Definitions And Background Of Telecom And Internet Service Terms

Written by: Michael Lemm - Nov 21, 2008

Below is a fairly comprehensive a list of Telecom and Internet Service Terms with definitions and/or background info for each. Hopefully you'll gain the necessary understanding you need for whatever your application.

10Base2

10 Mbps baseband Ethernet specification using 50 ohm thin coaxial cable. Also known as Thin Ethernet.

100BaseFX

100 Mbps baseband Fast Ethernet specification using two strands of multimode fibre-optic cable per link. To guarantee proper signal timing, a 100BaseFX link cannot exceed 1312 feet (400 meters) in length.

10BaseT

10 Mbps baseband Ethernet specification using two pairs of twisted-pair cabling. 100BaseT

100 Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BaseT technology on which it is based, 100BaseT sends link pulses over the network segment when no traffic is present. However, these link pulses contain more information than those used in 10BaseT.

A

ADM

Add/Drop Multiplexer. A device which inserts lower rate channel traffic [add] or removes the traffic [drop] from a higher rate aggregate channel in a synchronous transmission network (SDH or SONET). Typically adds or drops traffic at STM-1 or higher from a STM-64 aggregate signal. ADSL

Asymmetric Digital Subscriber Loop. A family of technologies used to deliver high-rate digital data over the existing copper local loop. One-way rates of up to 6 Mbps downstream (from the central office to the subscriber) and up to 640 kbps upstream have been achieved, although the technology is still evolving and higher data rates are expected in the future.

ADSL is expected to grow to become the main connection to the Net for the home and small business user due to the relatively low cost of the technology. ANSI

American National Standards Institute. www.ansi.org Application Layer

Seventh (top) layer in the OSI seven layer model. Layer Contains functions for particular applications services such as file transfer. ASCII

American Standard Code for Information Interchange. Method of encoding characters digitally. ASP

Applications Service Provider. An organization which provides applications (word processing, accounting packages, e-business, etc) remotely over a network. ATM

Asynchronous Transfer Mode. ATM is a connection-oriented packet switching technique where all cells follow the same path through the network. Cells are made up of 48 bytes of data plus a 5 byte header (53 bytes total). See www.atmforum.com for more details. Availability

The percentage of time for which a circuit or system is available for use. Carrier class is typically 99.999% - about five minutes downtime per year.

B

Backbone

The high-speed - usually long-haul - central portions of a telecommunications network. Bandwidth

Describes the width of the pipe into the customer. ’Bandwidth on demand’ refers to the ability to increase the bandwidth as needed. Baud

Baud - Unit of signaling speed in a communications system. Not to be confused with bps. One baud means one signal element transmitted per second.

A signal element may contain zero, one or more than one bit of information,depending on the method of modulation. BGP4

Border Gateway Protocol version 4. The major exterior gateway protocol used in the internet. Specified in RFC 1772. bit

BInary digiT. A 1 or a 0. The basic element of digital communication. Bluetooth

A specification for local area wireless communication. Bluetooth allows devices to discover each other and communicate without human intervention. See www.bluetooth.com for more details. bps

Bit(s) per second. Also b/s. Transmission capacity of a channel or system. BRI

Basic Rate Interface ISDN connection providing 2B+D, where B is a 64 kbps Bearer and D is a 16 kbps data channel. Bridge

Device that connects two or more networks together and forwards packets between them. The networks may use dissimilar protocols. A bridge operates at the data link layer (layer two) as opposed to a router which operates at layer three. Broadband

High-speed or high-capacity channel or system Byte

8 bits of information.

C

Carrier Class

A statement of system or network availability. Carrier class is typically 99.999% - about five minutes of downtime per year. CIR

Committed Information Rate. A specified amount of guaranteed bandwidth (measured in bits per second), usually on a Frame Relay service. Typically, when purchasing a Frame Relay service, a company can specify the CIR level they wish. The Frame Relay network vendor guarantees that frames not exceeding this level will be delivered. It's possible that additional traffic may also be delivered, but it's not guaranteed. Some Frame Relay vendors offer inexpensive services with a CIR equal to zero. This essentially means that the network will deliver as many frames as it can, but it doesn't guarantee any bandwidth level. CPE

Customer Premises Equipment. This is the equipment at the customer site which terminates the connection into the network and connects to the LAN for private networks, Internet connectivity and voice services.

