goldstein%delni.DEC@decwrl.dec.com (Fred R. Goldstein dtn226-7388) (05/11/89)
In Telecom V9I160, John Gilmore <gnu@toad.com> writes, >It appears that Sun will not support plugging your SPARCstation into an >ISDN phone line, because some standards committee somewhere decided >that, when used for data, the "B" channels should carry SDLC-formatted >data, and the SPARCstation (and the Am79C30) has no support for this. >I find this the height of lunacy. Yes, I agree, your assertion above fails the sanity test. ISDN does NOT require any particular formatting of data on the B channel. ISDN's circuit-switched 64 kbps (unrestricted) bearer service places absolutely no constraints on what you do with your 64 kbps of isochronous bandwidth. You wanna run SDLC, run SDLC. You wanna run DDCMP, run DDCMP. You wanna run bisync, run bisync. Or fax, or low-bit-rate video, or 7 kbps ADPCM audio or whatever. The network's not allowed to touch your bits. In some US implementations, you may be limited to the 64 kbps Restricted bearer service. This is merely an artifact of the use of T1 carrier, which doesn't allow the all-zero octet to be transmitted, so that applies to 64R calls. Inverted HDLC of course runs fine in that mode. However, B8ZS and ZBTSI are two techniques for removing the restriction from T1; the telcos are installing them so 64R may be rare or nonexistent in practice. If the Sparcstation can't be used over ISDN, it's not the fault of the standards. fred (voting member, ANSI T1S1: ISDN Architecture, Services and Protocols)