ISDN

1. ISDN Lecture 5 Paul Flynn

2. I.327 Functional Architecture OSI Low-layer capabilities High-layer Capabilities B-ISDN Broadband Capabilities N-ISDN TE or Service Provider 64 kbps based Capabilities Local Functional Capabilities Local Functional Capabilities TE SS7 Inter-exchange Signaling Capabilities User-to-Network Signaling User-to-User Signaling

3. Component Functionality Model Switching Control Control Transport Access End End User User

4. Analog Switch FDM MUX Integrated Digital Network 4kHz Analog 4kHz Analog

5. Digital Switch IDN Integrated Digital Network TDM/PCM TDM/PCM

6. Present Service Access Subscriber PSTN - Public Switched Telephone Network CSPDN - Public Circuit Switched Data Network PSPDN - Public Packet Switched Data Network Multiple, Disjoint, Access Lines (Digital and Analog) Analog Dedicated Lines Digital Dedicated Lines

7. ISDN Service Access PSTN - Public Switched Telephone Network Integrated Services Digital Network CSPDN - Public Circuit Switched Data Network Subscriber PSPDN - Public Packet Switched Data Network Analog Dedicated Lines Digital Dedicated Lines

8. ISDN Standards

9. 10 +3 +1 11 11 0 01 +1 00 00 +3 Line Encoding2 Binary, 1 Quaternary (2B1Q) • Two bits select one of four voltage levels • Amplitude and polarity vary • Utilizes up to 392 kHz • NO room for concurrent POTS voice as separate entity

10. ISDN Channel Structure B-Channel -Bearer Services D-Channel -Signaling -LBR telemetry -LBR data H-Channel -HBR Data / Fax -Video -Hi-quality Audio

11. User Interface Structures BRI: 2B+D 160 kbps = 2 B @ 64k each D: 16 k + 16 k overhead Basic Access PRI: (NA) 23B+D 1.544 kbps = 23 B @ 64k each D: 64k + 8 k framing Primary Access

12. 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits PRI Channel Structures • North America Primary Rate Interface (PRI) • B8ZS Line Coding • AMI Signals 193 bits (125 Microseconds) 1 F Time # 0 Time # 1 Time # 2 Time#23 B-Channels D-Channel • ITU-T PRI 256 bits (125 Microseconds) Time # 0 Time # 1 Time # 2 Time #16 Time #17 Time #18 Time #31 Timing & Sync B-Channels D-Channel

13. ISDN Reference Points& Functional Groups • Architecture on subscriber premises is divided functionally into groupings separated by reference points • Functional Groupings: arrangements of physical equipment or combinations of equipment • Reference points: conceptual points used to separate groups of functions • Separation permits development of interface standards at each reference point

14. Integrated Services Bus Network (ISBN)

15. U S ISD N N E T W O R K TE1 NT1+2 I.411 T U S TE1 NT2 NT1 S U R TE2 TA NT1+2 ISDN Reference Configurations

16. ISDN Internetworking Telephony networks or dedicated networks K ISDN P Specialized network resource M Specialized Service Provider N T Customer Equipment ISDN

17. TE1 (Terminal equipment type 1) - Subscriber equipment that uses ISDN with standard ISDN I/F (e.g. digital phone, voice/data terminal, Fax) Reference Point S (system) - Interface of individual ISDN terminals. Separates user’s equipment from network related communications functions. S T U TE1 NT2 NT1 Reference Point U - Interface between carrier ISDN exchange & NT1 NT2 (Network Termination 2) - Intelligent device performing switching & concentrating functions (e.g. digital PBX, terminal controller or LAN). Up to Layer 3. Supports Multi-drop. NT1 (Network Termination 1) - Physical & Electrical termination on user premises (Layer 1). Isolates user from subscriber loop technology. Reference Point T (terminal) - Minimal ISDN termination on customer premises. ISDNReference Points & Functional Groups

