1. Integrated Services Digital Network (ISDN)
Developed by ITU-T in 1976
Set of protocols that combines digital telephony and data transport services. The whole idea is to digitize the telephone network to permit the transmission of audio, video and text over existing telephone lines.
The goal is to form a WAN that provides universal end-to-end connectivity over digital media.

2. ISDN Services
Bearer services – provide the means to transfer information (voice, data, video) between users without the network manipulating the content of that information. Belongs to the first 3 layers of the OSI model.
Teleservices – the network my change or process the contents of the data.
- correspond to layers 4-7 of the OSI model
- rely on the facilities of bearer services
Supplementary services – provide additional functionality to the bearer services and teleservices.

3. ISDN Services

4. Voice Communication over an Analog Telephone Network

5. Voice and Data Communication over an Analog Telephone Network

6. Analog and Digital Services over the Telephone Network
3 types of customers – the first one is the most prominent

7. Integrated Digital Network (IDN)
A combination of networks available for different purposes.
Access to these networks is by digital pipes
digital pipes – time-multiplexed channels sharing very-high-speed paths.

8. Integrated Services Digital Network
(ISDN)
ISDN incorporates all communication connections in a home or building into a single interface
With ISDN all customer services will become digital rather than analog.

9. Subscriber Access to the ISDN
Subscriber loops – organized into multiple channels of different sizes
B channel
basic user channel
Can carry any type of digital info in Full-duplex mode
Carries transmissions end-to-end
D channel
Primary function is to carry control signaling for the B channel
Acts like an operator between the user and the network at the network layer
Channel
Data Rates (Kbps)
Bearer (B) 64
Data (D)
16, 64
Hybrid (H)
384 (H0), 1536(H11), 1920(H12)
H Channels
- For high data rate applications such as video, teleconferencing and so on

10. Two Types of Digital Subscriber Loops
Basic rate interface (BRI)
Primary rate interface (PRI)
Each type is suited to a different level of customer needs
Both include one D channel and some number of either B or H channels

11. Basic Rate Interface (BRI)
Designed to meet the needs of residential and small-office customers
The same twisted pair local loop that delivers analog transmission
can be used to handle digital transmission

12. Primary Rate Interface (PRI)
Other channel combinations:
– 3H0 + D
– 4H0 + D
– H12 + D
PRI was designed to be compatible with existing T-1 lines
In Europe, the PRI includes 30 B channels and 2 D channels
= capacity of Mbps – the capacity of E-1 line

13. Functional Grouping Defines the function of each type of equipment
NT – network termination
TE – terminal equipment
NT1
Controls the physical & electrical termination of the ISDN at the user’s premises
Connects the user’s internal system to the digital subscriber loop
Organizes the data stream s from a connected subscriber into frames that can be sent over the digital pipe
Translates the frames received from the network into a format usable by the subscriber’s devices.

14. NT2 ( ex. Digital PBX, LAN)
Performs functions at the physical (multiplexing), data link (flow control), network layers (packetizing) of the OSI model
Provides intermediate signal processing between the data-generating devices and an NT1
Used primarily to interface between a multiuser system and an NT1 in a PRI.

15. TE1 – same thing as DTE TE2 Any non-ISDN device
Any device that supports the ISDN standards
Ex. Digital telephones,integrated voice/data terminals
TE2
Any non-ISDN device
Ex. Terminal workstation, regular telephone
Can be used with the help of Terminal Adapter (TA)

16. Reference Points
Label used to identify individual interfaces between two elements of an ISDN installation
Defines the functions of the connections

17. ISDN Layers

18. OSI Model

19. The OSI Model Open Systems Interconnection
Standard Model for Data Communications
Specified by International Standards Organization (ISO)
Adopted by CCITT/ITU
Official Model Explained in X.200 Series

20. The OSI Model Layered Approach to Communications
Seven Layers Altogether
Each Layer Performs a Unique Function
Each Layer Has Its Own Protocol
Protocol Messages in Upper Layer is Data to Layer Below

21. 7 Layers All People Seem To Need Data Processing 7. Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
All
People
Seem To
Need
Data
Processing

22. The OSI Model The Seven Layers Layer Name Description Examples
Physical
Link
Network
Transport
Session
Presentation
Application
Unreliable Wire, Telco Line
Reliable Across Physical Line
Unreliable Thru Multi-Node Network
Reliable End to End
Sync Points and Dialogs
Data Representation & Syntax
User Level Processing
RS232, T1, 802.x
LAPB, HDLC
X.25 Pkt, IP
TCP
ISO Session
ISO Presentation
Telnet, FTP, Mail

