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Locator ID Separation Protocol

(Also locator/identifier separation protocol, LISP)

Locator ID separation protocol definition

The locator ID separation protocol (LISP) is a network architecture and protocol created to solve scalability issues in the current internet routing system. It separates the two main functions of IP addresses and offers multiple benefits:

  • Scalability. LISP reduces the size of routing tables because the core of the internet only needs to route based on RLOCs.
  • Mobility. Devices can move and change their RLOC without changing their EID, maintaining stable connections.
  • Multihoming. Devices can have multiple RLOCs for redundancy and load balancing, enhancing reliability.

See also: Endpoint authentication, Endpoint device, Automatic location identification

How LISP works

IP addresses serve two purposes: identifying a specific device on the network and specifying the device's location in the network.

Combining these two roles can cause problems, especially as the internet grows. The routing tables (maps used by routers to find paths) become very large and complex. And if a device is mobile, its IP address changes as it moves, which in turn disrupts ongoing connections. 

This is where LISP comes in. It separates the IP address into two distinct roles:

  1. 1.The endpoint identifier (EID) identifies the device and remains constant, even if the device moves to a different location.
  2. 2.The routing locator (RLOC) specifies the device's current location in the network.

When a source device wants to communicate with a destination device, it uses the EID of the destination. The LISP infrastructure maps this EID to the corresponding RLOC. Devices in the LISP architecture encapsulate data packets with an additional header containing both the EID and RLOC. This encapsulation allows the LISP routers to direct the packet to its correct destination based on the RLOC.