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Using Nagle's algorithm

I just heard someone talking about using Nagle's algorithm and how it's a useful tool for maintenance. What is it and how do I use it?
The Nagle congestion control algorithm is something that many people turn on to improve the performance of their telnet session to and from the router. When using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed. On larger networks, many small packets use up bandwidth and contribute to congestion.

John Nagle?s algorithm (RFC 896) helps alleviate the small-packet problem in TCP. In general, it works this way: The first character typed after connection establishment is sent in a single packet, but TCP holds any additional characters typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace them out to the network at a rate matching the round-trip time of the given connection. This method is usually good for all TCP-based traffic, and helps when connectivity to the router is poor or congested, or the router itself is busier than normal.

So when you telnet to the router command line, enabling Nagle's algorithm will improve your perceived telnet performance.

However, do not use the service Nagle command if you have XRemote users on X Window sessions.

This was last published in April 2001

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