Huber, M.N., Daigle, J N, Bannister, J, Gerla, M, Robrock Il, R.B. Networks The Electrical Engineering Handbook Ed. Richard C. Dorf Boca raton crc Press llc. 2000
Huber, M.N., Daigle, J.N., Bannister, J., Gerla, M., Robrock II, R.B. “Networks” The Electrical Engineering Handbook Ed. Richard C. Dorf Boca Raton: CRC Press LLC, 2000
72 Networks 72.1 B-ISDN Manfred N. Huber B-ISDN Services and applic Mode. Transmission of B-ISDN Signals.ATM Adaptation Layer.B-ISDN Signaling N. Daigle 72.2 Computer Communication General Networking Concepts Communication Network Architecture Local-Ar s and internets·Some Joseph Bannister Additional Recent Developments ty of Southern 2.3 Local-Area Networks California Information The LAn Service Model. Other Features. The Importance of Sciences Institute LAN Standards Mario gerla 72.4 The Intelligent Network University of california, Los A History of Intelligence in the Network. The Intelligent Network· ntelligent Network Systems· The CCS7 Network The Service Control point Data base 800 Richard B. robrock it Service. Alternate Billing Services. Other Services. The Bell Communications research Advanced Intelligent Network. Back to the Future 72.1 B-ISDN Manfred N. Huber Since the mid-1980s the idea of the integrated services digital network(ISDN)has become reality. In ISDN voice services with supplementary features and data services with a bit rate of up to 64 kbit/s are integrated in one network. For voice communication and many text and data applications the 64-kbit/s ISdn will be sufficient. Although it is minor as yet, there exists already a growing demand for broadband communication with bit rates from some megabits per second up to approximately 130 Mbit/s [Wiest, 1990](e.g, high-speed data communication, video communication, high-resolution graphics In order to provide the same advantages of isdn to broadband communication users, network operat and service providers, the development of an intelligent broadband-ISDN(B-ISDN)is necessary. The future B-iSDN will become the universal network integrating different kinds of services with their individual features and requirements. B-ISDN will support switched, semipermanent and permanent, point-to-point, and poin to-multipoint connections and provide on-demand, reserved, and permanent services. B-ISDN connection support packet mode and circuit mode services of mono-and/or multimedia type of a connection-oriented or connectionless nature in a unidirectional or bidirectional configuration [Handel and Huber, 1991b] B-ISDN Services and Applications As already mentioned, there exists some demand for broadband communication which originates from business customers as well as residential customers. In the residential area, on the one hand, people are interested in video distribution services for entertainment purposes, like television and high-definition TV; on the other c 2000 by CRC Press LLC
© 2000 by CRC Press LLC 72 Networks 72.1 B-ISDN B-ISDN Services and Applications • Asynchronous Transfer Mode • Transmission of B-ISDN Signals • ATM Adaptation Layer • B-ISDN Signaling 72.2 Computer Communication Networks General Networking Concepts • Computer Communication Network Architecture • Local-Area Networks and Internets • Some Additional Recent Developments 72.3 Local-Area Networks The LAN Service Model • Other Features • The Importance of LAN Standards 72.4 The Intelligent Network A History of Intelligence in the Network • The Intelligent Network • Intelligent Network Systems • The CCS7 Network • The Service Control Point • Data Base 800 Service • Alternate Billing Services • Other Services • The Advanced Intelligent Network • Back to the Future 72.1 B-ISDN Manfred N. Huber Since the mid-1980s the idea of the integrated services digital network (ISDN) has become reality. In ISDN voice services with supplementary features and data services with a bit rate of up to 64 kbit/s are integrated in one network. For voice communication and many text and data applications the 64-kbit/s ISDN will be sufficient. Although it is minor as yet, there exists already a growing demand for broadband communication with bit rates from some megabits per second up to approximately 130 Mbit/s [Wiest, 1990] (e.g., high-speed data communication, video communication, high-resolution graphics). In order to provide the same advantages of ISDN to broadband communication users, network operators, and service providers, the development of an intelligent broadband-ISDN (B-ISDN) is necessary. The future B-ISDN will become the universal network integrating different kinds of services with their individual features and requirements. B-ISDN will support switched, semipermanent and permanent, point-to-point, and pointto-multipoint connections and provide on-demand, reserved, and permanent services. B-ISDN connections support packet mode and circuit mode services of mono- and/or multimedia type of a connection-oriented or connectionless nature in a unidirectional or bidirectional configuration [Händel and Huber, 1991b]. B-ISDN Services and Applications As already mentioned, there exists some demand for broadband communication which originates from business customers as well as residential customers. In the residential area, on the one hand, people are interested in video distribution services for entertainment purposes, like television and high-definition TV; on the other Manfred N. Huber Siemens J. N. Daigle University of Mississippi Joseph Bannister University of Southern California Information Sciences Institute Mario Gerla University of California, Los Angeles Richard B. Robrock II Bell Communications Research
