Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!apple!portal!cup.portal.com!cec From: cec@cup.portal.com (Cerafin E Castillo) Newsgroups: comp.dcom.modems Subject: Re: Telebits "PEP" protocol Message-ID: <36853@cup.portal.com> Date: 13 Dec 90 01:57:09 GMT References: <1990Dec8.025415.2920@amd.com> <8sHZT4w163w@mudos.ann-arbor.mi.us> <3592@jaytee.East.Sun.COM> <87673@lll-winken.LLNL.GOV> Distribution: na Organization: The Portal System (TM) Lines: 111 Casey quotes and writes: | Open letter to Telebit: if you think PEP is worth anything, license it | (with or without fee). Otherwise it will be bypassed by a (possibly | inferior) but widely available standard. V.32 is coming up fast. Telebit does license PEP/DAMQAM in an 18 kbps non-LZ compression (No S110) form to Ventel (ie Ventel Pathfinder) and Racal-Milgo (1822S). Various form factors have also been available in the DCA Fastlink, GTE TrailBlazer, etc., mostly OEM-type deals. >Telebit's DAMQAM (Dynamic Adaptive Multicarrier Quadrature Amplitude >Modulation) has a couple of definite features over V.32 and possibly even >the upcoming V.32bis standard: > > o Ability to handle line noise and changing line conditions. > > o Higher raw bandwidth -- in one direction at a time. This is true. the one direction at a time (half-duplex / "adaptive duplex) is a benefit, as well as a problem, especially in interactive work. > The protocol spoofing is nice, but mostly a because of stupidity in the >higher layer protocols -- notably a fixed window size of 1. Correct. In UNIX UUCP ('g' protocol), the window size is usually a fixed size of 3. SCO UNIX and other such O/S UUCPs have adjustable sizings up to 7 for use with slower (<= V.32) modems. PEP forces a window size of 3, then performs the spoof at each end in order to be able to do the PEP/DAMQAM (half-duplex) modulation between the two modems without causing the full duplex 'g' protocol to timeout. Both a necessity and a feature! This comes in handy with UUPC, Waffle, or other such DOS programs with a window size of 1. The spoof will automatically make this software do a 3 window size and effect performance radically (if the serial I/O drivers can hack it! ;-). >(From what I understand, SLIP spoofing, when it becomes available, will >actually be making up for the half duplex nature of DAMQAM.) SLIP spoofing, from what Telebit has told me, will never exist. the Telebit NetBlazer is the current SLIP/CSLIP/PPP solution offered by Telebit. As to protocol spoofing: >My only complaint is that I should be able to do it (protocol spoofing) >over any ``error free'' channel, such as V.32/V.42/V.42bis. You can. The current GF7.00 firmware for T2500/T1500 allows protocol support in V.32 (with or without V.42/V.42bis) between Telebit modems (ONLY!). The New, T1600 modem is also capable of doing this. From my test of this firmware feature, it is not very impressive. Maybe a 10% gain over raw V.32 throughput. > PEP is simply a packetization protocol. Who cares? Please feel free >to flame me if I'm misstating the extent of PEP's features. No problem. PEP is a sales/marketing term for the layman. DAMQAM is the correct modulation method. PEP is just an ECC layer. > But, the real winner is DAMQAM. >After struggling with a V.32 connection for the last couple of weeks... >I've changed my mind about telling people to forget ``PEP'' modems and >just go with V.32. I have to agree. V.32, and for that fact V.32bis or V.32turbo (Rockwell option) all using single carrier technology and echo cancellation/trellis techniques, are only as good as the line you are using them on. While this is true for DAMQAM as well, the multicarrier technology assures that you will find available carriers for your data on any phone line (except a dead one...;-) amongst the 511 carriers it makes avaialble. Furthermore, you will be able to move anywheres from 2,4, or 6 bits of data through these carriers at speeds between 7.3 and 88.26 baud. Of course, those of you who know about the hidden registers (See Telebit Tech Support for documentation...) also know of how to squeeze even more throughput out of a bad line using DAMQAM packetization modification methods. 38.4 kbps is available on the T1600. > My only problem is I can't stand using PEP. The echo delays are >terrible to behold when I try to use my X terminal and it's just barely >passable with a normal terminal. Visual editors are gruesome. I agree. I use V.32 with V.42bis compression in the receive direction when using a Graphon OptimaX 200 X-Windows solution. Since the mouse and typing yielded small bits of data as opposed to the screen redraws coming in from the system, this method worked well, but not always reliably. This was due to the combination of V.32 line problems. PEP was very frustrating to deal with and could not provide this level of intelligence in handling data on a per carrier basis. > It would be really nice if Telebit could come up with a follow on to >DAMQAM that was ``TRUE'' full duplex... >support ``TRUE'' 38.4Kbps ... :-) V.34 Asym seemed to have died in CCITT. This was the proposal for a 28 Kbps PEP with a reverse 300-600 channel. Maybe in light of multicarrier cellular, satellite, microwave, or fax modulation methods, it might be given new life... I hope these personal and technical insights help. As a Telebit modem user I share the same problems and complaints, but have the added benefit of a little more product education thanks to Telebit. =============================================================================== Cerafin E. Castillo || //\\ ||\\ || Network Consultant || //__\\ || \\ || Los Altos Los Altos Networks || // ---\\|| \\|| Networks 340 Second St. #6 ||___// \ | \ | Los Altos, CA 94022 (415) 941-8031 UUCP: {apple,sun,uunet}!portal!cup.portal.com!cec INTERNET: cec@cup.portal.com "...No hay mal que por bien no venga..." ===============================================================================