RSCS
Encyclopedia
RSCS,the fundamental software that powered the world’s largest network (or network of networks) prior to the Internet
and which directly influenced both internet development and user acceptance of networking between independently managed organizations, was an acronym for the Remote Spooling Communications Subsystem produced by Edson Hendricks
and T.C. Hartmann. Both as an IBM
product and as an IBM internal network, it later became known as VNET
. The network interfaces continued to be called the RSCS compatible protocols and were used to interconnect with IBM systems other than VM
systems (typically MVS
) and non-IBM computers.
The history of this program, and its influence on IBM and the IBM user community, is described in contemporaneous accounts and interviews by Melinda Varian. Technical goals and innovations are described by Creasy and by Hendricks and Hartmann in seminal papers. Among academic users, the same software was employed by BITNET
and related networks worldwide.
In 1971, Norman L. Rasmussen, Manager of IBM’s Cambridge Scientific Center
(CSC), asked Hendricks to find a way for the CSC machine to communicate with machines at IBM’s other Scientific Centers. CPREMOTE had taught Hendricks so much about how a communications facility would be used and what function was needed in such a facility, that he decided to discard it and begin again with a new design. After additional iterations, based on feedback from real users and contributed suggestions and code from around the company, Hendricks and Tim Hartmann, of the IBM Technology Data Center in Poughkeepsie, NY, produced RSCS, which went into operation within IBM in 1973.
The first version of RSCS distributed outside of IBM (1975) was not a complete networking package. It included uncalled subroutines for functions such as store-and-forward that were included in the IBM internal version. The store-and-forward function was added in the VNET
PRPQ, first for files, and then for messages and commands.
Once those capabilities were added, “the network began to grow like crazy.” Although at first the IBM network depended on people going to their computer room and dialing a phone, it soon began to acquire leased lines.
At SHARE
XLVI, in February, 1976, Hendricks and Hartmann reported that the network, which was now beginning to be called VNET, spanned the continent and connected 50 systems. By SHARE 52, in March, 1979, they reported that VNET connected 239 systems, in 38 U.S. cities and 10 other countries. “VNET passed 1000 nodes in 1983 and 3000 nodes in 1989. It currently (1990s) connects somewhat more than 4000 nodes, about two-thirds of which are VM systems.”
In comparison, by 1981 the ARPANET consisted of 213 host computers. Both ARPANET and VNET continued to grow rapidly.
By 1986, IBM’s Think magazine estimated that VNET was saving the company $150,000,000 per year as the result of increased productivity.
, Hartmann reverse-engineered the HASP Network Job Interface protocol, which enabled the network to grow rapidly. He later added the JES2 Network Job Entry as an RSCS/VNET line driver.
BITNET
was a cooperative USA university network founded in 1981 by Ira Fuchs
at the City University of New York
(CUNY) and Greydon Freeman at Yale University
which was based on VNET. The first network link was between CUNY and Yale.
The BITNET (RSCS) protocols
were eventually ported to non-IBM mainframe operating systems, and became widely implemented under VAX/VMS in addition to DECnet.
At its zenith around 1991, BITNET extended to almost 500 organizations and 3,000 nodes, all educational institutions. It spanned North America (in Canada it was known as NetNorth), Europe (as EARN), India (TIFR) and some Persian Gulf
states (as GulfNet). BITNET was also very popular in other parts of the world, especially in South America, where about 200 nodes were implemented and heavily used in the late 1980s and early 1990s.
Over time, BITNET was eventually merged into the Internet.
Details of the design of RSCS as a virtual machine subsystem are described in the IBM Systems Journal.
From a technical point of view, RSCS differed from ARPANET
in that it was a point-to-point "store and forward
" network. Unlike ARPANET, it did not require dedicated interface message processor
or continuous network connections. Messages and files were transmitted in their entirety from one server to the next until reaching their destination.
