Introduction

Your Web server thinks that there has been too long an interval of time between 1) the establishment of an IP connection (socket) between the client (e.g. your Web browser or our CheckUpDown robot) and the server and 2) the receipt of any data on that socket, so the server has dropped the connection. The socket connection has actually been lost - your Web server has 'timed out' on that particular socket connection. The request from the client must be repeated - in a timely manner.

408 errors in the HTTP cycle

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle:

• Obtain an IP address from the IP name of your site (your site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
• Open an IP socket connection to that IP address.
• Write an HTTP data stream through that socket.
• Receive an HTTP data stream back from your Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

This error occurs in the final step above when the client receives an HTTP status code that it recognises as '408'.

Resolving 408 errors - general

408 errors are often difficult to resolve. They typically involve one-off variations in system workload or operations.

If you see persistent 408 errors, the first thing to consider is the workload on your Web server - particularly around the time the 408 errors were generated. If this is light, then you also need to consider workload on the client system. If the computer systems on both ends of the socket connection seem to be running normally, then temporary Internet surges may be to blame.

Resolving 408 errors - CheckUpDown

This error is highly unlikely to occur on your CheckUpDown account, because there is usually only a tiny interval of time (milliseconds) between our 1) opening of the socket and 2) writing the HTTP data stream through that socket. In exceptional circumstances, this interval may increase because of some operations on our computer systems e.g. we temporarily suspend an executing process and this happens immediately after the socket was created. Or the two steps may follow quickly on our systems, but the second step encounters an unreasonable delay on the Internet. The acceptable interval between the two steps could also be set very low on your Web server e.g. your server is very busy, and has become a bit 'impatient' with attempted connections it views as a bit slow.

Any of these conditions may generate an 408 error. But they are all fairly unlikely to occur. In normal IP communications, the time interval between the two steps should be much less than 10 seconds, which should be completely acceptable to your Web server. Please contact us (email preferred) if you see persistent 408 errors, so that we can agree the best way to resolve them.