Serial Line Internet Protocol: Difference between revisions
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|date=May 8, 1994}}</ref> is an [[encapsulation (networking)|encapsulation]] of the [[Internet Protocol]]{{efn|SLIP does not actually care about the internal structures of IP: any [[network layer]] protocols can be sent over the wire.}} designed to work over [[serial port]]s and [[router (computing)|router]] connections. It is documented in {{IETF RFC|1055}}. On personal computers, SLIP has largely been replaced by the [[Point-to-Point Protocol]] (PPP), which is better engineered, has more features, and does not require its IP address configuration to be set before it is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 [[Internet Protocol|IP packets]], due to its very small overhead. | |date=May 8, 1994}}</ref> is an [[encapsulation (networking)|encapsulation]] of the [[Internet Protocol]]{{efn|SLIP does not actually care about the internal structures of IP: any [[network layer]] protocols can be sent over the wire.}} designed to work over [[serial port]]s and [[router (computing)|router]] connections. It is documented in {{IETF RFC|1055}}. On personal computers, SLIP has largely been replaced by the [[Point-to-Point Protocol]] (PPP), which is better engineered, has more features, and does not require its IP address configuration to be set before it is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 [[Internet Protocol|IP packets]], due to its very small overhead. | ||
Some people refer to the successful and widely used RFC 1055 Serial Line Internet Protocol as "Rick Adams' SLIP",<ref name="rfc1547">{{IETF RFC|1547}}: "Requirements for an Internet Standard Point-to-Point Protocol" </ref> to avoid confusion with other proposed protocols named "SLIP". Those other protocols include the much more complicated {{IETF RFC|914}} appendix D [[Serial Line Interface Protocol]].<ref name="rfc1547" /> | Some people refer to the successful and widely used RFC 1055 Serial Line Internet Protocol as "[[Rick Adams (Internet pioneer)|Rick Adams]]' SLIP",<ref name="rfc1547">{{IETF RFC|1547}}: "Requirements for an Internet Standard Point-to-Point Protocol" </ref> to avoid confusion with other proposed protocols named "SLIP". Those other protocols include the much more complicated {{IETF RFC|914}} appendix D [[Serial Line Interface Protocol]].<ref name="rfc1547" /><ref name="rfc-editor/rfc914">{{cite web |title=Thinwire protocol for connecting personal computers to the Internet |url=https://www.rfc-editor.org/rfc/rfc914 |website=rfc-editor.org |publisher=[[Internet Engineering Task Force]] |access-date=20 May 2026 |date=September 1984}}</ref> | ||
==Description== | ==Description== | ||
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== History == | == History == | ||
{{see|Rick Adams (Internet pioneer)#Creation of SLIP}} | |||
{{See also|History of the Internet}} | {{See also|History of the Internet}} | ||
RFC 1055, a "non-standard" for SLIP, traces its origins to the 3COM UNET TCP/IP implementation from the 1980s. Rick Adams added SLIP to the popular [[4.2BSD]] in 1984 and it "quickly caught on". By the time of the RFC (1988), it is described as "commonly used on dedicated serial links and sometimes for dialup purposes".<ref name=rfc1055>{{cite web |title=RFC 1055: Nonstandard for transmission of IP datagrams over serial lines: SLIP |url=https://datatracker.ietf.org/doc/html/rfc1055 |website=IETF Datatracker |language=en |date=1 June 1988}}</ref> | RFC 1055, a "non-standard" for SLIP, traces its origins to the 3COM UNET TCP/IP implementation from the 1980s. Rick Adams added SLIP to the popular [[4.2BSD]] in 1984 and it "quickly caught on". By the time of the RFC (1988), it is described as "commonly used on dedicated serial links and sometimes for dialup purposes".<ref name=rfc1055>{{cite web |title=RFC 1055: Nonstandard for transmission of IP datagrams over serial lines: SLIP |url=https://datatracker.ietf.org/doc/html/rfc1055 |website=IETF Datatracker |language=en |date=1 June 1988}}</ref> | ||
Latest revision as of 11:30, 20 May 2026
Template:Short description Template:IPstack
The Serial Line Internet Protocol (SLIP)[1][2] is an encapsulation of the Internet ProtocolTemplate:Efn designed to work over serial ports and router connections. It is documented in Template:IETF RFC. On personal computers, SLIP has largely been 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.
