How to use two OBI110 as a Local Area Network Intercom
ianobi:
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Is there a buffer adjustment on the OBI I can set?
Not that I know of. I'm guessing that OBi design is simply optimised for the codecs it uses. Pure data was never a consideration.
I have never really understood this setting:
Service Providers > ITSP Profile A > RTP > DSCPMark
It has something to do with DiffServ, which has something to do with QoS. It's default value is 46. Any DiffServ experts out there?
QBZappy:
Lots of other interesting things on that site as well.
DiffServ -- The Scalable End-to-End QoS Mode
http://www.cisco.com/en/US/technologies/tk543/tk766/technologies_white_paper09186a00800a3e2f.html
ianobi:
Wow! I drifted into this thread looking for beer and pizza and ended up with homework :D
Pinky:
Guess what? The modems work on the OBIs! Two identical modems on OBi-100s
9600 baud totally stable. I have not used the automatic ringdown config outlined above but I tried it using the direct OBItalk numbers as well as my DID PSTN #s on voip.ms. The modem training sequence takes about 20 seconds but it locks on and stays. I've left them connected overnight and all day on direct mode and they're totally solid.
I think the long training is due to the fat jitter buffer in the OBI. The modem test indicates about 450-500ms delay- and that's when they are going direct to each other on the same switch.
It would be great to see Obihai make the jitter buffer length setable in the next firmware release. Seems like that should not be too big a deal considering all the other variables you can set in these bad boys. The Obi seems like an extraordinarily well thought out piece that delivers for very little money.
I think my next step is to get them registering with an Asterisk server and let the server do the interconnection.
ianobi:
That's interesting. Using OBiTALK the default codec would be G711U for both legs of the call so uncompressed all the way. G711U and G711A are widely used by most voip providers, so looks like your idea is workable for dial-up end to end modems at 9600 baud or lower.
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Wow! I drifted into this thread looking for beer and pizza and ended up with homework :D
Well I did my homework, so kindly provided by QBZappy. I now understand why the default for this is 46:
Service Providers > ITSP Profile A > RTP > DSCPMark: 46
46 is the best setting for voip. I now don't understand why the setting is configurable, but I'm not going to do any more homework on this issue :)
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