Date: Fri, 3 Jun 94 04:30:01 PDT From: Advanced Amateur Radio Networking Group Errors-To: TCP-Group-Errors@UCSD.Edu Reply-To: TCP-Group@UCSD.Edu Precedence: Bulk Subject: TCP-Group Digest V94 #108 To: tcp-group-digest TCP-Group Digest Fri, 3 Jun 94 Volume 94 : Issue 108 Today's Topics: help with setting MSS Linux SCC drivers Send Replies or notes for publication to: . Subscription requests to . Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the TCP-Group Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: Thu, 2 Jun 94 13:46:13 PDT From: Glenn Elmore Subject: help with setting MSS To: tcp-group@ucsd.edu Here in northern California, we are in the process of replacing 10 MHz KISS Tiny2 TNC2s with Ottawa PI2 cards to drive my higher speed 904 MHz radios. With some assistance from Dave Perry, VA3DP, I've been successful in hacking PI.C to allow the cards to provide internal RxClock recovery but to run the DPLL with an external clock input instead of the BRG. This allows for an extra factor of 4 in speed. The cards successfully drive the radios at 230.4 kbps when the DPLL is sourced from the on-board oscillator. Operation with JNOS 110C has been something of a problem though. While I find that aggragate throughput of >200 kbps is possible with long pings and a repetition rate just a bit longer than the RTT, data throughput with FTP or SMTP is pretty disappointing. Increasing the radio speed from 38.4 kbps to 230.4 kbps only results in best FTP throughput numbers going from about 3.5 kchar/sec to 5.5 kchar/sec. In order to better understand the problem, I went back to an Ethernet card and compared JNOS to Clarkson FTP. On the same host&file that Clarkson transfers at 50 and 140 kchar/sec kbps (386DX33 host) JNOS only does 4.5kchar/sec and 7 kchar/sec for GET and PUT respectively. In poking around, I notice that in spite of tcp mss=1540 and tcp window of N*mss, n=1-8, and an attached card driver with an MTU of 2048, the maximum packet size actually transmitted is 512 bytes. I've found nothing that I can do from autoexec.nos that makes it larger. It appears that 512 bytes is the negotiated value. I see in tcp.h: #define DEF_MSS 512 /* Default maximum segment size */ What am I not doing right that is preventing larger than default MSS and better throughput? Could someone with a well-performing Ethernet configuration with JNOS give me some hints? I suspect that if I can make Ethernet work well, I can also make the radios&PI cards work well. Thanks, Glenn Elmore n6gn amateur IP: glenn@SantaRosa.ampr.org Internet: glenne@sr.hp.com ------------------------------ Date: Fri, 03 Jun 1994 12:53:36 +0100 (MET) From: Joerg Reuter DL1BKE Subject: Linux SCC drivers To: tcp-group@UCSD.EDU : I have a file of something that claims to be a beta of a generic SCC driver for : the Linux kernel, written by PE1NNZ. The "INSTALL" notes say that it is : implemneted as part of the kernel and was tested with several different : software packages, including WAMPES and KA9Q Linux ports. However, the author : says that he only tested it with the OptoSCC hardware. : You can get a newer version from me (1.4 beta). It works with the BayCom USCC card now and does not patch serial.c anymore (serial.c changes with every kernel patchlevel, I hope tty_io.c does NOT!). The code is based on the well-known PE1CHL-driver and ported to Linux by Guido PE1NNZ. I added some modifications from Rene DG0FT (for the BayCom USCC) and the KISS-mode settings. I`ll try to upload the driver to the "incoming" directory on UCSD.EDU next week. vy 73, -- Joerg Reuter Internet: dl1bke@melaten.ihf.rwth-aachen.de ampr-net: dl1bke@db0pra ax25 : DL1BKE @ DK0MWX.DEU.EU ------------------------------ End of TCP-Group Digest V94 #108 ******************************