lron@easy.hiam (Dwight Hubbard) (01/13/91)
In article <GHOST.91Jan13020101@bucsf.bu.edu>, Jay Adelson writes: >Can someone please tell me what the difference between the standards >v.32, v.32bis, v.42, v.42bis is? And which modems have which? (Between >the Telebit and the USRobotics?) This information was posted to comp.dcom.modems a while back, it should provide more information than you need. PEP Before even 2400 bps dialup modems received public acceptance, a company called Telebit Technologies was developing a 9600 bps modem based on a multicarrier modulation scheme. The Telebit TrailBlazer sends data at speeds from 0 to 8 baud on each of 511 carriers (spaced every 7.8 Hz from DC to 4 kHz) using Quadrature Amplitude Modulation (QAM). PEP stands for the Packetized Ensemble Protocol, which the TrailBlazer uses to correct errors, reassemble the data, and adjust the modems' operating parameters to achieve optimum performance. This was called Dynamically Adaptive Multicarrier QAM, or DAMQAM. Telebit later added MNP support for non-DAMQAM connections and PEP2 (a protocol with data compression) to what became known as the TrailBlazer Plus. The TrailBlazer gained great acceptance in the Unix world not only for its speed and ability to operate reliably over a wide range of line conditions, but also because it featured 'protocol spoofing', which means that the modem would recognize the initiation sequence of selected protocols and intercept them. In effect, the computer systems would be using XMODEM, Kermit, or UUCP-g only to carry the data as far as the modem, which would then send the data using its own fast and efficient protocol, to the other modem... which simulated the same protocol for the other host, giving each computer the impression that it was indeed speaking directly to the other. This resulted in tranbsfer rates never before seen over dialup lines or even long serial wire connections. Modems from Microcom and other manufacturers also featured protocol spoofing, but they were not compatible with Telebit's multicarrier modulation scheme, and thus never gained extensive popularity in the market. MNP Microcom Networking Protocol, or MNP as it is called, consists of several layers of software protocols, often implemented within the modem itself, which detect and correct errors and provide improved throughput. i. Basic link: MNP service classes 1 through 3. MNP1 is much like XMODEM or Kermit in that the stream of characters is broken into blocks of fixed length, and a checksum is attached to each. After each block is sent, the transmitter waits for an acknowledgement from the receiver that the block arrived intact before moving on. If the receiver indicates an error, the block is retransmitted. MNP2 implements a 'sliding window' protocol; that is, several blocks are sent, and the receiver identifies intact and damaged blocks by number. Because the transmitter is permitted to send a fixed number of blocks ahead of the oldest unacknowledged block, the wasted capability (the time that the transmitter must wait, silent, for the signal to continue) is drastically reduced or entirely eliminated. Throughputs approaching the bit rate divided by ten are possible. MNP3 uses the same sliding window arrangement as MNP2, but takes advantage of synchronous data links, such as those in the carriers of modems operting at 1200 bps and above. It strips the start and stop bits of incoming characters, and sends only the 8 data bits. Thus, the throughput may approach the bit rate divided by eight, or a 25% boost over asynchronous framing techniques. All MNP connections use one of these three service classes as the foundation for their operation. ii. Features MNP4, called dynamic packet assembly, permits the use of data blocks of varying size. Because the relative overhead of larger packets is smaller than that of standard packets, MNP4 should increase throughput. by using larger packets under good conditions and smaller ones under noisy conditions (reducing the volume off data that must be retransmitted). MNP4 may be used with any of MNP1 through MNP3. MNP5 implements a form of dynamic data compression. It detects repeated patterns in the data stream and reduces redundancy in the transmissions. When transitting text files, this can significantly increase throughput but, when used on files which have already been compressed using run-length, Huffman, or Lempel-Ziv techniques, the overhead may actually reduce the effective data throughput. It is wiesest to disable MNP service class 5 when it is known that the majority of information to be transmitted is