Local Area Transport

Last updated

Local Area Transport (LAT) [1] [2] is a non-routable (data link layer) networking technology developed by Digital Equipment Corporation [3] to provide connection between the DECserver terminal servers and Digital's VAX and Alpha and MIPS host computers via Ethernet, giving communication between those hosts and serial devices such as video terminals and printers. The protocol itself was designed in such a manner as to maximize packet efficiency over Ethernet by bundling multiple characters from multiple ports into a single packet for Ethernet transport. [4]

Contents

One LAT strength was efficiently handling time-sensitive data transmission. [1] [5] Over time, other host implementations of the LAT protocol appeared allowing communications to a wide range of Unix and other non-Digital operating systems using the LAT protocol.

History

In 1984, the first implementation of the LAT protocol connected a terminal server to a VMS VAX-Cluster in Spit Brook Road, Nashua, NH. By "virtualizing" the terminal port at the host end, a very large number of plug-and-play VT100-class terminals could connect to each host computer system. Additionally, a single physical terminal could connect via multiple sessions to multiple hosts simultaneously. Future generations of terminal servers included both LAT and TELNET protocols, one of the earliest protocols created to run on a burgeoning TCP/IP based Internet. Additionally, the ability to create reverse direction pathways from users to non-traditional RS232 devices (i.e. UNIX Host TTYS1 operator ports) created an entirely new market for Terminal Servers, now known as console servers in the mid to late 1990s, year 2000 and beyond through today.

LAT and VMS drove the initial surge of adoption of thick Ethernet by the computer industry. By 1986, terminal server networks accounted for 10% of Digital's $10 billion revenue. These early Ethernet LANs scaled using Ethernet bridges (another DEC invention) as well as DECnet routers. Subsequently, Cisco routers, which implemented TCP-IP and DECnet, emerged as a global connection between these packet-based Ethernet LANs.

Over time, when terminals became less popular, terminal emulators had a built-in LAT client.

LAT features

If a computer communicating via LAT doesn't receive an acknowledgment within 80 milliseconds for a packet it transmitted, it resends that packet; this can clog a network. [1] No data is sent if no data is offered and under heavy loads LAT limits the number of packets sent per second to twenty-four: twelve transmits and twelve receives. As more characters are sent, the packets get bigger but not more numerous. Above 80 milliseconds latency a touch typist will notice the sluggish character echo. The LAT 80 millisecond delay offloads both the network by sending fewer larger packets which also reduces interrupts at each system.

Early terminal server vendors

Open Source solutions

Most Linux distributions offer a client and server lat package, that can easily be installed via a package manager. This allows e.g. to access a local area network server while being connected to a corporate VPN network that would otherwise block local TCP/IP traffic.

See also

Related Research Articles

AppleTalk is a discontinued proprietary suite of networking protocols developed by Apple Computer for their Macintosh computers. AppleTalk includes a number of features that allow local area networks to be connected with no prior setup or the need for a centralized router or server of any sort. Connected AppleTalk-equipped systems automatically assign addresses, update the distributed namespace, and configure any required inter-networking routing.

<span class="mw-page-title-main">Digital Equipment Corporation</span> U.S. computer manufacturer (1957–1998)

Digital Equipment Corporation, using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until he was forced to resign in 1992, after the company had gone into precipitous decline.

<span class="mw-page-title-main">Router (computing)</span> Device that forwards data packets between computer networks

A router is a computer and networking device that forwards data packets between computer networks, including internetworks such as the global Internet.

<span class="mw-page-title-main">Wake-on-LAN</span> Mechanism to wake up computers via a network

Wake-on-LAN is an Ethernet or Token Ring computer networking standard that allows a computer to be turned on or awakened from sleep mode by a network message. It is based upon AMD's Magic Packet Technology, which was co-developed by AMD and Hewlett-Packard, following its proposal as a standard in 1995. The standard saw quick adoption thereafter through IBM, Intel and others.

A network operating system (NOS) is a specialized operating system for a network device such as a router, switch or firewall.

<span class="mw-page-title-main">Network address translation</span> Technique for making connections between IP address spaces

Network address translation (NAT) is a method of mapping an IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device. The technique was originally used to bypass the need to assign a new address to every host when a network was moved, or when the upstream Internet service provider was replaced, but could not route the network's address space. It has become a popular and essential tool in conserving global address space in the face of IPv4 address exhaustion. One Internet-routable IP address of a NAT gateway can be used for an entire private network.

DECnet is a suite of network protocols created by Digital Equipment Corporation. Originally released in 1975 in order to connect two PDP-11 minicomputers, it evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s. Initially built with three layers, it later (1982) evolved into a seven-layer OSI-compliant networking protocol.

Systems Network Architecture (SNA) is IBM's proprietary networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in itself, is not a piece of software. The implementation of SNA takes the form of various communications packages, most notably Virtual Telecommunications Access Method (VTAM), the mainframe software package for SNA communications.

