Path: utzoo!utgpu!attcan!uunet! From: prindle@NADC.ARPA (Frank Prindle) Newsgroups: comp.sys.cbm Subject: Re: Kermit question Message-ID:Date: 18 Aug 88 13:05:00 GMT Sender: prindle@NADC.ARPA (Frank Prindle) Lines: 72 1. Kermit is definitely worth buying considering that it is FREE! Kermit is not a commercial product, but a series of implementations of a public domain protocol, where each of the implementations is also public domain. C64 Kermit was originally developed by Eric Lavitsky and others. It has recently been refined considerably by Ray Moody. It is available for the downloading from Columbia University or from many C64 oriented bulletin board systems. If you order it from Dr. Evil Labs on disk, Ray will charge $5.00 only for the diskette, postage, and handling; the software itself is FREE. 2. To upload a 4K file from C64 to VAX takes approximately 1 to 2 minutes at 1200 baud, depending on the handshake response time of the VAX system (i.e. how busy it is), and what kind of file is being transferred. Downloading is just a tad faster. 3. There really is only one "official" Kermit package for the C64, though it is available in several historically subsequent versions, the latest being version 2.1 (highly recommended for C128 owners because of it's support for the 80 column chip and it's VT100 emulation). Older versions (pre 2.0) supported a 25 line by 40 column, or 25 line by 80 column VT52 emulation on the C64 40-column screen only. The Kermit protocol may be embedded in other commercial terminal packages that are available, but these are not the "official" kermit implementation. 4. The factors that limit file transfer speed are: a. Baud rate: 1200 baud means that the theoretical maximum transfer rate is about 130 bytes/second. b. Packet Size: Kermit packets are limited to a maximum length of 96 bytes; after each 96 byte data packet is sent by the sending Kermit, the receiving Kermit must validate the packet and transmit either an ACK or NAK packet (about 5 or 6 bytes) back to the sender. c. Quoting: To avoid communication problems over a wide variety of networks, Kermit only utilizes the 95 printing ASCII characters and SOH (^A). A file that contains any other bytes (e.g. a binary file or PRG file) must have each non-printing character quoted by preceeding it with a special printing character. Thus a file containing many bytes in the ranges 00-1f, 7f-9f hex will take twice as long to transfer as a text file. Quoting increases even more if the communication path doesn't support 8 bits of data. d. Disk Read/Write speed: We all know what this is on the C64! Reads or writes to disk cause occasional delays in transmission. e. Response time of the remote system: If the remote host is a busy time sharing system, serving many users, it may not be able to validate packets and provide ACK responses quickly. f. Communication line delay: Telephone electronics between you and the remote host, if over long distance circuits, can cause noticable slowdown if delays are a substantial fraction of a second. All in all, therefore, the Kermit error-correcting protocol reduces a 1200 baud connection to an effective text transfer speed of typically 60 bytes/ second; obviously there can be considerable variation, with PRG files slowed down by about 25% more due to quoting. One really nice feature of Kermit protocol is that it supports multiple file transfers with a single command. However, C64 Kermit currently supports this only for downloads: you can start a transfer of 10 files, then go do something else for a half hour or so and come back when they are all done - you don't have to babysit each file. Future versions of C64 Kermit should support this for uploading too. For a complete discussion of the Kermit protocol by it's creators, Frank da Cruz and Bill Catchings, consult the June and July 1984 issues of Byte magazine. They have also published a book on Kermit. Sincerely, Frank Prindle Prindle@NADC.arpa