From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Goodman Date: Fri, 19 Sep 2014 20:42:15 +0000 Subject: Correctly calculating overheads on unknown connections Message-Id: <541C9527.1070105@yescomputersolutions.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Hi, I am looking to figure out the most fool proof way to calculate stab overheads for ADSL/VDSL connections. ppp0 Link encap:Point-to-Point Protocol inet addr:81.149.38.69 P-t-P:81.139.160.1 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1492 Metric:1 RX packets:17368223 errors:0 dropped:0 overruns:0 frame:0 TX packets:12040295 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:17420109286 (16.2 GiB) TX bytes:3611007028 (3.3 GiB) I am setting a longer txqueuelen as I am not currently using any fair queuing (buffer bloat issues with sfq) The connection is a BT Infinity FTTC VDSL connection synced at 80mbit/20mbit. The modem is connected directly to the ethernet port on a server running a slightly tweaked HFSC setup that you folks helped me set up in July - back when I was on ADSL. I am still running pppoe I believe from my server. The largest ping packet that I can fit out onto the wire is 1464 bytes: # ping -c 2 -s 1464 -M do google.com PING google.com (31.55.166.216) 1464(1492) bytes of data. 1472 bytes from 31.55.166.216: icmp_seq=1 ttlX time.7 ms 1472 bytes from 31.55.166.216: icmp_seq=2 ttlX time.9 ms # ping -c 2 -s 1465 -M do google.com PING google.com (31.55.166.212) 1465(1493) bytes of data. From host81-149-38-69.in-addr.btopenworld.com (81.149.38.69) icmp_seq=1 Frag needed and DF set (mtu = 1492) From host81-149-38-69.in-addr.btopenworld.com (81.149.38.69) icmp_seq=1 Frag needed and DF set (mtu = 1492) Based on this I believe overhead should be set to 28, however with 28 set as my overhead and hfsc ls m2 20000kbit ul m2 20000kbit I seem to be loosing about 1.5mbit of upload... No traffic manager enabled: http://www.thinkbroadband.com/speedtest/results.html?id1116089424883990118 HFSC traffic manager: http://www.thinkbroadband.com/speedtest/results.html?id1116216621093133034 Am I calculating overhead incorrectly? Alan