AN INTRODUCTION TO ISDN
By
Mohammad AlianNejadi
Fardin Sabouri
Master
Mahdy Abbasi Ph.D.
Autumn 2009
WHAT IS ISDN?(CONT.)
Rapid advances in computer and communication technologies.
Demands for efficient and timely collection and processing of information.
Integrated Services Digital Network
Worldwide public telecommunication
Standard user interface Multiple networks in national boundaries
A single network from the user’s point of view
WHAT IS ISDN?
Generations of ISDN First: Narrowband ISDN
Based on use of 64 Kbps channel
Circuit-switch orientation
Major technical: Frame Relay
Second: Broadband ISDN Supports very high data rates: 100s Mbps
Packet-switch orientation
Major technical: ATM
PRINCIPLES OF ISDN
1. Support of voice and non-voice applications using a limited set of standardized facilities.
2. Support, for switched and non-switched applications.
3. Reliance on 64-kbps connections.4. Intelligence in the network.5. Layered protocol architecture.6. Variety of configurations.
THE USER INTERFACE
A local interface is between the user and digital pipe.
The digital pipe has a certain bit rate.
A complex control must an appropriate service.
The user is charged according to the capacity used rather than “connect time”.
CONCEPTUAL VIEW OF ISDN CONNECTION FEATURES
ISDN CHANNELS
B Channel: 64 Kbps Basic user channel
D Channel: 16 or 64 Kbps Signaling information for circuit-switch Used for packet-switch
H Channel: H0: 384 Kbps H11: 1536 Kbps H12: 1920 Kbps High-speed use like video
ACCESS TYPES
Basic Access Two full-duplex 64-kbps B Channels One full-duplex 16-k-kbps D Channel Framing and other overheads
Simultaneous use of voice and other data applications
Primary Access For users with greater capacity requirements U.S., Canada and Japan: 1.544 Mbps Europe: 2.048 Mbps
May user B and D structure or H and D structure
192 Kbps
ISDN PROTOCOLS
Layer 1-3 Protocols Physical Layer
Basic and Primary Access B and D Channels are multiplexed over the same
physical interface Data Link Layer: LAPD
Based on HDLC
Channel B Circuit-switched connection Packet-switched connection
WHAT IS LAPD?
Link Access Protocol-D Channel
Unacknowledged information-transfer service No error control Fast data transfer Broadcast
Acknowledged information-transfer service Like HDLC
LAPD PROTOCOL
Frame format: Address field Two-level Multiplexing:
Subscriber site Multiple types of traffic
Terminal Endpoint Identifier Automatically Manually
Service Access Point Identifier Corresponds layer-3 protocol
LAPD PROTOCOL (CONT.)
LAPD PROTOCOL (CONT.)
Acknowledged: Same as HDLC Unacknowledged:
User Information (UI) frame UI is sent to a LAPD entity Sent to the destination with no ack returned
Physical Layer Basic Access: Pseudoternary Coding Primary Access
1.544 Mbps: B8ZS 2.048 Mbps: HDB3
QUESTION
Q