D

Dark Fiber

A fiber-optic strand with no optical transmission equipment. Customers add their own equipment and build their own network, retaining complete control over all aspects of it. Datagram

The basic unit of information passed across the Internet. It is a self-contained packet containing source and destination addresses as well as data. See also frame and packet. Data Link Layer

Second layer in the OSI seven layer model. Layer Transmits packets from node to node. dB

deciBel. A logarithmic unit which defines the ratio between two powers P1 and P2. Ratio in dB = 10 log10 (P1/P2). The original unit was the Bel, named after Alexander Graham Bell, but is inconveniently large.

Used in power budgets to describe the optical loss over a particular link and therefore the optical power needed over the link in order to get a signal to the other end.

Used in fiber specifications to describe the loss per meter in the fibre, where the lower the loss the better. DBS

Direct Broadcast Satellite - where the end-user receives the broadcast signal direct from the satellite. As opposed to a satellite feed to a cable TV head end, for subsequent distribution to end-users via the cable network. DCN

Data Communication Network. Used to convey Network Management commands and reports around a communications network infrastructure. DHCP

Dynamic Host Configuration Protocol. A method of assigning an IP address dynamically to a device each time it connects to a network. DHCP simplifies network administration and means that normal PC's on a network do not need a fixed IP address. Dispersion

Normally refers to chromatic Dispersion. Chromatic Dispersion is the variation of propagation velocity - speed of travel of the light - in an optical fiber with frequency - and with wavelength - causing the pulses of light to be degraded and merge into each other as the light travels down the fibre. See also PMD. Different types of fiber have different Dispersion characteristics. Management of Dispersion is key to network design at the fiber level. DMZ

Demilitarized Zone. Part of the network to which access is controlled by a Firewall. DNS

Domain Name System. A distributed database which provides the mapping/translation between the domain name and the individual IP address allocated to that host. Domain Name

The domain name is the unique name that identifies an organization on the Internet. The Fully Qualified Domain Name (FQDN) includes the hostname and is easier to use than the numerical IP addresses which are used to route traffic to the correct destination. This means that you only need to remember the name of the web site rather than its IP address.

A given server may have or support more than one domain name, but a given FQDN points to only one host.

com Commercial edu Educational gov Government (US unless specified) int International mil Military (US unless specified) net Network org Non-profit organization

Subsequently the system was extended to allow an optional final two-letter country group. Examples are given below.

au Australia it Italy br Brazil jp Japan ca Canada mx Mexico de Germany nl Netherlands es Spain no Norway fi Finland se Sweden gr Greece tr Turkey hu Hungary uk United Kingdom in India us United States DS-0, DS-1

Digital Service. DSF

Dispersion Shifted fiber (G.653). fiber manufactured to achieve zero chromatic dispersion at 1550 nm - the wavelength of lowest loss. DWDM

Dense Wavelength Division Multiplexing. Multiplexing of signals by transmitting them on typically eight or more different wavelengths on the same fibre. The ’dense’ prefix usually signifies systems where the spacing between wavelengths is smaller than the first generation WDM systems.

E

E-1

Describes the first level in the European digital hierarchy and is 30 channels of 64 kbps, plus two channels signaling and framing, to give an overall rate of 2.048 Mbps. EDFA

Erbium Doped fiber Amplifier. Optical fibres doped with the rare earth element erbium, which can amplify light in the wavelength region from 1530nm to 1625nm when pumped by an external light source. EDFAs allow an optical pulse to travel long distances before electrical regeneration is required. Ethernet

A LAN access method defined in IEEE 802.3. It is a shared medium approach originally developed at Xerox Palo Alto Research Center using ideas from the University of Hawaii Aloha packet radio network. Available at 10 Mbps (10BaseT), 100 Mbps (100BaseT) and now 1 Gbps (Gigabit Ethernet).

