The Serial Line Internet Protocol (SLIP) is a mostly obsolete encapsulation of the Internet Protocol designed to work over serial ports and modem connections. It is documented in RFC 1055. On PCs, SLIP has been largely replaced by the Point-to-Point Protocol (PPP), which is better engineered, has more features and does not require its IP address configuration to be set before it is established. On microcontrollers, however, SLIP is still the preferred way of encapsulating IP packets due to its very small overhead.

SLIP modifies a standard Internet datagram by appending a special "SLIP END" character to it, which allows datagrams to be distinguished as separate. SLIP requires a port configuration of 8 data bits, no parity, and either EIA hardware flow control, or CLOCAL mode (3-wire null-modem) UART opperation settings.

SLIP does not provide error detection, being reliant on other higher-layer protocols for this. Therefore SLIP on its own is not satisfactory over a particularly error-prone dial-up connection. It is however useful for testing real-time OS capabilities under load (by looking at flood-ping statistics).

A version of SLIP with header compression is called CSLIP (Compressed SLIP).

The Parallel Line Internet Protocol (PLIP) is very similar to SLIP, but works at higher speeds via a parallel port and null-printer cable.

For most uses both SLIP and PLIP have been replaced by increasingly-common Ethernet protocol based networking support and cross-cable setups –– or other point-to-point connections such as USB host-to-host cables –– used to transfer files between two computers where a network is not necessary or available.

External links

• RFC 1055
• Debian GNU/Linux: TCP/IP over null-modem by Stefan Ott
• TLDP: PLIP-Install-HOWTO
• A description of the PLIP protocol

Internet protocols

Serial Line Internet Protocol | SLIP | Serial Line Internet Protocol | SLIP | Serial Line Internet Protocol | SLIP | Протокол інтернет для послідової лінії | 串行线路IP协议