How to insert jitter for certain RTP streams

[bkirnum]

Got a Linksys E8450 and installed OpenWRT. Have 3 MacBooks and LAN connected to it. Basic setup works fine where I have a media server running on one MacBook and media clients on each of the other two. RTP capture at media server shows very little jitter and no packet loss, a very clean environment. Now I would like to be able to insert impairments from one of the clients, specifically jitter. I had tried using tc netem but could only seem to get jitter out the LAN port. Is it possible to control jitter coming into the router from just one of the clients?

Thanks,
Bob

[flygarn12]

You must be the first one here wanting to insert jitter!? Why?

[lleachii]

@flygarn12

You must be the first one here wanting to insert jitter!?

Nope, in fact the OP asked about 3 weeks prior to this thread (I was searching for the old topic and shocked to find it's the same user):

@flygarn12

Why?

Simulating network impairments

I need to simulate network impairments between two computers (likely using tc-netem). Would like something which is relatively easy to set up but powerful enough for the job. Hoping to not have to spend hundreds of dollars. Any suggestions? Thanks!

And here's another topic from someone else (but another user there appears to have deleted most of their portion of the discussion):

• Change latency using NETEM - #11 by Hudra

@bkirnum

Is it possible to control jitter coming into the router from just one of the clients?

If they are on the same network/bridge/VLAN, no.

You can:

• Place them in separate networks
• Make the configuration on the client

[flygarn12]

So this gent is not the first but instead the only one…
I still don’t get the point of inserting jitter, doesn’t we want as little jitter as possible!?

Not to brag but standard in this country is 0 or maybe on a bad day 1ms in jitter and never any packages loss and that is on pretty much a public national level.

One easy solution is to buy like 100000km of opto fiber for the client you don't like and make him connect to the router with that fiber. Then he gets about 330ms of jitter and he can sit on the other side of the table and complain.
The length of the cable or fiber all depends on how much jitter you want to give your client?

[lleachii]

@flygarn12

So this gent is not the first but instead the only one…

Well, he's the second that I found, actually.

@flygarn12

opto fiber for the client you don't like and make him connect to the router with that fiber. Then he gets about 330ms of jitter and he can sit on the other side of the table and complain.
The length of the cable or fiber all depends on how much jitter you want to give your client

This works too!

Good idea!

@flygarn12

I still don’t get the point of inserting jitter, doesn’t we want as little jitter as possible!?

I assumed "simulation".

(I'd just try to find a video stream from the far-East, use a VPN with a known endpoint far away, etc.)

[bkirnum]

My company builds cloud services for media processing and real-time communication. I need a local, controlled environment for testing and debugging the robustness of our software in response to jitter, packet loss, etc. Was hoping this setup would allow me to run tc netem for this purpose but it seems it may not.

[lleachii]

@bkirnum

My company

Donations

[murraydr44]

speedtest.net's test results show jitter for wireless tests. Introduce jitter with a wireless bridge?

[flygarn12]

No it doesn’t show measured jitter on wifi just because you use wifi, if you have jitter you have low quality equipment or something else that is inducing jitter.