Serial Line IP (SLIP) is a simple protocol for framing IP datagrams so they can be sent over a serial connection. It marks packet boundaries with special control characters; it does not configure IP addresses, identify different network protocols, or detect transmission errors.
What does SLIP stand for?
SLIP stands for Serial Line IP. In RFC 1055, published in June 1988, J. Romkey describes it as a way to transmit IP datagrams over serial lines. Its job is limited to framing: as Romkey puts it, “SLIP defines a sequence of characters that frame IP packets on a serial line, and nothing more.” RFC 1055
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How does SLIP frame a packet?
SLIP uses the END control byte to mark the end of a packet. Since that byte, or the SLIP ESC byte, might also occur in packet data, SLIP substitutes a two-byte escape sequence for either value inside the data.
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problems| Meaning | Value in RFC 1055 | How it is used |
|---|---|---|
| END | Octal 300 (decimal 192) | Marks a packet boundary; an END byte terminates a packet. |
| ESC | Octal 333 (decimal 219) | Introduces an escape sequence inside packet data. |
| END within packet data | ESC followed by octal 334 (decimal 220) | Represents an END value without ending the packet. |
| ESC within packet data | ESC followed by octal 335 (decimal 221) | Represents an ESC value as packet data. |
Romkey also relays an implementation suggestion from Phil Karn: send an END byte before the packet as well as after it. The leading END can flush stray bytes left by line noise so they are less likely to be treated as part of the next packet. This is a suggested framing practice, not a negotiated SLIP feature. RFC 1055
#1 Best Overall
- This is a serial RS232 to Ethernet server, used for data transparent transmission. USR-TCP232-302 is a low-cost serial device server,whose function is to realize bidirectional transparent transmission between RS232 and Ethernet. USR-TCP232-302 is internally integrated with TCP/IP protocol. User can apply it to device networking communication.
- Support DHCP, automatically obtain an IP address and query IP address through serial setting protocol, Support DNS function, Set parameters through webpage, Upgrade firmware via network.
- Auto-MDI/MDIX, RJ45 port with 10/100Mbps, Serial port baud rate from 600 bps to 230.4 Kbps, Check bit of None, Odd, Even, Mark and Space.
- Work Mode: TCP Server, TCP Client, UDP Client, UDP Server, HTTPD Client. Support virtual serial port and provide corresponding software USR-VCOM, Heartbeat package mechanism to ensure connection is reliable, put an end to dead link, User-defined registration package mechanism, check connection status and use as custom packet header.
- Under TCP Server mode, Client number ranges from 1 to 16; default number is 4, The global unique MAC address bought from IEEE, user can define MAC address, Across the gateway, switches, routers, Can work in LAN, also can work in the Internet (external network).
What does SLIP not provide?
SLIP is not a complete link-control protocol. RFC 1055 says it has no mechanisms for communicating IP addresses, identifying packet types, detecting or correcting errors, or compressing packets. RFC 1547 further notes that SLIP lacks even parity and has no protocol-type field; without that field, it cannot distinguish multiple higher-level protocols on the same connection or support option negotiation and extensibility. RFC 1055 RFC 1547
That distinction matters: SLIP supplies packet boundaries, not delivery guarantees or address assignment. The protocols and configuration at either end must handle needs beyond that framing role.
Rank #2
- DB9 to RJ45 adapter: used for TCP/IP network interface with serial port network function, support serial data and network data bidirectional transparent transmission.Compatible with desktop computer, digital machine tools, PDA, bar code and other standard DB9 serial devices, stable and reliable performance, support maximum distance 66ft.
- The DB9 RS232 COM signal is transmitted over the network cable,When using this adapter, it is recommended to use within a distance of 1-15 meters.Requires no external power, easy and Convenient to use.
- High quality alloy transmission port reduce the transmission impedance and interference,environmentally friendly PVC material, super wear-resistant, Integral injection molding. improve data transmission rate and transmission quality.