18. The U-Interface G.961, Digital Transmission System for Metallic Local Lines for ISDN Basic Rate Access, 1993 ANSI T1.601, Integrated Services Digital Network – Basic Access Interface for Use on Metallic Loops for Application on the Network Side of the NT, 1992

19. TE2 (Terminal equipment type 2) - Non-ISDN equipment. Require terminal adapter (TA) S T U TE1 NT2 NT1 S R TA TE2 Reference Point R (rate) - Defines interface to non-ISDN equipment (e.g. RS232) TA (Terminal adapter) - interfaces non-ISDN equipment to NT2 ISDNReference Points & Functional Groups

20. T U S R Reference Point T – Same description as S, occurs between NT1 and NT2 devices. Reference Point S – Occurs between NT2 capable device and terminal devices. ISDNReference Points & Functional Groups Functional Groups can be combined into single devices. NT2+1 TE1 TA TE2

21. ISDNReference Points & Functional Groups User Owned ?????????? Telco Owned S T U V TE1 NT2 NT1 LT ET R TE2 TA Transmission Line to Switching Office Analog Terminal

22. ISDN User InterfaceLayered Models Reference Model C.O. S T U V TE1 NT2 NT1 ET LT Procedural Model D-Channel B-Channel 3

23. TE1 Device Physical Layer Analog-to-Digital Conversion, Data sources / sinks, etc. ( Control Requests / Indications Circuit B1 Circuit B2 Data Packet Switched Data Circuit Switched Control D-Channel Control S-Bus Multiplexing

24. Multidrop on the S-Bus ISDN—Term ISDN—Term ISDN—Network Term Ckt Pkt Ckt Pkt Pkt Ckt Cont Data Cont Data Data Cont D B1 B2

25. ISDN Packet Switched ServiceCircuit-Switched Mode Packet Switched PDN ISDN Central Office X.25 Terminal Terminal Adapter X.25 Used for X.25 Data on B-Channel

26. How does it work? TE1 TE1 ISDN CO Switch NT D Interface NT Bonding X.25 PSPDN X.25 U Ref Point

27. ISDN Protocols and Services

28. ISDN Circuit-Switching Concept ISDN User #1 OSI layer ISDN User #2 OSI layer User Plane 7 7 6 6 5 5 B channel B channel 4 4 3 3 2 2 Digital 1 OSI Layer 1 OSI Layer 1 1 Network Control Control 4 4 3 3 3 3 D channel D channel Local exchange Local exchange 2 2 2 2 1 1 1 1 Control Plane CCSS No.7 network

29. ISDN Protocol Architectureat the User-Network Interface

30. ISDN Call-Control Protocol 8 7 6 5 4 3 2 1 • Protocol discriminator: • used to distinguish messages for user-network call control • Call reference: • identifies the B-channel call to which this message refers • Message type: • identifies which 1.45 1/Q.931 message is being sent e.g. SETUP, DISCONNECT. • The contents of the remainder of the message depend on the message type. Protocol discriminator 0 0 0 0 Length of call-ref value Flag Call ref value 0 Message type Other info elements as required

31. Q.931 Messages • Circuit-mode connection control: • refers to the functions needed to set up, maintain, and cleara circuit-switched connection on a B channel. This function corresponds to call control in existing circuit-switching telecommunications networks. • Packet-mode access-connection control: • refers to the functions needed to set up a circuit-switched connection (called an access connection in this context) to an ISDN packet-switching node; this connects the user to the packet-switching network furnished by the ISDN provider.

32. Functions of Q.931 messages • Call establishment: • used to set up a call initially. This group includes messages between the calling terminal and the network and between the network and the called terminal. • Call information: • sent between user and network once a call has been set up but prior to the disestablishment (termination) phase. One of the messages in that group allows the network to relay, without modification, information between the two users of the call. • Call clearing: • sent between user and network in order to terminate a call. • Miscellaneous: • to negotiate network features (supplementary services).