Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!texbell!vector!telecom-gateway From: desnoyer@apple.com (Peter Desnoyers) Newsgroups: comp.dcom.telecom Subject: Re: TCP/IP over ISDN Basic Rate Message-ID: Date: 13 Nov 89 18:56:25 GMT Sender: news@vector.Dallas.TX.US Organization: Apple Computer, Inc. Lines: 40 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 508, message 1 of 7 In article euatdt@euas11c05. ericsson.se (Torsten Dahlkvist) writes: > munnari!cit5.cit.oz.au!jwb@uunet.uu.net (Jim Breen) and I have been having a > little discussion about byte/bit transmission over ISDN. I said: > >> The basic ISDN-frame is byte-oriented and the hardware ... > >> [...] TELEPHONY transmission is byte oriented.......... > ... and he countered: > >Ok I'll bite. WHERE in the Red or Blue books does it say the B > >channels are byte oriented. In my opinion that is what "8 kHz integrity" means when applied to ISDN data calls. (ref. Q.931, low-layer compatibility info element.) This only suggests such a guarantee, however - to prove it would require the appropriate reference from the ISDN service specification. > We're looking at different levels of the system. The ISDN frame > consists of a frame recognition pattern, D-channel bits and B-channel > BYTES. Your basic ISDN chip will extract the clock frequency, ... > Now do you see what I'm getting at? Up until the codec/shift register, > a strictly byte-wise transmission is essential for the function of > your equipment. That is irrelevant, as it applies only to voice calls. There is no reason why a telco must treat voice and data calls identically. If you don't want to risk getting your data ADPCM'd or sent over analog facilities by some el-cheapo LD company*, you'd better request data service. In that case, only the guarantees in the spec for data service hold. Peter Desnoyers Apple ATG (408) 974-4469 * I don't mean to suggest that any major LD companies would do this. Someone will, however.