Computer networks networking fundamentals

Computer networks, networking fundamentals, mạng máy tính

Outline

2.1 Networking Terminology

Data networks Network history Networking devices Network topology Network protocols Local-area networks (LANs) Wide-area networks (WANs) Metropolitan-area networks (MANSs)

Storage-area networks (SANs)

Virtual private network (VPN) Benefits of VPNs

Intranets and extranets 2.2 Bandwidth

Importance of bandwidth

Analogies Measurement Limitations Throughput Data transfer calculation Digital versus analog

2.3 Networking Models

Using layers to analyze problems

in a flow of materials Using layers to describe data communication

OSI model OSI layers Peer-to-peer communications TCP/IP model

Detailed encapsulation process

2.1 Networking Terminology

lf two people modified the file and then tried to share It, what will happen 2

Businesses needed a solution to address the following problems:

How to avoid duplication of equipment and resources How to communicate efficiently

How to set up and manage a network networking technology could increase productivity while saving

money

In the mid-1980s, each company that created network hardware and software used its own

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Data networks (cont )

company standards Network technologies were incompatible with each other Difficult to communicate with each other

This often required the old network equipment to be removed to implement the new equipment

LAN standards provided an open set of guidelines for creating network hardware and software, the equipment from different companies could then become compatible

In a LAN system, each department of the company is a kind of electronic island

WANs could connect user networks over large geographic areas

Network history

1900 carrier pigeon, optical telegraph, electrical telegraph

1890s Bell invents the telephone; telephone service expands rapidly

1901 Marconi's first transatlantic wireless transmission

1920s AM Radio

1939 FM Radio 1940s WWII spurs radio and microwave development

1947 Shockley, Barden and Brittain invent the solid-state (semiconductor) transistor

1948 Claude Shannon publishes "A Mathematical Theory of Communication"

1950s Invention of Integrated Circuits

1957 ARPA is created by DoD

1960s Mainframe Computing

1962 Paul Baran at RAND works on “packet switching" networks

1967 Larry Roberts publishes first paper on ARPANET

1969 ARPANET established at UCLA, UCSB, U-Utah, and Stanford

1970s Widespread use of digital integrated circuits; advent of digital personal computers

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Network history (cont )

1973 Bob Kahn and Vint Cerf begin work on what later becomes TCP/IP.The

ARPANET goes international with connections to University College in London,

England and the Royal Radar Establishment in Norway

1983 Transmission Control Protocol/Internet Protocol (TCP/IP) becomes the

universal language of the Internet ARPANET is split into ARPANET and MILNET

1984 Cisco Systems founded; gateway and router development begins Domain

Name Service introduced The number of Internet hosts exceeds 1000

Network history (cont )

1990 ARPANET becomes the Internet

1991 The World Wide Web (WWW) is born Tim Berners-Lee develops code for

WWW

1992 Internet Society (ISOC) is chartered Number of Internet hosts breaks

1,000,000

1993 Mosaic, the first graphics-based Web browser, becomes available

1994 Netscape Navigator introduced

1996 The number of Internet hosts exceeds 10 million The Internet covers the

1998 Cisco hits 70% of sales via internet, Networking Academies launched

1999 Internet 2 backbone network deploys IPv6 Major corporations race toward the

video, voice and data convergence

2001 The number of Internet host exceeds 110 million ¬

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Network devices : They include all the devices that connect the end-user devices together to allow them to communicate End-user devices that provide users with a connection to the

network are also referred to as hosts

The host devices can exist without a network, but without the network the host capabilities are greatly reduced

A NIC is a printed circuit board that fits into the expansion slot of

a bus on a computer motherboard, or it can be a peripheral device It is also called a network adapier

Networking devices (cont.)

Network devices provide transport for the data that needs to be transferred between end-user devices

Network devices provide extension of cable connections,

concentration of connections, conversion of data formats, and management of data transfers

Networking devices : Repeater : Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation The purpose

of a network repeater is to regenerate and retime network signals at the bit level This allows them to travel a longer distance on the media A repeater does not perform intelligent routing like a bridge or router

Hubs : They concentrate connections In other words, they take

a group of hosts and allow the network to see them as a single unit This is done passively, without any other effect on the data transmission Active hubs not only concentrate hosts, but they also regenerate signals Multi-ported Repeater

Networking devices (cont.)

Routers : They have all the capabilities listed above Routers can regenerate signals, concentrate multiple connections,

convert data transmission formats, and manage data transfers They can also connect to a WAN, which allows them to connect LANs that are separated by great distances None of the other devices can provide this type of connection

Networking devices (cont.)

Networking devices (cont )

Networking devices (cont.)

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Cisco Catalyst 1924 Switch

Total Weight = 7 Ibs

Networking devices (cont.)

Network topology

Network topology defines the structure of the network

Physical topology, which is the actual layout

of the wire or media

Logical topology, which defines how the

media is accessed by the hosts for sending data

Network topology (cont }

star topology

It connects all cables to a central point of concentration

Extended star topology

It links individual stars together by connecting the hubs and/or switches

This topology can extend the scope and coverage

of the network

Network topology (cont }

Hierarchical topology

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It is similar to an extended star

Instead of linking the hubs and/or switches together, the system is linked to a computer that controls the traffic on the topology

Tree

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Network topology (cont ye

Network topology (cont }

Two examples of networks that use token passing are [Token Ring and Fiber Distributed Data Interface (FDDI) A variation of Token Ring and FDDI is Arcnet Arcnet is token passing on a bus topology

Token Bus

Network topology (cont }

Network protocols

Protocol suites are collections of protocols that enable network

communication from one host through the network to another host

A protocol is a formal description of a set of rules and conventions that

govern a particular aspect of how devices on a network communicate Protocols determine the format, timing, Sequencing, and error control in data communication Without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the Original format

Protocols control all aspects of data communication, which include the

following:

How the physical network is built How computers connect to the network How the data is formatted for transmission How that data is sent

How to deal with errors

IEEE, ANSI, TIA, EIA, ITU, CCITT

Network protocols (cont.)

