Communications Systems Modeling

1
Chapter 2

• Communications Systems Modeling

2
Contents

• Introduction
• Example a diplomatic negotiation
• Principles of a layered model
• Connection oriented and connectionless
  communications
• Communication networks according to a layered
  model

3
Contents

• Introduction
• Example a diplomatic negotiation
• Principles of a layered model
• Connection oriented and connectionless
  communications
• Communication networks according to a layered
  model

4
Layered Network Models

• The problem
• Complexity of networked systems
• The solution
• Decomposition into independent subsystems
• Layered network model
• Introduced by IBM (SNA, 1971)
• Standardized by ITU (X200) and ISO (7498)
• Method universally adopted
• Standards not really obeyed in practice

5
Contents

• Introduction
• Example a diplomatic negotiation
• Principles of a layered model
• Connection oriented and connectionless
  communications
• Communication networks according to a layered
  model

6
A diplomatic negotiation
Political arguments
Service Access Points
Translation Cryptography Transmission
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A diplomatic negotiation
Political arguments
Service Access Points
Single language messages
Cryptography Transmission
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A diplomatic negotiation
Political arguments
Service Access Points
Single language messages
Encrypted messages
Transmission
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A diplomatic negotiation
Political arguments
Service Access Points
Single language messages
Encrypted messages
Electromagnetic waves
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Contents

• Introduction
• Example a diplomatic negotiation
• Principles of a layered model
• Connection oriented and connectionless
  communications
• Communication networks according to a layered
  model

11
Layered Model Definitions
Level (n1) entity
Level (n1) entity
Virtual level n1 communication path using a
level n1 protocol
Physical Communication Path
Level n Service Access Points
Level (n) entity
Level (n) entity
Virtual level n communication path using a level
n protocol
Level n Addresses
Level (n-1) Service Provider
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Layered Model DefinitionsExample The Telephone
Service
Virtual Interpersonal communication path
Physical Communication Path
Telephone Service Access Points
Telephone Numbers
Telephone Network
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Layered Model DefinitionsProtocol Data Units
(n1)PDU
Level (n1) entity
Level (n1) entity
PDU encapsulation
(n)PDU
Level (n) entity
Level (n) entity
Level (n-1) Service Provider