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- Path: sparky!uunet!cis.ohio-state.edu!ucbvax!CU.NIH.GOV!RAF
- From: RAF@CU.NIH.GOV ("Roger Fajman")
- Newsgroups: comp.dcom.modems
- Subject: ISDN for data
- Message-ID: <9207300705.AA04214@ucbvax.Berkeley.EDU>
- Date: 29 Jul 92 22:42:28 GMT
- Sender: daemon@ucbvax.BERKELEY.EDU
- Distribution: world
- Organization: The Internet
- Lines: 33
-
- I'm interested in information on ISDN terminal interfaces. We
- are getting a AT&T 5ESS which will be essentially a private PBX
- for us, but will be operated by C&P Telephone. They want to sell
- us ISDN for data, both async and sync.
-
- For async, they started out pitching X.25 connections over the 16
- kbps D channel on a Basic Rate Interface. It seems to me that
- this is going to be slower than a V.32bis modem, especially one
- with V.42bis compression. Then there's V.fast to think about.
-
- Today they demonstrated some ISDN terminal interfaces that send
- data over a 64 kbps B channel. There was an AT&T ISDN phone set
- with a 19200 bps RS232 interface, a Hayes unit with a 38400 bps
- interface, and a UDS unit whose interface speed I don't recall.
- While 38400 bps seems more in the ballpark, at least today, why
- is the rest of the bandwidth being wasted? Why do none of these
- units implement something like V.42bis compression?
-
- There was also an interesting unit (I've forgotten the brand)
- that could do 128 kbps sync over 2 B channels. The Hayes unit
- could do 64 kbps sync on one B channel. This, at least, is a
- step up from 14400 bps in V.32bis.
-
- Anyway, given the relative prices of ISDN terminal interfaces and
- V.32bis modems, I wonder if we shouldn't just continue to run
- analog modems, at least for async data. Then there is no need to
- worry about the difference between off-switch and on-switch
- users.
-
- Roger Fajman Telephone: +1 301 402 1246
- National Institutes of Health BITNET: RAF@NIHCU
- Bethesda, Maryland, USA Internet: RAF@CU.NIH.GOV
-
-