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Note for Advanced Computer Network - ACN by Ashutosh Jaiswal

  • Advanced Computer Network - ACN
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22-01-2017    Media: This is the physical path that is used to transmit an electrical or optical signal. It might be wired or wireless, copper, or a fiber optic cable. Network devices: These are used to interconnect multiple end devices as a single point of interconnection, route communication through different networks, or for providing network security. Examples of network devices are switches, routers, firewalls, and directors. 1/22/2017  5 1.1 What Is the Internet? what is the Internet? There are a couple of ways to answer this question.  First, we can describe the nuts and bolts of the Internet, that is, the basic hardware and software components that make up the Internet.  Second, we can describe the Internet in terms of a networking infrastructure that provides services to distributed applications  a global computer network providing a variety of information and communication facilities, consisting of interconnected networks using standardized 6 1/22/2017 communication protocols.  1.1 A Nuts-and-Bolts Description The Internet is a computer network that interconnects hundreds of millions of computing devices throughout the world.  these computing devices were primarily traditional desktop PCs, Linux workstations, and so-called servers that store and transmit information such as Web pages and e-mail messages. Increasingly, however, non traditional Internet end systems such as laptops, smartphones, tablets, TVs, gaming consoles, Web cams, are being connected to the Internet.  In Internet, all of these devices are called hosts or end systems 7 1/22/2017  1/22/2017 8 2

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22-01-2017     End systems are connected together by a network of communication links and packet switches. there are many types of communication links, which are made up of different types of physical media, including coaxial cable, copper wire, optical fiber,. Different links can transmit data at different rates, with the transmission rate of a link measured in bits/second. When one end system has data to send to another end system, the sending end system segments the data and adds header bytes to each segment. 1/22/2017  9   End systems access the Internet through Internet Service Providers (ISPs), including residential ISPs such as local cable or telephone companies; corporate ISPs; university ISPs; and ISPs that provide WiFi access in airports, hotels, coffee shops, and other public places. The Transmission Control Protocol (TCP) and the Internet Protocol (IP) are two of the most important protocols in the Internet. 10 1/22/2017 A protocol defines the format and the order of messages exchanged between two or more communicating entities, Figure 1.2 A human protocol and a computer network protocol 1/22/2017 11 1/22/2017 12 3

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22-01-2017  1.2 The Network Edge   Recall from the previous section that in computer networking jargon, the computers and other devices connected to the Internet are often referred to as end systems. They are referred to as end systems because they sit at the edge of the Internet, as shown in Figure 1.3 The Internet’s end systems include desktop computers (e.g., desktop PCs, Macs, and Linux boxes), servers (e.g., Web and e-mail servers), and mobile computers (e.g., laptops, smartphones, and tablets)    1/22/2017 1/22/2017 13 15 End systems are also referred to as hosts because they host (that is, run) application programs such as a Web browser program, a Web server program, an e-mail client program, or an e-mail server program Hosts are sometimes further divided into two categories: clients and servers. 1/22/2017 14  1.2.1 Access Networks  Having considered the applications and end systems at the “edge of the network,” let’s next consider the access network—the network that physically connects an end system to the first router (also known as the “edge router”) on a path from the end system to any other distant end system. Figure 1.4 shows several types of access 1/22/2017 16 4

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22-01-2017 1/22/2017   17  Home Access: DSL, Cable, FTTH, DialUp.  Today, the two types of broadband residential access are digital subscriber line (DSL) and cable. A residence typically obtains DSL Internet access from the same local telephone company (telco) that provides its wired local phone access 1/22/2017 18 1/22/2017 20 As shown in Figure 1.5, each customer’s DSL modem uses the existing telephone line (twistedpair copper wire,) to exchange data with a digital subscriber line access multiplexer (DSLAM) located in the telco’s local central office (CO). The residential telephone line carries both data and traditional telephone signals simultaneously. 1/22/2017 19 5

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