ATM

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Chapter 19
ATM (Asynchronous Transfer Mode)
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Asynchronous Transfer Mode (ATM)

• Cell Relay Protocol
• ATM Forum ITU-T
• Design Goals
• Needed for a transmission system to optimize the
  use of high-data-rate transmission media.
• Needed for a system
• Can interface with existing systems.
• Can wok with and support the existing
  telecommunications hierarchies.
• Must be connection-oriented to ensure accurate
  and predictable delivery.
• Needed for a design that can be implemented
  inexpensively.
• Needed for moving as many of the functions to
  hardware as possible and eliminating as many
  software functions as possible.

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Figure 19-1
Multiplexing Using Different Packet Sizes

• Packets A, B, and C experience larger delay.

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Figure 19-2
Multiplexing Using Cells

• A cell is a small, fixed-sized block of
  information.
• None suffers a long delay.
• Handle real-time transmissions.

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Figure 19-3
ATM Multiplexing
Empty Cells

• ATM uses asynchronous time-division multiplexing
  (TDM).

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Figure 19-4
Architecture of an ATM Network

• UNI User-to-network interface
• NNI Network-to-network interface

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Figure 19-5
TP, VPs, and VCs

• Transmission path (TP) Physical connections
• Virtual Path (VP) and Virtual Circuit (VC)
  Logical connections

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Figure 19-6
Example of VPs and VCs
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Figure 19-7
Connection Identifiers

• Virtual Path Identifier (VPI) and Virtual Circuit
  Identifier (VCI)
• A virtual connection is defined by a pair of
  numbers the VPI and the VCI

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Figure 19-8
Virtual Connection Identifiers in UNIs and NNIs
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Figure 19-9
An ATM Cell
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Figure 19-10
SVC Setup

• ??) PVC connection is established by the network
  operator.

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Figure 19-11
Routing with a VP Switch
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Figure 19-12
A Conceptual View of a VP Switch

• The VPI change, but the VCI will remain the same.

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Figure 19-13
Routing with a VPC Switch

• A VPC switch as a combination of a VP switch and
  a VC switch

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Figure 19-14
A Conceptual View of a VPC Switch
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Figure 19-15
Crossbar Switch
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Figure 19-16
Knockout Switch

• Knockout switch is inefficient.
• - Avoid collision
• - Need n2 crosspoints (n inputs and n output s).

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Figure 19-17
A Banyan Switch

• Banyan Switch
• - Does not perfectly avoid internal collision.
• - Need log2(n) stages with n/2 microswitches at
  each stage.

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Figure 19-18-Part I
Example of Routing in a Banyan Switch (a)
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Figure 19-18-Part II
Example of Routing in a Banyan Switch (b)
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Figure 19-19
Batcher-Banyan Switch

• Batcher switch
• -Sort the arriving cells based on their
  destination port.
• Trap module
• - Prevent duplicate cells from passing to the
  Banyan switch simultaneously.

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Figure 19-20
ATM Layers
End points use three layers.
Switches use the two bottom layers.
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Figure 19-21
ATM Layers in End-Point Devices and Switches
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Figure 19-22
AAL Types
Every application not necessary sequencing and
error control mechanisms
Connection-oriented data services
(3) Connectionless data services (4)
Constant bit rate services
Variable bit rate services
SONET and T-3
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Figure 19-23
AAL1

• CSI used for signaling purposes that are not yet
  clearly defined.
• CRC First four bits
• P First 7 bits in the header

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Figure 19-24
AAL2

• CSI used for signaling purposes that are not yet
  clearly defined.
• IT Identify data segments (the beginning,
  middle, or end of the message)
• LI Used with the final segment of a message to
  indicate
• how much of the final cell is data and
  how much is padding.
• CRC The entire data unit.

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Figure 19-25
AAL3/4
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Figure 19-26
AAL5

• T Not yet defined

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Figure 19-27
ATM Layer
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Figure 19-28
ATM Header
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Figure 19-29
PT Fields
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Figure 19-30
Service Classes

• Constant bit rate
• Variable bit rate Real time VBR and Non real
  time VBR
• Available bit rate
• Unspecified bit rate

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Figure 19-31
Service Classes and Capacity of Network
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Figure 19-32
Quality of Service (QoS)

• Sustained cell rate
• Peak cell rate
• Minimum cell rate
• Cell variation delay tolerance

• Cell loss ratio
• Cell transfer delay
• Cell delay variation
• Cell error ratio

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Figure 19-33
ATM WAN
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Figure 19-34
Ethernet Switch and ATM Switch
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Figure 19-35
LAN Emulation (LANE) Approach

• LANE client (LEC)
• LANE server (LES)
• Broadcast/unknown server (BUS)

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Figure 19-36
LEC, LES, and BUS
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Summary

• ATM is a cell relay protocol
• Cell a small fixed-size block information (53
  bytes)
• Application adaptation, ATM, and Physical layers
• AAL Convergence sub-layer (CS), Segmentation and
  reassembly (SAR)
• AAL type 1, 2, 3/4, and 5
• Connection between two end points
• VP VC PVC SVC
• A virtual connection identification VPI VCI
• ATM service classes
• CBR, RT-/NRT-VBR, ABR, UBR
• ATM QoS
• User Related Attributes SCR, PCR, MCR, CVDT
• Network Related Attributes CLR, CTD, CDV, CLR