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
and which directly influenced both internet development and user acceptance of networking between independently managed organizations, was an acronym for the Remote Spooling Communications Subsystem produced by Edson Hendricks
Edson Hendricks
Edson Hendricks , an IBM computer scientist, developed RSCS , fundamental software that powered the world’s largest network prior to the Internet and which directly influenced both Internet development and user acceptance of networking between independently managed organizations...
and T.C. Hartmann. Both as an IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
product and as an IBM internal network, it later became known as VNET
VNET
VNET is an international computer networking system deployed in the mid 1970s and still in current, but highly diminished use. It was developed inside IBM, and provided the main email and file-transfer backbone for the company throughout the 1980s and 1990s...
. The network interfaces continued to be called the RSCS compatible protocols and were used to interconnect with IBM systems other than VM
VM (operating system)
VM refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370...
systems (typically MVS
MVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
) and non-IBM computers.
The history of this program, and its influence on IBM and the IBM user community, is described in contemporaneous accounts and interviews by Melinda Varian. Technical goals and innovations are described by Creasy and by Hendricks and Hartmann in seminal papers. Among academic users, the same software was employed by BITNET
BITNET
BITNET was a cooperative USA university network founded in 1981 by Ira Fuchs at the City University of New York and Greydon Freeman at Yale University...
and related networks worldwide.
Background
RSCS arose because people throughout IBM recognized a need to exchange files. Hendricks’s solution was CPREMOTE, which he completed by mid-1969. CPREMOTE was the first example of a “service virtual machine” and was motivated partly by the desire to prove the usefulness of that concept.In 1971, Norman L. Rasmussen, Manager of IBM’s Cambridge Scientific Center
Cambridge Scientific Center
The IBM Cambridge Scientific Center, established in February 1964 by Norm Rasmussen, was situated at 545 Technology Square , Cambridge, Massachusetts in the same building as MIT's Project MAC...
(CSC), asked Hendricks to find a way for the CSC machine to communicate with machines at IBM’s other Scientific Centers. CPREMOTE had taught Hendricks so much about how a communications facility would be used and what function was needed in such a facility, that he decided to discard it and begin again with a new design. After additional iterations, based on feedback from real users and contributed suggestions and code from around the company, Hendricks and Tim Hartmann, of the IBM Technology Data Center in Poughkeepsie, NY, produced RSCS, which went into operation within IBM in 1973.
The first version of RSCS distributed outside of IBM (1975) was not a complete networking package. It included uncalled subroutines for functions such as store-and-forward that were included in the IBM internal version. The store-and-forward function was added in the VNET
VNET
VNET is an international computer networking system deployed in the mid 1970s and still in current, but highly diminished use. It was developed inside IBM, and provided the main email and file-transfer backbone for the company throughout the 1980s and 1990s...
PRPQ, first for files, and then for messages and commands.
Once those capabilities were added, “the network began to grow like crazy.” Although at first the IBM network depended on people going to their computer room and dialing a phone, it soon began to acquire leased lines.
At SHARE
SHARE (computing)
SHARE Inc. is a volunteer-run user group for IBM mainframe computers that was founded in 1955 by Los Angeles-area IBM 701 users. It evolved into a forum for exchanging technical information about programming languages, operating systems, database systems, and user experiences for enterprise users...
XLVI, in February, 1976, Hendricks and Hartmann reported that the network, which was now beginning to be called VNET, spanned the continent and connected 50 systems. By SHARE 52, in March, 1979, they reported that VNET connected 239 systems, in 38 U.S. cities and 10 other countries. “VNET passed 1000 nodes in 1983 and 3000 nodes in 1989. It currently (1990s) connects somewhat more than 4000 nodes, about two-thirds of which are VM systems.”
In comparison, by 1981 the ARPANET consisted of 213 host computers. Both ARPANET and VNET continued to grow rapidly.
