half-duplex talk path?

Oct 11, 2005 9 Replies

Has anyone else noticed that sometimes the talk path is half duplex? One of the uses here was complaining that the other side didn't appear to hear her, assumed it was a prank call and hung up. She called back a few minutes later and things were fine.


-wolfgang


"Wolfgang S. Rupprecht"

On what system..? It would help if we knew what network and equipment you are referring to.

Ivor

Wolfgang S. Rupprecht skrev:

Yes - yes - yes.

I thought it was always like that and that you had to learn to live with it.

Tine

I was trying to get a feel for how common half-duplex talk paths were and perhaps have someone propose a model for why they would happen. Embarrassing the SIP gatewaying service I was using wasn't my intention. Leaving out voip service provider names, the talk path looks like this:

grandstream_budgetone -> asterisk_current -> VOIP_service_provider

All devices have routable IP addresses and asterisk is setup to use "can-reinvite" to short-circuit the RTP path, allowing both RTP endpoints to talk to each other directly.

-wolfgang

Thanks! I wasn't sure how common this was. I hadn't heard it mentioned yet.

Seems like this has the potential to really annoy the people being called.

-wolfgang

Ivor Jones skrev:

I'm not very experienced in this. I just downloaded SKYPE, put on a headset, paid 10 euro, and started to talk.

I have an ADSL line with 256/256 speed.

Is this officially a "talk path" or am I answering the wrong thread?

Tine, Denmark

I've never come across any VoIP providers that aren't full duplex. Are there really providers like this?

They are only half-duplex when things are going badly. A second call a few minutes later might work fine.

A second observation is that sometimes the talk path is just slow to open. One can hear the other side, but it takes 5-10 seconds or so for the other side to start to hear you. Often the other side has decided it is a prank phone call and hung up, so it isn't clear if the bad calls would have eventually started working.

-wolfgang

A "talk path" comes from old telephone jargon where one has two pairs of wires used to carry the conversation, one in each direction. Each direction is a "talk path". If one pair is broken one party can hear the other, but the other can't hear the first. With careful software design, this "feature" now appears to be available for VOIP too. ;-)

-wolfgang

snipped-for-privacy@yahoo.com skrev:

In may case it turned out it was my sound board and I didn't know. I bought a skype telephone and don't have a problem anymore.

Tine

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