COMPUTER COMMUNICATION NETWORKS. Department of ECE, ACE. Page 2. Every layer clubs together all procedures, protocols, and methods which it. Communication and Computer Networks. Prerequisites. Before proceeding with this tutorial, you need a basic understanding of Computer. You should know the. PDF | On Jan 1, , D B Hoang and others published Computer Communication Networks—Lecture Notes.
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“No man but a blockhead ever wrote, except for money.” - Samuel Johnson. The textbook world is changing. On the one hand, open source. This book is concerned with post-computer communication networks and two of increasingly relying on digital computer technology, and data communication. Computer Networking: Principles, Protocols, and Practice was written by Dr. Olivier tween the communication devices is larger than one kilometer. There are.
Also, there are RJ Connector plugs designed for both solid core wire and stranded wire. Others are designed specifically for one kind of wire or the other. Be sure you download plugs appropriate for the wire you are going to use. We normally use plugs designed to accommodate both kinds of wire.
Network cabling tools 1. Modular Plug Crimp Tool You will need a modular crimp tool. This is very similar to the ones which have been used for many years for all kinds of telephone cable work and it Figure 3. Modular plug crimp tool works just fine for Ethernet cables.
Some crimpers have cutters which can be used to cut the cable and individual wires, and possibly stripping the outer jacket. It is highly recommending for anyone who will make a lot of cables.
Diagonal Cutters Figure 3. Figure 3. Each transmission line is a pair of twisted wires. One pair receives data signals and the other pair transmits data signals. A much simplified schematic for one of these lines and its transmitter and receiver follows: The principal components of these pulses of energy are the potential difference between the wires and the current flowing near the surface of the wires.
This energy can also be considered as residing in the magnetic field which surrounds the wires and the electric field between the wires. In other words, an electromagnetic wave which is guided by, and travels down the wires.
The main concern are the transient magnetic fields which surround the wires and the magnetic fields generated externally by the other transmission lines in the cable, other network cables, electric motors, fluorescent lights, telephone and electric lines, lightning, which may literally bury the Ethernet pulses, the conveyor of the information being sent down the line. The twisted-pair Ethernet employs two principal means for combating noise.
The first is the use of balanced transmitters and receivers. A signal pulse actually consists of two simultaneous pulses relative to ground: The receiver detects the total difference between these two pules.
Since a pulse of noise usually produces pulses of the same polarity on both lines, it is essentially canceled out at the receiver. Also, the magnetic field surrounding one wire from a signal pulse is a mirror of the one on the other wire.
At a very short distance from the two wires the magnetic fields are opposite and have a tendency to cancel the effect of each other out. The second and the primary means of reducing cross-talk the term cross-talk came from the ability to overhear conversations on other lines on your phone between the pairs in the cable, is the double helix configuration produced by twisting the wires together.
This configuration produces symmetrical dentinal noise signals in each wire. Ideally, their difference as detected at the receiver, is zero. In actuality it is much reduced. Straight through and cross over cable Again, the wire with colored backgrounds may have white stripes and may be denoted that way in diagrams found elsewhere. For example, the green wire may be labeled Green-White.
The background color is always specified first. Straight through and crossover cable wire scheme A Straight-through cable has identical ends, whereas a Crossover cable has different ends.
Cable connector standard ordering It makes no functional difference which standard you use for a straight-through cable.
Your can start a crossover cable with either standard as long as the other end is the other standard. It makes no functional difference which end is which. Despite what you may have read elsewhere, a A patch cable will work in a network with B wiring and B patch cable will work in a A network.
Strip one end of the cable with the stripper or a knife and diags. If you are using the stripper, place the cable in the groove on the blade left side of the stripper and align the end of the cable with the right side of the stripper. If you turn it more, you will probably nick the wires. If you are using knife and diags, carefully slit the cable for about an inch or so and neatly trim around the circumference of the cable with diags to remove the jacket.
Inspect the wires for nicks. Cut off the end and start over if you see any. You may have to adjust the blade with the screw at the front stripper.
