ISDN Lecture 5 Paul Flynn 1. Functional Architecture 2 High-layer Capabilities TE TE or Service Provider Local Functional Capabilities Broadband Capabilities.

ISDNISDN

Lecture 5

Paul Flynn

1

Functional ArchitectureFunctional Architecture

2

High-layer Capabilities

TETE or

Service Provider

Local Functional Capabilities

Local Functional Capabilities

Broadband Capabilities

Inter-exchange Signaling

Capabilities

64 kbps basedCapabilities

Low-layer capabilities OSIB-ISDN

N-ISDN

SS7User-to-Network Signaling

User-to-User Signaling

I.327

3

Component Functionality ModelComponent Functionality Model

SwitchingSwitching

TransportTransport

AccessAccess

End User

End User

Co

ntr

ol

Co

ntr

ol

Co

ntr

ol

Co

ntr

ol

4

Integrated Digital NetworkIntegrated Digital NetworkAnalog Switch

FDM MUX

4kHz Analog 4kHz Analog

5

Integrated Digital NetworkIntegrated Digital NetworkDigital Switch

IDNTDM/PCM TDM/PCM

6

Present Service AccessPresent Service AccessSubscriber

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 AccessISDN 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

IntegratedServicesDigital

Network

8

ISDN StandardsISDN Standards

9

Line EncodingLine Encoding2 Binary, 1 Quaternary (2B1Q)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

11

01

00

10

11

00

+3

+1

0

+1

+3

10

ISDN Channel StructureISDN 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 StructuresUser Interface Structures

Basic Access

BRI:2B+D160 kbps =2 B @ 64k eachD: 16 k+ 16 k overhead

Primary Access

PRI: (NA)23B+D1.544 kbps =23 B @ 64k eachD: 64k+ 8 k framing

12

PRI Channel StructuresPRI Channel Structures• North America Primary Rate Interface (PRI)

– B8ZS Line Coding

– AMI Signals

F

1193 bits (125 Microseconds)

• ITU-T PRI

Time # 0

8 bits

256 bits (125 Microseconds)

Time # 1 Time # 2 Time #16 Time #17 Time #18 Time #31

8 bits 8 bits 8 bits8 bits 8 bits 8 bits

Timing & Sync B-Channels

Time # 0 Time # 1 Time # 2

8 bits 8 bits 8 bits

B-Channels

Time#23

D-Channel

D-Channel

13

ISDN Reference PointsISDN Reference Points& Functional Groups& 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 Integrated Services Bus Network (ISBN)Network (ISBN)

15

ISDN Reference ConfigurationsISDN Reference Configurations

NT1+2ISDN

NETWORK

NT1

TE2

TE1

TA

NT2

TE1

NT1+2

S

S T

R S

U

U

U

I.411

16

ISDN InternetworkingISDN Internetworking

ISDN

ISDNCustomer Equipment

Specialized Service Provider

Telephony networks or dedicated networks

Specialized network resource

K

M

N

T

P

17

ISDNISDNReference Points & Functional GroupsReference Points & Functional Groups

TE1 NT1NT2

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 subscriberloop technology.

NT2 (Network Termination 2) - Intelligent device performing switching & concentrating functions (e.g. digital PBX, terminal controller or LAN). Upto Layer 3. Supports Multi-drop.

S UT

Reference Point S (system) - Interface of individual ISDN terminals. Separates user’s equipment from network related communications functions.

Reference Point T (terminal) - Minimal ISDN terminationon customer premises.

Reference Point U - Interface between carrier ISDN exchange & NT1

18

The U-InterfaceThe 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

ISDNISDNReference Points & Functional GroupsReference Points & Functional Groups

S UT

R

Reference Point R (rate) - Defines interface tonon-ISDN equipment (e.g. RS232)

S

TE1 NT1NT2

TATE2

TA (Terminal adapter) - interfacesnon-ISDN equipment to NT2

TE2 (Terminal equipment type 2) - Non-ISDNequipment. Require terminal adapter (TA)

20

ISDNISDNReference Points & Functional GroupsReference Points & Functional Groups

T U

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

TATE2

Functional Groups can be combined into single devices.

21

?????????? Telco OwnedUser Owned

ISDNISDNReference Points & Functional GroupsReference Points & Functional Groups

TE1 NT2 NT1

TE2 TA

AnalogTerminal

R

S T

LT ET

VU

Transmission Line to Switching Office

22

ISDN User InterfaceISDN User InterfaceLayered ModelsLayered Models

3 3

2 2 2 2

1 1 1 1 1 1

1 1 1 1 1 1

Procedural Model

D-Channel

B-Channel

Reference Model

NT1TE1 NT2S T U

LT ETV

C.O.

3

23

TE1 Device Physical LayerTE1 Device Physical LayerAnalog-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-BusMultidrop on the S-Bus

D

ISDN—Term ISDN—Term ISDN—Network Term

Pkt Data

Ckt Cont

Pkt Data

Ckt Cont

Pkt Data

Ckt Cont

B1B2

25

ISDN Packet Switched ServiceISDN Packet Switched ServiceCircuit-Switched ModeCircuit-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?How does it work?ISDN CO Switch

Bonding

U Ref Point

X.25

TE1

NT

D InterfaceD Interface

PSPDNX.25

TE1

NT

27

ISDN Protocols and ServicesISDN Protocols and Services

Application

End-to-end End-to-end User User

SignalingSignaling

Presentation

Session

Transport

Network Q.931Q.931Call ControlCall Control

X.25 PLPX.25 PLP FutureFuture X.25 PLPX.25 PLP

Data Link LAPD (Q.921)LAPD (Q.921) Frame RelayFrame Relay LAPBLAPB

Physical I.430 Basic Interface, I.431 Primary InterfaceI.430 Basic Interface, I.431 Primary Interface

D-ChannelD-Channel B, H-ChannelsB, H-Channels

28

ISDN Circuit-Switching ISDN Circuit-Switching ConceptConcept

OSI Layer 112

34

56

7

1

234

123

Localexchange

D channel

B channel

Control

OSI Layer 1 12

34

56

7

1

234

123

Localexchange D

cha

nnel

B c

hann

el

Control

CCSS No.7 network

DigitalNetwork

ISDN User #1OSI layer

ISDN User #2OSI layer

Control Plane

User Plane

29

ISDN Protocol ArchitectureISDN Protocol Architectureat the User-Network at the User-Network

InterfaceInterfaceNetwork Call control

Q.931X.25

Packet level

Data Link LAPD (Q.921) V.120 or frame relay LAPB

Physical I.430 basic interface + I.431 primary interface

Signal Packet Circuit-switeched

Semi-permanent

Packet-switched

D channel B channel

30

ISDN Call-Control ProtocolISDN 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 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.

8 7 6 5 4 3 2 1

Protocol discriminator

Call ref value

Message type

Other info elementsas required

Length ofcall-ref value

0 0 0 0

Flag

0

31

Q.931 MessagesQ.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 Functions of Q.931 messagesmessages

• 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).