An inexpensive local-area network (LAN) architecture built into all Apple Macintosh computers and laser printers. AppleTalk supports Apple's
LocalTalk cabling scheme, as well as Ethernet and IBM Token Ring. It can connect Macintosh computers and printers, and even PCs if they are equipped with special AppleTalk hardware and software.
ATM Asynchronous Transfer Mode
Asynchronous Transfer Mode is a network technology based on transferring data in cells or packets of a fixed size of 53 byte
(5 byte header information and 48 byte payload). The cell used with ATM is relatively small compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and
computer data over the same network, and assure that no single type of data hogs the line. The adaptation to different network transport services and requirements is done by different ATM Adaptation Layers (AAL)
AAL1: Real time services with constant bit rate, connection-oriented, circuit emulation
AAL2: Real time services with variable bit rate, connection-oriented
AAL3/4: Services without necessary timing relation, variable bit rate, connection-less/oriented
AAL5: Services without necessary timing relation, variable bit rate
ATM creates a fixed channel, between two points whenever data transfer begins. This differs from TCP/IP, in which messages are divided into packets and each packet can take a different route from source to
destination. This difference makes it easier to track and bill data usage across an ATM network, but it makes it less adaptable to sudden surges in network traffic.
When purchasing ATM service, you generally have a choice of four different types of service:
Constant Bit Rate (CBR) specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line.
Variable Bit Rate (VBR) provides a specified throughput capacity but data is not sent evenly. This is a popular choice for voice and videoconferencing data.
Unspecified Bit Rate (UBR) does not guarantee any throughput
levels. This is used for applications, such as file transfer, that can tolerate delays.
Available Bit Rate (ABR) provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is
An overview about AAL (Adaptation Layer) AAL0, AAL2, AAL3/4 and AAL5 with descriptions of the different ATM service classes and parameters of the AAL PDUs can be found here:
DECT Digital Enhanced Cordless Telecommunications
DECT is a flexible digital radio access standard for cordless communications in residential and public
environments for voice and multimedia traffic. The standard makes use of several advanced digital radio techniques to achieve efficient use of the radio spectrum; it delivers high speech quality and security with low risk of
radio interference and low power technology.
TDMA (Time Division Multiple Access) radio access, with its low radio interference characteristics, provides high system capacity.
ADPCM (Adaptive Differential Pulse Code Modulation) is used for speech encoding to ensure a speech quality, which is comparable to wireline telephony.
DCS/DCA (Dynamic Channel Selection / Allocation) is a unique DECT capability that guarantees the best radio channels available to be used. This happens when a cordless phone is in stand-by mode and
throughout a call. This capability ensures that DECT can coexist with other DECT applications and with other systems in the same frequency range.
Other features of the DECT standard include encryption for call security and optimized radio transmission for maximum battery life.
DECT basic technology and the various profiles enhance the DECT standard to introduce new applications and services.
DQDB Dual Queue Dual Bus
DSL / xDSL Digital Subscriber Line
Refers collectively to all types of digital subscriber lines, the two main categories being ADSL and SDSL. Two other
types of xDSL technologies are High-data-rate DSL (HDSL) and Symmetric DSL (SDSL). DSL technologies use sophisticated modulation schemes to pack data onto copper wires. They are sometimes referred to as last-mile technologies
because they are used only for connections from a telephone switching station to a home or office, not between switching stations.
xDSL is similar to ISDN in as much as both operate over existing copper telephone lines
(POTS) and both require the short runs to a central telephone office (usually less than 20,000 feet). However, xDSL offers much higher speeds up to 32 Mbps for downstream traffic, and from 32 Kbps to over 1 Mbps for upstream
ADSL Asymmetric Digital Subscriber Line
Technology that allows more data to be sent over existing copper telephone lines (POTS). ADSL supports data rates of from 1.5 to 9 Mbps when receiving
data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). ADSL requires a special ADSL modem.
G.SHDSL High-data-rate Digital Subscriber Line
Also known as G.991.2, G.SHDSL is an international standard for symmetric DSL developed by the ITU. G.SHDSL provides for sending and
receiving high-speed symmetrical data streams over a single pair of copper wires at rates between 192 kbps and 2.31 Mbps. G.SHDSL was developed to incorporate the features of other DSL technologies, such as ADSL and SDSL
and will transport T1,E1, ISDN, ATM and IP signals. This is the first DSL technology to be developed from the ground up as an international standard. G.SHDSL was ratified by the ITU in February 2001.
SDSL Symmetric Digital Subscriber Line
Technology that allows more data to be sent over existing copper telephone lines (POTS). SDSL supports data rates up to 3 Mbps.
SDSL works by sending
digital pulses in the high-frequency area of telephone wires. Since these high frequencies are not used by normal voice communications, SDSL can operate simultaneously with voice connections over the same wires.
requires a special SDSL modem. SDSL is called symmetric because it supports the same data rates for upstream and downstream traffic. A similar technology that supports different data rates for upstream and downstream data
is called asymmetric digital subscriber line (ADSL). ADSL is more popular in North America, whereas SDSL is being developed primarily in Europe.
FC Fiber Channel
A serial data transfer architecture developed by a consortium of computer and mass storage device manufacturers and now being standardized
by ANSI. The most prominent Fibre Channel standard is Fibre Channel Arbitrated Loop (FC-AL). This was designed for new mass storage and other peripheral devices that require very high bandwidth. Using optical fiber to connect
devices, FC-AL supports full-duplex data transfer rates of 100MBps. FC-AL is compatible with, and is expected to eventually replace SCSI for high-performance storage systems. FC-AL loops are hot-pluggable and tolerant of
The FC standard supports bandwidths of 133 Mbps, 266 Mbps, 532 Mbps., 1.0625 Gbps, and 4 Gbps at distances of up to ten kilometers. Gigabit Fibre Channel's maximum data rate is 100 MBps (200 MBps full-duplex) after
accounting for overhead.
