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Uses of Computer Networks
 Business Applications
 Home Applications
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 Business Applications
•Resource Sharing
•Communication Medium
•E-commerce (Electronic Commerce)
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 Business Applications of Networks
A network with two clients and one server.
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 Business Applications of Networks
The client-server model involves requests and replies.
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 Home Network Applications
•Access to remote information
•Person-to-person communication
•Interactive entertainment
•Electronic commerce
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 Business Applications of Networks
In peer-to-peer system there are no fixed clients and servers.
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Network Hardware
 PANs (Personal Area Networks)
 Local Area Network (LAN) & Wireless LANs
 Metropolitan Area Network (MAN)
 Wide Area Network (WAN)
 Internetworks
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Network Hardware (Broadcast Networks)
Types of transmission technology
•Broadcast links
•Point-to-point links
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Classification of interconnected
processors by scale.
 Personal Area Networks
PANs (Personal Area Networks) let devices communicate over
the range of a person. A common example is a wireless
network that connects a computer with its peripherals.
Bluetooth PAN Configuration.
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 Local Area Networks (LAN)
Two broadcast networks
(a) Bus
(b) Ring
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 Wireless LANs
Figure 1-8. Wireless and wired LANs. (a) 802.11. (b) Switched
Ethernet.
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 Metropolitan Area Networks
A metropolitan area network based on cable TV.
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 Wide Area Networks (WAN)
WAN that connects three branch offices in Australia.
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 Internetworks
The assumption so far is that a network is
homogeneous: there is hardly any variation in
hardware and software. In practice, large networks
can only be constructed by interconnecting different
kinds of networks internet(work).
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Network Software
 Protocol Hierarchies
 Design Issues for the Layers
 Connection-Oriented and Connectionless Services
 Service Primitives
 The Relationship of Services to Protocols
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 Protocol Hierarchies
Layers,
protocols,
and
interfaces.
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 Protocol Hierarchies(2)
Example information flow supporting virtual communication in
layer 5.
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 Design Issues for the Layers
•
•
•
•
•
Addressing
Error Control
Flow Control
Multiplexing
Routing
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 Connection-Oriented and Connectionless Services
Six different types of service. •
Six different types of service.
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 Service Primitives
Five service primitives for implementing a simple connectionoriented service.
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 Service Primitives (2)
Packets sent in a simple client-server interaction on a
connection-oriented network.
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 Services to Protocols Relationship
The relationship between a service and a protocol.
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Reference Models
• The OSI Reference Model
• The TCP/IP Reference Model
• A Comparison of OSI and TCP/IP
• A Critique of the OSI Model and Protocols
• A Critique of the TCP/IP Reference Model
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 The OSI Reference Model
The OSI
reference
model.
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 The OSI Reference Model
1. Physical Layer
1. Convert the logical 1’s and 0’s coming from
6 Presentation
layer 2 into electrical signals.
7 Application
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
2. Transmission of the electrical signals over
a communication channel.
Main topics:
• Transmission mediums
• Encoding
• Modulation
• RS232 and RS422 standards
• Repeaters
• Hubs (multi-port repeater)
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 The OSI Reference Model
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
2. Data Link Layer
1. Error control to compensate for the imperfections of
the physical layer.
2. Flow control to keep a fast sender from swamping a
slow receiver.
Main topics:
• Framing methods
• Error detection and correction methods
• Flow control
• Frame format
• IEEE LAN standards
• Bridges
• Switches (multi-port bridges)
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 The OSI Reference Model
7 Application
3. Network Layer
6 Presentation
a) Controls the operation of the subnet.
5 Session
b) Routing packets from source to
destination.
4 Transport
3 Network
2 Data Link
1 Physical
c) Logical addressing.
Main topics:
• Internetworking
• Routing algorithms
• Internet Protocol (IP) addressing
• Routers
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 The OSI Reference Model
7 Application
4. Transport Layer
6 Presentation
a) Provides additional Quality of Service.
5 Session
b) Heart of the OSI model.
4 Transport
Main topics:
3 Network
• Connection-oriented and connectionless
services
• Transmission Control Protocol (TCP)
• User Datagram Protocol (UDP)
2 Data Link
1 Physical
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 The OSI Reference Model
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
5. Session Layer
a) Allows users on different machines to
establish sessions between them.
b) One of the services is managing
dialogue control.
c) Token management.
d) Synchronization.
1 Physical
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 The OSI Reference Model
7 Application
6 Presentation
5 Session
6. Presentation Layer
a) Concerned with the syntax and
semantics of the information.
4 Transport
b) Preserves the meaning of the
information.
3 Network
c) Data compression.
2 Data Link
d) Data encryption.
1 Physical
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 The OSI Reference Model
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
7. Application Layer
a) Provides protocols that are commonly
needed.
Main topics:
• File Transfer Protocol (FTP)
• HyperText Transfer Protocol (HTTP)
• Simple Mail Transfer Protocol (SMTP)
• Simple Network Management Protocol
(SNMP)
• Network File System (NFS)
• Telnet
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 The TCP/IP Reference Model
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 Comparing OSI and TCP/IP Models
Concepts central to the OSI model:
•Services
•Interfaces
•Protocols
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 A Critique of the OSI Model and Protocols
Why OSI did not take over the world
•Bad timing
•Bad technology
•Bad implementations
•Bad politics
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 A Critique of the TCP/IP Reference Model
Problems:
•Service, interface, and protocol not
distinguished
•Not a general model
•Host-to-network “layer” not really a layer
•No mention of physical and data link layers
•Minor protocols deeply entrenched, hard to
replace
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