1. B-ISDN and ATM
B-ISDN and ATM

2. ATM / B-ISDN Broadband Integrated Services Digital Network
In the 1970s the telecommunications industry conceived that digital services would follow much the same pattern as voice services, and conceived a grandiose vision of end-to-end circuit switched services, known as the Broadband Integrated Services Digital Network (B-ISDN).
This was conceived as a logical extension of the end-to-end circuit switched data service, ISDN.
The technology for B-ISDN was going to be Asynchronous Transfer Mode (ATM), which was intended to carry both synchronous voice and asynchronous data services on the same transport.
The B-ISDN vision has been overtaken by the technology of the Internet. The ATM technology survives as a low-level layer in most DSL technologies.
Over fibre optic lines, the maximum Data bandwidth is 1.5 Megabits and point-to-point protocol is typically used to carry data over the B channels.

3. ATM / B-ISDN Asynchronous Transfer Mode (ATM)
cell relay network protocol which encodes data traffic into small fixed sized (53 byte; 48 bytes of data and 5 bytes of header information) cells instead of variable sized packets as in packet-switched networks (such as the Internet Protocol or Ethernet).

4. Characteristics of ATM
Uses small, fixed-sized cell
Connection oriented
Bandwidth allocation on demand
Supports multiple service types
Applicable to LAN and WAN

5. ATM Signaling UNI : User to Network Interface
NNI : Network to Network Interface
Different protocol in the different domain

6. Virtual Path / Virtual Channel
Connection Identifier : VPI/VCI
Physical Link : Contains multiple VPs
Virtual Path : Contains multiple VCs
Virtual Channel : Logical path between ATM endpoint

7. VP and VC Switching

8. ATM Cell Header PTI Payload Type Identifier(3 Bits)
- 1 bit : User/Control Data bit : Congestion flag. - 3 bit : Last Cell flag
CLP Cell Loss Priority Bit
HEC Header Error Check(8 Bits)

9. Permanent Virtual Circuit
Manual updates of VPI/VCI tables in network equipment

10. Switched Virtual Curcuit
Setup connection using UNI/NNI signaling

11. ATM Reference Model SAAL Signaling ATM Adaptation Layer Q.2931, Q2971
PHY
SAAL
Signaling ATM Adaptation Layer

12. ATM Service Criteria Traffic parameters Quality of Service
Peak Cell Rate(PCR), Sustainable Cell Rate(SCR)
Maximum Burst Size(MBS), Minimum Cell Rate(MCR)
Quality of Service
Maximum Cell Transfer Delay(MCTD)
Cell Delay Variation Tolerance(CDVT)
Cell Loss Ratio(CLR)

13. ATM Service Categories

14. Traffic Management - I CAC(Connection Admission Control)
Determine whether a connection can be progressed or not
- satisfy the traffic contract of the connection - not disturb traffic contracts of the other connections

15. Traffic Management - II
UPC(Usage Parameter Control)
Protect network resources from malicious as well as unintentional misbehavior - based on traffic contract of the connection - action : cell discard, cell tagging

16. Traffic Management - III
CLP(Cell Loss Priority) Control
In Congestion state - EFCI(Explicit Forward Congestion Control)
- CLP(Cell Loss Priority)

17. Traffic Management – IV
CAC / Connection Management
UPC (Policing)
CLP / EFCI control
Frame Discard
Traffic Shaping
ABR Congestion Feedback

18. ATM Signaling Protocol
Point-to-Point ATM Connection(Q.2931)

19. Reserved VPI/VCI
Q.2971
Q.2931

20. Message Structure Information Element Length Protocol discriminator
Distinguish Message 1
Call reference
Identify call at the local UNI 4
Message type
Identify the function of message 2
AAL parameter
4-21
ATM traffic descriptor
12-20
Broadband bearer capability
6-7
QoS parameter 6 …

21. END.