Communicating over the
Network
Network Fundamentals – Chapter 2
Version 4.0
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Objectives

Describe the structure of a network, including the
devices and media that are necessary for successful
communications.

Explain the function of protocols in network
communications.

Explain the advantages of using a layered model to
describe network functionality.

Describe the role of each layer in two recognized
network models: The TCP/IP model and the OSI
model.

Describe the importance of addressing and naming
schemes in network communications.
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Network Structure
 The elements of communication
– 3 common elements of communication
• Message source
• The channel
• Message destination
 A network: the definition
– Data or information networks capable of carrying many different
types of communications
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Network Structure
 How messages are communicated?
– Data is sent across a network in small “chunks” called
segments
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Network Structure
 The components of a network
– Network components
• Hardware
• Software
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Network Structure
 End Devices and their Role in the Network
– End devices form interface with human network &
communications network
– Role of end devices:
• Client
• Server
• Both client and server
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Network Structure
– Role of an intermediary device
• Provides connectivity and ensures data flows
across network
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Network Structure
 Network media
 Criteria for making a network media choice
– Network media – this is the channel over which a message
travels
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Network Types
 Local Area Networks (LANs)
– A network serving a home, building or campus is considered a
Local Area Network (LAN)
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Network Types
 Wide Area Networks (WANs)
– LANs separated by geographic distance are connected by a
network known as a Wide Area Network (WAN)
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Network Types
 The Internet
– The internet is defined as a global mesh of interconnected
networks
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Network Topology
 Star Topology
 Ring Topology
 Bus Topology
 Tree Topology
 Mesh Topology
 Hybrid Topology
 http://www.edrawsoft.com/Network-Topologies.php
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Network Types
 Network representations
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Function of Protocol in Network Communication
 Protocols
– A protocol is a set of predetermined rules
– used to facilitate communication over data networks
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Function of Protocol in Network Communication
 Network protocols
– Network protocols are used to allow devices to communicate
successfully
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Function of Protocol in Network Communication
 Protocol suites and industry standards
– A standard is a process or protocol that has been endorsed by
the networking industry and ratified by a standards organization
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Function of Protocol in Network Communication
 Protocols and how they interact
 Ethernet
 Local Talk
 Token Ring
 FDDI
 ATM
 http://www.edrawsoft.com/Network-Protocol.php
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Function of Protocol in Network Communication
 Technology independent Protocols
– 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
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Layers with TCP/IP and OSI Model
 Benefits of using a layered model
– Benefits include
• Assists in protocol design
• Fosters competition
• Changes in one layer do not affect other layers
• Provides a common language
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Layers with TCP/IP and OSI Model
 TCP/IP Model
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Layers with TCP/IP and OSI Model
 The Communication Process
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Layer
Description
Protocols
Application
Defines TCP/IP application protocols and how host programs interface
with transport layer services to use the network.
HTTP, Telnet, FTP, TFTP, SNMP, DNS, SMTP,
X Windows, other application protocols
Transport
Provides communication session management between host computers.
Defines the level of service and status of the connection used when
TCP, UDP, RTP
transporting data.
Internet
Packages data into IP datagrams, which contain source and destination
address information that is used to forward the datagrams between hosts IP, ICMP, ARP, RARP
and across networks. Performs routing of IP datagrams.
Network interface
Specifies details of how data is physically sent through the network,
including how bits are electrically signaled by hardware devices that
interface directly with a network medium, such as coaxial cable, optical
fiber, or twisted-pair copper wire.
Ethernet, Token Ring, FDDI, X.25, Frame
Relay, RS-232, v.35
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Layers with TCP/IP and OSI Model
 Protocol data units (PDU) and encapsulation
PDU
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Layers with TCP/IP and OSI Model
 The process of sending and receiving messages
TCP is one of the main protocols in TCP/IP
networks. Whereas the IP protocol deals only
with packets, TCP enables two hosts to establish
a connection and exchange streams of data.
TCP guarantees delivery of data and also
guarantees that packets will be delivered in the
same order in which they were sent.
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Layers with TCP/IP and OSI Model
 Protocol and reference models
– A protocol model provides a model that closely matches the
structure of a particular protocol suite
– A reference model provides a common reference for maintaining
consistency within all types of network protocols and services
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Layers with TCP/IP and OSI Model
 OSI
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
The sending process passes data to the application layer. The application layer attaches an application header
and then passes the frame to the presentation layer.

The presentation layer can transform data in various ways, if necessary, such as by translating it and adding a
header. It gives the result to the session layer. The presentation layer is not aware of which portion (if any) of
the data received from the application layer is the application header and which portion is actually user data,
because that information is irrelevant to the presentation layer's role.

The process of adding headers is repeated from layer to layer until the frame reaches the data link layer. There,
in addition to a data-link header, a data-link trailer is added. The data-link trailer contains a checksum and
padding if needed. This aids in frame synchronization. The frame is passed down to the physical layer, where it
is transmitted to the receiving computer.

On the receiving computer, the various headers and the data trailer are stripped off one by one as the frame
ascends the layers and finally reaches the receiving process.
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Layers with TCP/IP and OSI Model
 OSI and TCP/IP model
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Addressing and Naming Schemes
 Labels in encapsulation headers are used to manage
communication in data networks.
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Addressing and Naming Schemes
 Ethernet MAC Addresses, IP Addresses, and TCP/UDP
Port numbers
Layer 2 addresses (e.g., Ethernet) are used to move messages to the correct
end device.
Layer 3 addresses (e.g., IP addresses) are used to move message between
different parts of the network and to identify the correct end device . IP
addresses have two parts:
-the network (e.g., the IP number assigned to google.com) and
-the specific computer within that part of the network (e.g., a specific web
server or e-mail server within the Google network).
Layer 4 addresses (e.g., TCP port numbers) are used to move the message
to correct Application layer conversation at the end device (e.g., the Web
browser or e-mail software on your computer).
Layer 7 addresses (e.g., a Web URL: www.google.com) are used by the
Application layer programs.
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Addressing and Naming Schemes
 Labels in encapsulation headers are used to manage
communication in data networks
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Addressing and Naming Schemes
 Information in the encapsulation header is used to
identify the source and destination processes for data
communication
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Summary
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