[c-nsp] SLAs on a Gigabit Ethernet link

[Rolf Mendelsohn]

Hi Adam,

I think your're looking / thinking about IP when you should focus on the 
radio's ;>).

Firstly verify that they are full gigabit capacity (i.e. Gigabit ethernet 
capacity not Gigabit radio capacity).

Secondly verify that the radios are actually full-duplex (most are not!).

Lastly your assumtion that the link 'either passes traffic or doesn't' is also 
incorrect, as you might experience interference (leading to packet loss), or 
other related radio problems (perhaps changing the modulation from 256QAM (in 
you case 1G) to 64QAM - perhaps 100M or 16QAM - 16M (just an example).

So the best way of monitoring real performance and problems on the link would 
be to poll the SNMP MIB's on you radio kit and not on your ciscos.

HTH

cheers
/rolf

On Monday 18 September 2006 22:23, Adam Greene wrote:
> Hi,
>
> Perhaps this is asking a lot, but if anyone is able to point me in the
> right direction or provide some good summary answers, I'd be grateful.
>
> I need to generate a Service Level Agreement for a customer that we're
> going to be providing a point-to-point link for. On either end of the link
> will be a 3560G. The link will actually be wireless, via Gigabit radios,
> but that's not so relevant. We'll be connecting two branches of a Radiology
> department. They plan to pass large MRI files between the two locations.
>
> First off, I am trying to figure out how to conceptualize the SLA. Network
> availability is a no-brainer (the link passes traffic or it doesn't).
> However, the customer wants to be sure that the link is always performing
> well, and that the maximum bandwidth capacity of the link is always
> available to him.
>
> I'm thinking of making use of Cisco's IP SLAs functionality to monitor any
> performance guarantees I may make to the customer.
>
> Some questions:
> -    do the 3560G's even support IP SLAs? According to CCO, all IOS
> supports it (except for some obscure exceptions), but I don't find any
> reference to it in the 3560 configuration guide, and when I grope around on
> a 3750 in the lab, the switch seems not to support SLAs ("sh ip sla" is an
> unknown command; "ip sla ..." is an unknown configuration command)
> -    it seems that the UDP jitter operation could be a good way to get
> information about packet loss and latency on the link. However, I'm not
> sure that obtaining these values will necessarily enable me to provide the
> customer with exactly what he needs. The customer needs to know that the
> link supports up to 1Gbps of data traffic (minus any overhead) at all
> times; if the customer himself is maxing out the link and I measure latency
> and packet loss, the results could appear poor. On the contrary, though,
> the link would be doing exactly what it is supposed to be doing: passing
> ~1Gbps traffic.
>
> Perhaps one way to approach monitoring of the SLA could be to continuously
> graph the utilization of the link and then associate the utilization values
> to the packet loss and latency at any given moment. But then it seems that
> I would need an algorithm of some kind to determine what acceptable latency
> and packet loss are on a 1Gbps link at varying traffic loads.
>
> Does anyone have any tips about how to approach these issues?
>
> Thanks,
> Adam