Integrated Services Digital Network (ISDN) Developed by ITU-T in 1976 Set of protocols that combines digital telephony and data transport services. The whole idea is to digitize the telephone network to permit the transmission of audio, video and text over existing telephone lines. The goal is to form a WAN that provides universal end-to-end connectivity over digital media. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -1 ISDN Services Bearer services – provide the means to transfer information (voice, data, video) between users without the network manipulating the content of that information. Belongs to the first 3 layers of the OSI model. Teleservices – the network my change or process the contents of the data. - correspond to layers 4 -7 of the OSI model - rely on the facilities of bearer services Supplementary services – provide additional functionality to the bearer services and teleservices. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -1 ISDN Services Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -2 Voice Communication over an Analog Telephone Network Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -3 Voice and Data Communication over an Analog Telephone Network Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -4 Analog and Digital Services over the Telephone Network 3 types of customers – the first one is the most prominent Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -5 Integrated Digital Network (IDN) A combination of networks available for different purposes. Access to these networks is by digital pipes – time-multiplexed channels sharing very-high-speed paths. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -6 Integrated Services Digital Network (ISDN) ISDN incorporates all communication connections in a home or building into a single interface With ISDN all customer services will become digital rather than analog. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Subscriber Access to the ISDN • Subscriber loops – organized into multiple channels of different sizes • B channel • basic user channel • Can carry any type of digital info in Full-duplex mode • Carries transmissions end-to-end Channel Data Rates (Kbps) Bearer (B) 64 Data (D) 16, 64 Hybrid (H) 384 (H 0), 1536(H 11), 1920(H 12) • D channel • Primary function is to carry control signaling for the B channel • Acts like an operator between the user and the network at the network layer Mc. Graw-Hill H Channels - For high data rate applications such as video, teleconferencing and so on ©The Mc. Graw-Hill Companies, Inc. , 2001
Two Types of Digital Subscriber Loops • Basic rate interface (BRI) • Primary rate interface (PRI) • Each type is suited to a different level of customer needs • Both include one D channel and some number of either B or H channels Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -7 Basic Rate Interface (BRI) Designed to meet the needs of residential and small-office customers The same twisted pair local loop that delivers analog transmission can be used to handle digital transmission Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -8 Primary Rate Interface (PRI) Other channel combinations: – 3 H 0 + D – 4 H 0 + D – H 12 + D PRI was designed to be compatible with existing T-1 lines In Europe, the PRI includes 30 B channels and 2 D channels = capacity of 2. 048 Mbps – the capacity of E-1 line Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -9 Functional Grouping Defines the function of each type of equipment NT – network termination TE – terminal equipment NT 1 • Controls the physical & electrical termination of the ISDN at the user’s premises • Connects the user’s internal system to the digital subscriber loop • Organizes the data stream s from a connected subscriber into frames that can be sent over the digital pipe • Translates the frames received from the network into a format usable by the subscriber’s devices. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
NT 2 ( ex. Digital PBX, LAN) • Performs functions at the physical (multiplexing), data link (flow control), network layers (packetizing) of the OSI model • Provides intermediate signal processing between the data-generating devices and an NT 1 • Used primarily to interface between a multiuser system and an NT 1 in a PRI. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
TE 1 – same thing as DTE • Any device that supports the ISDN standards • Ex. Digital telephones, integrated voice/data terminals TE 2 • Any non-ISDN device • Ex. Terminal workstation, regular telephone • Can be used with the help of Terminal Adapter (TA) Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -10 Reference Points Label used to identify individual interfaces between two elements of an ISDN installation Defines the functions of the connections Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -11 Mc. Graw-Hill ISDN Layers ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -12 Simplified Layers of ISDN Mechanical and electrical specs of interfaces R, S, T, U Encoding Multiplexing Power supply Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -13 BRI Interfaces R interface – not defined by ISDN, it can be any EIA standards or V or X series S interface – ISO standard, ISO 8887, four-, six-, or eight-wire connections. U interface - Single-pair twistedpair cable in each direction - Two binary, one quaternary (2 B 1 Q) encoding Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -14 S Interface Name TE NT a Power source Power sink 3 3 b Power source Power sink 3 3 c Transmit Receive d Receive Transmit e Receive Transmit f Transmit Receive g Power sink 2 Power source 2 h Power sink 2 Power source 2 Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -15 2 B/1 Q Encoding 00 10 11 -3 Mc. Graw-Hill 01 -1 +3 +1 ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -16 BRI Frame overhead Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
BRI Topology Point-to-point Multipoint -limited distance to ensure frame synchronization As many as 8 devices can be connected to NT 1, two can access the B -channels at 1 time D channels use a mechanism like CSMA Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -18 R and S – same as those defined for the BRI Mc. Graw-Hill PRI Interfaces T – identical to S standard - B 8 ZS Encoding U – same for both, different rates ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -19 Mc. Graw-Hill PRI Frame ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -20 LAPD Address Field SAPI – Service Access Point Identifier - identifies the type of upperlayer service (network layer) C/R – Command (0) / Response (1) TEI – Terminal Equipment Identifier 000000 – call control for network layer (signaling use of D-channel) 000001 – call control for upper layer (ene-to-end signaling), not yet in use 010000 – packet communication ( data use of D channel) 111111 - management Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -21 Network Layer Packet Format Protocol discriminator – identifies the protocol in use, for Q. 931 = 0000 1000 Call Reference – sequence number of the call Message Type – identifies the purpose of the message - call establishment Reading assignment: - call information Different messages under - call clearing these four message types - call miscellaneous Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -22 Mc. Graw-Hill Call Reference Field ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -23 Information Elements Carries specific details about the connection that are required for call establishment: - addresses of the sender and receiver - routing information - type of network that is desired for the B-channel exchange (X. 25, ATM, Frame Relay) Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -24 Information Element Types ID – identify the information being sent Length – length of the content in bytes Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -25 Addressing in ISDN Addressing – important information element type in ISDN NC – national Code Subaddress – identify the device connected to NT 1 Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -26 Bit Rates for Different Applications Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -27 B-ISDN Services Broadband ISDN – based on a change from metal cable to fiber optic cable at all levels of telecommunications Interactive services – those that require two-way exchanges between either 2 subscribers or between a subscriber & a service provider - conversational – real time exchanges such as telephone calls - messaging – store & forward exchanges such as voice mail - retrieval –retrieve info from a central office Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -27 B-ISDN Services Distributive services – unidirectional services sent from a provider to subscribers, broadcast to the user - without user control – user choice is limited to whether or not to receive the service at all - with user control – allow the user a choice of times during which to receive them Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
Figure 16 -28 B-ISDN Accesses 155. 520 Mbps – fill the needs of most residential and many business subscribers 155. 520/622. 080 Mbps – fill the needs of businesses that require the simultaneous receipt of multiple services and video conferencing Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2001
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