From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ed Wildgoose Date: Tue, 22 Jun 2004 21:50:19 +0000 Subject: Re: [LARTC] Modems: Cable or DSL digital blunders that lartc may Message-Id: <40D8A99B.4020302@wildgooses.com> List-Id: References: <20040622043359.75922.qmail@web11905.mail.yahoo.com> In-Reply-To: <20040622043359.75922.qmail@web11905.mail.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org >http://www.lammertbies.nl/comm/info/RS-232_flow_control.html >ECN is software flow control. There is also icmp for software FC? The >idea is too prevent 'buffer underruns' in the modem, any SNMP or other >stats on this buffer would also provide SWFC. > > I don't consider this to be "flow-control" in the sense of throttling sending. This is really a syncronisation protocol. >http://www.nwfusion.com/netresources/0913flow.html >This is ethernets HWFC, that any directly connected modem could use. The >idea then is for the directly connected computer to use SwFC(ECN or >?icmp?) to pass this FC onto other hosts using the modem. > > Hmm, I wasn't aware of a "pause" ability for ethernet. But still this is a very low level layer 1 protocol. In other words this will calm your 100mb net card talking to your 10mbit port on your cable modem. But it has no idea that the cable modem only has a 256kb link You need something which works at IP level or above. TCP (level higher) has some stuff, but (I repeat) it basically involves dropping traffic until the sender slows down. There are protocols like ECN, but they are broadly unsupported. ICMP stuff is frequently dropped by routers/firewalls making it problematic (look at how difficult it is just to do MTU discovery!) What's your question though? Read the LARTC howto and the ADSL QOS howto. They are both excellent docs. Also read up on some basic TCP notes. There is nothing really clever that you can do - it's all in the docs you just have to work around the limitations of the protocols Ed W _______________________________________________ LARTC mailing list / LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/