Chapter 2Communicating Over the Network Quangkien@gmail.com.OverviewDescribe the structure of a network, including the devices and media that are necessary for successful communications. Explain the function of protocols in network communications. Ex potx

Intermediary Devices and their Role on the Network Intermediary devices to provide connectivity and to work behind the scenes to ensure that data flows across the network.. Intermediary

Chapter 2

Communicating Over the Network Quangkien@gmail.com

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

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.

The Platform for Communications

Elements of Communication

Communicating the Messages

00101010100101010101010101010101010

I have to wait…

Continuous stream of bits

Single communications (e.g video, e-mail message) could be:

Continuous stream of bits

Take over (hog) the network

I have to wait…

Communicating the Messages

Communicating the Messages

Disadvantage

of

Segmentation

Disadvantage – added level of complexity.

Analogy: 100 page letter one page at a time

Separate envelopes

Sequencing

Components of the Network

Devices (hardware)

End devices, switch, router, firewall, hub

Media (wired, wireless)

End devices

End devices or hosts:

The source or destination of a message.

Source Address: 209.67.102.55 Destination Address: 107.16.4.21

Servers and Clients

Server

Client

A host

Client, Server, or both

Software determines the role.

Servers provide information and services to clients

e-mail or web pages

Clients request information from the server

Server

Intermediary Devices and their Role on the Network

Intermediary devices to provide connectivity and to work behind the

scenes to ensure that data flows across the network

These devices connect the individual hosts to the network and can

connect multiple individual networks to form an internetwork

Examples of intermediary network devices are:

Examples of intermediary network devices are:

– Network Access Devices (Hubs, switches, and wireless access

points)

– Internetworking Devices (routers)

– Communication Servers and Modems

– Security Devices (firewalls)

Intermediary Devices and their Role on the Network

Processes running on the intermediary network devices perform

these functions:

– Regenerate and retransmit data signals

– Maintain information about what pathways exist through the network

and internetwork

and internetwork

– Notify other devices of errors and communication failures

– Direct data along alternate pathways when there is a link failure

– Classify and direct messages according to QoS priorities

– Permit or deny the flow of data, based on security settings

Network media: The medium over which the message travels

Metallic wires - electrical impulses

Fiber optics – pulses of light

Wireless – electromagnetic waves.

Network

Media

Different types of network media have different features and benefits

Criteria for choosing a network media are:

– The distance the media can successfully carry a signal.

– The environment in which the media is to be installed.

– The amount of data and the speed at which it must be transmitted.

Local Area Network (LAN)

Local Area Network (LAN)

An individual network usually spans a single geographical area, providing services and applications to people within a common organizational

structure, such as a single business, campus or region.

Wide Area Network (WAN)

Wide Area Networks (WANs)

T1, DS3, OC3

PPP, HDLC

Frame Relay, ATM

ISDN, POTS

Wide Area Networks (WANs)

Leased connections through a telecommunications service provider

network

Networks that connect LANs in geographically separated locations

Telecommunications service provider (TSP) interconnect the LANs at the

different locations.

Voice and data on separate networks or converged networks

Connect their customers to the Internet.

The Internet – ISPs connected to other ISPs

The Internet – A Network of Networks

•Although there are benefits to using a LAN or

WAN, most of us need to communicate with a

resource on another network, outside of our local

organization.

• Examples of this type of communication include:

– Sending an e-mail to a friend in another country

– Sending an e-mail to a friend in another country

– Accessing news or products on a website

– Getting files from a neighbor's computer

– Instant messaging with a relative in another city

– Following a favorite sporting team's performance

on a cell phone

Network

Representations

Network Interface Card (NIC)

Ports and interfaces (used interchangeably)

Physical Port ( connector or outlet)

Interface - Connect to individual networks

Protocols

A protocol stack shows how the individual protocols

within the suite are implemented on the host The

protocols are viewed as a layered hierarchy, with each

higher level services depending on the functionality

defined by the protocols shown in the lower levels.

Protocol – Rules that govern communications.

