[Asterisk-Dev] TDMoE explanation/documentation/implementation ?

[Paul Cadach]

Hello,

> Anybody can provide TDMoE documentation ?

I don't think this exists... Most powerful documentation is sources...

> Is TDMoE similar to some telco's standart, especially for forming frames.

Not sure. ztd-eth does encapsulation to real ethernet frames, while for example RAD devices (as documented) uses TCP and
could run over WAN, not LAN only as ztd-eth.

> Is TDMoE really a kind of TDM (how/algorithm ?) encapsulated in Ethernet
> frame.

Mostly looks like... TDMoE is point-to-point connection, single end is "master" device which located on host provides
real clocking (i.e. have installed Zaptel hardware device(s)), other end is "slave" which gets timing from "master" one.
Zaptel hardware generates host interrupts every 1 ms and passes audio/etc frames to the host system. ztd-eth driver
delivers data over Ethernet at the same times (+/- something due to processing audio frames within interrupt handler
while networking code requires to operate outside interrupt routines), so TDMoE could be treated as real TDM structure
(and, Ethernet link must not be overloaded to minimize jitter and eliminate packet drops on network side, best if TDMoE
runs over point-to-point Ethernet link made with cross-over cable).

Also, ztd-eth doesn't handle CAS signalling as it done with E1/T1 hardware (i.e. there is no timeslot #0, but emulation
for CAS bits is available), so not all features are possible (for example, V5.2 uses/requires manipulation of Sa? bit at
TS #0, and it WILL NOT passed over TDMoE).

I'm using TDMoE to pass PRI trunk (30 B + 1 D channels), all works more-or-less fine for me.


WBR,
Paul.