Cable diameters and jacket thicknesses vary. Spread and arrange the pairs roughly in the order of the desired cable end. Untwist the pairs and arrange the wires in the order of the desired cable end. Flatten the end between your thumb and forefinger.
Trim the ends of the wires so they are even with one another. Flatten again. There should be little or no space between the wires. Hold the RJ plug with the clip facing down or away from you. Push the wire firmly into the plug. Now, inspect before crimping and wasting the plug! Looking through the bottom of the plug, the wire on the far-left side will have a white background. The wires should alternative light and dark from left to right. The furthest right wire is brown. The wires should all end evenly at the front of the plug.
The jacket should end just about where you see it in the diagram-right on the line. Hold the wire near the RJ plug with the clip down and firmly push it into the left side of the front of the Crimper it will only go in one way.
Hold the wire in place and squeeze the crimper handles quite firmly. This is what will happen: Crimping Crimp it once. The crimper pushes two plungers down on the RJ plug. Test the crimp… if done properly an average person will not be able to pull the plug off the cable with his or her bare hands.
And that quite simply, besides lower cost, is the primary advantage of twisted-pair cables over the older thin wire, coaxial cables. In fact, the ease of installation and the modular RJ plug is the main reason coaxial cable is no longer widely used for small Ethernet. It could stretch the cable and change its characteristics. Look at the side of the plug and see if it looks like the diagram and give it a fairly firm tug to make sure it is crimped well. Prepare the other end of the cable so it has the desired end and crimp.
If both ends of the cable are within reach, hold them next to each other and with RJ clips facing away. Look through the bottom of the plugs.
If the plugs are wired correctly, and they are identical, it is a straight-through cable. If they are wired correctly and they are different, it is a crossover cable. Try to avoid running cables parallel to power cables. If you bundle a group of cables together with cable ties zip ties , do not over-clinch them. Keep cables away from devices which can introduce noise into them. Do not use a stapler to secure UTP cables. Use telephone wire hangers, which are available at most hardware stores.
Give the reason why it is not advisable to bend UTP cables more than four times the diameter of the cable. Why is it not advisable to run UTP cable outside of a building? In order to do well in the labs, we need to understand the basic set-up of the lab. You will be using the PC as a terminal to talk to the routers. One of them has RJ connectors and the other has serial connectors. Ethernet ports are pre-connected to the RJ patch panel.
Serial ports are pre-connected to the serial patch panel. The ports are labeled on their left. You will find the console cable as a UTP cable with one of its ends connected through a small devices to a serial port on the PC. Cisco routers support different modes of operation. Cisco routers use many other modes, but let us keep it simple for now. Connect the PC to R1. Question mark lists commands that can be used in a certain context.
You only need to type enough of a command to differentiate it from all other commands. Type the following commands: The prompt ends with router-config? Go into configuration mode and type the following commands: Type these commands: Now you can configure interface Ethernet0.
This command will bring them up. Now type the following command: Again type this command: Cisco commands are not case-sensitive. Determine which mode you operate in when you first access the router. The command used to save changes made in the running configuration to start-up configuration is: List the interfaces on three routers of your choice. Be sure to indicate the router number. Which of the condition s are possible for an interface: Figure 5.
In this kind of protocols we require an addressing scheme and sub netting. Addressing scheme will be used to determine the network to which a host belongs and to identifying that host on that particular network. All hosts on an internetwork use the services of a routed protocol. It makes possible for routers to build and maintain routing tables.
Although dynamic routing protocols are flexible and adjust to network changes, they do have associated network traffic which competes for network bandwidth with the user data traffic.
Configuring Static Routes Static routes specify a fixed route for a certain destination network. They need to be configured on any router that needs to reach a network that it is not directly connected to. The IOS command used to configure static routes is ip route. The syntax is: Multiple networks may be combined such that the destination- address and subnet-mask combination matches all hosts on those networks.