L, M,N Layers in our model of computer communications

Msource, Mdestination Peer layers

— Peer to peer communications

M layer Protocol The rules by which Msource communicates with Mdestination

Local-area networks (LANs)

LANs consist of the following components:

Computers Network interface cards Peripheral devices

Networking media Network devices Locally share files and printers efficiently

lt makes internal communications possible They tie data, local communications, and computing equipment together

Some common LAN technologies are:

Ethernet Token Ring

FDDI

Repeaters, Hubs, Bridges, Switches, Routers

Wide-area networks (WANs)

WANs connect user networks over a large geographical area

lt allows computers, printers, and other devices on a LAN to share and be shared with distant locations

Allow access over serial interfaces operating at lower speeds Provide full-time or part-time connectivity to local services

Provide e-mail, World Wide Web, file transfer, and e-commerce services

Some common WAN technologies are:

Modems

Integrated Services Digital Network (ISDN)

Digital Subscriber Line (DSL) Frame Relay

US (T) and Europe (E) Carrier Series —T1, E1, T3, E3

synchronous Optical Network (SONET)

Metropolitan-area networks (MANSs)

communication lines or optical services

A MAN can also be created using wireless bridge technology by beaming signals across public areas

Metropolitan-area networks (cont )

Customer Premises

Customer Premises Core POP

storage-area networks (SANs)

Performance — SANs enable concurrent access of disk or

tape arrays by two or more servers at high speeds, providing enhanced system performance

Availability — SANs have disaster tolerance built in,

because data can be mirrored using a SAN up to 10 kilometers (km) or 6.2 miles away

Scalability — Like a LAN/WAN, it can use a variety of

technologies This allows easy relocation of backup data, operations, file migration, and data replication between

sysiems

Storage-area networks (cont.)

Virtual private network (VPN)

Benefits of VPNs

A VPN is a service that offers secure, reliable connectivity over a shared

public network infrastructure such as the Internet

The most cost-effective method of establishing a point-to-point connection

Pa remote users and an enterprise customer's network (vs Leased ines

The following are the three main types of VPNs:

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Access VPNs — Access VPNs provide remote access to a mobile worker and small office/home office (SOHO) to the headquarters of the Intranet or Extranet over a shared infrastructure Access VPNs use analog, dialup, ISDN, digital subscriber line (DSL), mobile IP, and cable technologies to securely connect mobile users, telecommuters, and branch offices

Intranet VPNs — Intranet VPNs link regional and remote offices to the headquarters of the internal network over a shared infrastructure using dedicated connections Intranet VPNs differ from Extranet VPNs in that they allow access only to the employees of the enterprise

Extranet VPNs — Extranet VPNs link business partners to the headquarters of the network over a shared infrastructure using dedicated connections Extranet VPNs differ from Intranet VPNs in that they allow access to users outside the enterprise

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ISDN/DSL Router Client on Laptop Computer

Intranets and extranets

Applications and services that are Intranet based

Secure access to external users or enterprises

ex : username / password

Intranets and extranets (cont.)

2.2 Bandwidth

Importance of bandwiath

Why bandwiath is important :

Bandwidth is finite Bandwidth is not tree

Bandwidth requirements are growing at a rapid rate

Bandwidth is critical to network performance

Importance of bandwiath (cont.)

Bandwidth is finite

Bandwidth is limited by the laws of physics and by the technologies used to place information on the media

56 kops modems with twisted-pair phone wires

Newer technologies, DSL also use the same twisted-pair

phone wires, it provides much greater bandwidth than

Importance of bandwiath (cont.)

Bandwidth requirements are growing at a rapid rate New network technologies and infrastructures are built to provide greater bandwidth

New applications are created to take advantage of the greater capacity

Streaming video and audio

IP teleohony systems

The successful networking professional must anticipate the need for increased bandwidth and act accordingly

Bandwidth is critical to network performance

It is a key factor in analyzing network performance, designing new networks, and understanding the Internet

Information flows as a string of bits from computer to computer throughout the world

The Internet is bandwidth

Analogies

Bandwidth has been defined as the amount

of information that can flow through a network ina given time

There are two analogies that may make it

easier to visualize bandwidth in a network

Bandwidth is like the width of a pipe

Bandwidth Is like the number of lanes ona

highway

In digital systems, the basic unit of bandwidth is bits per second (bps)

= thousands of bits per second (kbps)

=" millions of bits per second (Mbps)

= billions of bits per second (Gbps)

= trillions of bits per second (Tbps)

Unit of Bandwidth Abbreviation Equivalence

Bits per second bps 1 bps = fundamental unit of bandwidth

‘Kilobits per second | kbps 1 kbps = ~1,000 bps = 103 bps

Megabits per second Mbps 1 Mbps = ~1,000,000 bps = 105 bps

Gigabits per second Gbps 1 Gbps = ~1,000,000,000 bps = 109 bps

Terabits per second Tbps 1 Tbps = ~1,000,000,000,000 bps = 1012 bps

Measurement (cont.)

Bandwidth vs Speed

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They are not exactly the same thing

One may say, for example, that a 13 connection at

45Mbps operates at a higher speed than a | 1 connection at 1.544Mbps ??

lf only a small amount of their data-carrying capacity is being used, each of these connection types will carry data at roughly the same speed

It is usually more accurate to say that a 13 connection has greater bandwidth than a T1 connection

This is because the T3 connection is able to carry more information in the same period of time, not because it has a higher speed

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