cc1 vCc 2 GFC VPI I VCI PLT CLP HEC 口 rtual cha FIGURE 72.1 ATM principl hand, they will use video telephony with acceptable quality. Over the long term, video mail services and video retrieval services will become more important. ice and text are no longer sufficient for business customers. In the offices and factories of tomorrow, interactive broadband services will be required. Handling complex tasks in the future demands comprehensive ipport by services for voice, text, data, graphics, video, and documents. In addition to the individual services, the multimedia services and the simultaneous or alternating use of several services with multifunction work stations will gain importance [Armbruster, 1990] Interconnection of local-area networks(LANs)or large computers, computer-aided design, and computer aided manufacturing will become important data applications. The first video services will be video telephony and video conferencing(studio-to-studio and workstation video conferencing). Initially these services may have diminished quality, but for the long term Tv quality can be expected The bit rates of all services mentioned above are in the range of 2 to 130 Mbit/s( depending on the individual application). Taking into account that in the future more enhanced video coding mechanisms will be available, the required bit rates for video services will become lower without influencing quality significantly Asynchronous Transfer Mode In today's public switched networks the synchronous transfer mode(STM) predominates. Applying STM technology, for the duration of a connection a synchronous channel with constant bit rate is allocated to that onnection. StM does not fit very well for the integration of services with bit rates from some kilobits per second to 130 Mbit/s. Therefore, in B-Isdn a new transfer mode called asynchronous transfer mode(Atm) is used In ATM all kinds of information is transported in cells. A cell is a block of fixed length, which consists of a 5-octet cell header and a 48-octet cell payload(see Fig. 72.1 ). The cell header contains all necessary information for transferring the cell through the network and the cell payload includes the user information. The cell rate of a connection is proportional to the service bit rate. Only if information is available is a cell used by the connection. By having different routing labels, cells of different connections can be transported on the same transmission line (cell multiplexing). If no connection has information ready to transport, idle cells will be inserted Idle cells do not belong to any connection; they are identified by a standardized cell header ATM uses only cells; multiplexing and switching of cells is independent of the applications and of the bit rates of the individual connections. Applying ATM technology, the idea of one universal integrated network becomes a reality. However, the aTM technology also causes some problems. Because of the asynchronous ultiplexing buffers are necessary, which results in cell delay, cell delay variation, and cell loss. In order to compensate for these effects additional measures have to be provided e 2000 by CRC Press LLC
© 2000 by CRC Press LLC hand, they will use video telephony with acceptable quality. Over the long term, video mail services and video retrieval services will become more important. Voice and text are no longer sufficient for business customers. In the offices and factories of tomorrow, interactive broadband services will be required. Handling complex tasks in the future demands comprehensive support by services for voice, text, data, graphics, video, and documents. In addition to the individual services, the multimedia services and the simultaneous or alternating use of several services with multifunction workstations will gain importance [Armbrüster, 1990]. Interconnection of local-area networks (LANs) or large computers, computer-aided design, and computeraided manufacturing will become important data applications. The first video services will be video telephony and video conferencing (studio-to-studio and workstation video conferencing). Initially these services may have diminished quality, but for the long term TV quality can be expected. The bit rates of all services mentioned above are in the range of 2 to 130 Mbit/s (depending on the individual application). Taking into account that in the future more enhanced video coding mechanisms will be available, the required bit rates for video services will become lower without influencing quality significantly. Asynchronous Transfer Mode In today’s public switched