[asterisk-dev] TDMOE protocol

Antonio potxoka at gmail.com
Fri Dec 18 12:14:12 CST 2009

On 12/11/09 13:44, Andrew Kohlsmith (Mailing List Account) wrote:
> Actually TDMoE is pretty straightforward.
> Aside from the ethernet header, there is a very thin TDMoE header which
> describes type, sub-address (span # basically), number of channels, format,
> signalling, alarms and the ever-important sequence number.  The rest of the
> payload is just a linear array of DAHDI_CHUNKSIZE (8 bytes) channel data.
> The sequence number (seqno) is just a number which is ever-incrementing and is
> used by the receiving side to ensure that no frames were missed.
> The rest of it is VERY much like normal TDM circuits. The alarms operate the
> same way, the signalling operates the same way... if all it is that you're
> interested in is the bits on the wire, ztdynamic.c is what you're after (not
> sure what it's called in DAHDI offhand.)
> I did a fair amount of work with this a number of years back. If you have any
> specific questions I'd be happy to help.
> -A.

If, before writing the post on the list see the source code in svn but 
you have not program in C and do not fully understand it. I have also 
been looking catches tcpdump or similar to this, to see if some examples 
could understand, but I have not really got :-(.

 From what I understood (probably wrong):
- Byte 0: number (size) of samples per channel.
- Byte 1: Alarms.
- Byte 2-3: Timer. Auto-increment value of what was sent?. I do not 
understand this
- Byte 4-5: Number of channels in the message.
- Byte 6 ...:
- Rest: Messaging

Can get messages from various channels in the same package TDMoE? If so, 
byte 0 would apply to all channels even though they are smaller and are 
filled in with null values is that correct?. Byte 4, 5 and 6, I do not 
have very clear ...

I will try to mount an asterisk and I'll set TDMoE test to see if I can 
catch some tmdoe and try analyze. thanks.

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