Download Objectives Network Structure Network Structure Network Structure

Objectives
Communicating over the
Network
Network Fundamentals – Chapter 2
ƒ
Describe the structure of a network, including the
devices and media that are necessary for successful
communications.
ƒ
Explain the function of protocols in network
communications.
ƒ
Explain the advantages of using a layered model to
describe network functionality.
ƒ
Describe the role of each layer in two recognized
network models: The TCP/IP model and the OSI
model.
ƒ
Describe the importance of addressing and naming
schemes in network communications.
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Network Structure
Network Structure
ƒ Network
ƒ Data is sent across a network in small “chunks” called
segments
Multiple computers connected together via a communications
system
ƒ Enables multiplexing – interleaving many conversations
together over a single link
ƒ 3 common elements of communication
– message source
– the channel
– message destination
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Network Structure
End Devices
ƒ Computers: work stations,
laptops, servers, web servers
ƒ Network components
– hardware
the physical components, devices and media
– software
programs, operating systems, services, etc.
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ƒ Network printers
ƒ VoIP phones
ƒ Security cameras
ƒ Mobile handheld devices
ƒ End devices are also called hosts.
ƒ A host device is either the source or destination of a
message transmitted over the network.
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ƒ Each host requires a network address.
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Intermediary Devices
Network Media
ƒ Role of an Intermediary Device
ƒ The Network Media connects the devices together and
provides a path over which the signals can travel
–Provides connectivity for End Devices and ensures
data flows across the network
ƒ Copper cables – UTP, coaxial cable. Electrical signals
ƒ Optical fibre cable. Laser signals.
ƒ Network Access Devices (Hubs, switches, and wireless
access points)
ƒ Wireless media. Electro-magnetic signals.
ƒ Internetworking Devices (routers)
ƒ Communication Servers and Modems
ƒ Security Devices (firewalls)
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Local Area Networks (LANs)
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Wide Area Networks (WANs)
ƒ A network serving a home, building or campus is
considered a Local Area Network (LAN)
ƒ LANs separated by geographic distance are connected
by a network known as a Wide Area Network (WAN)
ƒ Covers a limited area, owned and administered by a
single organization
ƒ Organizations usually lease WAN services from a
Service Provider
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Internets and Intranets
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Data Network Symbols
ƒ An internetwork is a
connection of individual
networks, sometimes
abbreviated to internet
ƒ The Internet is a global mesh
of public networks
ƒ An intranet is a collection of
interconnected private
networks owned by one
organization and only
accessible to its employees
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Function of Protocols in Network Communication
ƒ A protocol is a set of predetermined rules
The Interaction of Protocols
ƒ When accessing a Web server, you are using a number
of different protocols
ƒ Network protocols are used to
enable devices to
communicate successfully
ƒ A protocol suite is a set of
protocols designed to work
together, e.g. TCP/IP
ƒ Industry standard
a process or protocol that
has been endorsed by the
networking industry and
ratified by a standards
organization
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Technology Independent Protocols
Layered Network Models
ƒ Many diverse types of devices can communicate using
the same sets of protocols. This is because protocols
specify network functionality, not the underlying
technology to support this functionality.
ƒ Using a layered model helps in the design of complex
multi-use, multi-vendor networks
ƒ Benefits include
– assists in protocol design
– fosters competition between vendors
– changes in one layer do not affect other layers
– provides a common language
ƒ There are two important models
– ISO Reference Model – a seven-layered model
– TCP/IP Protocol Model – a four layered model
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Layers with TCP/IP and OSI Model
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The TCP/IP Model
ƒ A protocol model
provides a model that
closely matches the
structure of a
particular protocol
suite.
ƒ A reference model
provides a common
reference for
maintaining
consistency within all
types of network
protocols and
services.
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The Communication Process
Protocol data units (PDU) and Encapsulation
ƒ Creation of data at the application layer of the
originating source end device
ƒ Segmentation and encapsulation of data as it
passes down the protocol stack in the source end
device
ƒ Generation of the data onto the media at the
network
t
k access layer
l
off the
th stack
t k
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The OSI Layered Model
Protocol data units (PDU) and Encapsulation
7. Application
Provide access to network services for users.
6. Presentation
Common data representation
5. Session
Manage dialogues
4 Transport
4.
Segment/reassemble the data.
3. Network
Routing between networks
2. Data Link
Exchanges frames between connected devices
1. Physical
Bit transmission on the media
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Comparison of TCP/IP and OSI Models
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Encapsulation Headers
ƒ Each PDU header contains information about
the Source and Destination
Transport
Port number
Network
Host machine IP address
Datalink
Ethernet MAC address
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Addressing and Naming Schemes
ƒ Ethernet MAC Addresses, IP Addresses, and TCP/UDP
Port numbers
Addressing Schemes
ƒ Transport Port number
80
ƒ Network
IP address
209.165.202.130
ƒ Datalink
MAC address
00-0C-76-6D-7E-AF
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Port Numbers
Summary
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