Ethernet functions at layers one and two of the OSI model.

Also known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Ethernet is the most common LAN mechanism within an organization See also Fast Ethernet. ETSI

European Telecommunications Standards Institute. Located at Sophia-Antipolis near Nice, France. Defines technical standards and interfaces in Europe. See also ANSI and ITU.

F

Fast Ethernet

A 100 Mbps version of 10 Mbps Ethernet. FEC

Forward Error Correction. Technique for detecting and correcting errors (from imperfect transmission) by adding a small number of extra bits. FEC allows optical transmission over longer distances by correcting errors that can happen as the signal-to-noise ratio decreases with distance. See also Raman Amplification. Fibre-optic Cable

Network cabling that employs one or more Optical Fibres. Firewall

Device placed between an organization’s private network and the Internet to authenticate incoming users. A Firewall is normally a specially configured computer which is set up to only allow specific incoming traffic and users onto the network. Frame

1. A block of data in a specified format. 2. A rack housing telecommunications equipment. Frame Relay

High-speed packet switching technique used to interconnect LANs. Capable of any payload up to 4096 bytes per packet. Defined in ITU-T I.122. Typically used to build VPN's, particularly where guarantees of bandwidth are required. FWM

Four Wave Mixing. Describes the generation of unwanted sidebands when two or more high-power optical signals exist in the same non-ideal medium.

FWM is one of the elements that need to be taken into account when designing optical networks, and must be minimized if interference is to be avoided. FTP

File Transfer Protocol. Operates at layers five, six and seven of the OSI model and allows log-on to a remote host, directory listing and file transfer.

G

Gigabit

109 bits. Gateway

The router which provides the connection between the LAN and the WAN. GPS

Global Positioning System. Allows a GPS device to determine its location to better than 20m anywhere on, or above, the Earth by interpreting the signals from up to five orbiting satellites. Grooming

The process of combining partially filled trunks into a smaller number of fully filled trunks. GSM

Global System for Mobile communications. Used by second generation mobile phones to connect to the mobile networks. G.xxx

ITU-T recommendation G.xxx.

H

HTML

HyperText Markup Language. Simple hypertext document formatting language that uses tags to indicate how a given part of a document should be interpreted by a viewing application, such as a Web browser. HTTP

HyperText Transfer Protocol. Part of the TCP/IP suite. The underlying protocol of WORLd Wide Web pages, used to communicate between the user’s browser and the Web server. Hub

Central connecting point for star-connected circuits. Active hubs contain regeneration facilities.

I

IAB

Internet Architecture Board. Board of internet work researchers who discuss issues pertinent to Internet architecture. Responsible for appointing a variety of Internet-related groups. IETF

Internet Engineering Task Force. Task force consisting of over 80 working groups responsible for developing Internet standards (produced as RFC's). The IETF operates under the auspices of ISOC. ILA

In-Line Amplifier. Internet

The interconnection of computers across the world that evolved from the ARPAnet (Advanced Research Projects Agency).

The Internet is made up of many networks each run by a different company and interconnected at peering points. The common use of IP and Internet standards allows users connected to one network to communicate with users on another network. IP

Internet Protocol. Defines the unit of information passed between systems providing a basic packet delivery service within the TCP/IP. IP is a standard that describes how packets of data are transported across the Internet and recognized as incoming messages. IP addresses/ addressing (IPv4)

The unique 32 bit address for a specific TCP/IP host in the Internet. IPSec

IPSec provides security for transmission of sensitive information over unprotected networks such as the Internet. IPSec acts at the network layer, protecting and authenticating IP packets between participating IPSec devices. IPv6

Latest version of IP (www.ipv6.org). IPv6 uses 128 bit address space compared with the 32 bit IPv4 address. IRU

