ASYNCHRONOUS TRANSFER MODE

1. ASYNCHRONOUS TRANSFER MODE Presented by Amiya Kumar Sahu Roll # EC200118243 Under the Guidance of Mr. N. Srinivas

2. Asynchronous Transfer Mode is a very high speed and low cost transmission technology for voice, data, video,and television. • It delivers high – capacity transmission at various speed. • Delivers speeds of 155 Mbps to 622 Mbps (compatible with SONET and can transmit HD TV). • Handles both Constant Bit Rate(Voice and Video) and Variable Bit Rate(Data) • Key to ATM’ success is cell switching, which is faster than traditional multiplexing techniques • It is Connection oriented. • It offer a simplified network infrastructure. • It is used for user applications that require High bandwidth ,high speed data transfer. INTRODUCTION

3. B-ISDN(Broadband Integrated Services Digital Network)uses ATM technology which has high data rate and services ATM provide larger bandwidth, high speed data transfer rate, quality of service and grade of service. ATM transmits all information in small, fixed-size packets called cells.cell switching was chosen because First, cell switching is highly flexible and can handle both constant rate traffic (audio, video) and variable rate traffic (data) easily. Second , at the very high speeds envisioned (gigabits per second are within reach), digital switching of cells is easier than using traditional multiplexing technique, especially using fiber optics. Third, for television distribution, broadcasting is essential, cell switching can provide this and circuit switching cannot. WHY ATM ?

4. ATM CELLS Fixed-size • 5 byte header • virtual channel information • virtual path information • payload type information • cell loss priority • 48 bytes information Advantages to use of small, fixed-size cells : - reduce queuing delay for a high-priority cell - can be switched more efficiently - easier to implement the switching mechanism in hardware

5. ATM CELL FORMAT

6. ATM VIRTUAL CONNECTIONS • Two types of ATM connections exist: virtual paths, which are identified by virtual path identifiers, and virtual channels, which are identified by the combination of a VPI and a virtual channel identifier (VCI). • A virtual path is a bundle of virtual channels, all of which are switched transparently across the ATM network on the basis of the common VPI. • A transmission path is a bundle of VPs. Figure below illustrates how VCs concatenate to create VPs, which, in turn, concatenate to create a transmission path.

7. Management plane Control plane User plane Higher Layers Higher Layers ATM Adaptation Layer Virtual Channel Functions Plane management ATM Layer Virtual Path Functions Layer management Physical Layer (PMD) ATM PROTOCOL ARCHITECTURE

8. Physical layer - specify a transmission medium & signal encoding scheme - specify the data rate ( normally, 25.6 Mbps to 622.08 Mbps) ATM layer - roughly analogous to the data link layer of the OSI reference model - responsible for the simultaneous sharing of virtual circuits over physical link - passing cells through the ATM network ATM Adaptation layer ( AAL ) - combined with the ATM layer - maps higher-layer information into ATM cells - collects information from ATM cells to higher layers ATM PROTOCOL ATCHITECTURE

9. Three separate planes : User Plane - provides for user information transfer e.g. flow control, error control Control Plane -performs call & connect control functions Management Plane - Plane management whole system functions - Layer management Resources and parameters in protocol entities ATM PROTOCOL ARCHITECTURE

10. ATM ADAPTATION LAYERS

11. This division leads to four types of services: Class A: CBR, connection-oriented, with timing relation Class B: VBR, connection-oriented, with timing relation Class C: VBR, connection-oriented, no timing relation Class D: VBR, connection-less, no timing relation 5 AALs are defined in the standards: AAL0 - cell transport AAL, cell-based services (i.e. no adaptation) AAL1 - CBR traffic with strong timing relationship AAL2 - VBR traffic with strong timing relationship AAL3/4 - connection-oriented/connection-less VBR “bursty” data AAL5 - connection-less/connection-oriented VBR service (simplified version of AAL3/4, intended for high speed LANs) ATM ADAPTATION LAYER

12. ATM CONNECTION TYPES ATM supports two connection types • Point-to-point—Connections of this type can be unidirectional or bidirectional. • Point-to-multipoint—Connections of this type are unidirectional only.

13. Advantages of ATM are many. Among these are: Simplified network infrastructure interoperability with existing conventional technology (migration occurs at user’s pace) Scalability and flexibility Effective use of network capacity because of 'bandwidth on demand' principle of ATM. Low transfer delay and support for both non-real-time and real-time applications. Supports multimedia applications and mixed traffic through VPs and VCs. expected to be the transport mode for a seamless unified, universal, broadband integrated network operating in local and/or wide fixed/mobile environment. large support from standard and industry forums ADVANTAGES OF ATM

14. Since the need of information and data transfer is in growing demand ATM will hold a greater demand in the days to come. Time is a critical factor in data transfers so ATM plays a great role since it have a high speed of data transfer as well as security. CONCLUSION

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