[c-nsp] 7500 RSP8 Throughput Ability

[Pete Templin]

Bill Wichers wrote:

>>I have a large inventory of 7500 hardware.  I was thinking 7513, Dual
>>RSP8's with 256MB of RAM.  VIP 4-80's with 256MB of RAM.  I will be
>>using 4 PA-GE's and 1 Dual DS3 Chan cards.
> 
> I think you might run into memory issues with the RSP from all those BGP
> sessions. The only real solution to this on the 7500 platform is the RSP16
> which is expensive.

I agree, 256MB will be potentially tight.  Another key factor is the 
IP-CyBus interface is PCI, so you're limited to ~330Mbps per IP slot.

> I personally have not seen an RSP fail in active service, although I've
> heard stories... I don't think RSP redundancy alone should be a big factor
> in your decision making here, especially since you're currently using a
> 7200 w/o redundancy.

Not only have I seen them fail, but I've also had situations where a 
funky BGP AS-path regexp caused an RSP to instantly crash.  SSO was our 
savior, keeping packets flowing while the other RSP finished converging.

>>Can you all give me an idea of what a 7513 running say 200 to 300MB a
>>sec agg. traffic would see for CPU load?  Can anyone tell me what I
>>can expect for a bandwidth limitation on the backplane of these
>>chassis?  I am pretty sure I am on crack to even thinking I could do
>>this, so any info at this point will be helpful (I have 	only loaded
>>a 7500 up to around 70MB running D-CEF/IP cache flow and never been
>>happy with the CPU load).

As mentioned above, IP-slot bandwidth limit is 330Mbps.  Think through 
your traffic patterns, both normal and failure-mode, and determine if 
that's suitable.  60% CPU sounds abnormally high, if you were only 
looking at the RSP CPU.  It shouldn't be forwarding packets if dCEF is 
enabled.

> I think you could get your 200-300 Mb/s with the configuration you're
> planning, but I don't think you'll have much upgrade room. Personally, if
> you're looking at used hardware anyway, I'd look at a 12008 with a GRP-B
> and whatever interfaces you need.

I'd be worried about 12008 though - for customer-facing GE ports of any 
flavor, I'd insist on the 4GE-SFP card, which would probably exceed the 
price point of the Sup720s on the used market, especially since it's 
easy to oversubscribe it by 60%.  And channelized T3 options have some 
unique limitations that the 7500 series doesn't incur.  (But don't get 
me wrong - I love the performance of the 12008s, now that I know what 
buttons not to push).

pt