Remote Initial Program Load (RIPL or RPL) is a protocol for starting a computer and loading its

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

from a

server Server may refer to: Computing *Server (computing), a computer program or a device that provides requested information for other programs or devices, called clients. Role * Waiting staff, those who work at a restaurant or a bar attending custome ...

via a network. Such a server runs a

network operating system A network operating system (NOS) is a specialized operating system for a network device such as a router, switch or firewall. Historically operating systems with networking capabilities were described as network operating systems, because they ...

such as

LAN Manager LAN Manager is a discontinued network operating system (NOS) available from multiple vendors and developed by Microsoft in cooperation with 3Com Corporation. It was designed to succeed 3Com's 3+Share network server software which ran atop a h ...

, LAN Server,

Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...

Server,

Novell Novell, Inc. () was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi-platform network operating system known as NetWare. Novell technolog ...

NetWare NetWare is a discontinued computer network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a personal computer, using the IPX network protocol. The final update release was ver ...

, LANtastic,

Solaris Solaris is the Latin word for sun. It may refer to: Arts and entertainment Literature, television and film * ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem ** ''Solaris'' (1968 film), directed by Boris Nirenburg ** ''Sol ...

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

. RIPL is similar to

Preboot Execution Environment In computing, the Preboot eXecution Environment (PXE; often pronounced as ''pixie''), often called PXE boot (''pixie boot''), is a specification describing a standardized client–server environment that boots a software assembly, retrieved ...

(PXE), but it uses the Novell NetWare-based

boot A boot is a type of footwear. Most boots mainly cover the foot and the ankle, while some also cover some part of the lower calf. Some boots extend up the leg, sometimes as far as the knee or even the hip. Most boots have a heel that is clearl ...

method. It was originally developed by

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

IBM LAN Server

IBM LAN Server enables clients (RIPL requesters) to load the operating systems

DOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

OS/2 OS/2 is a Proprietary software, proprietary computer operating system for x86 and PowerPC based personal computers. It was created and initially developed jointly by IBM and Microsoft, under the leadership of IBM software designer Ed Iacobucci, ...

via the 802.2/ DLC-protocol from the LAN (often

Token Ring Token Ring is a Physical layer, physical and data link layer computer networking technology used to build local area networks. It was introduced by IBM in 1984, and standardized in 1989 as IEEE Standards Association, IEEE 802.5. It uses a sp ...

). Therefore, the server compares the clients' requests with entries in its RPL.MAP table. Remote booting DOS workstations via

boot image A boot image is a type of disk image that when on a boot device allows the associated computer to Booting, boot. A boot image usually includes an operating system, utilities, diagnostics, boot and data recovery information and applications used ...

s was supported as early as 1990 by IBM LAN Server 1.2 via its PCDOSRPL protocol. IBM LAN Server 2.0 introduced remote booting of OS/2 stations (since OS/2 1.30.1) in 1992.

RPL and DOS

For DOS remote boot to work, the RPL boot loader is loaded into the client's memory over the network before the operating system starts. Without special precautions the operating system could easily overwrite the RPL code during boot, since the RPL code resides in unallocated memory (typically at the top of the available

conventional memory In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system ...

). The RPL code hides and thereby protects itself from being overwritten by hooking INT 12h and reducing the memory reported by this BIOS service by its own size. INT 12h is used by DOS to query the amount of available memory when initializing its own real-mode memory allocation scheme. This causes problems on more modern DOS systems, where free real-mode address ranges may be utilized by the operating system in order to relocate parts of itself and load drivers high, so that the amount of available conventional memory is maximized. Typically, various operating system vendor and version specific "dirty tricks" had to be used by the RPL code in order to survive this very dynamic boot process and let DOS regain control over the memory occupied by RPL once the boot is complete in a seamless manner. Since

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

/ PC DOS 5.0 and DR DOS 6.0, the operating system checks if the RPL has hooked INT 2Fh by looking for a "RPL" signature at the code pointed to by INT 2Fh. If present, DOS calls INT 2Fh/AX=4A06h to retrieve the amount of memory from the RPL and integrate it into its own memory allocation, thereby protecting the RPL code from being overwritten by other programs. Still, it remained the RPL's difficult responsibility to cleanly remove itself from memory at the end of the boot phase, if possible.

RPLOADER and DR-DOS

In addition to this "RPL" interface, DR DOS 6.0 and higher since 1991 support a more flexible extension named "RPLOADER". If DR DOS detects the presence of RPLOADER rather than RPL only, it starts to issue INT 2F/AX=12FFh/BX=0005h broadcasts at certain critical stages in the boot process. The RPL code can use them to relocate itself in memory (in order to avoid conflicts with other resident software or to avoid

memory fragmentation In computer storage, fragmentation is a phenomenon in the computer system which involves the distribution of data in to smaller pieces which storage space, such as computer memory or a hard drive, is used inefficiently, reducing capacity or perfo ...

when the RPL memory is freed later on), or to hook into and better integrate with the operating system in order to perform its final cleanup tasks in a well-defined and coordinated manner through a robust and supported backend interface rather than mere hacks. This helps to improve compatibility without having to adapt the RPL code with each new version of the operating system, and it avoids unnecessary memory fragmentation and thereby increases available memory for DOS programs to run. The interface can also be utilized to run DR DOS as a task under a host operating system such as

Concurrent DOS Multiuser DOS is a real-time multi-user multi-tasking operating system for IBM PC-compatible microcomputers. An evolution of the older Concurrent CP/M-86, Concurrent DOS and Concurrent DOS 386 operating systems, it was originally developed by ...

. Since 2018,

RxDOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

7.24 supports the "RPLOADER" broadcasts as well.

IBM LAN Server

RPL and DOS

RPLOADER and DR-DOS

See also

References

Further reading