Fast Local Internet Protocol
# Fast Local Internet Protocol

The Fast Local Internet Protocol (FLIP) is a communication protocol for LAN and WAN, conceived for distributed applications. FLIP was designed at the Vrije Universiteit Amsterdam to support remote procedure call (RPC) in the Amoeba distributed operating system.

## Comparison to TCP/IP

In the OSI model, FLIP occupies the network layer (3), thus replacing IP, but it also obviates the need for a transport layer (4) protocol like TCP.

Layers of functionality in OSI, TCP/IP, and FLIP. :

| Layer | OSI | TCP/IP | FLIP |
| - | - | - | - |
| 7 | Application | User-defined | User-defined |
| 6 | Presentation | User-defined | Amoeba Interface Language (AIL) |
| 5 | Session | Not used | RPC and Group communication |
| 4 | Transport | TCP or UDP | Not needed |
| 3 | Network | IP | FLIP |
| 2 | Data Link | E.g., Ethernet | E.g., Ethernet |
| 1 | Physical | E.g., Coaxial cable | E.g., Coaxial cable |

## Properties

FLIP is a connectionless protocol designed to support transparency (with respect to the underlying network layers of the OSI model: 2. data link and 1. physical), efficient RPC, group communication, secure communication and easy network management. The following FLIP properties helps to achieve the requirements of distributed computing:

* FLIP identifies entities with a location-independent 64-bit identifier called Network Service Access Points (NSAPs). An entity can, for example, be a process; contrary to the IP protocol where an IP address identify a host.
* FLIP uses a one way mapping between the “private” address, used to register an endpoint of a network connection, and the “public” address used to advertise the endpoint.
* FLIP routes messages based on NSAP (transparency).
* FLIP discovers routes on demand.
* FLIP uses a bit in the message header to request transmission of sensitive messages across trusted networks.
