Fog Creek Software
Discussion Board




ping - puzzling behavior

I have noticed a lot of times this strange phenomenon:

Let's say TCP connection to an IP (let's say a HTTP download, or a POP3 mail download) is slow, or has stopped transmitting (transfer rate = 0).

Then I issue a ping command:

ping -t IP

Suddenly the transfer rate starts to increase.

Also, if the connection stopped transmitting, it starts transmitting again.

This has happened in about 90% of the cases I tried it, and on several ISPs, both modem and cable.


I don't understand this - why does the TCP connection speed improve when I issue a ping?

It is a very strange phenomenon!

Thank you!

Jack Thybolt
Tuesday, September 16, 2003

Routing....

Simon Lucy
Tuesday, September 16, 2003

Well, if routing is designed so that ping-ing the other computer improves performance of the communication, why isn't it built into TCP itself?

Why doesn't TCP also run a ping -t automatically, for each connection?

Jack Thybolt
Tuesday, September 16, 2003

The only thing I can think of (if it turns out to be real) is that the ICMP traffic might kick some bad flow-control implementation out of a slump.

Just me (Sir to you)
Tuesday, September 16, 2003

It used to be common to set your macnine to ping every five minutes to keep the connections alive. Some sites used to try and ban it mind you

Stephen Jones
Tuesday, September 16, 2003

*  Recent Topics

*  Fog Creek Home