Frame Relay Frame Relay

158 Communication Networks Copyright © 2005 PragSoft • The L reference point is used for interfacing ISDN to an existing, non-ISDN voice or data network, where the internetworking mappings are performed by the non-ISDN network. • The M reference point is used for interfacing ISDN to a specialized network e.g., MHS, where the internetworking mappings are performed by the latter. • The N reference point is used for interfacing two ISDN networks, where both networks may need to do internetworking mappings to provide a common set of services.

11.5. ISDN Standards

Figure 11.134 provides a high-level view of CCITT ISDN recommendations. Each of the series consists of many parts. The I.100 series provides a general introduction to ISDN, its principles, objectives, and envisaged evolution path. The I.200 series defines the ISDN end-user services and a set of attributes for each service. The I.300 series defines the ISDN network and its functions and protocols in relation to ISDN services. The I.400 series defines the physical and logical interfaces between ISDN and its users. The I.500 series deals with the issues of internetworking between ISDN networks and between ISDN and non-ISDN networks e.g., PSTN. The I.600 series deals with the issues of maintenance of subscriber access and installation. Figure 11.134 High-level view of CCITT ISDN recommendations. Part Series Description I: I.100 Series General description of ISDN concepts II: I.200 Series Service capabilities III: I.300 Series Overall network aspects and functions IV: I.400 Series User-network interfaces V: I.500 Series Internetwork interfaces VI: I.600 Series Maintenance principles Figure 11.135 summarizes the major ISDN-related standards for four areas of basic rate, primary rate, SS7, and packet-switched network. Figure 11.135 Major ISDN-related standards. Layer Standard Description 1 I.430 2B+D channels D=16 kbps Basic Rate 2 I.441 LAP-D with multiple TEs 3 I.451 User-network interface 1 I.431 23B+D or 30B+D channels D=64 kbps Primary Rate 2 I.441 LAP-D point-to-point 3 I.451 User-network interface www.pragsoft.com Chapter 11: Integrated Services Digital Network 159 1-3 Q.701-Q.708 Message Transfer Part MTP Signaling System 7 4 Q.711-Q.714 Signaling Connection Control Part SCCP 4+ Q.761-Q.766 ISDN User Part IUP 4+ Q.791-Q.795 Operation, Admin and Maintenance OAM 1 X.21 Physical interface Packet Network 2 LAP-B Link access 3 X.25, X.75 Packet interface

11.6. Further Reading

Black 1989 and Freeman 1989 both contain introductory chapters on ISDN. Griffiths 1990, Helgert 1991, Stallings 1992, and Kessler 1993 provid detailed discussions of ISDN architecture, services, and protocols. Dickson and LLoyd 1992 discuss many of ISDN protocols within the context of the OSI model. Deniz 1993 describes the use of ISDN for interconnecting LANs. Lai 1989 provides a useful introduction to frame relay. Deatiled descriptions of frame relay applications and protocols can be found in Chen and Rege 1989, Smith, P. 1993, and Black 1994.