1. ASYNCHORONOUS TRANSFER MODES

2. Points to be discussed are:
Definition
ATM standard
ATM network
ATM interfaces
ATM cell
ATM Adaptation layer(AAL)
to be contd...

3. ATM Application
ATM Services Categories
ATM advatages
ATM advantages
ATM challenges
References

4. ATM-Definition
Asynchronous Transfer Mode (ATM) is a technology that has the potential of revolutionizing data communications and telecommunications.
ATM is a packet switching.

5. What is it really? Low-level network layer Single transport mechanism
Streamlined protocol

6. ATM Standard ITU-T I.361 Defines the ATM Layer functions. ITU-T I.363
Defines the ATM Adaptation Layer-
protocols.
ITU-T I.610
Defines the ATM Operation and Maintenance (OAM) functions

7. The ATM network 1) User-to-Network Interface (UNI)
2) Network-to-Network Interface (NNI)
3) Inter-Carrier Interface (ICI)

8. ATM Interfaces 1. User-to-Network Interface (UNI)
Exists between a single end user and a public ATM network.
2. Network-to-Network Interface (NNI)
Exists between switches in a single public ATM network.
3. Inter-Carrier Interface (ICI)
It is located between two public ATM networks

9. Important parameters Virtual channel:
A channel that provides transportation of ATM cells between two or more endpoints for information transfer.
Virtual paths:
It is a group of Virtual Channels that are carried on the same physical facility and share the same Virtual Path Identifier (VPI) value.

10. ATM cells Small size, may reduce queuing delay of high priority cells
Fixed size, more efficient switching
Diagram of the UNI ATM Cell
Diagram of the NNI ATM Cell

11. ATM cell content 1) 5 bytes header: (I) General flow control
defined across the UNI
flow across the UNI
intended to control the traffic
4 bits must be set to 0's.
(II) Virtual path control
routing field for network
an 8-bit field for the UNI and a 12-bit field for the NNI, is used to identify virtual paths.

12. Continue…. Virtual Channel Identifier (VCI)
16-bit field is used to identify a virtual channel
For idle cells, the VCI is set to all 0's.
Payload Type Identifier (PTI)
three bits of the PTI

13. Cell Loss Priority (CLP)
The 1-bit CLP field
used for explicit indication of the priority of the cell
Header Error Control (HEC)
8-bit fieldIt capable of detecting all single-bit errors and some multiple-bit errors.

14. ATM Applications

15. ATM Service Categories
Real-time services
Constant bit rate – uncompressed audio/video info
Videoconferencing, TV, pay-per-view, VOD, etc.
Non-real-time services
Available bit rate – bursty apps requiring reliable end- to-end connection
e.g. LAN, router-to-router reliability

16. ATM Advantages Universality
Mixed traffic types, real-time and non-real time
Scalability
LANs, WANs, WLANs
Efficient use of network resources Bandwidth on demand concept
Simplified network infrastructure

17. ATM challenges In-network mux/buffering can lead to cell delay or loss
Many types of traffic
Large geographic distribution

18. References http://www.iec.org
Amos E. Joel, Jr., Asynchronous Transfer Mode (IEEE Press, 1993)
"Broadband ISDN and ATM".

19. THANK YOU