
> these terms or please share a link which can clearly show the queue
> architecture?

It depends on which architecture you are looking at.
A complex one to have a variety of things to see is the 6500/7600 chasis.

-Carlos

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
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