networks the synchronous transfer mode (STM) predominates. Applying STM technology, for the duration of a connection a synchronous channel with constant bit rate is allocated to that connection. STM does not fit very well for the integration of services with bit rates from some kilobits per second to 130 Mbit/s. Therefore, in B-ISDN a new transfer mode called asynchronous transfer mode (ATM) is used. In ATM all kinds of information is transported in cells. A cell is a block of fixed length, which consists of a 5-octet cell header and a 48-octet cell payload (see Fig. 72.1). The cell header contains all necessary information for transferring the cell through the network and the cell payload includes the user information. The cell rate of a connection is proportional to the service bit rate. Only if information is available is a cell used by the connection. By having different routing labels, cells of different connections can be transported on the same transmission line (cell multiplexing). If no connection has information ready to transport, idle cells will be inserted. Idle cells do not belong to any connection; they are identified by a standardized cell header. ATM uses only cells; multiplexing and switching of cells is independent of the applications and of the bit rates of the individual connections. Applying ATM technology, the idea of one universal integrated network becomes a reality. However, the ATM technology also causes some problems. Because of the asynchronous multiplexing buffers are necessary, which results in cell delay, cell delay variation, and cell loss. In order to compensate for these effects additional measures have to be provided. FIGURE 72.1 ATM principle
Figure 72. 1 also shows the individual subfields of the cell header. The first field, called generic flow control (GFC), is only available at the user-network interface(UNI). Its main purpose is media access control in shared medium configurations(LAN-like configurations) within the customer premises [Goldner and Huber, 1991] The proposed GFC procedures are based either on the distributed queue algorithm or the reset timer control mechanism [Handel and Huber, 1991a]. At the network-node interface(NNI) these bits are part of the virtual The VPI together with the virtual channel identifier(vCI)form the routing label (identifier of the connec- on). The VPI itself marks only the virtual path(VP). The VP concept allows the flexible configuration of individual subnetworks(e.g, signaling network or virtual private network), which can be independent of the underlying transmission network. VP networks are under the control of network management. The bandwidth of a Vp will be allocated according to its requirements within the Vp network the individual connections are established and cleared down dynamically(by signaling The payload type field in the cell header differentiates the information in the cell payload of one connection (e.g, user information, operation and maintenance information for ATM). The value of the cell loss priority bit distinguishes cells that can be discarded under some exceptional network conditions without disturbing the quality significantly from those cells that may not be discarded. The last field of the cell header forms the header error control field. The cell header is protected against errors with a mechanism that allows the correction of a single bit error and the detection of multibit errors. The high transmission speeds for ATM cell transfer require very high-performance switching nodes. There fore, the switching networks(SNs) have to be implemented in fast hardware. Within the SN the self-routing principle will be applied [Schaffer, 1990]. At the inlet of the sn the cell is extended by an SN-internal header It is evident that the SN-internal operational speed has to be increased. When passing the individual switching elements, for the processing of the SN-internal header only simple hard-wired logic is necessary. This reduces the control complexity and provides a better failure behavior. When starting several years ago with the imple mentation of the ATM technology, only the emitter coupled logic(ECL) was available. Nowadays, the comple mentary metal-oxide semiconductor( CMOS) technology with its low power consumption is used [Fischer etal,1991] Transmission of b-isdn Signals Transmission systems at the UNI provide bit rates of around 150 and 622 Mbit/s. In addition to these rates, at the NNI around 2.5 Gbit/s and up to 10 Gbit/s will be used in the future [Baur, 1991]. In addition to the high capacity switching and multiplexing technology, high-speed transmission systems are required. Optical fibers are especially suitable for this purpose; however, for the lower bit rates coaxial cables can be used. Optical transmission uses optical fibers as the transmission medium in low-diameter and low-weight cables to provide large transmission capacities over long distances without the need for repeaters. Optical transmission equipment currently tends to mono-mode fiber and laser diodes with wavelengths of around 1310 nm. For both directions in a transmission system either two separate fibers or one common fiber with wavelength division multiplexing can be used. The second solution may be a good alternative for subscriber lines and short trunk lines[ Bauch, 1991] For ATm cell transmission, two possibilities exist, which are shown in Fig. 72. 