By 1986, IBM’s Think magazine estimated that VNET was saving the company $150,000,000 per year as the result of increased productivity.
Other RSCS Protocol Compatible Networks
Due to the key role RSCS played in building networks, the line drivers became known as the “RSCS Protocols.” Ironically, the supported protocols were drawn from other programs. The CPREMOTE protocol may have been the very first symmetrical protocol (sometimes called a “balanced” protocol). To expand the RSCS network to include MVSMVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
, Hartmann reverse-engineered the HASP Network Job Interface protocol, which enabled the network to grow rapidly. He later added the JES2 Network Job Entry as an RSCS/VNET line driver.
BITNET
BITNET
BITNET was a cooperative USA university network founded in 1981 by Ira Fuchs at the City University of New York and Greydon Freeman at Yale University...
was a cooperative USA university network founded in 1981 by Ira Fuchs
Ira Fuchs
Ira H. Fuchs is an internationally known authority on innovative technology solutions for higher education and is a co-founder of BITNET, an important precursor of the Internet.Since 2010 he has been Executive Director of Next Generation Learning Challenges...
at the City University of New York
City University of New York
The City University of New York is the public university system of New York City, with its administrative offices in Yorkville in Manhattan. It is the largest urban university in the United States, consisting of 23 institutions: 11 senior colleges, six community colleges, the William E...
(CUNY) and Greydon Freeman at Yale University
Yale University
Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...
which was based on VNET. The first network link was between CUNY and Yale.
The BITNET (RSCS) protocols
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
were eventually ported to non-IBM mainframe operating systems, and became widely implemented under VAX/VMS in addition to DECnet.
At its zenith around 1991, BITNET extended to almost 500 organizations and 3,000 nodes, all educational institutions. It spanned North America (in Canada it was known as NetNorth), Europe (as EARN), India (TIFR) and some Persian Gulf
Persian Gulf
The Persian Gulf, in Southwest Asia, is an extension of the Indian Ocean located between Iran and the Arabian Peninsula.The Persian Gulf was the focus of the 1980–1988 Iran-Iraq War, in which each side attacked the other's oil tankers...
states (as GulfNet). BITNET was also very popular in other parts of the world, especially in South America, where about 200 nodes were implemented and heavily used in the late 1980s and early 1990s.
Over time, BITNET was eventually merged into the Internet.
Technical Issues
R. J. Creasy described RSCS as an operating system and considered it an essential component of the VM/370 Time-Sharing System. “The Virtual Machine Facility/370, VM/370 for short, is a convenient name for three different operating systems: the Control Program (CP), the Conversational Monitor System (CMS), and the Remote Spooling and Communications Subsystem (RSCS). Together they form a general purpose tool for the delivery of the computing resources of the IBM System/ 370 machines to a wide variety of people and computers. …..RSCS is the operating system used to provide information transfer among machines linked with communications facilities.”.Details of the design of RSCS as a virtual machine subsystem are described in the IBM Systems Journal.
From a technical point of view, RSCS differed from ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
in that it was a point-to-point "store and forward
Store and forward
Store and forward is a telecommunications technique in which information is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or node in a networking context, verifies the integrity of...
" network. Unlike ARPANET, it did not require dedicated interface message processor
Interface Message Processor
The Interface Message Processor was the packet-switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a ruggedized Honeywell DDP-516 minicomputer with...
or continuous network connections. Messages and files were transmitted in their entirety from one server to the next until reaching their destination.
Key differences
- VNET was the first large-scale connectionless network, making it possible for a computer to join the network using dial-up lines, making connection inexpensive while ARPANET required dedicated 50kb lines at first (later raised to 230KB. Most leased lines at the time typically operated at a maximum rate of 9600 baud.
- VNET employed a vastly simplified routing and path finding approach, later adopted for the Internet.
- VNET was a true “distributed control” while ARPANET required a “control” center operated at Bolt, Beranek, and Newman in Cambridge, MA.