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Lecture-7: Integrated Services for Digital Network (ISDN) By : Ashwaq fahad Supervision : Dr.Ouiem Bchir.

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Presentation on theme: "Lecture-7: Integrated Services for Digital Network (ISDN) By : Ashwaq fahad Supervision : Dr.Ouiem Bchir."— Presentation transcript:

1 Lecture-7: Integrated Services for Digital Network (ISDN) By : Ashwaq fahad Supervision : Dr.Ouiem Bchir

2 Outline Definition Integrated Services for Digital Network (ISDN) Types interface ISDN ISDN Components and Reference Points ISDN Benefits Advantages and disadvantages of ISDN ISDN Uses ISDN Protocols ISDN Protocol Operating OSI Layers ISDN Encapsulation

3 Definition Integrated Services for 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 [1]


5 Cisco supports the following two ISDN interface types, which combine the channel types in the preceding list: Basic Rate Interface (BRI) One 16-kbps D channel + two B channels Primary Rate Interface (PRI) 1 64-kbps D channel + 23 B channels in North America and Japan, for a total capacity of 1536 kbps kbps D channel + 30 B channels in Europe and other parts of the world, for a total capacity of 1984 kbps.[2]


7 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 videoconferencing 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). [2]

8 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 [3]

9 Advantages 1. 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. 2. The digital signals broadcasting transversely the telephone lines. 3. ISDN provides high data rate because of digital scheme which is 56kbps. 4. 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 5. ISDN takes only 2 seconds to launch a connection while other modems take 30 to 60 second for establishment [4]

10 Disadvantages 1. The disadvantage of ISDN lines is that it is very costly than the other typical telephone system. 2. ISDN requires specialized digital devices just like Telephone Company [4]

11 Remote Access (Telecommuters) Remote Nodes (Voice and Data) SOHO Connectivity (Small Branches) [5]

12 Remote Access (Telecommuters)

13 Remote Nodes (Voice and Data)

14 SOHO Connectivity (Small Branches)

15 E-series protocolsTelephone network standards for ISDN. I-series protocolsSpecify ISDN concepts and interfaces. Q-series protocolsStandards for ISDN switching and signaling. Operate at the physical, data link, and network layers of the OSI reference model [6]

16 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 ) [6]


18 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 [6]


20 Network layer ISDN protocols ITU-T I.930 and ITU-T Q.931 defines switching and signaling methods using the D channel.

21 Two Layer 3 specifications are used for ISDN signaling: ITU-T I.450 (also known as ITU-T Q.930) ITU-T I.451 (also known as ITU-T Q.931) Together, these protocols support : User-to-user circuit-switched connections User-to-user packet-switched connections A variety of standards for: Call establishment Call termination [6]

22 Note With Q.921/Q.931 the second digit indicates the OSI layer.

23 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 [7]

24 [1] tal_Network tal_Network [2] CCIE_Practical_Studies_I&seqNum=84 CCIE_Practical_Studies_I&seqNum=84 [3] honesystems/isdn/featuresandbenefits/ honesystems/isdn/featuresandbenefits/ [4] [5] [6] technologies/238-isdn-layers-protocols- components.html technologies/238-isdn-layers-protocols- components.html [7]

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