T1 PRI- Channel ds0 vs times slots

[philippe.cousineau]

Hi I am reading a cisco book right now and I have a little question regarding a PRI.

in the book it says :

"when using T1 interfaces, channel 23 (time-slot 24) is always the signaling channel. "

So I guess Channels start from 0 to 23  and time-slot 1 to 24 ? is that right ?

also If I do a "show voice port summary"  I guess the Port 0/0/0:23 is the Chnnel-D. Channel #23 wich is the times slot 24 but there is no sens if the row CH is the Channel, there would be a sens if CH would be for Times-slot because we can see that CH 23 can be used as voice port

Can some one give me a track on that...

controller T1 0/0/0
framing esf
linecode b8zs
cablelength short 133
pri-group timeslots 1-24

2811-RTR#sh voice port summary
                                          IN       OUT
PORT           CH   SIG-TYPE   ADMIN OPER STATUS   STATUS   EC
============== == ============ ===== ==== ======== ======== ==
0/0/0:23       01  isdn-voice  up    dorm none     none     y
0/0/0:23       02  isdn-voice  up    dorm none     none     y
0/0/0:23       03  isdn-voice  up    dorm none     none     y
0/0/0:23       04  isdn-voice  up    dorm none     none     y
0/0/0:23       05  isdn-voice  up    dorm none     none     y
0/0/0:23       06  isdn-voice  up    dorm none     none     y
0/0/0:23       07  isdn-voice  up    dorm none     none     y
0/0/0:23       08  isdn-voice  up    dorm none     none     y
0/0/0:23       09  isdn-voice  up    dorm none     none     y
0/0/0:23       10  isdn-voice  up    dorm none     none     y
0/0/0:23       11  isdn-voice  up    dorm none     none     y
0/0/0:23       12  isdn-voice  up    dorm none     none     y
0/0/0:23       13  isdn-voice  up    dorm none     none     y
0/0/0:23       14  isdn-voice  up    dorm none     none     y
0/0/0:23       15  isdn-voice  up    dorm none     none     y
0/0/0:23       16  isdn-voice  up    dorm none     none     y
0/0/0:23       17  isdn-voice  up    dorm none     none     y
0/0/0:23       18  isdn-voice  up    dorm none     none     y
0/0/0:23       19  isdn-voice  up    dorm none     none     y
0/0/0:23       20  isdn-voice  up    dorm none     none     y
0/0/0:23       21  isdn-voice  up    dorm none     none     y
0/0/0:23       22  isdn-voice  up    dorm none     none     y
0/0/0:23       23  isdn-voice  up    dorm none     none     y

[paolo bevilacqua]

Cisco use x/y:23 (T1), or x/y:15 (T1), or x/y:D (AS5xxx) to indicate a PRI voice or data port.

That's all.

[Gary Cabezas]

The question is, why are there 23 channels, where channel 0 should be?... it would make sense if those were TS because of TS 24 is used for signaling.

[yahsiel2004]

+5 Paolo

Gary I take it as you're curious as to how Cisco references channels and time slots. The "CH" are the 23 "B Channels"

Regards,

Yosh

[Gary Cabezas]

Thank you... It makes sense, but I still confused because of this:

http://www.aculab.com/questions/how-many-voice-channels-does-a-t1-primary-rate-interface-pri-have/

Channel 0-22     -           B-Channel (Voice)

Channel 23         -           D-Channel (Signalling)

channel 23 is a D-Channel so it shouldn't be shown on the output.