ATM_Essentials

ATM_Essentials - Asynchronous Transfer Mode ATM Part 1...

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1 Asynchronous Transfer Mode “ATM” Part 1: Network and Services EE555: Broadband Network Architectures Professor: A. Zahid Fall 2007
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2 Why ATM? In “Circuit Switching”, Bandwidth is assigned in fixed- size channels (time slots) and are dedicated to the application for the duration of the application’s session Inefficient use of network resources for bursty traffic Support single QoS In IP-based “Packet Switching”, Bandwidth is assigned on a per demand basis (i.e. variable) Best effort service model Require a lot of software-based processing to do error checking, flow control, etc… Increased delays and hence not suitable for real-time applications.
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3 ATM: Asynchronous Transfer Mode ATM is a fast-packet , connection-oriented (Virtual Circuit) , switching and transport technology based on Asynchronous (Statistical) TDM ATM provides a guaranteed QoS that is negotiated at the beginning of a session. Network resources are reserved (but not dedicated) to meet the negotiated QoS ATM uses fixed-size frames called Cells. Each cell is 53 Octets with 5 Octets as Header and 48 Octets as payload.
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4 ATM Basic Concepts Virtual Circuits Fixed Size, Small Cells Statistical Multiplexing Integrated Services Good Management & Traffic Engineering features Scalability in Speed and Size Carry multiple types of traffic Provide for end-to-end QoS
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5 Advantages of Fixed-size Cells It simplifies buffer management It simplifies the design of the ATM switch The high bandwidth at which ATM operates requires switching to be performed in hardware . It is easier to synchronize the switches with fixed- length cells It reduces the delay and the delay variation (Jitter) and hence is ideal for voice and video traffic It simplifies processing and Scheduling since there is no need to calculate cell length.
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6 Advantages of ATM ATM provides for high, on demand, variable and/or constant bandwidth and hence it is used to support all types of services including voice, video, data and multimedia Integrated services over a single network reduced equipment/operation and maintenance costs ATM is flexible because it is not based on a specific physical transport technology ATM can run over T1, T3, ADSL, Cable, SONET, DWDM, satellite, etc… ATM provide for LAN/WAN integration
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7 ATM Markets ATM Deployments Frame Relay Backbones Internet Backbones Aggregating Residential Broadband Traffic (DSL/Cable) Carrier Infrastructure for PSTN and Private Line Networks Failed Market Tests of ATM ATM workgroups and campus networks ATM enterprise network End-to-end ATM….
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8 ATM Market (Continued) Hub Hub Public ATM Network Enterprise Backbone Campus/Site Network Campus/Site Network
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