Stan@li.psi.com (Stanfield L. Smith ) (06/05/91)
I need HELP in trying to understand how LAPD is going to work on the ISDN B channel of the telephone network. What I have been able to find out is there are many DIFFERENT standards for LAPD, the CCITT, ATT, French and others. I have the CCITT book, but no documentation about the other variations. 1) Does anyone have documentation on the non-CCITT "standards" that is Emailable or suitable to FTP? 2) Can anyone explain how these different incarnations for LAPD are going to inter-operate as a world wide telephone system? Thanks in advance, Stanfield L. Smith stan@seadog.cns.com 516-277-0203
marc@uunet.uu.net> (06/08/91)
In article <telecom11.429.10@eecs.nwu.edu> Stan@li.psi.com (Stanfield L. Smith ) writes: > I need HELP in trying to understand how LAPD is going to work on the > ISDN B channel of the telephone network. LAPD runs on the D channel. One of the many "rate adaption" protocols that runs on a B channel is V.120 which is based upon LAPD. > What I have been able to find out is there are many DIFFERENT > standards for LAPD, the CCITT, ATT, French and others. I have the > CCITT book, but no documentation about the other variations. Forget LAPD. What you are really talking about is Q.921 (layer two signaling between the switch and CPE) and Q.931 (layer three). Layer two is quite standard, layer three -- the call control layer -- is another story. While some countries mandate strict conformance to CCITT what you need to know is what type of switch you'll be connecting to and then grab the documentation from the switch vendor. Examples are AT&T's "5ESS Switch: ISDN BASIC RATE INTERFACE SPECIFICATION" which has version for the various generics and Nothern Telecom's "ISDN BASIC RATE ACCESS USER-NETWORK INTERFACE SPECIFICATION". The CCITT specs are in Fascicle VI of the Blue Books and are only available in hard copy. Call the switch vendor for information about ordering their manuals. > 2) Can anyone explain how these different incarnations for LAPD are going > to inter-operate as a world wide telephone system? You only need CPE that talks to your switch. Once you get to your switch it's the switches job to get the call the rest of the way. Rate adapted data on the B channel does require use of the same standard. The common standards in use are DMI Mode 2 (an AT&T proprietary protocol used by AT&T 7500 series phones and terminal adapters), V.110 (defines which bits will be used to for data), and V.120 (the Q.921/LAPD look-alike). Fujitsu phones and TA's probably define the "standard" V.120. At least that's the TA you see in many test labs when testing interworking. marc work: marc@ascend.com uunet!aria!marc home: marc@dumbcat.sf.ca.us {ames,sun}!pacbell!dumbcat!marc
TRADER@uunet.uu.net (06/09/91)
I've been working on an ISDN interface and I have also had questions about Layer 3 services (call control). I have a copy of the CCITT Q.931 specs, but I also have a copy of Bellcore Technical Reference TR-TSY-000776, "Network Interface Description for ISDN Customer Access" (You can get this from the CIC). The manual states that the call control protocol is a subset of Q.931, sort of a generic ISDN call control protocol. What's the status on this? From what I can see, the generic call control stuff looks like it would work with AT&T 5ESS switches and probably others, although there aren't many features that are used. If I wrote code for this kind of generic switch, would that be enough for simple call setup?? Paul McGinnis / TRADER@cup.portal.com