E1 uses CAS or CCS

[hamid ghani]

hi guys;

i am configuring e1 line and the service provider give me configuration, to put on my router

controller E1 0/0/0
framing NO-CRC4
ds0-group 0 timeslots 1-15 type r2-digital r2-compelled ani
ds0-group 1 timeslots 17-31 type r2-digital r2-compelled ani
cas-custom 0

country saudiarabia use-defaults
cas-custom 1
  country saudiarabia use-defaults

the thing that bothers me this configuration is for CAS signal not CCS so why are we getting 30 channels instead of 32.

30 channels are according to CCS sig

32 channels are according to CAS sig

please clarify my confussion

[paolo bevilacqua]

E1 is always 30 voice channels.

Add one for framing (TS0), another one reserved for CCS (TS16) = 32.

[hamid ghani]

why 16th is reserved for CCS if we are using CAS configuration,

my doubt is not clear..

[nitsinha]

In E1, the 16th channel is always reserved for signalling whether or not you are using CAS or CCS. The only difference is that in CCS, the 16th channel in every frame carries the signalling information for the rest of the 30 voice channels whereas in CAS E1, the 16th channel still carries the signalling(CAS information) info but in a frame it carries the signalling for 2nd and 17th channel, the next frame carries signalling for 3rd and 18th channel and so on. Hence in an entire superframe(16 frames), the 16th channel ultimately carries signalling info for all the remaining 30 channels.

http://telecom.tbi.net/e1_frm.html

HTH

Regards

Nitesh

PS:Pl rate helpful posts

[trifu02]

Thank you !
We would need professors like you in our University, not some guys who fail to even explain the basics.

[nitsinha]

Hi Hamid,

You can also have a look at the following doc for further clarification

http://cisco.iphelp.ru/faq/27/ch02lev1sec3.html

HTH

Regards

Nitesh

PS:Pl rate helpful posts.

[hamid ghani]

Hi Nitesh,

thank you very much for your help, but i your post you say

in CAS E1, the 16th channel still carries the signalling(CAS information) info but in a frame it carries the signalling for 2nd and 17th channel, the next frame carries signalling for 3rd and 18th channel and so on.

this thing remain doutful

[nitsinha · Accepted solution]

Hi Hamid,

A multiframe consists of 16 E1 frames.

The time slots in a frame are numbered 1 though 32, although the channels are numbered 0 through 31, as shown in fig below.

Multiframe time slots are configured as follows:

• Time slot 1 carries only framing information.

• Time  slot 17, in the first frame of the 16-frame multiframe, declares the  beginning of the multiframe, which is indicated by the M symbol in fig. above

• The remaining slot 17s carry signaling information for all the other time slots:

  - Slot 17 of the first frame declares the beginning of a 16-frame multiframe (M).

  - Slot 17 of the second frame carries ABCD signalling for voice slot 2 (X) and ABCD signalling for voice slot 18 (Y).

  - Slot 17 of the third frame carries ABCD for voice slot 3 (X) and ABCD for voice slot 19 (Y).

  This process continues for all the remaining frames.

Thus for a complete multiframe the signalling info, as you can see in fig. above, is still carried by timeslot 17.

Check this for more details

http://cisco.iphelp.ru/faq/27/ch02lev1sec3.html

Hope this clears all your doubts.

Regards

Nitesh

PS: Pl rate helpful posts.