Tài liệu Integrated service digital network

ISDN Chapter 1 Integrated Service Digital Network (ISDN) Korea-Vietnam Friendship IT College ISDN Overview • • • • • • • ISDN Introduction ISDN Technical Fundamentals ISDN Channels ISDN Transmission ISDN Frames ISDN Protocol Architecture Khảo sát các ứng dụng hiện nay của ISDN tại Việt Nam và thế giới • Ưu nhược điểm so với các công nghệ khác 2 Korea-Vietnam Friendship IT College ISDN ISDN Introduction • Integration – Before WWII, integration of telegraph/telex and voice – More recently, integration of fax and voice – ISDN: integrate digital voice, 64-Kbps data, telex, fax, slow-scan video – Broadband ISDN: all of above plus video, multimedia,… 3 Korea-Vietnam Friendship IT College ISDN ISDN Introduction • Channels – Analog public switched telecommunication network (PSTN) based on the 4-kHz voice channel – Present digital network based on PCM 64-Kbps voice channel – In-channel signaling and framing corrupted the 64Kbps channel, so integration of data required a dropback to 56-Kbps – ISDN: local interface to a “digital pipe” enables higher data rates 4 Korea-Vietnam Friendship IT College ISDN Principles of ISDN (1) • Support of voice and non-voice applications in the same network – Interfaces and data transmission facilities standadized by ITU-T • Switched and Non-Switched connections – Packet & circuit switching, leased lines • 64-Kbps channel – Chosen because at the time was the standard rate for digitized voice 5 Korea-Vietnam Friendship IT College ISDN Principles of ISDN (1) • Layered protocol structure – Mapped into OSI model (advantages in utilizing existing standards as well as in developing new one) • Variety of configurations – According to specific national situations & state of technology 6 Korea-Vietnam Friendship IT College ISDN ISDN Conceptual View 7 Korea-Vietnam Friendship IT College ISDN Benefits of ISDN (1) • To the user: cost saving and flexibility – Integration of voice/data means users do not have to buy multiple services to meet multiple needs – Single access line to all services – Services tailored to diverse requirements (information volume, traffic pattern, response time, interface types) • To network providers: – Standards support universality and larger potential market for services, drive down equipment costs 8 Korea-Vietnam Friendship IT College ISDN Benefits of ISDN (2) • To manufacturers – Larger potential market, economies of scales – Standards decrease risk of obsolescence • To enhanced service providers – Simplified user access 9 Korea-Vietnam Friendship IT College ISDN 10 Korea-Vietnam Friendship IT College ISDN ISDN Technical Fundamentals • • • • • • • Basic ISDN Installation requirements ISDN Terminal Adapters (TAs) ISDN Terminal Equipment (TE) ISDN Network Termination (NT) Devices ISDN Codecs (Coders and Decoders) ISDN Digital Pipe ISDN Reference Points 11 Korea-Vietnam Friendship IT College ISDN Basic ISDN Installation Requirements ISDN Architecture 12 Korea-Vietnam Friendship IT College ISDN Basic ISDN Installation Requirements • Involving the number of locations and types of devices that will be attached to the configuration and bandwidth or transmission rate requirements • Requires reconfiguration of PC software to support ISDN links and rewiring or replacing a single phone jack with a dual port to enable ISDN connections. • Involving utilization of ISDN Terminal Equipment (TE), ISDN Network Termination (NT) devices, and ISDN Terminal Adapters (TAs). 13 Korea-Vietnam Friendship IT College ISDN ISDN Terminal Adapters (TAs) • Facilitate conversion of analog voice signals into digital signal formats that are fully compatible with ISDN telephony service and ISDN TAs at the local telephone exchange. • Allow non-ISDN equipment to support operations via the in-place ISDN configuration. • Distinguish between voice and non-voice signals so that voice calls and data frames can be directly routed to designated destination addresses. 14 Korea-Vietnam Friendship IT College ISDN ISDN Terminal Equipment (TE) • Devices that employ ISDN directly and foster ISDN services are called Terminal Equipment Type 1 (TE1) • By contrast, non-ISDN devices are called Terminal Equipment Type 2 (TE2). T • E2 devices are not compatible with the ISDN specification. As a consequence, these devices require the use of Terminal Adapters (TAs). 15 Korea-Vietnam Friendship IT College ISDN ISDN Network Termination (NT) Devices • Network Termination Type 1 (NT1) refers to a network terminal device situated at the customer premise for handling Physical Layer or Layer 1 and Data-Link Layer or Layer 2 connections. • Network Termination Type 2 (NT2) devices perform Physical Layer and Data-Link Layer functions. In addition, NT2 equipment enables voice and data switching and seamless aggregation or BONDING (Bandwidth On-Demand Interoperability Group) of multiple ISDN channels. 16 Korea-Vietnam Friendship IT College ISDN ISDN Codecs (Coders and Decoders) • A codec or chip performs digital-to-analog and analog-todigital conversions. • 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. 17 Korea-Vietnam Friendship IT College ISDN 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. 18 Korea-Vietnam Friendship IT College ISDN ISDN Reference Points ISDN Reference Points 19 Korea-Vietnam Friendship IT College ISDN ISDN Reference Points (2) • The R reference point refers to communications between TE2 and TA devices. • The S reference point refers to communications between TE1 or TA devices and Network Termination (NT) equipment or NT1 and NT2. • The T reference point indicates links between customer premise switching equipment (NT2) and local loop termination (NTI) devices. • The U reference point refers to the link between the local telephone exchange and NT1 equipment. Every U interface frame consists of 240 bytes. 20 Korea-Vietnam Friendship IT College