Technology Infrastructure-Data Communication and Computer Networks-Presentation, Slides of Data Communication Systems and Computer Networks

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Module Objectives:

 Understand the fundamental concepts of the Web

technologies.

 Understand the underlying protocols and typical ways of

delivering static and dynamic material from a server to a

browser.

By the end of the Module you’ll be able to:

• Lecture

Objectives

You will learn about the following in this lecture:

 Overview of the Internet History.

 Looking closer into the network structure of the internet

 Understand the concept of Client/Server model

 Requirements and types of Internet connections

 Access networks and physical media

 Began switching to TCP/IP protocols in the late 70's

• Had grown too large for then current communication protocols to handle.
• Finished switching to TCP/IP by 1983.

 Split into two networks in 1983

• MILNET: reserved for the military use.
• ARPANET: open to public.

 NSFNET was created in 1987

• By National Science Foundation to support education and research.
• Meant to be a high-speed "backbone“ network to connect various networks and to support new bandwidth-intensive applications.

 ARPANET and NSFNET merged in the late 1987

• Due to their similarities in structures and purposes.
• Remained noncommercial.
• Acceptable use policies implemented.

 Commercial Internet Exchange was created in 1991

• Composed of a group of small commercial networks.
• To allow commercial use and be free of nasty use policies.

 Today's Internet

• Consists of various interconnected networks: ARPANET, NSFNET, CIX, BITNET, commercial networks, private networks, individual computers, etc.
• Allows scientific, educational, research, commercial, and various other applications.
• Keeps growing in a vary fast pace.

(1) network edge: applications and hosts

(2) network core:

• routers
• network of networks

(3) access networks, physical media: communication links

A closer look at network structure:

Network Edge

• end systems (hosts):
  • run application programs
  • e.g., WWW, email
  • at “edge of network”
• client/server model
  • client host requests, receives service from server
  • e.g., WWW client (browser)/ server; email client/server
• peer-peer model:
  • host interaction symmetric
  • e.g.: teleconferencing, Gnutella, LimeWire

(1) The network edge:

(1) Network edge: connectionless service

connectionless is data transfer between end systems  same as before! ► UDP - User Datagram Protocol: Internet’s connectionless service

 unreliable data transfer

 no flow control

 no congestion control

 Examples streaming media, teleconferencing, and Internet

telephony

(2) The Network Core

• Routers
  • A router is a network device that connects multiple network segments into an internet work.
  • Routers are intelligent devices that make routing decisions i.e. Determine the best possible path for data block to travel between sender and receiver.
  • In large networks data may be sent to many routers before it reaches its final destination.
  • Routers use routing tables to determine the next hop and they also keep track of the condition of the network to possibly send a packet on a route with less traffic or interference.
  • Routers have multiple ports or connection points for connection to different network segments to enable routing. At a minimum, most routers have at least three (3) ports which connects to different devices and have different uses.

Example

(2) The Network Core

network resources (e.g., bandwidth) divided into “pieces”

• pieces allocated to calls
• resource piece idle if not used by owning call (no sharing)
• dividing link bandwidth into “pieces”
  • frequency division
  • time division

Circuit switching

(2) The Network Core

each end-end data stream divided into packets

• user A, B packets share network resources
• each packet uses full link bandwidth
• resources usedas needed, resource contention:
• congestion: packets queue, wait for link use
• store and forward: packets move one hop at a time
• transmit over link
• wait turn at next link

Packet Switching

Example (1)

 The Internet can be viewed as the "Information Superhighway".

In order to get on the Internet, you have to pay people at access points. These access points are called Internet Service Providers (ISPs).

 ISPs have very high-speed connections to the Internet and they

in turn sell users slower dial-up or dedicated connections.

 ISPs have a high speed LAN with many components, which

includes a large, complex router that connects the LAN to the Internet.

 Other components include the ISP's mail, news and Web servers

and routers for dedicated leased line and dial-up access to the Internet for users.

 ISPs also allows server hosting where a customer can place their

Web server at the ISP for the best possible performance.

INTERNET SERVICE PROVIDERS (ISPs)