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Lecture 8: Integrated Services for Digital Network (ISDN). By: Adal ALashban. Chapter Goals. - Explain what ISDN is. - Describe ISDN devices and how they operate. - Describe the specifications for ISDN data transmittal for the three layers at which ISDN transmits.
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Lecture 8: Integrated Services for Digital Network (ISDN) By: Adal ALashban
Chapter Goals - Explain what ISDN is. - Describe ISDN devices and how they operate. - Describe the specifications for ISDN data transmittal for the three layers at which ISDN transmits.
Integrated Services for Digital Network (ISDN) - Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. - It was first defined in 1988 in the CCITT red book Prior to ISDN, the telephone system was viewed as a way to transport voice.
ISDN Channels - B: 64 kbps for data or voice. - D: 16 or 64 kbps for signaling or packet switched data. - H: 384 kbps (H0), 1536 kbps (H11), 1920 kbps (H12).
Services - There are two types of services associated with ISDN: Basic Rate Interface (BRI): Offers two B channels + one D channel (2B + D) = 2 × 64 + 16 = 144 kbps (192 kbps total) Primary Rate Interface (PRI):For LANs or PBX 23 B channels + D channel (23B + D) = 23 × 64 + 64 = 1.536 Mbps = T1 30 B channels + D channel (30B + D) = 30 × 64 + 64 = 1.984 Mbps = E1
ISDN Reference Points - U: Two wire cable that connects the customer’s equipment to the telecommunications provider. - R: Point between non ISDN equipment (TE2) and the TA. - S: Four wire cable from user terminals (TE1 or TA) to the NT1 or NT2. - T: Point between NT1 and NT2.
Functional Groupings - Terminal Adapter (TA):Converter device that converts standard electrical signals into the form used by ISDN; allows non ISDN devices to operate on an ISDN network. - Terminal Equipment Type 1 (TE1):Compatible with the ISDN network. Example: Telephones, personal computers, fax machine or video conferencing machine. - Terminal Equipment Type 2 (TE2):Not compatible with the ISDN network. Example: Analog phone or modem, requires a TA (TE2 connects to TA). - Network termination type 1 & 2 (NT1 and NT2): A small connection box that physically connects the customer site to the Telco local loop, provides a four-wire connection to the customer site and a two-wire connection to the network (PRI – CSU/DSU).
ISDN Benefits - Carries a variety of user traffic, such as digital video, data, and telephone network services, using the normal phone circuit-switched network. - Offers much faster call setup than modems by using out-of-band signaling (D channel) Often less than one second - Provides a faster data transfer rate than modems by using the 64-kbps bearer channel (B channel). Can combine multiple B channels to bandwidth of 128 kbps - Can negotiate PPP links.
Advantages of ISDN - The basic advantage of ISDN is to facilitate the user with multiple digital channels. These channels can operate concurrently through the same one copper wire pair. - The digital signals broadcasting transversely the telephone lines. - ISDN provides high data rate because of digital scheme which is 56kbps. - ISDN network lines are able to switch manifold devices on the single line such as faxes, computers, cash registers credit cards readers, and many other devices. These all devices can work together and directly be connected to a single line - ISDN takes only 2 seconds to launch a connection while other modems take 30 to 60 second for establishment.
Disadvantages of ISDN - The disadvantage of ISDN lines is that it is very costly than the other typical telephone system. - ISDN requires specialized digital devices just like Telephone Company.
ISDN Uses - Remote Access (Telecommuters). - Remote Nodes (Voice and Data). - SOHO Connectivity (Small Branches).
ISDN Uses Remote Access (Telecommuters)
ISDN Uses Remote Nodes (Voice and Data)
ISDN Uses SOHO Connectivity (Small Branches)
Protocol Reference Model - Similar to OSI 7-layer model. - Separate user, control, and management planes. - Control = signaling. - Management = network diagnosis, maintenance, and operation.
ISDN Protocol Operating OSI Layers - Physical layer ISDN protocols BRI (ITU-T I.430) / PRI (ITU-T I.431) Defines two ISDN physical layer frame formats: - Inbound (local exchange to ISDN customer) - Outbound (ISDN customer to local exchange)
ISDN Protocol Operating OSI Layers - Data link layer ISDN protocols LAPD signaling protocol (ITU-T Q.920 for BRI and Q.921 for PRI) for transmitting control and signaling information over the D channel. LAPD frame format similar to ISO HDLC frame format.
ISDN Protocol Operating OSI Layers - Network layer ISDN protocols ITU-T I.930 and ITU-T Q.931 defines switching and signaling methods using the D channel.
ISDN Encapsulation - The two most common encapsulations: PPP. HDLC. - ISDN defaults to HDLC. - PPP is much more robust. Open standard specified by RFC 1661. Supported by most vendors.
