Bouncer (networking)
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A bouncer, often abbreviated as BNC, is used to relay traffic and connections in computer networks. Using a bouncer allows a user to hide the original source of the user's connection, providing privacy as well as providing the possibility of routing traffic through a specific location. A bouncer can also be used to hide the true target to which a user connects. This should not be confused with e-mail, which redirects mail or "bounces" it backward to the sender when the recipient's mailbox is full.
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[edit] IRC use
One common usage is over Internet Relay Chat (IRC) via a bouncer running on remote servers. In such an environment, where it is very easy to ascertain a user's IP address a BNC may help to hide the original connection source, as well as providing the opportunity for fun "vhosts" or "virtual hosts". The use of a vhost does not conceal the connection any better, but merely adds a statement as the hostname.
A bouncer may also remain connected to an IRC server in the event the client should disconnect from the Internet. Often state changes are tracked so that they may be relayed to the client upon reconnection. Some implementations opt to store all messages sent across the network that the client would have normally received, and send them upon the clients reconnection; this is often considered to be much too resource dependent for commercial hosting services to provide. Other logging features and bot like functions may be included with various implementations but are not standard.
Example:
- User A logs onto IRC directly and appears as USER!user@255.255.255.0
- User A logs onto IRC indirectly through a bnc and appears as USER!user@example.net
- Note: example.net is a fictional example, and in this context it would resolve to the IP address, or hostname of the BNC.
[edit] Examples
This is a short, incomplete list of bouncers:
- DarkBNC
- ZNC
- miau
- muh
- sBNC
- dircproxy
- phpBNC
[edit] FTP use
BNCs are also often used for FTP, again to either hide the user and server from each other and also to route traffic through a specific location. FTP bouncers can be divided in two different categories, entry and traffic. Entry bouncer acts as a gateway to the server, but it doesn't hide the existence of the actual server. Entry bouncers, like cubnc can be used in multi-server setup for easy access to each server and load balancing. This removes the need to select which FTP server to login to, when trying to access the server farm.
Traffic bouncers relay traffic through the host they are installed on, and when used, it appears as the bouncer is actually the FTP server thus hiding the real location of the server completely. Multiple traffic bouncers can be installed parallel, in order to balance traffic load across different links. Most elaborate bouncers can even bounce secure SSL/TLS connections.