Adding a static route to an Ethernet or other broadcast interface for example, ip route 0. This configuration is not generally recommended. When the next hop of a static route points to an interface, the router considers each of the hosts within the range of the route to be directly connected through that interface, and therefore it will send ARP requests to any destination addresses that route through the static route.
If unspecified the default value is 1. Connect the network as shown in the network diagram. Configure appropriate ip addresses and clock rates if needed on the router interfaces as specified in the network diagram. For R1, enter the following static routes ip route On R2 enter: On R3 enter: After that verify the static routes by entering the following commands in the privilege mode: Run the command show IP route and write its output.
What is the default administrative distance of static route? Write the IP route command to modify the same. Create a loop back interface on R3 and assign an IP address Now add static routes to each of the other routers to reach this interface.
Verify your work by pinging the newly created interface from routers R1 and R2 respectively. Figure 6. An autonomous system is a collection of networks under a single administration, sharing a common routing strategy. A distance-vector protocol, RIP was designed to work with small to medium-sized networks.
Some advantages of using RIP, especially in small networks, is that there is very little overhead, in terms of bandwidth used and configuration and management time. RIP is also easy to implement, compared to newer IGPs, and has been implemented in networks around the world. All routers that use RIP send an update message to all of their neighbors approximately every 30 seconds; this process is termed advertising. The Cisco implementation sends updates every 30 seconds minus up to 15 percent, or 4.
When the neighbor has not responded for seconds, the route is marked invalid; seconds is long enough that a route won't be invalidated by a single missed update message. The neighbor is shown to be unreachable by sending a normal update message with a metric of "infinity;" in the case of RIP, this number is If an advertisement is received from a neighbor with a metric of infinity, then the route is placed into hold-down state, advertised with a distance of 16, and kept in the routing table.
No updates from other neighbors for the same route are accepted while the route is in hold-down state. If other neighbors are still advertising the same route when the hold-down timer expires, then their updates will then be accepted. The route will be advertised with infinity metric for a period of time after the hold-down state if no alternate paths are found.
The actual timers used to accomplish the above tasks are a routing-update timer, a route- invalid timer, a route-hold-down timer, and a route-flush timer.
The RIP routing-update timer is generally set to 30 seconds, ensuring that each router will send a complete copy of its routing table to all neighbors every 30 seconds. The route-invalid timer determines how much time must expire without a router having heard about a particular route before that route is considered invalid.
When a route is marked invalid or put in hold-down state, neighbors are notified of this fact. This notification must occur prior to expiration of the route-flush timer. When the route flush-timer expires, the route is removed from the routing table. Typical initial values for these timers are seconds for the route-invalid and route-holddown timers and seconds for the route-flush timer. The values for each of these timers can be adjusted with the timers basic router configuration command.
Several Stability Features To adjust for rapid network-topology changes, RIP specifies numerous stability features that are common to many routing protocols. RIP implements split horizon with poison-reverse and hold-down mechanisms to prevent incorrect routing information from being propagated.
Split horizon prevents incorrect messages from being propagated by not advertising routes over an interface that the router is using to reach the route. Implementing split horizon helps avoid routing loops.
Poison reverse operates by advertising routes that are unreachable with a metric of infinity back to the original source of the route. Hold-down is a method of marking routes invalid expired. As discussed above, no updates from other neighbors for the same route are accepted while the route is in hold-down state.
Triggered updates are also an included convergence and stability feature. Updates are triggered whenever a metric for a route changes. Triggered updates may also contain only information regarding routes that have changed, unlike scheduled updates. There is a minimum delay of five seconds between triggered updates to prevent update storms. Cable up the network as shown in the diagram.
Assign the IP address as shown in the diagram to the appropriate interfaces. For the serial links, has been used to indicate a DCE port. Issue RIP routing commands on all the routers starting from the global config mode.
On R1: Ping the host from R1. Type escape sequence to abort. Configure RIP version 1 on two routers. Run Debug ip rip and note the address on which updates are sent. Write commands to modify the default update and hold-down timers for RIP v1. RipV2 also sends its complete routing table to its active interfaces at periodic time intervals.
