gandrews@netcom.COM (Greg Andrews) (04/10/91)
In article <10334@pitt.UUCP> jonathan@cs.pitt.edu (Jonathan Eunice) writes: > >2. Would it be possible for the modem to hand the system data that is > still V.42 compressed? No need to use compress, the program, when > the h/w already puts it in a suitable form. Software for online > V.42 compression/decompression shouldn't be any harder to develop > than compress, right? And if there were lots of V.42 modems around, > which seems to be increasingly the case, V.42 might become a second > de facto standard in addition to today's compress. > You may not want to do that. If you're imagining a file transfer where the transmitting modem compresses the data and the receiving modem merely passes the data into the computer without any translation, then you're overlooking the file transfer protocol. The modems see just a stream of bytes. They don't discriminate between the protocol packet header and checksum bytes from the file data bytes. With compression on, the modem encodes the bytes into symbols that woudn't be recognizable to the transfer protocol on the receiving computer. (Telebit modems might appear to be an exception to this rule when spoofing is active, but the modems don't alter the packets - they just eliminate the need to pass acks back across the phone line) If the sending computer simply spewed the data out and the receiving computer captured it, you might be able to get that to work. However, you would have to ensure that a transparent flow control method is working properly between the modems and computers. A buffer overflow with consequent loss of bytes could have disastrous effects during the decompression phase. -- .------------------------------------------------------------------------. | Greg Andrews | UUCP: {apple,amdahl,claris}!netcom!gandrews | | | Internet: gandrews@netcom.COM | `------------------------------------------------------------------------'