From toaster-owner@m2xenix.psg.com Thu Mar 25 09:47:16 1993 Received: from m2xenix.psg.com by fido.wps.com (5.67/1.34) id AA02551; Thu, 25 Mar 93 09:47:05 -0800 Received: by m2xenix.psg.com (/\==/\ Smail3.1.25.1 #25.4) id ; Thu, 25 Mar 93 08:28 PST Return-Path: Received: by m2xenix.psg.com (/\==/\ Smail3.1.25.1 #25.4) id ; Thu, 25 Mar 93 08:28 PST Received: by rip.psg.com (Smail3.1.28.1 #1) id m0nbunR-000300C; Thu, 25 Mar 93 08:28 PST Message-Id: From: randy@psg.com (Randy Bush) Subject: ISDN fwatneq (frequently wrong answers to non-existent questions) (fwd) To: toaster@psg.com (ToasterNet List) Date: Thu, 25 Mar 1993 08:28:49 -0800 (PST) Content-Type: text Content-Length: 11510 Status: OR As ISDN hits River City, one of our local RAIN folk is doing the research. It looks like I can order ISDN today for the RAINet NOC. Ed, John, Stuart, ..., any of you folk care to go for it? >From m2xenix.psg.com!rain-owner Thu Mar 25 04:10:31 1993 To: rain-data@psg.com From: keithl@klic.rain.com (Keith Lofstrom) Date: Thu, 25 Mar 1993 07:36:43 GMT Subject: ISDN fwatneq (frequently wrong answers to non-existent questions) with help, this may become a FAQ: -------------------------------------------------------------------------- ISDN information for Portland and Washington County March 24, 1993 Rev 0.2 I will update/correct this file as I get more information. I am still talking to sales droids - anything they say is subject to their misinterpretations as well as my own. If you have better information (and can give me a source to check) send email and I will incorporate it. ---------- Background ---------- ISDN stands for Integrated Services Digital Network, or alternatively, "It Still Does Nothing". An ISDN 2B+D "T" interface uses the existing wire pairs to deliver 2 64 Kbps Bearer channels (which can be data or digitized voice) and a 16 Kbps control channel over up to 18 thousand feet of wire, to a special interface at the phone company's central office. Longer runs require repeaters. I've heard that the "modems" still cost $1000+ each, while other unreliable sources say there are cheaper alternatives. ISDN has been around for a while; everyone is waiting for someone else to go first. ISDN uses the normal switched dialup network - the ISDN interface takes the phone number, encodes it, and sends it down the "D" channel to tell the switch where to connect. Since the ISDN link uses the existing network, and the long distance networks are already digital, you can use an ISDN modem to call any other ISDN modem in the world at normal toll rates. Not bad for a potential of 128 Kbps. Since ISDN is all digital, a properly connected ISDN link will have no errors, and plenty of diagnostic information available about the link. Once installed, it should be far easier to maintain, even at lower bit rates, than a modem link. An ISDN to RS232 terminal adapter that goes at 38.4 Kbps async or 64 Kbps syncronous over an RS232 link is briefly described on page 4 of the Jan 93 Black Box Catalog (for $1300). I would prefer to use something that plugs into a PC - at these data rates, I would rather talk to a buffer in memory than a serial port. Anyone seen better gear? -------------------------------- What is needed for ISDN service? -------------------------------- The real trick is at the local exchange. Many older exchanges, such as the "Cherry exchange" in Southwest Portland, have analog switching rather than digital switching. Rather than move bits, these exchanges use frequency bands, like your radio, and relays to move analog signals around, rather than gates. ISDN won't arrive in these areas until the phone company adds new switches. The phone company plans on keeping some of its equipment for 25 years :-( [Somebody tell Lon Mabon that the Cherry phone switch building is an abortion clinic run by black communist vegetarian atheist lesbians. After a short service interruption, Cherry may get a digital switch] The other requirement is putting an ISDN "subscriber line interface card" (or SLIC) on the line rather than a voice SLIC. Changing the card converts the pair of wires running from the central office to your site from analog to digital. The wires have to be reasonably "clean" - for example, there can be no long sections of dead wire going off at right angles to some former connection, and after years of changing and repairing phone lines, this sort of thing accumulates. The wires also have to be less than 18,000 "telephony feet" from your site to the central office. Farther than this, a repeater is needed, and the phone company would rather not bother. Sometimes, however, the phone company puts a little satellite switch or encoder in a neighborhood, multiplexing the signal before it is shipped off to the switch. For example, the Brockman neighborhood in south Beaverton has all the phone lines connected to a machine which digitizes every phone line, then ships the whole bunch, unswitched, up to the Somerset exchange on a fiber. A GTD5 switch up there switches the information, that is, uses the phone number to make the specific connections in its electronic crossbar. GTE eventually plans to give this whole neighborhood its own switch, after it gets more built up. The distance that REALLY matters is how far you are from the digitizing box - it may be no further than the corner, if you are in a new and populous neighborhood. Another trick, used with analog exchanges, is the dreaded *CARRIER* multiplexer, where a box sits in the neighborhood and modulates each separate phone connection onto a different frequency, adds the signals together, and ships the whole modulated mess down a couple of pairs of regular phone wire to the central office. The signals are separated out at the CO by filtering and demodulating. I don't know whether the crosstalk and noise cause as much modem havoc as the nonlinearity, phase hits, and narrow bandwidth, but carrier stinks. This