full word VLR in networking

VLR stands for Visitor Location Register in networking. It is a database of the subscribers who have roamed into the jurisdiction of the Mobile Switching Center (MSC) which it serves. Each base station in the network is served by exactly one VLR, hence a subscriber cannot be present in more than one VLR at a time.

The VLR is responsible for a significant amount of the functionality of the GSM system such as the implementation of roaming. When a mobile phone roams into a new MSC area, the VLR connected to that MSC will request information about the new mobile from the Home Location Register (HLR) database. This process is known as location updating. Information is stored in the VLR about the mobile's identity, its authentication information, and its activity status. This information can be used by the MSC to provide services to the roaming mobile phone.

The VLR also provides temporary network data and routing information required for the call setup process. This includes the Mobile Station Roaming Number (MSRN) which is used to route the call to the MSC/VLR area where the mobile is currently located.

In summary, the VLR plays a crucial role in managing roaming and call setup for mobile phones in a GSM network.