ISDN Lecture 5 Paul Flynn 1

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

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

4 Integrated Digital Network Analog Switch FDM MUX 4kHz Analog

5 Integrated Digital Network Digital Switch IDN TDM/PCM

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

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

8 ISDN Standards

9 Line Encoding 2 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 Basic Access BRI: 2B+D 160 kbps = 2 64k each D: 16 k + 16 k overhead Primary Access PRI: (NA) 23B+D kbps = 23 64k each D: 64k + 8 k framing

12 PRI Channel Structures North America Primary Rate Interface (PRI) –B8ZS Line Coding –AMI Signals F bits (125 Microseconds) ITU-T PRI Time # 0 8 bits 256 bits (125 Microseconds) Time # 1Time # 2 Time #16Time #17Time #18Time #31 8 bits Timing & Sync B-Channels Time # 0Time # 1Time # 2 8 bits B-Channels Time#23 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 ISDN Reference Configurations NT1+2 ISDNNETWORKISDNNETWORK NT1 TE2 TE1 TA NT2 TE1 NT1+2 S S T R S U U U I.411

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

17 ISDN Reference Points & Functional Groups TE1NT1NT2 TE1 (Terminal equipment type 1) - Subscriber equipment that uses ISDN with standard ISDN I/F (e.g. digital phone, voice/data terminal, Fax) NT1 (Network Termination 1) - Physical & Electrical termination on user premises (Layer 1). Isolates user from subscriber loop technology. 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. SUT Reference Point S (system) - Interface of individual ISDN terminals. Separates user’s equipment from network related communications functions. Reference Point T (terminal) - Minimal ISDN termination on customer premises. Reference Point U - Interface between carrier ISDN exchange & NT1

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 ISDN Reference Points & Functional Groups SUT R Reference Point R (rate) - Defines interface to non-ISDN equipment (e.g. RS232) S TE1NT1NT2 TA TE2 TA (Terminal adapter) - interfaces non-ISDN equipment to NT2 TE2 (Terminal equipment type 2) - Non-ISDN equipment. Require terminal adapter (TA)

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

21 ?????????? Telco OwnedUser Owned ISDN Reference Points & Functional Groups TE1NT2NT1 TE2TA Analog Terminal R ST LTET VU Transmission Line to Switching Office

22 ISDN User Interface Layered Models Procedural Model D-Channel B-Channel Reference Model NT1TE1NT2 STU LT ET V C.O. 3

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

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

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

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

27 ISDN Protocols and Services Application End-to-end User Signaling Presentation Session Transport NetworkQ.931 Call Control X.25 PLP Future Data Link LAPD (Q.921) Frame Relay LAPB Physical I.430 Basic Interface, I.431 Primary Interface D-Channel B, H-Channels

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

29 ISDN Protocol Architecture at the User-Network Interface

30 ISDN Call-Control Protocol 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 /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 Call ref value Message type Other info elements as required Length of call-ref value 0 0 Flag 0

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).