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Simulating Latency / Delay

I need to drive up my latency between a link to test an applications behavior. I have multiple routers I could use (1x3825 & 3x2801). I could use traffic shaping, but that doesn't let me input a latency delay in ms between packets... Any other thoughts??? Is there a way to put in latency in a bridge-group?

Community Member

Re: Simulating Latency / Delay

As you say, traffic shaping is an option and imho would be your best bet here.

You could also alter the MTU of the links, which in turn would increase fragmentation and reduce efficency (thus increasing latency).

Unfortunatly these techniques will only give approximated behaviour and will not produce hard and fast data (e.g. it'll be hard to simulate propogation delay if using disimilar physical mediums). If you need that level of assurance then building a lab that is closely matches the production system may be required.

The trouble you'll face in general is that unless you use a packet generator tuned to simulate your production network, any test you do in isolation will be based on disimilar operating conditions. In which case the best you can hope for is an approximation of behaviour.

Depending on whether you're testing the application itself or its impact on the network you could use a network analysis system (e.g. Smartbits - to introduce a sending delay between packets or simulate general operating conditions.

Again, depending on your test objectives you could also write a TCL script to fluctuate the QoS parameters over time.



Community Member

Re: Simulating Latency / Delay

its not really a cisco solution but ive used monowall to do just exactly this many times in the past

sometimes its a bit hard to get working on spare hardware you may have due to compatibilty but ive had sucess with running it in a vmware virtual environment

the bad news is that it wont shape things in a bridge setup.

hope that helps somewhat...

ps; on a side note... it sounds as though you have some traffic shaping experiance, i dont suppose you have any insights into a post i just made ?

Community Member

Re: Simulating Latency / Delay

oh. nevermind. i see your post was from 2005.. youre most likely long gone and not looking at this any longer ...

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