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Rivier College
CS575: Advanced LANs
Chapter 11 ATM LANs 1
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ATM LAN Architecture
ATM LAN Emulation
* Protocol Architecture
* Emulated LANs
* LAN Emulation Clients and Servers
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* LAN Emulation Scenario and Frame Formats
Asynchronous Transfer Mode
* ATM Protocol Architecture
* ATM Logical Connections
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* ATM Cells
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
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The issue of interoperability of end systems on a variety of interconnected LANs.
End systems attached directly to an ATM network implement the
ATM and AAL protocols.
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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Possibility for a number of logically independent emulated LANs
An emulated LAN supports a single MAC protocol, of which two types are currently defined: Ethernet/IEEE 802.3 and Token Ring/IEEE 802.5
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
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.
It appears to LLC that all of the end systems on an emulated LAN are on the same shared-medium LAN.
Communication between end systems on different emulated LANs is possible only through routers and bridges.
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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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
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