Path: utzoo!utgpu!watserv1!watmath!att!emory!swrinde!elroy.jpl.nasa.gov!sdd.hp.com!hplabs!hpda!hpcupt1!hpindwa!raj From: raj@hpindwa.cup.hp.com (Rick Jones) Newsgroups: comp.protocols.tcp-ip Subject: Re: Re: TELNET slow through bridge. Message-ID: <36540024@hpindwa.cup.hp.com> Date: 14 Mar 91 04:43:19 GMT References: <1991Mar12.223827.12815@shl.com> Organization: Hewlett-Packard, Cupertino CA Lines: 48 >In an earlier posting to comp.dcom.lans, I mentioned a problem we were >having telneting to an HP 3000 through a bridge using PC/TCP. Well, it >turns out that the problem is not related to the bridge, and is actually >composed of three separate problems. > ><> >Questions: > >1. Is it normal for PC TCP implementations to drop packets fairly >frequently? Ie about one packet every 100 or so? > It depends on a number of factors - not the least of which is the PC's interface... >2. The original TCP spec seems to be silent here, but surely this can't >be the 'standard' way retransmission works? I would have though that >the retransmitter would send all outstanding packets all at once after >an ack timeout, rather than one packet every timeout interval, the way >the HP 3000 does. > Eghads NO! !-) If you were to do that, it would be asking for your network to go into congestive collapse ;-( When that timer pops (the first one at least...) the ONLY thing that you can surmise is that the first packet was lost - you really do not know if any of the other packets were lost. When (if) you upgrade the MPE/V systems to an XL, you will find that the XL code is much better in its handling of those situations (it started-out like the V code, but I changed it ;-) It does NOT do batch-rtx, but will clear-out the rtxq much faster than the V code will. >3. Is it normal for TCP implementations to discard all out of sequence >packets? > Only on little systems like PC's where there is not much memory for the TCP code to hold onto. I think that newer PC code might be better though. >Thanks for any info! > no problem, I live to defend the honor of the MPE networking code ;-) ___ _ ___ |__) /_\ | Richard Anders Jones | HP-UX Networking Performance | \_/ \_/ Hewlett-Packard Co. | Was: MPE/XL Networking Person ------------------------------------------------------------------------ Being an employee of a Standards Company, all Standard Disclaimers Apply