ICMP tunnel

From Wikipedia, the free encyclopedia

An ICMP tunnel is a way to establish covert connection between two remote computers (named client and proxy) using only ICMP echo request and reply packets. Typical example of this technique would be tunneling complete TCP traffic over ping requests and replies.

1 Technical details
2 Uses
3 See also
4 References
5 External links

[edit] Technical details

This section is a stub. You can help by expanding it.

ICMP tunneling works by injecting arbitrary data into an echo packet sent to the remote computer. The remote computer replies in the same manner, injecting an answer into another ICMP packet and sending it back. The client performs all communication using ICMP echo request packets, while the proxy use echo reply packets. In theory, it is possible to have the proxy also use echo request packets (and make implementation much easier), but these packets are not necessarily forwarded to the client as the client could be behind a translated address (NAT). This bidirectional data flow can be abstracted with an ordinary serial line.

[edit] Uses

This section is a stub. You can help by expanding it.

Tunneling is often used to bypass firewalls which do not block ICMP packets, or to establish hard to trace, encrypted communication channel between two computers without direct network interaction.