[c-nsp] IP SLA Scalability

[Mikael Abrahamsson]

On Thu, 21 Oct 2010, Ben Steele wrote:

> Has anyone ran a rather large amount of SLA probes from a router who can
> comment on the cpu performance characteristics on how it scaled for your
> particular platform?

You should really contact your account team to get a comment from them. 
I've spoken to the product manager for IP SLA and I was quite surprised by 
some comments I got regarding the functionality and the thinking/handling 
of it within Cisco.

> Specifically looking to see if its feasible to expect a router to be able to
> go upwards of 500+ simultaneous monitors(looking at a total of about 10-15k
> pps of udp-jitter probes in total).

I'd say Cisco doesn't have a product that has been designed to scale this 
far and is supposed to work for prolonged sustained testing like I guess 
you want to do. They consider 300 second of 50pps testing "extremely long" 
and if single high jitter packet in that "long" test occurs, the opinion 
seems to be that fixes for that is on a best-effort work priority. It's 
not something they really test on all platforms and all code.

> Before anyone says that I should look at another vendor/solution, this 
> is already being done in the background. I am purely after what a Cisco 
> router can offer in this regards, i've never come across more than about 
> 20 sla probes on a router before so am interested to hear the results.

If you're doing this in an MPLS VPN scenario, you might want to make sure 
you test your code so it has timestamping for arrival time for packets 
even if they are labeled. I ran into this on a 7301 5 years ago, took 14 
months for that TAC case to complete with the answer that "timestamping 
wasn't done in labeled packets" and as a result, any cpu spike would cause 
jitter in the measurements. Converting the router to IP only (putting it 
behind a MPLS PE router) "solved" the problem.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se