Indefeasible Right of Use. The provision of the Right of Use for a long period of time, usually 15+ years, of a bandwidth service - dark fibre, wavelengths or SDH - for an up front fee. ISDN

Integrated Services Digital Network. See also PRI. ISO

International Standards Organization ISOC

Internet Society. International non-profit organization founded in 1992 to coordinate the evolution and use of the Internet. In addition, ISOC delegates authority to other groups related to the Internet, such as the IAB. ISP

Internet Service Provider. Connects the end-user to the Internet. ITU

International Telecommunications Union

J

Jitter

Variation in timing, or time of arrival, of received signals; an unwanted lack of perfection which can lead to bit areas.

K

kilobit

One thousand bits (103).

L

LAN

Local Area Network. Used within a building to link computers and other devices, such as printers. Typically uses Ethernet. Latency

Time taken to deliver a packet from the source to the receiver. Includes propagation delay (the time taken for the electrical or optical signals to travel the distance between the two points) and processing delay. Due to the distance to a satellite and back (over 34,000km each way), the latency when communicating via a satellite connection is at least 270 milliseconds, making interactive services difficult, compared to a delay of about 10 milliseconds across Europe via fibre. Local Loop

Originally, the pair of wires (loop) between the subscriber (to a telephone system) and the local telephone exchange (switch or office). Now used as a generic term to describe the connection between the last switch/routing point and the subscriber, no matter what technology is used to deliver the service, nor what service (voice, data etc.) is delivered. M

MAN

Metropolitan Area Network. Megabit

One million bits (106 bits). MFD

Mode Field Diameter of an optical fibre. The diameter at which the electric and magnetic field strengths are reduced to 1/e of their maximum values (for a Gaussian distribution in a single mode fibre, and where e is the base of natural logarithms, 2.71828...). This is the practical replacement for core diameter in single-mode fibre. MIB

Management Information Base. Database of Network Management information that is used and maintained by a Network Management protocol such as SNMP or CMIP. The value of a MIB object can be changed or retrieved using SNMP or CMIP commands, usually through a GUI Network Management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches. Modem

MOdulator/DEModulator. Device for converting data signals to/from forms suitable for transmission over an analogue voice channel. MPLS

MultiProtocol Label Switching. A short fixed-length label is generated that acts as a shorthand representation of an IP packet's header. Subsequent routing decisions (made by Label Switched routers) are made based on the MPLS label and not the original IP address. This new technology allows core network routers to operate at higher speeds without needing to examine each packet in detail, and allows more complex services to be developed, allowing discrimination on a QoS basis. MS

Multiplex Section MS-SPRing

Multiplex Section Shared Protection Ring MTBF

Mean Time Between Failures. A key metric for the quality of equipment and a determining factor in the overall SLA that can be achieved. MTTR

Mean Time To Repair. The usual time taken to fix a problem that occurs on the network. Targets are normally set within an SLA and depend on the priority of the fault.

N

NAT

Network Address Translation. Used by a Firewall or Gateway to hide LAN IP addressing from devices on the WAN. NDSF

Non Dispersion Shifted fiber (G.652) Network Layer

Third layer in the OSI seven layer model. Determines routes based on network address. Network Management

The processes of managing, monitoring, and controlling a communications network. Modern Network Management systems also include the ability to re-configure network elements remotely. NOC

Network Operation Center nm

nanometer. 10-9 meter NZ-DSF

Non-Zero Dispersion Shifted fiber (G.655). Optical fiber which has been optimized for DWDM operation by having a small but finite amount of dispersion present at 1550nm.

O

Octet

Group of 8 data bits. OC-x

Optical Carrier - x. ODF

Optical Distribution Frame.

