From: coghlan@bnr.ca (Patrick Coghlan)
Subject: Re: Obtaining ISDN
Reply-To: coghlan@bnr.ca (Patrick Coghlan)
Organization: Bell-Northern Research Ltd.
Distribution: usa
Date: Tue, 17 Nov 92 14:56:59 GMT

In article <1992Nov16.235427.11813@advtech.uswest.com>, huntting@advtech.uswest.com (Brad Huntting) writes:
|> In article <1992Nov13.154757.28389@bmerh85.bnr.ca> coghlan@bnr.ca (Patrick Coghlan) writes:
|> >[With ISDN at home] you would have:
|> 
|> >- a 64 k/bit data line which does not interfere with your use of the 
|> >  telephone
|> 
|> As opposed to a 14.4Kb/s real throughput on a single POTS line.  For us
|> realistic folks it's really more like ~35Kb/s when you include V.42bis
|> compression.  Of course now I'll be flamed by the half of the group for
|> comparring apples and oranges again, but in the real world it's
|> perfectly reasonable to compare these because you cant buy ISDN with
|> compression.  (Or did I miss something?)

You don't need the ISDN switch to do the compression.  Each of your 
sessions (DMS 100 can support 256 logical channels on X.25, telcos
may restrict this though) can do their own compression (e.g. a file
tranfer session may do compression, an electronic mail session may
do compression AND encryption).  BTW, I wrote much of the DMS 100
X.25 S/W.

|> >- use of the X.25 protocol over this data line which can be used to
|> >  set up multiple sessions simultaneously
|> 
|> Has anyone tested this in the real world?  Can your local switch deal
|> with X.25 traffic at a reasonable rate (if at all)?  How many virtual
|> X.25 connections can you multiplex on one B channel?

The 256 logical channels are there.  The rest is up to application writers.

|> >- access to any X.25 device hooked up to the ISDN network or other public 
|> >  packet switching networks (most ISDN switches have an X.75 trunk to 
|> >  PPSNs)
|> 
|> But both of them are probably banks and will refuse talk to you...

What about all the ISDN CPEs that will be talking to each other (LAN
interconnect, elm, X-windows for telecommuting etc.)?

|> >- the ability to run data intensive protocols such as X to access
|> >  your office workstation from home
|> 
|> Without having to multiplex your network trafic over several POTS
|> lines.
|> 
|> >In summary, it's fairly fast (compared to 9600 modems) and it doesn't 
|> >tie up your telephone.
|> 
|> U S WEST has been offering second phone lines for $17/mo.

Analog lines are reaching their limits, even with compression.  ISDN
starts with 64 kbit/s, before compression.

|> > It should also be much cheaper to dial-up over long-distance than using
|> > telephones and modems since the charges for holding time on packet
|> > networks are much less than for voice...  I think.
|> 
|> Really?  Could some of the folks who work for interLATA carier's
|> comment on this creative billing mechanism?  This is the first I've
|> heard of it.  I find it hard to believe that an ISDN call could be
|> anything but more expencive than an POTS call.  But if you were being
|> billed by the packet then it could make sence.

Unlike voice, packet traffic is statistically multiplexed onto inter-office
trunks, therefore it SHOULD be cheaper than voice.  I am not the best 
person to ask however.

|> Of course this presuposes that your local RBOC and your longdistance
|> carrier can pass ISDN traffic...  I dont honestly know if U S WEST has
|> that capability with any longdistance provider yet.  What would it
|> take?  SS7?

DMS 100 hands off all packet calls to X.75, typically to a packet network.
The packet network delivers it to the destination ISDN switch, typically.

|> IDSN offers speed, but requires outragously high priced customer
|> premise equipment.  So you can get either 35Kb/s out of a second phone
|> line for $17/mo with a $300 modem, or 64Kb/s (mabey 128Kb/s) out of an
|> ISDN line which you also use as your primary telephone for $X/mo with
|> about $2000+ worth of equipment (unless you have a NeXT, a Sparc10 at
|> home).
|> 
|> Now how if you are going to shell out that extra $1700+ for the
|> hardware to use ISDN (on both ends of the connection probably!), then
|> what do you suppose X would have to be to make up for it?

You need a NT1 and a terminal adapter or ISDN card for your PC.  You
can get both for around $1000 today.  I paid $3000 for an original IBM
PC with 16K memory and no disk drives in 1983.  I can get a 386 for
around $1000 today.  Would you care to guess what it will cost to have
ISDN in a few years?

Newsgroups: comp.dcom.isdn