Netsplit

In computer networking, specifically Internet Relay Chat (IRC), netsplit is the disconnection of a given node from the previously established network or between two nodes. As an IRC network is an undirected acyclic graph, a split between any two nodes splits the entire network into two pieces.

Consider the graphic to the right, which represents the computer network. Each line represents an established connection between the two nodes; each node represents either a server or a user on the network. Therefore, the server C is connected directly to A, which is also connected to B and D.

If a disruption in the connection between C and A occurs, the connection may be terminated as a result. This can occur either by a socket producing an error, or by excessive lag in which the far server A anticipates this case (which is called a timeout).

When the connection between A and C is severed, users who were connected to other servers that are no longer reachable on the network appear to quit. For example, if user Sara is connected to server A, user Bob is connected to server B, and user Joe is connected to C, and C splits, or disconnects, from A, it will appear to Joe as if Sara and Bob both quit (disconnected from the network), and it will appear to both Sara and Bob that Joe quit. However, Joe can still talk to anyone who is connected to the same server (in this case server C). This happens because the servers to which they are connected are informed of the change in the network status, and update their local information accordingly to display the change.

Later, server C may relink (reconnect) to a server (or servers) on the network and the users who appeared to have quit will rejoin; the process of sending this updated information to all servers on the network is called a netburst (or sync).

Occasionally, users will attempt to use netsplits to gain access to private channels. If none of the channel users were on server C, a user could join a private channel and later gain access when the servers relink. This is commonly known as split riding or riding the split.

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Wikipedia