In addition to its strong channel characteristics, Fibre Channel also provides powerful networking capabilities, allowing switches and hubs to enable the interconnection of systems and storage into
The FC standard defines a layered protocol architecture consisting of five layers, the highest defining mappings from other communication protocols onto the FC fabric. Protocols supported include:
Because the details of the FC technology are hidden by the protocol interfaces, the impact on system software is minimal.
FDDI Fiber Distributed Data Interface
ANSI protocol for sending digital data over fiber optic cable. FDDI networks are token-passing networks, and support
data rates of up to 100 Mbps. FDDI networks are typically used as backbones in wide-area networks.
The FDDI-2 protocol extension, supports the transmission of voice and video information as well as data. Another
variation of FDDI, called FDDI Full Duplex Technology (FFDT) uses the same network infrastructure but can potentially support data rates up to 200 Mbps.
A packet-switching protocol for connecting devices on a Wide Area Network (WAN). Frame Relay networks in the U.S. support data transfer rates at
T1 (1.544 Mbps) and T3 (45 Mbps) speeds. Frame Relay service is provided for customers who want connections at 56 Kbps to T1 speeds. In Europe Frame Relay speeds vary from 64 Kbps to 2 Mbps.
LMDS Local Multipoint Distribution System
Local multipoint distribution system (LMDS) is the broadband wireless technology used to deliver voice, data,
Internet, and video services in the 25-GHz and higher spectrum. As a result of the propagation characteristics of signals in this frequency range, LMDS systems use a cellular-like network architecture, though services provided
are fixed, not mobile. In the United States, 1.3 MHz of bandwidth (27.5 B 28.35 GHz, 29.1 B 29.25 GHz, 31.075 B 31.225 GHz, 31 B 31.075 GHz, and 31.225 B 31.3 GHz) has been allocated for LMDS to deliver broadband services in a
point-to-point or point-to-multipoint configuration to residential and commercial customers. This tutorial details the underlying technology inherent in offering voice, data, Internet, and video services over LMDS through
integration with the wireline environment.
SNA System Network Architecture
Set of network protocols originally designed in 1974 for IBM's mainframe computers. SNA has evolved over the years so
that it now also supports peer-to-peer networks of workstations.
UMTS Universal Mobile Telecommunications System
One of the major new 'third generation' (3G) mobile communications systems being developed within the
framework defined by the ITU and known as IMT-2000. It will play a key role in creating the mass market for high-quality wireless multimedia communications that will exceed 2 billion users worldwide by the year 2010. This
market will be worth over 1 trillion US dollars to mobile operators over the next ten years.
UMTS will enable the wireless Information Society, delivering high-value broadband information, commerce and entertainment services
to mobile users via fixed, wireless and satellite networks and will speed convergence between telecommunications, IT, media and content industries to deliver new services and create fresh revenue-generating opportunities. UMTS
will deliver low-cost, high-capacity mobile communications offering data rates as high as 2Mbit/sec under stationary conditions with global roaming and other advanced capabilities.
The first UMTS services launched
commercially in 2001 with now over 100 3G awarded licenses while experimental systems are now in field trial with several leading vendors worldwide. UMTS will deliver pictures, graphics, video communications and other wideband
information as well as voice and data, direct to people who can be on the move. UMTS builds on the capability of today's mobile technologies (like digital cellular and cordless) by providing increased capacity, data capability
and a far greater range of services using an innovative radio access scheme and an enhanced, evolving core network. The new coding scheme for UMTS is WCDMA (Wideband Code Devision Multiplex Access).
HSDPA High Speed Downlink Packet Access
HSDPA is a packet-based data service in UMTS/WCDMA downlink and offers breakthrough in data speeds with data transmission up to 8-10 Mbps (and
20 Mbps for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search
and advanced receiver design.
HSDPA introduces a new transport channel type, called High Speed Downlink Shared Channel (HS-DSCH) that makes efficient use of valuable radio frequency resources and takes into account
bursty packet data.
HSDPA is based on WCDMA evolution, standardized as part of 3GPP Release 5 WCDMA specifications and backward compatible with Release 99 WCDMA systems, which is basically a voice service.
The new modulation method of HSDPA greatly improves the peak data rate and throughput, which enhances spectral efficiency. In addition to these benefits, users will perceive faster connections to services through
shorter round trip times which is based on:
adaptive modulation and coding
fast scheduling function, which is controlled in the base station (BTS), rather than by the radio network controller (RNC).
fast retransmissions from BTS with soft combining and incremental redundancy
As a result of these enhancements, operators using HSDPA will be able to support considerably higher numbers of high data rate users on a single radio carrier than is possible with any existing 3G technology.
ZigBee is an Alliance of semiconductor manufacturers, technology providers and OEM's dedicated to providing wireless applications and networking
layer to reside on top of the MAC of the IEEE low data rate WPAN standard 802.15.4, providing interoperability certification and testing. It includes security and application profile layers. Version 1.0 was ratified in Q4/2004
includes profiles for wireless home control. Additional application domains and related profiles will be released shortly.
ZigBee-compliant products take full advantage of a IEEE 802.15.4 physical radio standard and operate
in unlicensed bands worldwide at 2.4GHz (global), 915Mhz (Americas) and 868Mhz (Europe). Raw data throughput rates of 250Kbs can be achieved at 2.4GHz (16 channels), 40Kbs at 915Mhz (10 channels) and 20Kbs at 868Mhz (1
channel). Transmission distances range from 10 to 100 meters, depending on power output and environmental characteristics. Up to 64.000 network nodes per 'network coordinator' can be supported.
(last update: October 2005)