Prof' Choong Seon HONG

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ATM LANs

• Prof. Choong Seon HONG

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Introduction

• The strengths of ATM LAN approach
• Not constrained to a particular physical medium
  or data rate
• even 622 Mbps, 2.5 Gbps
• One of technologies of choice for wide area
  networking
• Can be used effectively to integrate LAN and WAN
  configurations

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11.1 ATM LAN Architecture

• Three generations of LANs
• First Generation
• CSMA/CD and token ring LANs
• Second Generation
• FDDI as backbone LANs
• Third Generation
• ATM LANs
• Designed to provide the aggregate throughputs
  and realtime transport guarantees that are needed
  for multimedia applications
• Fourth Generation (?)
• Wireless LAN
• Bluetooth
• Gigabit Ethernet

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ATM LAN Architecture (contd)

• Typical requirements for a third generation LAN
  as follows
• Supporting multiple, guaranteed classes of
  service
• Providing scalable throughput that is capable of
  growing both per-host capacity and aggregate
  capacity
• Facilitating the interworking between LAN and
  WAN technology

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ATM LAN Architecture (contd)

• Possible types of ATM LANs
• Gateway to ATM WAN
• acting as a router and traffic concentrator for
  linking a premises network complex to an ATM WAN
• Backbone ATM switch
• interconnecting LANs
• Workgroup ATM
• High-performance multimedia workstations and
  other end systems connecting directly to ATM
  switch

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ATM LAN Architecture (contd)

• ATM LAN Configurations

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ATM LAN Architecture (contd)

• Use of ATM Hub
• Each end system has point-to-point link to hub

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ATM LAN Architecture (contd)

• Each ATM Hub
• including a number of ports that operate at
  different data rates and use different protocols.
• consisting of a number of rack-mounted modules,
  with each module containing ports of a given data
  rate and protocol

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ATM LAN Architecture (contd)

• Configuration of a single node in a pure ATM LAN
• LAN based on an ATM switch

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11.2 ATM LAN Emulation

• End systems attached directly to one of the
  legacy LANs implement the MAC layer appropriate
  to that type of LAN
• End systems attached directly to an ATM network
  implement the ATM and AAL protocols
• Three areas of compatibility to consider
• Interaction between an end system on an ATM
  network and an end system on a legacy LAN
• Interaction between an end system on a legacy
  LAN and an end system on another legacy LAN of
  the same type (e.g., two IEEE 802.3 networks)
• Interaction between an end system on a legacy
  LAN and an end system on another legacy LAN of a
  different type (e.g., an IEEE 802.3 network and
  an IEEE 802.5 network)
• The most solution to the above problem use of
  router

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ATM LAN Emulation (contd)

• Coexistence of legacy LANs and ATM LANs
• ATM LAN emulation
• Objective of ATM LAN emulation
• To enable existing shared-media LAN nodes to
  interoperate across an ATM network
• To interoperate with devices that connect
  directly to ATM switches

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ATM LAN Emulation (contd)

• ATM LAN Emulation Configuration

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ATM LAN Emulation

• Requirements for ATM LAN Emulation
• The way in which end systems on two separate
  LANs of the same type (same MAC layer) can
  exchange MAC frames across the ATM network
• The way in which an end system on a LAN can
  interoperate with an end system emulating the
  same LAN type and attached directly to an ATM
  switch

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ATM LAN Emulation (contd)

• LAN Emulation Protocol Architecture

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ATM LAN Emulation (contd)

• Protocol Architecture
• The end system attached to a legacy LAN is
  unaffected.
• Various application level protocols are unaware
  that there is an ATM network underneath.
• In the previous Figure, the bridge logic
  converts MAC frames to and from ATM cells.
• ATM Forum specification calls for making use of
  ALL5 to segment MAC frames into ATM cells and to
  reassemble incoming ATM cells into MAC frames

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ATM LAN Emulation (contd)

• LAN Emulation Client and Servers a number of
  issues
• How are translations made between ATM-based
  addresses and MAC addresses ?
• How can the connectionless LAN MAC protocol be
  supported over this connection-oriented framework
  ?
• How are multicasting and broadcasting on a
  shared-medium LAN carried over into the ATM
  environment ?

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ATM LAN Emulation (contd)

• LAN Emulation Client and Servers

Description
Entity
Set up control connections to LAN emulation
servers sets up data connections to other
clients maps MAC addresses to ATM addresses.
LAN emulation client (LEC)
LAN emulation configuration server (LECS)
Assists client in selecting an LES
Performs initial address mapping accepts clients
LAN emulation server (LES)
Performs multicasting
Broadcast and unknown server (BUS)
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ATM LAN Emulation (contd)
- The link to the LECS is used by an LEC to gain
entrance to an emulated LAN and to locate an LES
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ATM LAN Emulation (contd)

• LAN Emulation Scenario
• Initialization
• establishing a virtual connection to the LECS
• Configuration
• getting the client information about the
  emulated LAN, including MAC protocol, maximum
  frame size, and the name of the emulated LAN
• Joining
• setting up a control connection to the LES
• Registration and BUS Initialization
• registration of a client
• setting up a data connection to the BUS
• Data Transfer
• Once a client is registered, it is able to send
  and receive MAC frames.

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ATM Protocol Architecture

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ATM Connection Relationship

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Call establishment using virtual paths

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ATM Cell Format
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AAL Protocols