Integrated service digital

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ATM
Chapter 2
Asynchronous Transfer Mode
(ATM)
Korea-Vietnam Friendship IT College
ATM
Overview
• Introduction
• Technical Fundamentals
• ATM Architecture
• ATM Connections
• Addressing and Signaling
• ATM Layer Service
• IP-over-ATM
• ATM Interworking
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ATM
Introduction
•Use small, fixed-sized cells
•Connection-oriented
•Supports multiple service types
•Applicable to LAN and WAN
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ATM
Introduction (2)
Creating cells from packets
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ATM
Introduction (3)
(a)
(b)
(a) Traditional Network Infrastructure
(b) Multi-service ATM-based Network
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ATM
ATM Technical Fundamentals
• ATM Cell
• ATM Applications
• ATM Transmission Rates
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ATM
ATM Cell
• Fixed-size 53-byte cell comprised of a 5-byte header and a 48-byte
payload or information field as the basic unit of transmission.
• The 5-byte header includes an error detection field and a Virtual
Channel Identifier (VCI) or Virtual Path Indicator (VPI) for
transporting a cell payload to a destination address.
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ATM
ATM Cell (2)
• Why 53 Bytes?
A 48 byte payload was the result of a compromise
between a 32 byte payload and a 64 byte payload
• Advantages
– Low packetization delay for continuous bit rate
applications (video, audio)
– Processing at switches is easier
• Disadvantages
– High overhead (5 Bytes per 48)
– Poor utilization at lower line rates links
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ATM
ATM Cell (3)
UNI Cell
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ATM
ATM Cell (4)
NNI Cell
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ATM
ATM Application
ATM technologies, standards, and services
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ATM
ATM Application (2)
• ATM is an enabler of basic and advanced applications
such as remote sensing, 3-D (three-dimensional)
interactive simulations, tele-instruction, biological
teleresearch, and medical teleconsultations.
• ATM technology is implemented in backbone, enterprise,
and edge switches as well as hubs, routers, bridges,
multiplexers, servers, server farms, and NICs (Network
Interface Cards) in high-end Internet appliances.
• The ATM Data Exchange Interface (DXI) enables fast
access to public network services.
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ATM
ATM Transmission Rates
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ATM
ATM Architecture
• ATM Reference Model
• Physical Layer
• ATM Layer
• ATM Adaptation Layer
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ATM
ATM Reference Model
ATM Technology has its own protocol architecture
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ATM
ATM Reference Model (2)
Layers of ATM
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ATM
ATM Reference Model (3)
- TC: Transmission
Convergence
- PM: Physical
Medium
Function of Layers
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ATM
Physical Layer
• Two sublayer:
– Transmission
convergence (TC)
• Framing
• HEC
– Physical Media (PM)
• Physical media
coding
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ATM
Physical Layer (2)
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ATM
ATM Layer
•Cell header insertion/removal
•Cell relay
•Multiplexes/Demultiplexes
cells of different connections
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