COMPUTER COMMUNICATION NETWORKS. Department of ECE, ACE. Page 2. Every layer clubs together all procedures, protocols, and methods which it. “No man but a blockhead ever wrote, except for money.” - Samuel Johnson. The textbook world is changing. On the one hand, open source. Communication and Computer Networks. Prerequisites. Before proceeding with this tutorial, you need a basic understanding of Computer. You should know the.
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PDF | On Jan 1, , D B Hoang and others published Computer Communication Networks—Lecture Notes. This book is concerned with post-computer communication networks and two of increasingly relying on digital computer technology, and data communication. Computer Communication Networks Lecture Notes Lecture 0, Course Overview, ps · pdf · ps · pdf · ps · pdf · ps · pdf, -. Lecture 1, Network Foundation, ps · pdf.
Finally, the performance of the digital approach is compared against analog transmission, explaining why digital transmission is so widely used. Chapter 6 Investigates how an information message can be robustly encoded into the signal for reliable transmission over a noisy channel. We describe the principles of channel coding techniques, where robustness is obtained at the price of reduced information rate and complexity of the decoding process. Then, based upon the fundamentals of information theory introduced in Chapter 3, we aim to establish upper bounds on the amount of information that can be effectively carried through a noisy channel, by introducing the concept of channel capacity.
We conclude by describing briefly how recently devised coding schemes allow such upper bounds to be approached closely while maintaining moderate complexity. Chapter 7 Introduces some basic statistical methods that are widely used in the performance analysis of telecommunication networks. The topics covered are the elementary theory of discrete-time and continuous-time Markov chains and birth-death processes.
This theory will be applied in Chapters 8 and 9, where we analyze simple queueing systems, and the performance of channel access and retransmission protocols.
It starts with the definition of a queueing system in terms of arrival, departure, service processes, queueing processes and service discipline. We then define some basic performance metrics for queueing systems, which are classified as occupancy measures number of customers in the different parts of the system , time measures system and queueing times and traffic measures average rate at which customer arrive and leave the system. The chapter concludes with a performance analysis of fundamental queueing models, featuring Markovian as well as non-Markovian statistics for the service process.
Examples of the application of the developed theory to practical problems, including some unrelated to telecommunications, are provided throughout the chapter. Chapter 9 Presents and analyzes link-layer algorithms, especially focusing on aspects related to channel access and retransmission of lost or corrupted data packets over point-to-point links — a technique often referred to as Automatic Retransmission reQuest ARQ. Channel access protocols are subdivided into the following classes: deterministic access, demand-based access, random access and carrier sense multiple access.
Mathematical models are given for each class of protocols, thus obtaining the related performance in terms of throughput and delay.
The different channel access schemes are then compared as a function of the traffic load of the system. Next, the chapter presents three standard ARQ schemes, namely, stop and wait, go back N and selective repeat ARQ, which are characterized analytically in terms of their throughput performance.
Chapter 10 Describes all the layers above the data link layer dealing with the interconnection of distinct devices so as to form a communication network.
The chapter begins by reviewing a useful mathematical tool for network analysis, namely graph theory. Routing methodologies, i.
In a telecommunication service at least three actors are usually involved: 1. Edited by Nevio Benvenuto and Michele Zorzi.
The carrier is normally a company owning equipment and resources, for example, frequencies, in the case of radio services. As an example the network serving an university campus is a local area network, while a large Internet provider network is a wide-area network.
Telecommunication networks can be categorized in many different ways. We would like to remark that the roles of source and receiver in a communication are not exclusive, that is, each party involved in the communication clearly can act as 1. A classical example is a telephone call or conference call. This is often the case for conference call services nowadays or for bulk-data transfers, usually scheduled overnight.
From the above examples, we would like to remark that in modern telecommunication networks there must be a mechanism to establish a service as easily as possible; this fundamental mechanism is actually hidden from users.
Here we have interactive services and broadcast services.
We can think of a protocol as a set of procedures and rules to exchange data or to let two entities agree on certain actions to be performed. An example could be the delivery of the same movie on a broadcast channel using different subchannels starting at different times, so that the user can somehow control the start of the movie at her convenience.
This values is constant over time regardless of whether the source user actually speaks or not. We can conclude that a voice signal encoded according to the ITU G. Example 1. If the speaker is silent a special sequence of bits is sent and then nothing is emitted until the speaker starts speaking again.
