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Asynchronous Transfer Mode (ATM) Network Current Deployment and Usage

Asynchronous Transfer Mode (ATM) Network Current Deployment and Usage. Presented By: Pariya Raoufi. Motivations. Future applications require: higher bandwidth, generate a heterogeneous mix of network traffic, low latency.

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Asynchronous Transfer Mode (ATM) Network Current Deployment and Usage

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  1. Asynchronous Transfer Mode (ATM) NetworkCurrent Deployment and Usage Presented By: PariyaRaoufi

  2. Motivations • Future applications require: • higher bandwidth, • generate a heterogeneous mix of network traffic, • low latency. • supporting all classes of traffics (voice, video, data and etc). • Promises to provide: • Greater integration of capabilities and services, • Increased and more flexible access to the network, • More efficient and economical service.

  3. Asynchronous Transfer Mode (ATM) • A network technology for both LANs and WANs. • supports real time voice and video as well as data. • topology uses switches that establish a logical circuit: • guarantees quality of service (QoS). • widely used as a backbone technology in carrier networks and large enterprises, • never became popular as in LANs .

  4. Basics • fixed-size packets (cells) • 5 bytes of header, • 48-byte information field (payload). • a connection-oriented technology • similar to the telephone networks. • each connection: virtual circuit. • Allow network to guarantee the quality of service (QoS) by limiting the number of VCs. • works at layer 2 of the OSI model. • typically uses SONET for framing and error correction over the wire.

  5. ATM Protocol Reference Model • based on standards developed by the ITU. • three layers: • the ATM adaptation layer (AAL), • the ATM layer, and • the physical layer.

  6. ATM Adaption Layer (AAL) • interfaces the higher layer protocols to the ATM Layer. • Four service classes and corresponding types: • Class A - Constant Bit Rate (CBR) service: ALL1, • Class B - Variable Bit Rate (VBR) service: AAL2, • Class C - Connection-oriented data service: AAL3/4 or AAL5, • Class D - Connectionless data service: AAL3/4 or AAL5.

  7. ATM Layer • provides an interface between the AAL and the physical layer. • Inside a switch: • Determine where the cells should be forwarded to, • resets the connection identifiers, • forwards the cells to the next link, • buffers incoming and outgoing cells, • handles various traffic management functions such as cell loss priority marking, congestion indication, and generic flow control access.

  8. ATM Layer(2) • Inside an end system: • receives data stream of cells form physical layer, • transmit either cells with new data or empty cell. • fields in the ATM header define the functionality of the ATM layer. • use at the user-to-network interface (UNI), • use internal to the network, the network-to-node interface (NNI).

  9. ATM Layer (3) • Header: • generic flow control (GFC): four bits. • Routing field: VCI+VPI. • payload type indicator (PTI). • cell loss priority (CLP) bit. • header error check (HEC).

  10. Physical Layer • defines the bit timing and other characteristics for encoding and decoding the data into suitable electrical/optical waveforms. • The Synchronous Optical Network (SONET) is often used for framing and synchronization at the physical layer. • ATM Forum has proposed a variety of physical layer standards, such as ATM over twisted-pair wire: • accelerate the acceptance of ATM.

  11. LAN Emulation • approaches have been proposed to support existing LAN applications: • consider ATM as a new link layer. • provision of an ATM protocol to emulate existing LAN services: • provide a huge cost benefit, • prevents higher layer applications from accessing ATM's unique services, • bandwidth management, • major difference: LANs are connectionless.

  12. LAN Emulation Architecture • Three components: • LAN emulation client (LEC), • LAN emulation server (LES), • Broadcast/Unknown Server (BUS).

  13. Traffic Management • deliver guaranteed quality of service on demand, • utilization of available network resources, • every aspect of ATM network operation contains some traffic management mechanisms.

  14. Quality of Service Attributes • Peak Cell Rate (PCR): The maximum instantaneous rate at which the user will transmit. • Sustained Cell Rate (SCR): This is the average rate as measured over a long time interval. • Cell Loss Ratio (CLR): The percentage of cells that are lost in the network. • Cell Transfer Delay (CTD): The delay experienced by a cell between network entry and exit Points.

  15. Quality of Service Attributes (1) • Cell Delay Variation (CDV): a measure of variance of CTD. • Burst Tolerance (BT): This determines the maximum burst size that can be sent at the peak rate. • Minimum Cell Rate (MCR): This is the minimum rate desired by a user.

  16. Traffic Contract • a traffic contract specifies one of the following classes of traffic: • Constant Bit Rate (CBR) • Variable Bit Rate (VBR) • real-time VBR (VBR-RT). • nonreal-time VBR (VBR-NRT). • Available Bit Rate (ABR) • Unspecified Bit Rate (UBR) • ABR or UBR: best effort traffic.

  17. Congestion Control Techniques • Connection Admission Control (CAC), • Generic Cell Rate Algorithm (GCRA), • Feedback Congestion Control.

  18. References • K. Y. Siu and R. Jain, `A brief overview of ATM: Protocol layers, LAN emulation, and traffic management,` Computer Communication Review 25, 2 (April 1995), pp 6-20. • R. J. Vetter, `ATM concepts, architectures, and protocols,` Communications of the ACM, 38(2):30-38,109, February 1995. • http://www.infosyssec.net/infosyssec/security/secatm1.htm

  19. Thanks

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