makes for noisy voice interconnection, lousy modem service, and makes impossible a baseband digital connection like ISDN. If you have carrier, burn down your house, and use the insurance money to move someplace else. :-) ======================== ISDN Status by exchange: ======================== ------- US West ------- The US West (former Pacific Northwest Bell) territory is divided up into a number of exchanges. The exchanges are named after the first two digits of the phone numbers that were assigned to them many years ago: CApitol - 22x - Downtown, Northwest Portland, Council Crest, Corbett. Also includes 323, 790, and a bunch of other new numbers... DIGITAL SWITCH, 5ESS, located near SW Broadway and Burnside. BElmont - 23x - Near east side, Burnside down to around Powell, out to Mount Tabor. DIGITAL SWITCH, 5ESS, located near SE 18th and Morrison. CHerry - 24x - 244, 245, 246, 293, and 452 (Agora and Percy). Southwest Portland. Analog switch (sigh), no ISDN, located near SW 28th and Multnomah. CYpress - 29x - Eastern Washington County. Includes West Tualatin Valley, Saint Vincents, some of Cedar Hills, West Slope, and Garden Home (m2xenix). DIGITAL SWITCH, 5ESS, located near SW Barnes and Leahy road. 291, 292, 297. NEptune - 63x - 635, 636, 697, 699. Lake Oswego. DIGITAL SWITCH, 5ESS, located near State street and "B". The other US West switches, such as North Portland, Milwaukee, Prescott (Mount Scott), Oak Grove, Milwaukee, Oregon City, and West Linn, are apparently analog (I would expect digital switches out in Gresham, where there is a lot of growth, but ...). Somebody check me on this. US West is now offering ISDN service in the exchanges with DIGITAL switches listed above. An ISDN connection costs $75 a month, with $295 installation. Thus, m2xenix can get ISDN connections, while agora and percy cannot. --- GTE --- GTE just filed a tariff with the state for ISDN, and is still getting this organized. GTE is already all digital; however, according to the person I talked to, they will only be offering ISDN on their GTD5 and DMS-100 switches, and not on their 5ESS switches. Sounds like bad information to me, since US West is offering ISDN on these same type of 5ESS switches. I'll ask again in another month. The GTE tariff offers ISDN *at the same rate* as normal residential and business connection rates. "After all, it is really just the same service" says the sales person. Thus, connections in Washington County, at $23 per month or so, will be a hell of a lot cheaper than connections in Portland. This may influence future RAIN topology (and where people should be moving). The following central offices connect to GTD5 switches and will be offering ISDN "real soon now" (a few months???) : Beaverton - many prefixes, from Western Cedar Hills down to south Beaverton. 520, 526, 626, 627, 641, 643, 644 (klicnet), 646, 671. The switching office is on Cedar Hills Boulevard across from the Westgate. Brockman - South Beaverton and Northern Tigard, connected to the Somerset Switch. 524 prefix. Qiclab. Somerset - northern Aloha, Oak Hills, Cornell Oaks, Somerset West. Probably includes most of the Sunset corridor hi-tech businesses. 531, 629, 645, 690 prefixes. Tigard - how far south, I don't know. 590, 598, 620, 624, 639, 684. The following exchanges are on 5ESS and will not have ISDN, according to the sales person (I don't believe them, though): Aloha (Damn!) which apparently starts about Baseline and goes south from there. 591, 642 (Noblenet), 649. Hillsboro. 640, 648, 681, 693, 696. Since US West *is* using these switches for ISDN, this sounds like bad information to me. I will pursue this. I don't know about these exchanges: Forest Grove - 357, 359, 985. Stafford/Tualatin/Wilsonville - 638, 682, 685, 691, 692. Sherwood - 625. Scholls - 628. North Plains - 647. Yamhill County? Note that a lot of Western Washington County is fairly rural, and the lines from the site to the central office will be longer than 18,000 feet anyway. You folks in West Armpit are probably out of luck. ------------------------- Other parts of the state: ------------------------- I will collect information as I become aware of it. ---------------- United Telephone ---------------- Just for giggles, I called United Telephone in Hood River. These folks cover a lot of rural areas, such as the Oregon Coast from Gearhart down to Newport (and probably farther). The nice granny who answered the phone for UTI had never heard of ISDN; the engineering department had never heard of it either, when she asked them. Their entire system has digital switching, though, so a sufficiently determined customer with large wads of money could probably get an ISDN connection. Someday, I may move to the coast - gotta plan ahead! ============= Speculations: ============= Since ISDN is digitally dialed and signaled, the time from initiating a call to flowing data may be only a second or two. This is not acceptable performance for moving an individual packet, but for single sessions it would be dandy, making uucp and tip connections work very quickly. Perhaps we can set up a shared dialup ISDN link into psg.com, and split the $75/month - this shared link could move netnews and mail quite rapidly, reducing the burden on the existing slip links. Perhaps other protocols besides IP would allow us to use these serial links for something like FTP - perhaps with the interactive stuff going over the slow, low latency slip links, and the big stuff travelling by ISDN quick dialup, with perhaps 2 minute latency. Imagine a line getting called every thirty seconds, with a million calls a year, shipping 200 kilobytes on each call... ----------------------------------------------------------------------------- Keith -- Keith Lofstrom keithl@klic.rain.com Voice (503)-520-1993 KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon" Design Contracting in Bipolar and CMOS - Analog, Digital, and Power ICs