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# Thread: network bandwidth simulation

1. ## network bandwidth simulation

Hi

if need to simulate the network bandwidth,
do i need to get the link speed or individual machine speed*# of vusers?

Example: A company has a connection 100MB which is shared among 100 users.

consider if we need a test with 10 virtual users of their corporate application if we give 100MB as the bandwidth, this may give incorrect results as 100MB will be shared among 10 virtual users...where as in actual it has been shared among 100 users.

So, in this scenario, we need inidividual average speed (e.g. 1 MB) * 10 and consider this (10MB) as the bandwidth.

Is this understanding correct?

2. ## Re: network bandwidth simulation

you dont always get that bandwidth, i have 100 mbps at my home but it is never so fast.Never used such a maths.

3. ## Re: network bandwidth simulation

Network simulation = Shunra. Their tools are test tool independent and they are pretty much the defacto industry standard for LAN/WAN simulation.

http://www.shunra.com/products

4. ## Re: network bandwidth simulation

if the internet connectivity speed of node is E.g 256Kbps

if i want to simulate for 10 users, do i need to derive a value like 256*10 or if we give 256 as a custom value, will silk performer consider the same value for each user (or wil SP will consider ~ 256/10 rate)?

5. ## Re: network bandwidth simulation

same value will be considered.i am not sure what is your objective here, but concepts involved in network testing is somewhat different and involves generally number of byes received and sent by routers, switches and whatever you have inbetween.
you can see the results by running the test with single user with 256kpbs and with 10 users with 256 kpbs for 10 mins or less.

6. ## Re: network bandwidth simulation

Still my confusion is,

With 256Kbps, if 1 user does 20 transactions,

in order to check the performance drop for 10 users we would need

a) 256*10 Kbps OR
b) still 256Kbps

If the answer is b), will SP simulate 256Kbps for each user thus we can ensure the bandwidth is consistent during 1 and 10 user tests. Pls correct me if iam wrong

7. ## Re: network bandwidth simulation

Good Question!

But I dont have any answer for that. Because we should not extrapolate the things in performance testing. we need to stick to the real time scenario...

If 100 users is the real time sccenario then what is the need and use to test with 10 Users?

But if you are trying to figure out any issues... like we are no getting any errors for 10 user test execution but we are getting errors in 100 users test execution. In that case what you are doing is correct. we can give a try like that. But for normal testing purposes we should avoid extrapolation

8. ## Re: network bandwidth simulation

So as per ur understanding would it be a) or b)?

9. ## Re: network bandwidth simulation

Answer is A but you need to understand that network testing tools are different so are bandwidth tools.

10. ## Re: network bandwidth simulation

i dont have a or b...

What i came to tell is, it is not fair to execute the actual test runs with such reduced number of users against reduced bandwidth...

we can do like that for executing some smoke tests at the debugging time... at that time also what you can do like
1. executing 10 users against 100 MB bandwidth
2. if it is ok, try executing with 50 users
3. if it fails, try with 25 users (just trail and error method)

Then it will give you the solution that howmany users can accomodate within that given bandwidth.

Also you need to check the ramp-up time of users while executing smoke like this... because we need to check the bandwidth usage when all the users are in steady state and doing some major transactions...

Hope this helps you?!

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