The timers, loop avoidance schemes and administrative distance are the same as Rip version 1. It also allows authentication using MD5 encryption scheme. And it also supports dis-contiguous networks. Configuring router with RIP version 2 is very simple. Just add the command version 2 under the config-router prompt and the router is running RIPv2. Note down the routing table for Router R1.
Run the command debug rip and note down the multicast address on which RIPv2 forwards the updates. Write down the source IP address for the ping packets when you ping H1 from R1.
While working on R1, how could you check if H1 can reach the loopback interface? In other words, how can you verify if a ping from H1 to loopback of R1 is successful? It is an open standards protocol—that is, it isn't proprietary to any vendor or organization.
Link-state routing protocols perform the following functions: Like all link state protocols, OSPF's major advantages over distance vector protocols are fast convergence, support for much larger internetworks, and less susceptibility to bad routing information. Other features of OSPF are: Each router on the network forms an adjacency with the DR which represents the pseudo-node. In other words, the DR is a property of a router's interface, not the entire router. Fig 8.
Router A: This is a block size of 8, which is a wildcard of 7.
Similarly the other subnet ,mask, and wildcard can be determined by looking at the IP address of an interface. Router B: Scenario for exercise problems Simulate the network shown above on packet tracer.
Write down the configuration commands entered on all three routers for configuration of OSPF. Router 1: Router 2: Router 3: It is important to understand EIGRP because it is probably one of the two most popular routing protocols in use today. EIGRP is sometimes referred to as a hybrid routing protocol because it has characteristics of both distance vector and link state protocols. And EIGRP has link state characteristics as well — it synchronizes routing tables between neighbours at startup and then sends specific updates only when topology changes occur.
EIGRP has a maximum hop count of the default is set to EIGRP metric calculation: Router1 config router eigrp 1 Router1 config-router network Router2 sh ip route Codes: Reply from The procedures differs depending on the platform and the software used, but in all cases, password recovery requires that the router be taken out of operation and powered down. Please use cisco as the password where necessary. Please be prepared to do password recovery right away. The group before you might have set a password other than cisco.
Use show version command to determine the platform before you try the password recovery. You will be working with the configuration register as part of this lab. The book is also a useful comprehensive reference for telecommunications professionals. The numerical solutions for these exercises are provided in the companion website, www.
The content of each chapter is briefly summarized below. The chapter revises the basics of signal theory and introduces both continuous and discrete time signals, and their Fourier transform with its properties. The concepts of energy, power and bandwidth are also reviewed, together with the vector representation of signals by linear space methodologies.
Lastly, this chapter introduces the basics of random variables and random processes, their common statistical description, and how statistical parameters are modified by linear systems. Chapter 3 Describes how information produced by a source, either analog or digital, can be effectively encoded into a digital message for efficient transmission.
We will first introduce the reference scheme for analog-to-digital conversion, and focus on quantization, the operation of approximating an analog value with a finite digit representation. We will also present the fundamentals of information theory with the notion of information carried by a digital message.
Lastly we introduce the principles of source coding, state the fundamental performance bounds and discuss some coding techniques. Chapter 4 Models a transmission medium. Firstly, a description of the two-port network is given. A model of noise sources is then provided and its description in terms of parameters such as the noise temperature and the noise figure is presented.
A characterization, especially in terms of power attenuation, of transmission lines, power lines, optical fibers, radio propagation and underwater propagation concludes this chapter. Chapter 5 Deals with digital modulations. The general theory is first presented, relying on concepts of linear spaces and hypothesis testing. Performance is measured by the bit error probability, which again can be expressed in terms of system parameters. Then, the most important modulations are presented as examples of the general concept.
These include pulse amplitude modulation, phase shift keying, quadrature amplitude modulation, frequency shift keying and others.
A comparison between the different modulation schemes is carefully drawn. Then, more advanced modulation techniques are briefly presented, namely orthogonal frequency division multiplexing and spread spectrum.
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.