Some people refer to the successful and widely used RFC 1055 Serial Line Internet Protocol as "Rick Adams' SLIP",[3] to avoid confusion with other proposed protocols named "SLIP". Those other protocols include the much more complicated Template:IETF RFC appendix D Serial Line Interface Protocol.[3][4]
Description
| Hex value | Dec Value | Oct Value | Abbreviation | Description |
|---|---|---|---|---|
| 0xC0 | 192 | 300 | END | Frame End |
| 0xDB | 219 | 333 | ESC | Frame Escape |
| 0xDC | 220 | 334 | ESC_END | Transposed Frame End |
| 0xDD | 221 | 335 | ESC_ESC | Transposed Frame Escape |
SLIP modifies a standard TCP/IP datagram by:
- appending a special "END" byte to it, which distinguishes datagram boundaries in the byte stream,
- if the END byte occurs in the data to be sent, the two byte sequence ESC, ESC_END is sent instead,
- if the ESC byte occurs in the data, the two byte sequence ESC, ESC_ESC is sent.
- variants of the protocol may begin, as well as end, packets with END.
SLIP requires a serial port configuration of 8 data bits, no parity, and either EIA hardware flow control, or CLOCAL mode (3-wire null-modem) UART operation settings.
SLIP does not provide error detection, being reliant on upper layer protocols for this. Therefore, SLIP on its own is not satisfactory over a link which is error-prone, such as a poor quality dial-up connection.
SLIP escape characters were also required on some modem connections to escape Hayes command set, allowing therefore to pass binary data through those modems that would recognize some characters as commands.
CSLIP
A version of SLIP with header compression is called Compressed SLIP (CSLIP).[5] The compression algorithm used in CSLIP is known as Van Jacobson TCP/IP Header Compression.[6] CSLIP has no effect on the data payload of a packet and is independent of any compression by the serial line modem used for transmission. It reduces the Transmission Control Protocol (TCP) header from twenty bytes to seven bytes. CSLIP has no effect on User Datagram Protocol (UDP) datagrams.
History
Template:See Script error: No such module "Labelled list hatnote". RFC 1055, a "non-standard" for SLIP, traces its origins to the 3COM UNET TCP/IP implementation from the 1980s. Rick Adams added SLIP to the popular 4.2BSD in 1984 and it "quickly caught on". By the time of the RFC (1988), it is described as "commonly used on dedicated serial links and sometimes for dialup purposes".[7]
The last version of FreeBSD to include "slattach" (a command for connecting to slip) in the manual database is FreeBSD 7.4, released 2011. The manual claims that auto-negotiation exists for CSLIP. The FreeBSD version is inherited from 4.3BSD.[8]
Linux formerly used the same code base for SLIP and KISS (TNC). The split occurred before the start of kernel git history (Linux-2.6.12-rc2, 2005).[9] The SLIP driver offers a special "6-bit" escaped mode to accommodate modems incapable of handling non-ASCII characters.[10] The Linux slattach command (written independently) also has the ability to auto-detect CSLIP support.[11]
See also
- Parallel Line Internet Protocol
- Slirp
- KA9Q
- Direct cable connection
- In-band signaling
- KISS (amateur radio protocol)
- Consistent Overhead Byte Stuffing
References
<templatestyles src="Reflist/styles.css" />
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ a b Template:IETF RFC: "Requirements for an Internet Standard Point-to-Point Protocol"
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1". — introduced the Van Jacobson TCP/IP Header Compression used by CSLIP
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ – Linux Programmer's Manual – Administration and Privileged Commands "Other possible values are slip (normal SLIP), adaptive (adaptive CSLIP/SLIP)...
Script error: No such module "Check for unknown parameters".
Script error: No such module "Authority control".