This is the point where the optical fiber within the backbone network terminates and the customer's equipment of fiber connects, providing the demarcation point between i-21 and the customer. Optical Fiber

A method of guiding light over long distances with very little reduction on strength (attenuation or loss). A central core of high-refractive index material - usually very pure glass - is covered with a cladding of lower refractive index material. Modern fibres have loss in the order of 0.25 dB/km, so 1 km of fiber has less loss than a pair of ordinary spectacles or reading glasses. Optronics

From Optoelectronics. The combination of optics and electronics. ORL

Optical Return Loss. Ratio of power reflected (from a connector or other discontinuity) to incident power. Usually expressed in dB. OSI

Open Systems Interconnection. An ISO standard defining a communications model with seven layers. The layers are: Layer 1 Physical layer - electrical or optical signals Layer 2 Data Link layer - transmits packets from node to node Layer 3 Network layer - determines routes based on network address Layer 4 Transport layer - manages end-to-end delivery, including flow control and error recovery Layer 5 Session layer - initiates and manages communications session Layer 6 Presentation layer - performs any necessary character code conversion to provide transparent communications Layer 7 Application layer - contains functions for particular applications services such as file transfer and file access.

More than one layer may be combined into one module or process.

P

Packet

A block of data. The terms packet, frame, and datagram are often used interchangeably. Peering

Internet interconnection as equals (peers) and thus no billing between the parties. This is the normal method of interconnection between the sub-networks which make up the Internet. Contrasts with supplier/ customer interconnection, e.g. ISP and end customer. Petabit

1015 bits. Physical Layer

First layer in the OSI seven layer model. The electrical or optical signals physically transported across the network. Plesiochronous

Almost synchronous because bits are stuffed into the frames as padding and the call’s location varies slightly - jitters - from frame to frame. PMD

Polarisation Mode Dispersion. Dispersion caused by different material properties for different planes of polarisation (direction of the electric field) in an optical fibre. PoP

Point of Presence (or Access Node). A site where customers can connect into the backbone network. POTS

Plain Old Telephone Service Power Budget

The optical budget in dB over a specific network link. Usually quoted as an ’end-of-life’ figure which takes into account some margin for repairs and expected very small deterioration in the quality of the fiber over time. Presentation Layer

Sixth layer in the OSI seven layer model. Performs any necessary character code conversion to provide transparent communications. PRI

Primary Rate Interface. ISDN connection at E1 (30B + D at 2.048 Mbps) or T1 (23B + D at 1.544 Mbps) speed, where B is a 64 kbps Bearer and D is a 64 kbps data channel.

Q

QoS

Quality of Service. A definition of the service provided to a customer.

R

Raman Amplification

A technique for amplifying optical signals in which high-power laser light is sent in the direction opposite that traveled by the data signals, transforming part of the transmission fiber into an amplifier of the signals passing through it. Raman Amplification is named after the scientist who discovered the phenomenon in the scattering of light, called the Raman Effect, in 1928. Typically used to extend the distance that optical signals can be transmitted. See also FEC. RADIUS

Remote Dial-In User Service. Database for authenticating modem and ISDN connections and for tracking connection time. RFC

Request For Comments. Document series used as the primary means for communicating information about the Internet. Some RFC's are designated by the IAB as Internet standards. Most RFC's document protocol specifications such as Telnet and FTP but some are humorous or historical. RFC's are available online from www.rfc-editor.org. RIPE

Réseaux IP Européens. Group formed to coordinate IP based networks in Europe. This is the organization within Europe that allocates IP addresses to ISP's who in turn allocate them to customers. Router

Device connecting two or more networks together which forwards packets between them. Routers read the network address and use routing tables to find the best route between the networks. The routing tables can be created automatically by the system. Routers can also implement load balancing and generate statistics. A router operates at the network layer (layer three) as opposed to a bridge which operates at layer two.

S

SC/SPC

Type of optical connector. Type SC, Super Physical Contact. The type SC connector was originally developed by NTT of Japan. The suffixes /PC, /SPC, /APC are terms which describe connector end-faces and also relate to the ORL designation.

PC means Physical Contact, a description of the contacting spherical end-face. PC has come to mean an ORL greater than 35db. SPC means Super PC, which means a PC connector with ORL >45db.

