[c-nsp] 7600 Linecard decisision

Sun May 6 03:45:38 EDT 2007

Phil, thanks for your answer,

i read that guides but it's hard to channelize this amount of information.

2007/5/6, Phil Bedard <philxor at gmail.com>:
>
> Take a look at the "PFC QoS" and "MPLS PFC QoS" guides on cisco.com.
>
> The PFC can classify incoming packets based on EXP, .1q CoS, DSCP, or
> IPP.  It uses an "internal DSCP"
> value as an interim value to use for further processing. You can
> create EXP-to-DSCP
> tables to map EXP to the internal DSCP.  When you output on a LAN
> interface with WRR/DWRR you create a
> "DSCP to CoS" table, and then you map a CoS to an output queue and
> WRED threshold.   The PFC can also set
> the EXP value in the outgoing packet as well as IPP, DSCP, or CoS.
> In certain trust modes it will just copy the
> incoming DSCP and EXP on egress.   In short, it does deeper packet
> inspection than just the first L2 header when
> doing QoS, and will probably satisfy  your requirements for MPLS QoS.

Does that mean that the PFC uses the the EXP to DSCP/CoS mapping on
every core router to queue the labeled packet in the right queue?
Or does that mean that it maps the EXP to DSCP/CoS but can only queue
on that value if the label is removed on final LER egress and not in core
where
no imposition/disposition is done?

The Sup720 PFC has 1 priority queue, 4 normal queues and 8 thresholds
> per queue.   One caveat to the priority queue
> on PFC QoS is that it's like a Cat3550/3750/etc. where the priority
> queue is emptied before normal queues, even in
> non-congestion situations...

I thought LLQ behaves exact the same way.

On the SIP400 GigE ports, you get all the fancy queueing methods like
> CBWFQ/LLQ; those ports also
> give you enough memory to buffer up to 200ms line rate.  They also do
> shaping like a WAN port.
> The LAN-based cards aren't anywhere near that, but the cost isn't
> nearly as high.

Yeah, the SIP costs for a few GE ports are very high :-(

Reading your original question, I would probably do the SIP400/OC3
> for the SONET uplink, and unless you really need
> very good QoS, go with the LAN-based WS-xxxx blades for your GigE.
> The ports are very cheap and port-channels work
> well.   The FlexWans have known to be buggy, I'd stay away from those.
>
> Phil

Thanks Phil for your advice.

On May 5, 2007, at 5:16 PM, Peter Basquiat wrote:
>
> > 2007/5/5, Arie Vayner (avayner) <avayner at cisco.com>:
> >>
> >>  PFC can do policing (actually it has some different policing
> >> options over
> >> the regular policing in regular IOS), but it can't do shaping.
> >> Queuing is done on the egress linecard.
> >>
> >
> > As i understood the 1pXqXt WRR/DWRR queueing is only possible with
> > COS-Mapping. Does this mean that's not possible in MPLS core
> > to prioritize? I assume that on MPLS swapping LSR only EXP values are
> > available and not DSCP or Prec.
> >
> > Arie
> >>
> >>  ------------------------------
> >> *From:* Peter Basquiat [mailto:peter.basquiat at googlemail.com]
> >> *Sent:* Saturday, May 05, 2007 21:33 PM
> >> *To:* Arie Vayner (avayner)
> >> *Cc:* cisco-nsp at puck.nether.net
> >> *Subject:* Re: [c-nsp] 7600 Linecard decisision
> >>
> >> Arie, thanks for your answer.
> >>
> >> When comparing this two different QoS models with each other,
> >> where are
> >> the main differences?
> >> Are there real disadvantages compared to "normal" CBWFQ?
> >> I believe that I will never use all possible classes in CBWFQ. It
> >> seems
> >> that PFC-QoS only supports
> >> up to 8 queues, this would be enough for our purposes.
> >> Per (Ethernet Subinterface/Frame-Relay VC) Queueing/Shaping/Policing
> >> should be possible, i dont think
> >> that the PFC isnt able to do that, right?
> >>
> >>
> >>
> >>
> >> 2007/5/5, Arie Vayner (avayner) <avayner at cisco.com>:
> >>>
> >>> Peter,
> >>>
> >>> The main difference is that all the "native" LAN modules on the 7600
> >>> (meaning all the WS-X65/67 etc) can't actually support the "normal"
> >>> class-based QoS model, but use a different model.
> >>> You can read about it here:
> >>> http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/
> >>> swcg/q
> >>> os.htm
> >>>
> >>> This has to do with the way the packets are being handled inside the
> >>> device. For the native LAN modules, all QoS functionality is done
> >>> on the
> >>> PFC, and it supports only the above QoS functionality.
> >>>
> >>> When using SIP modules (or older OSM/FlexWan modules), the QoS
> >>> functionality (as well as other things such as MPLS features) are
> >>> enhanced by the fact that the SIP has extended processing
> >>> resources on
> >>> the module and the software allows using this processing power for
> >>> features which are not available on the native LAN modules. This
> >>> explains the additional cost - the SIPs have much more hardware
> >>> on them
> >>> (such as processor, memory etc)
> >>>
> >>> I think you can find some interesting reading on the SIPs here:
> >>> http://www.cisco.com/univercd/cc/td/doc/product/core/
> >>> cis7600/76sipspa/si
> >>>
> >>> pspasw/index.htm
> >>>
> >>> Arie
> >>>
> >>> -----Original Message-----
> >>> From: cisco-nsp-bounces at puck.nether.net
> >>> [mailto: cisco-nsp-bounces at puck.nether.net] On Behalf Of Peter
> >>> Basquiat
> >>> Sent: Saturday, May 05, 2007 19:09 PM
> >>> To: cisco-nsp at puck.nether.net
> >>> Subject: Re: [c-nsp] 7600 Linecard decisision
> >>>
> >>> It's not really clear in which direction our QoS stuff will
> >>> expand. At
> >>> the moment Iam thinking on typically class-based wfq on core and
> >>> edge.
> >>>
> >>> What are the differences regarding QoS on the WS-X6582-2PA
> >>> compared to
> >>> SIP400/SPA?
> >>>
> >>> Other question: talking about features, what's with the WS-X67xx
> >>> modules, are there other/more features available or do they have
> >>> only
> >>> more bandwidth?
> >>>
> >>> SIP400+SPA is much more expensive, without knowledge about the exact
> >>> advantages it's really
> >>> hard to judge.
> >>>
> >>>
> >>>> Peter,
> >>>>
> >>>> Going for the SIP/SPA combination would allow you more features
> >>>> especially
> >>> with regards to QoS and VPN PE-CE support.
> >>>> Can you expand a bit about what kind of core/access QoS you
> >>>> require?
> >>>>
> >>>> Arie
> >>> _______________________________________________
> >>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> >>> https://puck.nether.net/mailman/listinfo/cisco-nsp
> >>> archive at http://puck.nether.net/pipermail/cisco-nsp/
> >>>
> >>
> >>
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