2: synchronous pulse frame or continuous cell stream(cell-based). The basis for the pulse frame concept is the existing synchronous digital hierarchy(SDH). In SDH the cells are transported within the SDh payload; the frame overhead includes operation and maintenance(OAM)of the transmission system. In the cell-based system the oAm for the transmission system is transported within cells. The SDH solution is already defined, whereas for cell-based transmission some problems remain to be solved (e. g, OAM is not yet fully defined). ATM Adaptation Layer The ATM adaptation layer(AAL) is between the ATM layer and higher layers. Its basic function is the enhanced adaptation of the services provided by atM to the requirements of the layers above. In order to minimize the number of AaL protocols, the service classification shown in Fig. 72.3 was defined. This classification was made with respect to timing relation, bit rate, and connection mode. e 2000 by CRC Press LLC
© 2000 by CRC Press LLC Figure 72.1 also shows the individual subfields of the cell header. The first field, called generic flow control (GFC), is only available at the user-network interface (UNI). Its main purpose is media access control in shared medium configurations (LAN-like configurations) within the customer premises [Göldner and Huber, 1991]. The proposed GFC procedures are based either on the distributed queue algorithm or the reset timer control mechanism [Händel and Huber, 1991a]. At the network-node interface (NNI) these bits are part of the virtual path identifier (VPI). The VPI together with the virtual channel identifier (VCI) form the routing label (identifier of the connection). The VPI itself marks only the virtual path (VP). The VP concept allows the flexible configuration of individual subnetworks (e.g., signaling network or virtual private network), which can be independent of the underlying transmission network. VP networks are under the control of network management. The bandwidth of a VP will be allocated according to its requirements. Within the VP network the individual connections are established and cleared down dynamically (by signaling). The payload type field in the cell header differentiates the information in the cell payload of one connection (e.g., user information, operation and maintenance information for ATM). The value of the cell loss priority bit distinguishes cells that can be discarded under some exceptional network conditions without disturbing the quality significantly from those cells that may not be discarded. The last field of the cell header forms the header error control field. The cell header is protected against errors with a mechanism that allows the correction of a single bit error and the detection of multibit errors. The high transmission speeds for ATM cell transfer require very high-performance switching nodes. Therefore, the switching networks (SNs) have to be implemented in fast hardware. Within the SN the self-routing principle will be applied [Schaffer, 1990]. At the inlet of the SN the cell is extended by an SN-internal header. It is evident that the SN-internal operational speed has to be increased. When passing the individual switching elements, for the processing of the SN-internal header only simple hard-wired logic is necessary. This reduces the control complexity and provides a better failure behavior. When starting several years ago with the implementation of the ATM technology, only the emitter coupled logic (ECL) was available. Nowadays, the complementary metal-oxide semiconductor (CMOS) technology with its low power consumption is used [Fischer et al., 1991]. Transmission of B-ISDN Signals Transmission systems at the UNI provide bit rates of around 150 and 622 Mbit/s. In addition to these rates, at the NNI around 2.5 Gbit/s and up to 10 Gbit/s will be used in the future [Baur, 1991]. In addition to the highcapacity switching and multiplexing technology, high-speed transmission systems are required. Optical fibers are especially suitable for this purpose; however, for the lower bit rates coaxial cables can be used. Optical transmission uses optical fibers as the transmission medium in low-diameter and low-weight cables to provide large transmission capacities over long distances without the need for repeaters. Optical transmission equipment currently tends to mono-mode fiber and laser diodes with wavelengths of around 1310 nm. For both directions in a transmission system either two separate fibers or one common fiber with wavelength division multiplexing can be used. The second solution may be a good alternative for subscriber lines and short trunk lines [Bauch, 1991]. For ATM cell transmission, two possibilities exist, which are shown in Fig. 72.2: synchronous pulse frame or continuous cell stream (cell-based). The basis