Whenever you saturate your link, the DSL modem has the opportunity to queue packets. You (or the remote server sending data to you, depending on direction) are sending data faster than the line can handle it, so the buffer starts filling up until it can't take any more. Aparently this is roughly two seconds worth of download or 5 second worth of upload. 2 seconds * 512kbit/sec = 1Mbit = 128Kbytes. A fairly reasonable buffer size. 4 sec * 128 Kbit/sec = 512Kbit = 64Kbyte. So, you can see that it doesn't take much data to put your modem several seconds behind the real world. Of course, the queue that would be active in a heavy DOWNLOAD would be in the DSL modem at your ISP, whereas the queue that would govern in an UPLOAD would be in your modem (assuming the ISP can retransmit your data to the internet at 128Kbit -- they'd better). If these ping times are frusterating to you, you might consider traffic shaping and policing. Check out lartc.org for info on traffic control. On Sat, 28 Aug 2004, Marcin Sura wrote: > Date: Sat, 28 Aug 2004 22:16:28 +0200 > From: Marcin Sura <slacklist@xxxxx> > To: netfilter@xxxxxxxxxxxxxxxxxxx > Subject: OT: Pings phenomen :) > > Hi > > I have 512/128 adsl. I wonder why, when I download files at full > speed, pings to site X are about 2000ms. But when I upload files at > full speed, pings to X are about 3000 to 5000ms. Can someone explain > this to me from tcp/ip point of view? ;) > > -- > Pozdrawiam > Marcin mailto:slacklist@xxxxx > >
