=?iso-8859-1?q?maine=20dude?= wrote: > > Hi All, > > Quick question I hope you can help me with. > > How many D channels does a PRI have?
Just one D channel, used for signaling. U.S. 23B +1D Europe 30B +1D See more comments below. > > I always thought it was two, but its states 1 in most places. > > Text taken from the CCNP remote access guide (to make it more > confusing): > > there are 30 timeslots, leaving 2 timeslots for signalling and > framing. > Timeslot 0 is used for framing and timeslot 16 is used for > signalling (counting 0-31). E1 PRI makes use of this same > principle. Timeslot 16 is the D channel and timeslot 0 is used > for framing information. Please advise. Regards,DJ That's the European standard that you described (twice). European ISDN PRI uses an E1 facility. In Europe, they do things a lot more cleanly than we do here in the U.S. ;-) Does 2.048 Mbps look familiar? It's 64 Kbps times 32, 2^6 x 2^5. That's 32 channels or timeslots. Timeslot 0 is used for framing. Timeslot 16 is used for signalling with ISDN. E1 uses Common Channel Signaling (CCS). In the CCS format, a single timeslot provides a reserved 64-Kbps transparent signaling channel that can be used to exchange signaling information of any type and in any format. In the case of ISDN, timeslot 16 is used as the D channel for sending ISDN signalling material. In the U.S., PRI uses the T1 facility. Does 1.544 Mbps look familiar? It's a little harder to figure out because it's not so clean. But it consists of 24 64-Kbps channels with 8-Kbps for framing. Both E1 and T1 need framing information, which is distinct from signalling. Whereas signaling sends information like the LAPD protocol and dial tone and ringing for telephony, framing specifies a method for a sender to group multiple channels into one circuit. Framing allows the recipient to detect the beginning and end of the data for each set of channels. According to the books, ISDN on T1 uses an entire 64-Kbps channel for signalling. It uses timeslot 24. I'm not sure it really has to be timeslot 24. Howard would know for sure! :-) But it is definitely 64-Kbps taken from somewhere. Priscilla > > > > --------------------------------- > With Yahoo! Mail you can get a bigger mailbox -- choose a size > that fits your needs > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=65067&t=64999 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
