Saturday, July 10, 2010

OSX Network: Network Error (tcp_error)

If website not loaded and the following error is displayed usually it's caused by DNS cache.

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Network Error (tcp_error)
A communication error occurred: "Operation timed out"
The Web Server may be down, too busy, or experiencing other problems preventing it from responding to requests. You may wish to try again at a later time.

For assistance, contact your network support team.

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DNS request are usually cache, that’s good as it speeds up the lookups within the same host but sometimes we will want to clear the cache so it don’t hold the values that are no longer valid.

In Leopard (Mac OSX 10.5) or Snow Leopard (10.6) to clear DNS cache , just type this in your Terminal and hit enter:

dscacheutil -flushcache


Note:
A DNS server matches the URL of a website (eg www.domain.com) with its numeric IP address - it translates www.domain.com into the unique numeric IP address (XX.XX.XX.XXX). Whenever you request a web page, your browser asks the name server to find the numeric translation of the URL.

Without the DNS servers, it would be a complicated web because we would have to know all the IP addresses rather than the nice friendly name, like Google.com.