for the pulse frame concept is the existing synchronous digital hierarchy (SDH). In SDH the cells are transported within the SDH payload; the frame overhead includes operation and maintenance (OAM) of the transmission system. In the cell-based system the OAM for the transmission system is transported within cells. The SDH solution is already defined, whereas for cell-based transmission some problems remain to be solved (e.g., OAM is not yet fully defined). ATM Adaptation Layer The ATM adaptation layer (AAL) is between the ATM layer and higher layers. Its basic function is the enhanced adaptation of the services provided by ATM to the requirements of the layers above. In order to minimize the number of AAL protocols, the service classification shown in Fig. 72.3 was defined. This classification was made with respect to timing relation, bit rate, and connection mode
SDH-based transmission Cell-based transmission Synchronous pulse frame( 125 us) Frame overhead Frame payload ATM onous digital hierarchy ATM FIGURE 72.2 Transmission principles for B-ISDN Class A Class B Class C Class D Timing relation between source and destination Not required Bitrate Constant variable Connection oriented Connection Connection mode FIGURE 72.3 AAL service classification The AAL protocols are subdivided into two parts. The lower part performs, at the sending side, the segmen- tation of long messages into the cell payload and, at the receiving side, reassembly into long messages. The upper part is service dependent and provides the AAL service to the higher layer B-ISDN Signaling For signaling in B-ISDN, existing protocols and infrastructure will be reused as much as possible. Figure 72.4 shows the protocol stacks for UNI and NNI. The upper part concerns signaling applications and the lower part signaling transfer. For the introduction of simple switched services in B-ISDN, at UNI and NNI, existing signaling application protocols will be reused. The 64-kbit/s ISDN-specific information elements will be removed and new B-ISDN specific information elements will be added. Right from the beginning these protocols will provide means that llow smooth migration toward future applications, which will include highly sophisticated features like mul timedia services [Huber et al., 1992]. This approach guarantees compatibility for future protocol versions. the NNi the existing signaling system no. 7( SS7)can be reused(see right part of the NNI protocol stack in Fig. 72.4). SS7 is a powerful and widespread network that will continue to be applied for rather a long period until ATM penetration has been reached. For the middle term, however, a fully ATM-based network will be available which also carries signaling messages(see left part of the NNI protocol stack in Fig. 72. 4). ATM-based signaling at the NNI needs a suitable AAL which provides the services of the existing message transfer part level 2 the UNI, right from the beginning, all kinds of traffic(including signaling) is carried within cells. An AAL for signaling at the UNI is also required. This aal has to provide the services of the existing layer 2 UNI e 2000 by CRC Press LLC
© 2000 by CRC Press LLC The AAL protocols are subdivided into two parts. The lower part performs, at the sending side, the segmentation of long messages into the cell payload and, at the receiving side, reassembly into long messages. The upper part is service dependent and provides the AAL service to the higher layer. B-ISDN Signaling For signaling in B-ISDN, existing protocols and infrastructure will be reused as much as possible. Figure 72.4 shows the protocol stacks for UNI and NNI. The upper part concerns signaling applications and the lower part signaling transfer. For the introduction of simple switched services in B-ISDN, at UNI and NNI, existing signaling application protocols will be reused. The 64-kbit/s ISDN-specific information elements will be removed and new B-ISDNspecific information elements will be added. Right from the beginning these protocols will provide means that allow smooth migration toward future applications, which will include highly sophisticated features like multimedia services [Huber et al., 1992]. This approach guarantees compatibility for future protocol versions. At the NNI the existing signaling system no. 7 (SS7) can be reused (see right part of the NNI protocol stack in Fig. 72.4). SS7 is a powerful and widespread network that will continue to be applied for rather a long period until ATM penetration has been reached. For the middle term, however, a fully ATM-based network will be available which also carries signaling messages (see left part of the NNI protocol stack in Fig. 72.4). ATM-based signaling at the NNI needs a suitable AAL which provides the services of the existing message transfer part level 2. At the UNI, right from the beginning, all kinds of traffic (including signaling) is carried within cells. An AAL for signaling at the UNI is also required. This AAL has to provide the services of the existing layer 2 UNI FIGURE 72.2 Transmission principles for B-ISDN. FIGURE 72.3 AAL service classification