www.timgilbert.ca

Ok, I learned something today. Bell Sympatico can not handle a MTU higher than 1460. I had the default 1492 in my router and I experienced a strange slowness on certain pages. Not all pages, I particularly noticed it with mail.yahoo.com and my Pidgen would take a long time to connect. It was really quite frustrating. Also, I couldn’t maintain a ssh connection, it would mysteriously disconnect- same with SVN.

After consulting with a networking expert (thanks Andrew) he recommended I check into MTU (Maximum Transmittion Unit). So, I used the ping -s option in GNU/Linux and discovered that 1460 was the largest MTU that didn’t result in truncation of the packet.

This isn’t documented by Bell (as far as I could find) anywhere.

For example:

$ ping -s 1492 www.google.com
PING www.l.google.com (72.14.205.99) 1492(1520) bytes of data.
1440 bytes from qb-in-f99.google.com (72.14.205.99): icmp_seq=1 ttl=244 (truncated)
1440 bytes from qb-in-f99.google.com (72.14.205.99): icmp_seq=2 ttl=244 (truncated)
1440 bytes from qb-in-f99.google.com (72.14.205.99): icmp_seq=3 ttl=244 (truncated)
1440 bytes from qb-in-f99.google.com (72.14.205.99): icmp_seq=4 ttl=244 (truncated)