On the receiving side when this sequence is received, noise is randomly reproduced, as a comfort feature, just to keep the receiver aware that the link is not broken. The AMR is basically made of eight source encoders with bit rates of Indeed, even if the link between the transmitter and the receiver is fed at a constant bit rate, when the transmission channel deteriorates at some point in time, AMR is informed and selects a lower bit rate. Hence, more redundancy bits can be used resorting to channel coding techniques for protecting the voice encoded bits from channel errors.
We can conclude that a voice signal encoded according to the AMR standard is a variable-rate source.
As illustrated in Figure 1. Nodes can be either end-user or transit nodes. Links connect two nodes and indicate that it is possible to exchange telecommunication services between them. When discussing the nature of the links we may distinguish between physical and logical links; the former represent the presence of an actual resource that connects two nodes and may be used for the communication; the latter are a more general abstraction of the capability of two nodes to communicate.
That is to say, there could be many logical links conveyed by a physical link,4 whereas many physical links could be needed to establish a logical link. Two or more nodes are needed in order to form a network connection. Routers can connect two or more network segments. These are intelligent network devices that store information in its routing table such as paths, hops and bottlenecks. With this info, they are able to determine the best path for data transfer. It refers to a direct connection between two computers on a network.
Principles of Computer Communication Networks
A point to point connection does not need any other network devices other than connecting a cable to the NIC cards of both computers. Anonymous FTP is a way of granting user access to files in public servers. Users that are allowed access to data in these servers do not need to identify themselves, but instead log in as an anonymous guest. A subnet mask is combined with an IP address in order to identify two parts: the extended network address and the host address.
Like an IP address, a subnet mask is made up of 32 bits.
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A single segment of UTP cable has an allowable length of 90 to meters. This limitation can be overcome by using repeaters and switches. Data encapsulation is the process of breaking down information into smaller manageable chunks before it is transmitted across the network. It is also in this process that the source and destination addresses are attached into the headers, along with parity checks.
It shows how devices and cables are physically laid out, as well as how they connect to one another. VPN means Virtual Private Network, a technology that allows a secure tunnel to be created across a network such as the Internet. For example, VPNs allow you to establish a secure dial-up connection to a remote server.
This is a protocol that provides a way for multiple computers on a common network to share single connection to the Internet. The Network layer is responsible for data routing, packet switching and control of network congestion. Routers operate under this layer.
Network topology dictates what media you must use to interconnect devices. It also serves as basis on what materials, connector and terminations that is applicable for the setup.
RIP, short for Routing Information Protocol is used by routers to send data from one network to another. It efficiently manages routing data by broadcasting its routing table to all other routers within the network. It determines the network distance in units of hops. There are several ways to do this. Install reliable and updated anti-virus program on all computers. Make sure firewalls are setup and configured properly.
User authentication will also help a lot. All of these combined would make a highly secured network. This is a peripheral card that is attached to a PC in order to connect to a network. It is an interconnection of computers and devices that are geographically dispersed. It connects networks that are located in different regions and countries.
The physical layer does the conversion from data bits to electrical signal, and vice versa. This is where network devices and cable types are considered and setup. Proxy servers primarily prevent external users who identifying the IP addresses of an internal network. Without knowledge of the correct IP address, even the physical location of the network cannot be identified.
Proxy servers can make a network virtually invisible to external users. This layer provides the protocols and means for two devices on the network to communicate with each other by holding a session. This includes setting up the session, managing information exchange during the session, and tear-down process upon termination of the session.
Are there limitations? A fault tolerance system ensures continuous data availability.
Computer Communication Networks Lecture Notes
This is done by eliminating a single point of failure. However, this type of system would not be able to protect data in some cases, such as in accidental deletions.
The 10 refers to the data transfer rate, in this case is 10Mbps. The word Base refers to base band, as oppose to broad band. T means twisted pair, which is the cable used for that network.
Computer Communication Networks Lecture Notes
Private IP addresses are assigned for use on intranets. These addresses are used for internal networks and are not routable on external public networks. These ensures that no conflicts are present among internal networks while at the same time the same range of private IP addresses are reusable for multiple intranets since they do not "see" each other.
NOS, or Network Operating System, is specialized software whose main task is to provide network connectivity to a computer in order for it to be able to communicate with other computers and connected devices.
DoS, or Denial-of-Service attack, is an attempt to prevent users from being able to access the internet or any other network services.
Such attacks may come in different forms and are done by a group of perpetuators.If there is no network server configured, as is the case in our lab, the standard setup dialogue is started. This flag is propagated to all other switches to instruct them to rapidly age out their forwarding table entries.
The block size of a mask is always There are many different ways to access a router. This is what will happen: The group before you might have set a password other than cisco.