APC means Angled PC (the end face is polished at an angle, usually 8°) which improves ORL to >65db. SDH

Synchronous Digital Hierarchy. Session Layer

Fifth layer in the OSI seven layer model. Initiates and manages communications session. SGML

Standard Generalized Markup Language. Describes the relationship between a document's contents and its structure in an open (not vendor-specific) format. SGML is defined in "ISO 8879:1986 information processing - text and office systems - Standard Generalized Markup Language (SGML)." SI

Le Système International (d’Unités). The International system (metric) of units of measure. SMDS

Switched Multimegabit Data Service SMTP

Simple Mail Transfer Protocol. Part of the TCP/IP suite. This is the protocol used for transporting email over the Internet, between email servers (which hold and store email) and clients (which allow users to read the email). SNMP

Simple Network Management Protocol. An application layer protocol that facilitates the exchange of management information between network devices. Part of the TCP/IP suite. SONET

Synchronous Optical Network. Spam

Term used to describe unsolicited email or newsgroup posts, often in the form of commercial announcements. The act of sending a Spam is known as Spamming. Spoofing

1. A method of reducing network traffic by simulating local responses to 'keep alive' routine queries to distant devices. Typically used to conserve WAN bandwidth or to avoid unnecessary call set-up and resulting phone call charges.

2. A method of gaining unauthorized access to a system (hacking) by simulating the identity of a genuine user or of a trusted entity. SSH

Secure SHell. Protocol or program for secure logon to a remote host over an insecure network. SSL

Secure Socket Layer. Encryption technology for the Web used to provide secure transactions such as the transmission of credit card numbers for e-commerce. ST

Type of optical connector. The ’straight tip’ connector developed by AT&T, it features a physically contacting non-rotating 2.5mm ferrule design and bayonet connector-to-adapter mating. STM-1, STM-x

Synchronous Transport Module - 1, x. Synchronous

In a telecom's system synchronous means ’bits from one telephone call are always in the same location inside a digital transmission frame’.

T

TCP/IP

Transmission Control Protocol/Internet Protocol Terabit

1012 bits. Traffic Engineering

The process of determining the amount of network capacity (circuits, bandwidth) required to handle a specified amount of traffic without exceeding a specified number of lost calls or dropped packets. Transport Layer

Fourth layer in the OSI seven layer model. Manages end-to-end delivery, including flow control and error recovery. T-1, T-x

A T-1 system transports a DS-1 signal at 1.544 Mbps which comprises 24 DS-0 channels multiplexed together. Trunk

A multi-channel communication link such as an E-1 or T-1.

U

UMTS

Universal Mobile Telephone Service. Third generation cellular phone technology. URL

Uniform Resource Locator. Formerly Universal Resource Locator. A form of host address used on the Internet - e.g. http://www.t1shopper.com is the URL for the T1 Shopper web site UTP

Unshielded Twisted Pair. Cabling with typically four twisted pairs (eight wires), used for cabling within a building. Typically used for 10BaseT cabling.

V

Virtual Private Network

Virtual Private Network. A network provided to the customer which is invisible to any other users of the backbone network.

This provides security to the customer (if the network cannot be seen it cannot be interfered with) and allows Quality of Service specific to the customer to be provided. VPN's allow the customer’s view of the network to be greatly simplified and tailored to specific requirements. VoIP

Voice over IP. The ability to carry Packetised voice over an IP-based Internet with POTS-like functionality, reliability and voice quality.

