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Rivier CollegeCS575: Advanced LANs

Chapter 11: ATM LANs

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Overview

0 ATM LAN Architecture0 ATM LAN Emulation

* Protocol Architecture

* Emulated LANs

* LAN Emulation Clients and Servers

* LAN Emulation Scenario and Frame Formats0 Asynchronous Transfer Mode

* ATM Protocol Architecture

* ATM Logical Connections

* ATM Cells0 ATM Adaptation Layer

* ATM Service Categories

* AAL Services and Protocols

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Three Generations of LANs

0 First generation: Based on the CSMA/CD and Token Ring LANs. It provided terminal-to-host connectivity and supported client/server architectures at moderate data rates.

0 Second generation: Based on FDDI. It responds to the need for backbone LANs and for support of high-performance workstations.

0 Third generation: Typified by ATM LANs. It designed to provide the aggregate throughputs and real-time transport guarantees that are needed for multimedia applications.

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Types of ATM LANs

0 Gateway to ATM WAN: An ATM switch acts as a router and traffic concentrator for linking a premises network complex to an ATM WAN.

0 Backbone ATM switch: Either a single ATM switch or a local network of ATM switches interconnect other LANs.

0 Workgroup ATM: High-performance multimedia workstations and other end systems connect directly to an ATM switch.

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Example of a Backbone ATM LAN

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ATM LAN Hub Configuration

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ATM LAN Emulation

0 The issue of interoperability of end systems on a variety of interconnected LANs.

0 End systems attached directly to an ATM network implement the ATM and AAL protocols.

0 Three areas of compatibility:1. Interaction between an end system on an ATM network and end system on a legacy LAN.

2. Interaction between an end system on a legacy LAN and end system on another legacy LAN of the same type (e.g., two IEEE 802.3 networks).

3. Interaction between an end system on a legacy LAN and end system on another legacy LAN of a different type (e.g., an IEEE 802.3 network and an IEEE 802.5 network).

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Example: ATM LAN Emulation Configuration

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ATM LAN Emulation Architecture

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Emulated LANs

0 Possibility for a number of logically independent emulated LANs0 An emulated LAN supports a single MAC protocol, of which two types are

currently defined: Ethernet/IEEE 802.3 and Token Ring/IEEE 802.50 An emulated LAN consists of some combination of the following:

* End systems on one or more legacy LANs* End systems attached directly to an ATM switch An emulated

0 Each end system on an emulated LAN must have a unique MAC address. Data interchange between end systems on the same emulated LAN involves the use of the MAC protocol and is transparent to the upper layers.

0 It appears to LLC that all of the end systems on an emulated LAN are on the same shared-medium LAN.

0 Communication between end systems on different emulated LANs is possible only through routers and bridges.

0 The bridges or routers have to reassemble the cells into packets and chop them up into cells to send them to another emulated LAN.

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LAN Emulation Clients and Servers

0 ATM Forum developed a capacity based on a client/server approach to resolve the following issues:

1. Devices attached directly to ATM switches and ATM-to-LAN converter systems have ATM-based addresses. HOW are the translations made between these addresses and MAC addresses?

2. ATM makes use of a connection-oriented protocol involving virtual channels and virtual paths. HOW can the connectionless LAN MAC protocol be supported over this connection-oriented framework?

3. Multicasting and Broadcasting on a shared-medium LAN is easily achieved. HOW is this capability carried over into the ATM environment?

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LAN Emulation Clients and Servers (continued)

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LAN Emulation Client Connection across LAN Emulation User-to-Network Interface (LUNI)

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LAN Emulation Data Frame Format: IEEE 802.3

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LAN Emulation Data Frame Format: IEEE 802.5

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LAN Emulation Data Frame Format

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Asynchronous Transfer Mode Overview:ATM Protocol Architecture

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ATM Connection Relationships

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Call Establishment Using Virtual Paths

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Virtual Path/Virtual Channel Terminology

* Error-detection technique requires an Error-Detecting Code (e.g., CRC)

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ATM Cell Formats

* Error-detection technique requires an Error-Detecting Code (e.g., CRC)

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Payload Type (PT) Field Coding

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Header Error Control (HEC) Operation at Receiver

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Effect of Error in Cell Header

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Impact of Random Bit Errors on HEC Performance

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ATM Adaptation Layer (AAL)

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AAL Protocols and Protocol Data Units (PDUs)

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Segmentation & Reassembly (SAR) Protocol Data Units (PDUs)

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AAL Type 5 CPCS-PDU (Common Part Convergence Sublayer)

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Example of AAL 5 Transmission