23. The OSI Model The Standards Layer Name Standards Physical Link Network
Transport
Session
Presentation
Application
X.400, Telnet, FTP, Mail
ASN.1, X.409
X.225
X.224, TCP
X.25 Pkt, Q.931, IP
Reliable Across Physical Line
X.25 LAPB, Q.921 LAPD, ISO 3309 HDLC
RS232, V.35, EIA530, X.21, T1, E1
Unreliable Wire, Telco Line
Unreliable Wire, Telco Line

24. The OSI Model Physical Layer Message Has Begin and End Data in between
Data Passed up to Link Layer
Begin
End
Data
Link Layer

25. The OSI Model Physical Layer Begin Can Be Flag or STX
End Can Be Flag or ETX
End May Include Check Sum (CRC)
Data Transparency
Link Layer
Begin
Data
End

26. The OSI Model Link Layer Link Layer Header Has Frame Type
Sequence and Acknowledgement Numbers
Error Recovery Procedures
Limited to Local Wire or Circuit
Network Layer
LL Hdr
Data

27. The OSI Model Network Layer Network Header Has Packet Type
Sequence and Acknowledgement Numbers
No Error Recovery -- Data Can Be Lost
Addressing across Multi-Node Network
Transport Layer
Net Hdr
Data

28. The OSI Model Transport Layer Transport Header Has Packet Type
Sequence and Acknowledgement Numbers
Error Recovery Is End to End
Upper Layers Can Count on Reliability
Upper Layers
Trans Hdr
Data

29. The OSI Model Complete Picture A Message with All Headers
Session, Presentation, Application Omitted
Trans Hdr
Data
Net Hdr
LL Hdr
Begin
End

30. Simplified Layers of ISDN
Mechanical and electrical specs of interfaces R, S, T, U
Encoding
Multiplexing
Power supply

31. BRI Interfaces R interface
– not defined by ISDN, it can be any EIA standards or V or X series
S interface
– ISO standard, ISO 8887, four-, six-, or eight-wire connections.
U interface
- Single-pair twisted-pair cable in each direction
- Two binary, one quaternary (2B1Q) encoding

32. S Interface Name TE NT a Power source 3 Power sink 3 b c Transmit
Receive d e f g
Power sink 2
Power source 2 h

33. 2B/1Q Encoding 00 01 10 11 -3 -1 +3 +1

34. BRI Frame
overhead

35. BRI Topology Point-to-point Multipoint
-limited distance to ensure frame synchronization
As many as 8 devices can be connected to NT1, two can access the B-channels at 1 time
D channels use a mechanism like CSMA

36. PRI Interfaces R and S – same as those defined for the BRI
T – identical to S standard
- B8ZS Encoding
U – same for both, different rates

37. PRI Frame

38. LAPD Address Field SAPI – Service Access Point Identifier
– call control for network layer (signaling use of D-channel)
– call control for upper layer (ene-to-end signaling), not yet in use
– packet communication ( data use of D channel)
management
SAPI – Service Access Point Identifier
- identifies the type of upper- layer service (network layer)
C/R – Command (0) / Response (1)
TEI – Terminal Equipment Identifier

39. Network Layer Packet Format
Protocol discriminator – identifies the protocol in use, for Q.931 =
Call Reference – sequence number of the call
Message Type – identifies the purpose of the message
- call establishment
- call information
- call clearing
- call miscellaneous
Reading assignment:
Different messages under these four message types

40. Call Reference Field

41. Information Elements
Carries specific details about the connection that are required for call establishment:
- addresses of the sender and receiver
- routing information
- type of network that is desired for the B-channel exchange (X.25, ATM, Frame Relay)

42. Information Element Types
ID – identify the information being sent
Length – length of the content in bytes

43. Addressing in ISDN
Addressing – important information element type in ISDN
NC – national Code
Subaddress – identify the device connected to NT1

44. Bit Rates for Different Applications

45. B-ISDN Services
Broadband ISDN – based on a change from metal cable to fiber optic cable at all levels of telecommunications
Interactive services – those that require two-way exchanges between either 2 subscribers or between a subscriber & a service provider
- conversational – real time exchanges such as telephone calls
- messaging – store & forward exchanges such as voice mail
- retrieval –retrieve info from a central office

46. B-ISDN Services
Distributive services – unidirectional services sent from a provider to subscribers, broadcast to the user
- without user control – user choice is limited to whether or not to receive the service at all
- with user control – allow the user a choice of times during which to receive them

47. B-ISDN Accesses
Mbps – fill the needs of most residential and many business subscribers
/ Mbps – fill the needs of businesses that require the simultaneous receipt of multiple services and video conferencing

48. END.