ISDN Lecture 16
ISDN (Integrated Services Digital Network) An international standard for switched, digital dial-up telephone service for voice and data. Digital telecommunications network that operates over standard copper telephone wires or other media. ISDN connections are used to provide a variety of digital services to customers, including digital voice telephone, fax, e-mail, digital video, and access to the Internet.
ISDN • ISDN is a set of standards which define an end to end Digital Network. • WAN Technology
Analog Network Voice Communication over the analog telephone network.
Digital Processing Voice and Data Communication over the analog telephone network.
Digital Technologies Voice and Data Services over the analog telephone network.
Integrated Digital Networks IDN (integrated digital network) is a combination of networks available for different purpose—access is done through digital pipes which are time multiplexed channels sharing very high-speed lines.
Integrated Services Digital Networks ISDN ISDN (integrated services digital network) is a Digital telecommunications network that operates over standard copper telephone wires or other media.
Foundation Developed in the 1970s to provision digital voice and data services over copper wire phone lines, ISDN technology was expected to replace conventional PSTN (Public Switched Telephone Network) technology. The Consultative Committee for International Telephone and Telegraph or CCITT (now known as the International Telecommunications Union or the ITU) completed the initial I.210 Recommendations for ISDN implementation in 1984.
Foundation ISDN was initially distinguished by its capabilities in enabling subscribers at SOHO (Small Office/Home Office) venues to access the Internet at faster rates than speeds supported by conventional analog voice band modems. Despite ISDN capabilities in economically facilitating digital video, voice, and data delivery over the POTS (Plain Old Telephone System) infrastructure to the customer premise, ISDN services were not widely deployed or universally accepted.
ISDN Features • Uses Digital Signal • Uses Existing telephone wiring • Charges are generally based on the duration of call (How long the WAN link was used) • Alternate to using leased lines • Can transport many types of Network traffic (Voice, Data, Video, Text, Graphics etc) • Faster Data transfer rate than modems • Faster Call setup than Modems
ISDN Technical Fundamentals ISDN implementation involves determining the number of locations and types of devices that will be attached to the configuration and bandwidth or transmission rate requirements. In addition, ISDN deployment requires reconfiguration of PC (Personal Computer) software to support ISDN links and rewiring or replacing a single phone jack with a dual port to enable ISDN connections. The installation of additional PSTN wiring at the subscriber premise may also be required.
ISDN Components • Terminal Equipment type 1 (TE1) • ISDN compatible device (Router with ISDN Interface). • TE1s connect to the ISDN network through a four-wire, twisted-pair digital link.
ISDN Components • Terminal Equipment type 2 (TE2) • ISDN Non-compatible devices. • Will require a terminal adapter.
ISDN Components • Terminal Adapter (TA) • Converts standard electrical signals into the form used by ISDN • Needed for connection with TE2 devices • The ISDN TA can be either a standalone device or a board inside the TE2.
ISDN Components • Network termination type 1 (NT1) • Network-termination devices that connect the four-wire Subscriber wiring to the conventional two-wire local loop • Is a customer premises equipment (CPE) device (North America).
ISDN Components • Network termination type 2 (NT2) • Intelligent device that performs switching & concentrating. • Provides multiple ISDN interfaces on an ISDN line. The NT2 may be as simple as a bridging device connected to an NT1 unit or it may be as complicated as a PBX (Private Branch exchanges) .
ISDN Codecs A codec or chip performs digital-to-analog and analog to-digital conversions. In addition, a codec supports compression to minimize redundancies in voice, data, and video transmissions for facilitating high-quality videoconferences. To enable clear and robust ISDN telephony services, a codec converts analog signals into digital formats at call setup for network transmission and then reconstructs the digital signals into analog formats at call reception.
ISDN Digital Pipe The access path from the local telephone exchange to the customer premise over the last mile or the local loop in an ISDN network is commonly called a digital pipe. The size of the digital pipe for ISDN transmission depends on variables such as customer application requirements and fees established by the communications carrier.
ISDN Reference Points Reference points are a series of specifications that define the connection between specific devices, depending on their function in the end-to-end connection.
ISDN Encapsulations • HDLC (High-Level Data Link Control) • PPP (Point to Point Protocol) • LABP (Link Access Procedure Balance) ISDN interfaces allow only a single encapsulation type.
Telecommuter/Remote User • Using Modem> • Using ISDN>
Telecommuter/Remote Office • Components & Considerations • ISDN Router • Multiple remote users at the same location
ISDN Service BRI (Basic Rate Interface) • Connection from the ISDN office to the user location provides for access to three channels. The channels are two 64Kb B-channels and one 16Kb D-channel. • The B-channels and the D-channel provide the user with access to the circuit switched network.
ISDN Service PRI (Primary Rate Interface) • ISDN Primary Rate Interface service provides digital access via a T1 line. A T1 line provides a 1.544 bandwidth. This bandwidth is divided into 24 64Kb channels. The ISDN PRI service uses 23 B channel access and uses the 24th (D) channel for signaling purposes.
ISDN Protocols STATISTICAL TIME –DIVISION MULTIPLEXING(STDM) ISDN provides a digital framework for voice, text, video, and still-image transmission by utilizing Statistical Time-Division Multiplexing (STDM). Also called intelligent TDM, STDM is a sophisticated form of TDM (Time-Division Multiplexing). Conventional TDM divides bandwidth into fixed timeslots so that information from each channel is transported in a predetermined rotation. Multiplexing refers to the process of combining multiple information channels that consist of numerous analog or digital signals into a single, high-capacity transmission link.
ISDN Protocols LAP-D (LINK ACCESS PROTOCOL -D CHANNEL) Operating above the Physical Layer or Layer 1 of the OSI Reference Model, the D Channel employs the Link Access Protocol-D Channel (LAP-D) to enable acknowledged and unacknowledged information transfer services that support Layer 2 or Data-Link Layer operations. The LAP-D frame format features a 2-octet address field, a 2-octet CRC (Cyclic Redundancy Check) field for determining data errors, a 7-byte terminal endpoint identifier field, and a 6-byte SAPI (Service Access Point Identifier) field. ISDN Data-Link Layer capabilities are defined by the ITU-T Q series of Recommendations.
ISDN Protocols ISDN USER –TO –NETWORK SIGNALING PROTOCOL The ISDN User-to-Network Interface (UNI) signaling protocol defines Layer 3 or Network Layer operations. This protocol enables the establishment, maintenance, and termination of network connections via circuit-switched or packet-switched B Channel connections. ISDN Layer 3 signaling specifications are defined in the ITUT I.43 and the ITU-T I.431 Recommendations.
Broadband ISDN "Qualifying a service or system requiring transmission channels capable of supporting rates greater than the primary rate“.
ISDN Users LAN Connections
ISDN Users Small Office
ISDN Users Teleconferencing
ISDN Users Tele-course
ISDN Summery • Signaling and voice channels both physically and logically separated. • Any info for services can be added. • Multipoint structure complicated the implementation significantly. • ISDN adoption is measure by home internet user. • ISDN specified digital PBX access for the first time. This has been widely adopted.