- Interface: DB9 Male to RJ45 female; 9pin/8P8C.the adapter run RS232 data over long distances (up to 100m) using UTP Cat 5/ Cat6 cable to bridge the gap.
- Special Note: Usually this product needs to be used in pairs, specifically divided into: female to female, male to female, male to male three kinds of situations. Can also be used alone.
How large can a SLIP packet be?
RFC 1055 does not define a formal maximum packet size. For compatibility, Romkey says implementations should be prepared to accept datagrams of 1006 bytes, including the IP and transport-protocol headers but excluding SLIP framing characters, and should not send larger datagrams. Treat that figure as the RFC’s recommended compatibility limit, not a universal maximum built into SLIP. RFC 1055
Is SLIP an Internet standard?
RFC 1055 calls SLIP a de facto standard but explicitly says, “It is not an Internet standard.” The RFC Editor’s catalog associates RFC 1055 with STD 47, but that catalog grouping does not override the memo’s own status wording. RFC 1055 RFC Editor: STD 47
Rank #3
- ARM core, Cortex-M0 solution, equipped with deeply optimized TCP/IP protocol stack. It has low latency and strong scalability, stable and reliable.
- Supports Modbus RTU to Modbus TCP protocol conversion and multi-host polling
- Supports hardware and software watchdog, automatically restarts when the device goes down.
- 10/100Mbps Ethernet port and support Auto MDI/MDIX
- Support RS232, RS485 and RS422.
Why was SLIP used?
Romkey traces SLIP’s origins to 3COM UNET in the early 1980s and says Rick Adams implemented it for 4.2 Berkeley Unix and Sun systems around 1984. The 1988 memo describes use on dedicated and dial-up serial lines. Its speed figures—usually 1200 bps to 19.2 kbps—refer to the period described in that memo, not current serial-network practice or a present-day usage statistic. RFC 1055
For a reader choosing a point-to-point serial protocol, the key distinction is scope: SLIP is a minimal way to frame IP packets. RFC 1547 discusses its limitations in contrast with requirements for a point-to-point protocol, including addressing, protocol identification, error detection, and negotiation. It is a requirements discussion, not a current product comparison. RFC 1547
Quick Recap
Best Value
- A simple, cost effective solution to process serial data communication between RS232 COM port devices over inexpensive cat5 cat6 RJ45 network cable
- DB9 female to RJ45 modular adapter converts DB9 female connector into an RJ45 female connector (DB9 female - RJ45 Female pinout: 1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 7-7, 8-8, 9-x)
- A pair of DB9 to RJ45 socket coupler can be used a extender to extend rs232 serial signals up to 65ft
- Bi-directional DB-9 female to RJ-45 female converter comes with thumbscrews for easy and secure connection
- (Please be noted it's NOT 15 pin VGA video port) It's compatible with Standard 9 Pin D-sub RS-232 Devices e.g. computer laptop, printer, modem, router, PDA, POS device, digital CNC machine tool, Barcode scanner, etc.
Rank #4
- [Extend Serial Signal] RS232 serial extender coupler transmit RS232 serial data up to 65ft (20m) over affordable Cat5 Cat6 Ethernet LAN cables, replace bulky DB9 extension cords
- [Serial Extension Kit] has 1x DB9 Male to RJ45 female serial adapter, and 1x DB9 Female to RJ45 female RS232 serial dapter for serial data communication.
- DB9 to RJ45 modular adapter is compatible with computer desktop, PC terminal , laptop, industrial CNC machines, PDAs, POS terminals, bar code scanners, printer, modem, digital scales, router and 9 pin D-sub serial devices for serial line connections
- [Plug and play ] Bi-directional DB-9 to RJ-45 female RS232 serial adapter comes with thumbscrews for easy and secure RS232 COM port devices connection.
- [Usage Note] This is an RS232 serial DB9 adapter for Serial Data Only, NOT a DB15 VGA video adapter. It does NOT provide internet network connectivity.
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