Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!umd5!brl-adm!brl-smoke!w8sdz From: w8sdz@brl-smoke.ARPA (Keith B. Petersen ) Newsgroups: comp.binaries.ibm.pc.d Subject: Re: Zmodem Summary: Zmodem DOES work Keywords: Zmodem Unix DSZ Zcomm Sz Rz Message-ID: <8066@brl-smoke.ARPA> Date: 10 Jun 88 15:44:59 GMT References: <3079@crash.cts.com> <9599@e.ms.uky.edu> <22019@amdcad.AMD.COM> Reply-To: w8sdz@brl.arpa (Keith B. Petersen (WSMR|towson) ) Organization: Ballistic Research Lab (BRL), APG, MD. Lines: 56 The article below offers some good advice to those having problems with DSZ, ZCOMM or Unix Zmodem (rz/sz>. : Path: lll-tis!oodis01!uplherc!utah-gr!stride!tahoe!adonis : From: adonis@tahoe.unr.edu (Paul Graham) : Newsgroups: comp.binaries.ibm.pc.d : Subject: Re: DSZ Uploads : Date: 7 May 88 21:12:39 GMT : : [old article quotes deleted] : : More than likely, the problem is buffering in the network. Zmodem : is a streaming protocol, so it does not wait for a response after each : packet is sent. This results in the networks buffers becoming overridden : fairly quickly. (I would think that the reason it takes longer in Boneill's : case is that his network has larger buffers.) In order to force Zmodem to : stop and wait for a response, one must set the numeric parameter "w" to 1024 : or so (depending on the network). This tells Zmodem to stop and wait every : 256 bytes. In order to set it to 1024 (as an example) is to include in the : command line (before the "sz" or "rz", and after the speed and port settings) : "z pw1024". Experiment with this number. You want the largest number that : will allow transfers. This will be different for every network. I quote : from the Zcomm manual in regard to this parameter: : : w If non 0, restrict the ZMODEM transmitted window to the : specified number of bytes. Setting this parameter to N requests : acknowledgements from the receiver every N/4 characters. Pro-YAM : [Zcomm and DSZ too (my insertion)] then waits for acknowledgements : from the receiver whenever it has sent N more characters thean it : has received acknowledgements for. This parameter is uesful with : networks with defective flow control, and with networks that store : an excessive number of characters in transit. : : Another parameter that might be useful is the "l" parameter, described in : the following: : : l If non zero, forces ZMODEM to close a frame and wait for an : ACK after each # bytes (default 0). The frame length may be : adjusted to prevent buffer overflow in data PBX systems. : : Using one of these two parameters has given me error free transfers in both : directions through a Sytek network. This is particularly astonishing since : the Zmodem program on the UNIX end thinks that we are at 9600 baud, when : actually, after going through the network, things are at 1200 baud (ugh!). : Hope this help. : : -- : ----------------------------------------------------------------------------- : There are more important things to be | Derrick Hamner : than responsible. | {backbone}!tahoe.unr.edu!adonis -- Keith Petersen Arpa: W8SDZ@SIMTEL20.ARPA Uucp: {bellcore,decwrl,harvard,lll-crg,ucbvax,uw-beaver}!simtel20.arpa!w8sdz GEnie: W8SDZ