in compressed form. MNP5 may be used with any of MNP1 through MNP3, with or without MNP4. Higher levels of MNP are proprietary to Microcom and are rarely found in other manufacturers' modems. V.29 The CCITT developed standards for 9600 bps communication over the V.32 dialup telephone network. The CCITT recommendation V.29 described a half-duplex technique which required the modems to reverse the direction of the carrier whenever it was necessary to send data in the other direction. V.29 is used in many inexpensive 9600 bps modems, some of which are compatible with CCITT Group III Facsimile standad. V.32 specified that echo cancellation be used to permit simultaneous communication in both directions. Echo cancellation with the necessary precision is complex, and the electronics to do it proportionately expensive. Recently, the mass production of V.32 chipsets has lowered the cost of V.32 modems significantly. HST Because V.32 was, at the time of its introduction, very expensive to implement, USRobotics derived from V.32 an asymmetrical modulation technique which provided a 9600 bps 'forward channel' and a 300 bps 'back channel'. This allowed the HST to send keystrokes, ACK packets, etc. back to the host without requiring that the high-speed carrier direction be reversed - but was incompatible with any other 9600 bps modulation technique. The HST used a variation of MNP for its error correction. The HST became popular because of its relatively low price (compared to the complex Telebit modem and the premium Hayes product) and because of the 'SYSOP offer' (an agressive marketing plan designed to place many of these modems with operators of public-access systems, forcing those who communicated with them to consider the HST when they wanted to upgrade to 9600 bps). V-9600 At the same time, Hayes was also developing a less expensive V.32 derivative. In stead of accepting a reduced speed backchannel, Hayes concentrated on refining the ping-pong technique used to simulate full duplex using a single carrier. The resulting product, the V-Series Smartmodem 9600, was also incompatible with other 9600 bps modulation techniques. For error correction, Hayes offered a choice between X.25 and LAP-B (Link Access Protocol, Balanced), an SDLC derivative. Neither of these offered compatibility with the emerging industry standard, MNP. Hayes also introduced a 2400 bps modem which offered X.25 or LAP-B, and a "V-Series Modem Enhancer", which gave existing Hayes Smartmodem 2400 owners the same features. HST 14.4 Faced with significant competition from inexpensive V.29 modems (some of which used powerful data compression techniques to achieve outstanding throughput), USRobotics increased their physical bit rate from 9600 to 14400 bps. The resulting 50% boost in throughput gave them a performance edge over most other manufacturers. This model of HST is often called the "HST fourteen-four". T2500 It was not long before owners of Telebit, USRobotics, and Hayes HST DS modems became concerned that their considerable investment in high Ultra speed modems did not always permit them to communicate at 9600 bps with others who had also spent a lot on high speed modems. This pressure, combined with the lowering cost of V.32 chipsets, led each manufacturer to introduce a 'dual standard' model, which was capable of communicating both with the manufacturer's own modems and with others which supported V.32. These were the Telebit T2500, The USRobotics Courier HST Dual Standard, and the Hayes V-Series Ultra Smartmodem 9600. V.42 In the mean time, the CCITT had been meeting to develop a standard for error correction between dialup modems. The result, recommendation V.42, included two protocols: LAP-M (the Link Access Protcol for Modems, derived from SDLC) and MNP. The latter, up to service class 4, was included as 'Annex A' to maintain compatibility with the large pool of existing MNP-equipped modems. V.42bis Aware also that MNP5 and other data compression techniques had become popular, the CCITT released recommendation V.42bis, which specified a data compression technique which would provide dramatic performance improvements where possible, but which would not become a burden when the information being sent was already well compressed. V.32bis Currently in the discussion phase, V.32bis may be released by February of 1991. It will describe a full-duplex carrier technique that will provide 14400 bps physical bit rate, effectively 'catching up' to the HST 14.4. Some manufacturers have already begun advertising V.32bis modems, but there is no gusrantee that they will be compatible with the final specification. CDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDBDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD? 3 Dwight Hubbard 3 USENET : uunet!easy!lron 3 3 Kaneohe, Hawaii 3 GT-Power: 029/004 (lron) 3 3 3 CFR : 31:910/101 (Dwight Hubbard) 3 @DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDADDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDY
