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Transcript
ISDN Lecture 5 Paul Flynn 1 Functional Architecture OSI Low-layer capabilities B-ISDN I.327 High-layer Capabilities Broadband Capabilities N-ISDN Local Functional Capabilities TE User-toNetwork Signaling Local Functional Capabilities 64 kbps based Capabilities Inter-exchange Signaling Capabilities TE or Service Provider SS7 User-to-User Signaling 2 Component Functionality Model Control Control Switching Transport Access End User End User 3 Integrated Digital Network Analog Switch FDM MUX 4kHz Analog 4kHz Analog 4 Integrated Digital Network Digital Switch TDM/PCM IDN TDM/PCM 5 Present Service Access Subscriber PSTN - Public Switched Telephone Network CSPDN - Public Circuit Switched Data Network Multiple, Disjoint, Access Lines (Digital and Analog) PSPDN - Public Packet Switched Data Network Analog Dedicated Lines Digital Dedicated Lines 6 ISDN Service Access PSTN - Public Switched Telephone Network Subscriber CSPDN - Public Circuit Switched Data Network Integrated Services Digital Network PSPDN - Public Packet Switched Data Network Analog Dedicated Lines Digital Dedicated Lines 7 ISDN Standards 8 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 +3 +1 0 11 11 01 +1 +3 00 00 9 ISDN Channel Structure B-Channel -Bearer Services D-Channel -Signaling -LBR telemetry -LBR data H-Channel -HBR Data / Fax -Video -Hi-quality Audio 10 User Interface Structures BRI: Basic Access 2B+D 160 kbps = 2 B @ 64k each D: 16 k + 16 k overhead PRI: (NA) Primary Access 23B+D 1.544 kbps = 23 B @ 64k each D: 64k + 8 k framing 11 PRI Channel Structures • North America Primary Rate Interface (PRI) – – 1 F B8ZS Line Coding AMI Signals 193 bits (125 Microseconds) 8 bits Time # 0 8 bits Time # 1 8 bits Time # 2 Time#23 B-Channels D-Channel • ITU-T PRI 256 bits (125 Microseconds) 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits 8 bits Time # 0 Time # 1 Time # 2 Time #16 Time #17 Time #18 Time #31 Timing & Sync B-Channels D-Channel 12 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 13 Integrated Services Bus Network (ISBN) 14 ISDN Reference Configurations I.411 U S TE1 NT1+2 T S TE1 NT2 NT1 S R TE2 U TA U NT1+2 I S D N N E T W O R K 15 ISDN Internetworking K ISDN P Specialized network resource Telephony networks or dedicated networks M Specialized Service Provider N T Customer Equipment ISDN 16 ISDN Reference Points & Functional Groups 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 TE1 T NT2 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. Reference Point T (terminal) - Minimal ISDN termination on customer premises. U NT1 Reference Point U - Interface between carrier ISDN exchange & NT1 NT1 (Network Termination 1) - Physical & Electrical termination on user premises (Layer 1). Isolates user from subscriber loop technology. 17 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 18 ISDN Reference Points & Functional Groups TE2 (Terminal equipment type 2) - Non-ISDN equipment. Require terminal adapter (TA) S TE1 NT2 U NT1 S R TE2 T TA Reference Point R (rate) - Defines interface to non-ISDN equipment (e.g. RS232) TA (Terminal adapter) - interfaces non-ISDN equipment to NT2 19 ISDN Reference Points & Functional Groups Functional Groups can be combined into single devices. T NT2+1 TE1 S R TE2 U TA Reference Point T – Same description as S, occurs between NT1 and NT2 devices. Reference Point S – Occurs between NT2 capable device and terminal devices. 20 ISDN Reference Points & Functional Groups User Owned ?????????? S TE1 T NT2 Telco Owned U NT1 V LT ET R TE2 TA Transmission Line to Switching Office Analog Terminal 21 ISDN User Interface Layered Models Reference Model C.O. S T TE1 NT2 U NT1 V ET LT Procedural Model 3 3 D-Channel B-Channel 3 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 22 TE1 Device Physical Layer ( Analog-to-Digital Conversion, Data sources / sinks, etc. Circuit Circuit B1 B2 Control Requests / Indications Circuit Switched Control Data Packet Switched Data D-Channel Control S-Bus Multiplexing 23 Multidrop on the S-Bus ISDN—Term Ckt Pkt Cont Data ISDN—Term Ckt Pkt Cont Data ISDN—Network Term Pkt Data Ckt Cont D B1 B2 24 ISDN Packet Switched Service Circuit-Switched Mode X.25 Terminal Terminal Adapter ISDN Central Office X.25 Packet Switched PDN Used for X.25 Data on B-Channel 25 How does it work? TE1 TE1 ISDN CO Switch NT D Interface NT Bonding X.25 X.25 U Ref Point PSPDN 26 ISDN Protocols and Services Application Presentation Session End-to-end User Signaling Transport Network Data Link Physical Q.931 Call Control X.25 PLP LAPD (Q.921) X.25 PLP Future Frame Relay LAPB I.430 Basic Interface, I.431 Primary Interface D-Channel B, H-Channels 27 ISDN Circuit-Switching ISDN User #1 Concept ISDN User #2 OSI layer 7 B channel 6 5 6 5 4 3 4 3 2 1 2 1 D channel 4 3 2 1 OSI Layer 1 Digital Network Control 3 2 1 Local exchange OSI Layer 1 Control Local exchange CCSS No.7 network 3 2 1 4 3 2 D channel 7 OSI layer B channel User Plane 1 Control Plane 28 ISDN Protocol Architecture at the User-Network Interface Network Call control Q.931 Data Link X.25 Packet level LAPD (Q.921) Physical V.120 or frame relay LAPB I.430 basic interface + I.431 primary interface Signal Packet D channel CircuitSemiPacketswiteched permanent switched B channel 29 ISDN Call-Control Protocol 87654321 • Protocol discriminator: – used to distinguish messages for usernetwork call control Protocol discriminator 0000 Flag 0 Length of call-ref value • Call reference: – identifies the B-channel call to which this message refers Call ref value Message type Other info elements as required • 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. 30 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 31 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 32