W

WAN

Wide Area Network. As distinct from Local Area Network. A WAN connects multiple LANs together. Typically an ISP or service provider provides the WAN into which a company will connect their LANs from each site. WAP

Wireless Application Protocol. Delivers information and services to www.wapforum.org/. This is essentially a minimal form of the Web for mobile phones. WDM

Wavelength Division Multiplexing. Generic term for the technique of simultaneously transmitting more than one wavelength of light down an optical fibre. Also see DWDM

X

XML

eXtensible Markup Language. Text markup language designed to enable the use of SGML on the World-Wide Web. XML allows customized markup languages to be defined. X.xxx

ITU-T recommendations X.xxx. s for data communications. Y

Z

Cable Design

Fibre types SM - fiber in accordance with ITU-T G.652, G.653, G.654 or G.655

Number of fibres 96 Strength member ... 3.0 mm fiber reinforced polymer rod Stranding and coding ... 6 loose tubes are stranded around the strength member. Each of the tubes contain up to 16 fibres Filling ... Thixotropic jelly Wrapping ... Double layer of polyester tape Sheath Inner ... 1.0 mm polyethylene, 2.5 ± 0.5% carbon black Sheath Middle ... 1.5 mm lead Sheath Outer ... 1.8 mm polyethylene, 2.5 ± 0.5% carbon black Armouring ... Bedding, polypropylene yarn, all bedded in bitumen. Steel wire, bedded and floated in bitumen. Double layer of polypropylene yarn, bedded in bitumen

ITU-T Recommendations

G series recommendation - Transmission systems and media, digital systems and networks www.itu.int/itudoc/itu-t/rec/g/

G.652 ... Characteristics of a single-mode optical fiber cable G.653 ... Characteristics of a dispersion-shifted single-mode optical fiber cable G.654 ... Characteristics of a cut-off shifted single- mode optical fiber cable G.655 ... Characteristics of a non-zero dispersion shifted single-mode optical fiber cable G.692 ... Optical interfaces for multichannel systems with optical amplifiers G.703 ... Physical/electrical characteristics of hierarchical digital interfaces (includes Physical Interfaces for 2.048 Mbps E-1) G.704 ... Synchronous frame structures used at primary and secondary hierarchical levels. (Includes Framing Specifications for 2.048 Mbps E-1)

H series recommendation - Audiovisual and multimedia systems

H.261 ... Video codec for audiovisual services at p x 64 kbit/s H.263 ... Video coding for low bit rate communication H.320 ... Video/audio conferencing over switched digital telephone networks H.322 ... Video/audio/data conferencing over QoS packet switched networks H.323 ... Video/audio/data conferencing over non QoS packet switched networks H.324 ... Video/audio conferencing over POTS

V series recommendation - Data communication over the telephone network

V.34 ... A modem operating up to 33 600 bit/s on the switched telephone network V.90 ... Digital modem and analogue modem pair for use on the Public Switched Telephone Network (PSTN) at data signaling rates of up to 56 000 bit/s downstream and up to 33 600 bit/s upstream X series recommendation - Data networks and open system communication www.itu.int/itudoc/itu-t/rec/x

X.21 ... Interface between Data Terminal Equipment and Data Circuit-terminating Equipment for synchronous operation on public data networks X.21 ... bis Use on public data networks of Data Terminal Equipment (DTE) which is designed for interfacing to synchronous V-Series modems X.25 ... Packet Switched Public Data Networks (PSPDN) X.75 ... Packet switched signaling system between public networks providing data transmission services X.400 ... Message Handling System (Electronic Mail) X.500 ... Distributed electronic directories (Directory Services)

European and North American Digital Hierarchies Standard andwidth

DS-0 ... 64 Kb/s DS-1, T-1 ... 1.544 Mb/s DS-3, T-3 ... 44.736 Mb/s = 28 * T-1 E-1 ... 2.048 Mb/s = 30 voice channels E-2 ... 8.448 Mb/s = 4 * E-1 E-3 ... 34.368 Mb/s = 16 * E-1 STM-1, OC-3 ... 155.52 Mb/s STM-4, OC-12 ... 622.08 Mb/s STM-16, OC-48 ... 2.5 Gb/s STM-64, OC-192 ... 10 Gb/s OC-768 ... 40 Gb/s

European/SDH standards - E-1/2/3 and STM 1/4/16/64

US/SONET standards - DS-0/1/3, T-1/3 and OC-3/12/48/192/768