ghost@bucsf.bu.edu (Jay Adelson) (01/13/91)
Can someone please tell me what the difference between the standards v.32, v.32bis, v.42, v.42bis is? And which modems have which? (Between the Telebit and the USRobotics?) -- """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" [ Jay Adelson | BIX: j.adelson ] [ T.G.C. ] [ ghost@bucsf.bu.edu | Channel One: ] [ 1039 Commonwealth Ave. #18 ] [ GEnie: J.ADELSON1 | Jay Adelson ] [ Boston, MA. 02215-1008 ]
tron1@tronsbox.xei.com (Kenneth Jamieson) (01/14/91)
In article <GHOST.91Jan13020101@bucsf.bu.edu> ghost@bucsf.bu.edu (Jay Adelson) writes: > >Can someone please tell me what the difference between the standards >v.32, v.32bis, v.42, v.42bis is? And which modems have which? (Between >the Telebit and the USRobotics?) > >-- V.42 is the faster of the two standards, and seems to be the convergance point that may end most proprietary modes. The Telebit T2500 has V.42 and the V.32 standards, as well as all the normal stuff, and the PEP mode, as well as uucp protocol spoofing.. (can speed up UUCP x-fers). I think the HST Dual Standard has V.32/42 -- ========[ Xanadu Enterprises Inc. Amiga & Unix Software Development]======= = "I hate you, take your things and get out of this house!!!!!" = = (pause) - "Hold me!" ( same girl, elapsed time 6.5 seconds) = =========== Ken Jamieson: uunet!tronsbox.xei.com!tron1 =================== = NONE of the opinions represented here are endorsed by anybody. = === The Romantic Encounters BBS 201-759-8450(PEP) / 201-759-8568(2400) ====
lron@easy.hiam (Dwight Hubbard) (01/14/91)
In article <653@tronsbox.xei.com>, Kenneth Jamieson writes: > V.42 is the faster of the two standards, and seems to be the > convergance point that may end most proprietary modes. V.42 is a standard for error detection/correction, nothing else. If V.42 has almost nothing to do with the speed of the modem and in some cases will slow it down. V.32 and V.32bis are standards for the modulation of the actual signal and are what will determine whether a modem will connect at the 9600 (V.32) or 14.4(V.32bis) in the future. > The Telebit T2500 has V.42 and the V.32 standards, as well as > all the normal stuff, and the PEP mode, as well as > uucp protocol spoofing.. (can speed up UUCP x-fers). > > I think the HST Dual Standard has V.32/42 All the New Telebit and USR high speed modems support V.42/V.42bis The Telebit T2500 and the Dual Standard support V.32 as well. CDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDBDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD? 3 Dwight Hubbard 3 USENET : uunet!easy!lron 3 3 Kaneohe, Hawaii 3 GT-Power: 029/004 (lron) 3 3 3 CFR : 31:910/101 (Dwight Hubbard) 3 @DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDADDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDY
pondscum@zooid (Lima Bone) (01/29/91)
ghost@bucsf.bu.edu (Jay Adelson) writes: > > Can someone please tell me what the difference between the standards > v.32, v.32bis, v.42, v.42bis is? And which modems have which? (Between > the Telebit and the USRobotics?) > > -- > """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" > [ Jay Adelson | BIX: j.adelson ] [ T.G.C. > [ ghost@bucsf.bu.edu | Channel One: ] [ 1039 Commonwealth Ave. #18 > [ GEnie: J.ADELSON1 | Jay Adelson ] [ Boston, MA. 02215-1008 Wayll, I think any modem with v.42bis has also v.32bis..I have a USRobotics HST with v.42bis and it also has the capability of v.42bis...which I think is merely the name of the data-compression that it uses. I could be wrong, but that's what it looks like.
bruce@zuhause.MN.ORG (Bruce Albrecht) (02/01/91)
>In article <sJkiw2w162w@zooid> pondscum@zooid (Lima Bone) writes: >ghost@bucsf.bu.edu (Jay Adelson) writes: > >Wayll, I think any modem with v.42bis has also v.32bis..I have a USRobotics >HST with v.42bis and it also has the capability of v.42bis...which I think >is merely the name of the data-compression that it uses. I could be wrong, >but that's what it looks like. > Not true. V.42bis is a compression scheme, and is available on 2400 baud modems, but V.32bis is a 14400 baud protocol that is being approved by standards committees as we speak. A V.32bis modem implies V.32, though. -- bruce@zuhause.mn.org