From: San M. <net...@va...> - 2001-07-25 15:32:18
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Ard, This has been a common problem with network T/S's... when receiving data from the serial port, they wait for either a minimum number of bytes to arrive, or for a maximum timeout before sending the data over the network... these devices are normally optimized for streaming protocols (as they should be), and obviously it doesn't work with us... That's one of the reasons I like cisco's.. their RAW port *really* is raw... one byte of data from the serial port ends up sending a frame... which is why they work.... I also tried other network terminal servers like the Digi EtherLites, various Livingston beasties, etc... -san -----Original Message----- From: 'Ard van Breemen' [mailto:ar...@te...] Sent: Wednesday, July 25, 2001 7:29 AM To: San Mehat Cc: vac...@li... Subject: Re: [Vacm-general] Slow EMP handling On Wed, Jul 25, 2001 at 03:21:29PM +0200, 'Ard van Breemen' wrote: > On Tue, Jul 24, 2001 at 11:26:11AM -0700, San Mehat wrote: > > As I suspected, it looks like you're having a serial protocol issue.. > > The reason that only the cisco boxes are qualified as a *network* based > > connectivity method for EMP are that they have below 1 ms round trip > > latency on single byte transactions on their raw ports... The EMP > > protocol requires a MAXIMUM latency of 2ms per byte.. otherwise it will > > timeout the byte (and sometimes the fame). It is VERY difficult to > But how is the byte acked? What happens with modems? If I hook up a > modem, the round trip will probably exceed that 2 ms due to compression > and other stuff. We are after all talking about almost 4 byte-times. Allright... Debugging using tcpdump and ethereal. My system send a byte to the portmaster. 1.37 ms later the portmaster acks. 53 ms later the portmasters sends a packet containing data. Usually 1 byte as a reaction from my system. But sometimes up to 29 bytes. But always 53 ms... As if something was nagging... Or at least some timer seems to be involved... -- <ar...@te...> Telegraaf Elektronische Media http://wwwijzer.nl http://leerquoten.monster.org/ http://www.faqs.org/rfcs/rfc1855.html Let your government know you value your freedom. Sign the petition: http://petition.eurolinux.org/ |