[c-nsp] Getting ready to pull the trigger: RSP720/SUP720

[Phil Mayers]

Rick Ernst wrote:
> The stars are starting to come into alignment and I'm about ready to
> order equipment for a network refresh.
> 
> I currently have a edge/core/aggregation model with 7206VXR/NPE-G1 at the
> edge, 7500/RSP16/GEIP+ in the core, and various aggregation devices from
> 5500/RSM to 7500/RSP8 and dialup, DSL, etc.  We are migrating from OC-3 to
> GigE at our edge.
> 
> We currently push about 300mbs in each direction and that is expected to
> grow by at least 100mbs this year.  The rate of growth has increased
> dramatically.
> 
> I'm planning on collapsing the border/core into a pair of
> 7600/Sup720-3BXLs, and it looks like they will be almost idle with this
> amount of load.
> 
> The problem I am running into is spec'ing the aggregation layer.  Almost
> all of our traffic is ethernet now, and all the interfaces need
> bi-drectional rate-limiting/traffic-shaping/policing.  We have a variable
> bandwidth model and need to cap traffic at 1Mbs granularity. 1,5, and
> 10Mbs connections are common, and 20,50,100Mbs connections exist with a
> 200Mbs pipe in process.
> 
> The only traffic management I have used in the past is Cisco's rate-limit,
> and it is very CPU intensive.  I'm trying to find out if a Sup720/RSP720
> can handle hundreds of interfaces, each being rate-limited in some manner.
>  The Cisco data sheet is vague about "some features" and "QoS" in
> hardware, but isn't specific about what features are in hardware.
> 
> Is the Sup720 (RSP720 a better answer?) sufficient?  Is traffic-management
> in hardware, and should I be looking at rate-limit or some different
> mechanism?

QoS on the 6500/7600 platform is a pretty involved topic. You will want 
to read up on it carefully. See:

http://www.cisco.com/en/US/docs/routers/7600/ios/12.2SR/configuration/guide/qos.html

Assuming you're talking about "LAN" lincards e.g. 67xx series, then:

  * qos is done in hardware

  * the capabilities are reasonable, but limited and a bit complex 
because it's done in hardware

  * the capabilities depend on the exact model of linecard - some have 
fewer queues, smaller buffers, only 6708 support ingress DSCP mapping to 
queues etc.

In particular, you want to watch ingress rate limiting very carefully. 
My (limited) understanding is that it'll be tricky to do what you want.