Differences for page Path MTU discovery -- hping network security tool

hping wiki

Differences for page Path MTU discovery

Current version compared with version Mon Sep 20 06:56:14 GMT 2004

...
  Other sources of information:
  
  [link http://www.faqs.org/rfcs/rfc1191.html RFC1191]
- http://www.netheaven.com/pmtu.html
  
+ [link http://www.netheaven.com/pmtu.html]
  
+ 
  See Also:
  
  [Path MTU], [MTU], [Path MTU spoofing]

The following is the old page content

The Path MTU discovery, documented with the [link http://www.faqs.org/rfcs/rfc1191.html RFC1191], is  a technique for dynamically discovering the
maximum transmission unit ([MTU]) of an arbitrary internet path, with the goal of avoiding [IP fragmentation].

It works using an [IP] header bit called the `Don't fragment` bit. Usually when a gateway forwards a packet from a network to another with
an [MTU] value that's smaller than the packet size, the packet gets fragmented in smaller parts (called fragments).
Instead if the `Don't fragment` bit is set in the [IP] header, the gateway
will refuse to fragment the packet, and will instead send an [ICMP] error of type `Fragmentation required but Don't fragment big set` to the source of
the packet. The error will quote part of the original packet, so the source has a way to know that it must use packets with a minor length when sending
to a given destination. The sender will try with smaller packets, if still an ICMP error will return, it will try again with a smaller packet and so on,
until the outgoing packets will be smaller enough to ensure no fragmentation will occur.

Other sources of information:

[link http://www.faqs.org/rfcs/rfc1191.html RFC1191]
http://www.netheaven.com/pmtu.html