Virtual private network (VPN) is a network architecture for virtually extending a private network across one or multiple other networks which are either untrusted or need to be isolated.

<span class="mw-page-title-main">Ultrix</span> Series of discontinued Unix operating systems by DEC

Ultrix is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations.

<span class="mw-page-title-main">Network interface controller</span> Hardware component that connects a computer to a network

A network interface controller is a computer hardware component that connects a computer to a computer network.

TCP offload engine (TOE) is a technology used in some network interface cards (NIC) to offload processing of the entire TCP/IP stack to the network controller. It is primarily used with high-speed network interfaces, such as gigabit Ethernet and 10 Gigabit Ethernet, where processing overhead of the network stack becomes significant. TOEs are often used as a way to reduce the overhead associated with Internet Protocol (IP) storage protocols such as iSCSI and Network File System (NFS).

Interlink Computer Sciences, Inc., of Fremont, California, was a developer of hardware and software that allowed IBM mainframe computers running the MVS operating system to be connected to non-IBM networks.

<span class="mw-page-title-main">Terminal server</span> Device that interfaces serial hosts to a network

A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication. The primary application scenario is to enable serial devices to access network server applications, or vice versa, where security of the data on the LAN is not generally an issue. There are also many terminal servers on the market that have highly advanced security functionality to ensure that only qualified personnel can access various servers and that any data that is transmitted across the LAN, or over the Internet, is encrypted. Usually, companies that need a terminal server with these advanced functions want to remotely control, monitor, diagnose and troubleshoot equipment over a telecommunications network.

In computer networking, DECserver initially referred to a highly successful family of asynchronous console server / terminal server / print server products introduced by Digital Equipment Corporation (DEC) and later referred to a class of UNIX-variant application and file server products based upon the MIPS processor. In February 1998, DEC sold its Network Products Business to Cabletron, which then spun out as its own company, Digital Networks, in September 2000.

<span class="mw-page-title-main">Computer network</span> Network that allows computers to share resources and communicate with each other

A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.

PATHWORKS was the trade name used by Digital Equipment Corporation of Maynard, Massachusetts for a series of programs that eased the interoperation of Digital's minicomputers and servers with personal computers. It was available for both PC and Mac systems, with support for MS-DOS, OS/2 and Microsoft Windows on the PC. Before it was named PATHWORKS, it was known as PCSA.

Network Systems Corporation (NSC) was an early manufacturer of high-performance computer networking products. Founded in 1974, NSC produced hardware products that connected IBM and Control Data Corporation (CDC) mainframe computers to peripherals at remote locations. NSC also developed and commercialized the HYPERchannel networking system and protocol standards, adopted by Cray Research, Tektronix and others. In the late 1980s, NSC extended HYPERchannel to support the TCP/IP networking protocol and released a product allowing HYPERchannel devices to connect to the emerging Internet.

A VMScluster, originally known as a VAXcluster, is a computer cluster involving a group of computers running the OpenVMS operating system. Whereas tightly coupled multiprocessor systems run a single copy of the operating system, a VMScluster is loosely coupled: each machine runs its own copy of OpenVMS, but the disk storage, lock manager, and security domain are all cluster-wide, providing a single system image abstraction. Machines can join or leave a VMScluster without affecting the rest of the cluster. For enhanced availability, VMSclusters support the use of dual-ported disks connected to two machines or storage controllers simultaneously.

<span class="mw-page-title-main">Sniffer (protocol analyzer)</span> Network packet and protocol analyzer

The Sniffer was a computer network packet and protocol analyzer developed and first sold in 1986 by Network General Corporation of Mountain View, CA. By 1994 the Sniffer had become the market leader in high-end protocol analyzers. According to SEC 10-K filings and corporate annual reports, between 1986 and March 1997 about $933M worth of Sniffers and related products and services had been sold as tools for network managers and developers.

References

  1. 1 2 3 4 Len Grzanka (April 2, 1990). "LAT packets cross Interlink bridge first". Digital News . pp. 15, 61.
  2. ↑ "Local Area Transport (LAT) Specification" (PDF).
  3. ↑ Digital Equipment Corporation: VAX/VMS LAT control program reference manual, 1984.
  4. ↑ US 4823122,Mann, Bruce&Duffy, Darrell,"Local area network for digital data processing system",published 1989-04-18, assigned to Digital Equipment Corporation
  5. 1 2 Ciorey Sandler (July 10, 1989). "Datability's Howard: Aiming To Get The Message Across". Digital News . p. 86.
  6. ↑ "Cisco adds LAT support to TCP/IP terminal servers", Network World 7.15 (1990): 31.
  7. ↑ Bowen, Ted Smalley (November 13, 1989). "Ethernet PBX gateway, LAT-compatible server announced by Equinox". Digital Review. 6 (45). Reed Business Information: 8 – via Gale.
  8. ↑ Breidenbach, Susan: "HLS unveils file servers, software", Network World 6.33 (1989): 21,24.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.