Protocol suite - A group of inter-related protocols

Example: TCP/IP

A protocol stack (sometimes communications stack) is a particular software implementation of a

computer networking protocol suite The terms are often used interchangeably Strictly speaking, the suite is the

definition of the protocols, and the stack is the software implementation of them.

Network Protocols

At the human level, some communication rules are formal and others are simply understood, or implicit, based on custom and practice For devices to successfully communicate, a network protocol suite must

describe precise requirements and interactions

Networking protocols suites describe processes such as:

Networking protocols suites describe processes such as:

– The format or structure of the message

– The process by which networking devices share information about

pathways with other networks

– How and when error and system messages are passed between

devices

– The setup and termination of data transfer sessions

Message uses Multiple protocols (encapsulated)

HTTP Header Data

Multiple protocols (encapsulated)

HTTP Header Data

Protocols

Encapsulation – Process of adding a header to the data or any previous set of

Frame Header IP Header TCP Header App Header Frame Trailer

Data

Example: Protocol – IPv4

Frame Header IP Header TCP Header Frame Trailer

Data HTTP

Header

Protocol Suites and Standards

Early days – proprietary network equipment and protocols.

Now – Industry standards

Institute of Electrical and Electronics Engineers (IEEE)

Examples: 802.3 (Ethernet), 802.11 (WLAN)

Internet Engineering Task Force (IETF)

Internet standards

Example: RFC 791 IPv4

Interaction of

Protocols

Hypertext Transfer Protocol (HTTP)

Protocol that governs interaction between web server and a web client

Interaction

of

Transmission Control Protocol (TCP)

Responsible for controlling the information exchanged between the server and the client:

Size of data Flow control Reliability

Internetwork Protocol (IP)

Assigns the appropriate source and destination addresses,

Original source address of host

Final destination address of host

Interaction

of

Protocols

frame

Network access protocols (Data link and Physical layer protocols)

Format and physical transmission of data on the media

Using Layered Protocols

Layered

Model

Benefits of

a Layered

Model

Using a layered model:

Fosters competition because products from different vendors can

Protocol and Reference Models

There are two basic types of networking models: protocol models

and reference models

A protocol model provides a model that closely matches the

structure of a particular protocol suite Example: TCP/IP

A reference model provides a common reference for maintaining

A reference model provides a common reference for maintaining

consistency within all types of network protocols and services

The Open Systems Interconnection (OSI) model is the most widely

known internetwork reference model It is used for data network

design, operation specifications, and troubleshooting

Protocol and Reference Models

42

The Open Systems Interconnection (OSI) model is the most widely known

internetwork reference model

The International Organization for Standardization (ISO) released the OSI

TCP/IP Model

The Communication Process - Encapsulation

Server

Data

HTTP Header

TCP Header

IP Header

Data Link Header

Data Link Trailer

HTTP Data

Encapsulation – Process of adding control information as it passes down

through the layered model.

The Communication Process - Decapsulation

Data

HTTP Header

TCP Header

IP Header

Data Link

Header

Data Link Trailer

Client

HTTP Data

Wireshark will let us examine protocols!

The

Communication

Process

Protocol Data Unit (PDU) - The form that a piece of data takes at any layer

PDUs are named according to the protocols of the TCP/IP suite.

Data - Application layer PDU

Segment - Transport Layer PDU

Packet - Internetwork Layer PDU

Frame - Network Access Layer PDU

The sending host builds message with multiple encapsulations.

Dest MAC

00-10

Source MAC 0A-10

Type 800

Trailer

Layer 2 Data Link Frame

Dest IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Type 800

Trailer

Dest IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Type 800

Trailer

The sending host builds message with multiple encapsulations

Data

HTTP Header

TCP Header

IP Header

Data Link

Header

Data Link Trailer

Data

HTTP Header

TCP Header

IP Header

Data Link

Header

Data Link Trailer

The receiving host receives the message with multiple decapsulations

Getting Data to the Right Application

Layer 4 (TCP/UDP) contains a port number which represents the application

or service carried in the IP packet

Getting Data to the Right Application

50

the data to

Examples:

80 = HTTP (www)

23 = Telnet

20, 21 = FTP

Summary

Chapter 2

Communicating Over the Network