Project Report On Computer Networks 134m27

Chapter -1 INTRODUCTION 1.1 Networking Networking is a practice of linking of two or more computing devices such as PCs, printers, faxes etc., with each other Connection between two devices is through physical media or logical media to share information, data and resources. Networks are made with the hardware and software.

Cable/media Fig1.1: Computer network There are many different ways to connect your computer to another computer or a network. Using Windows 2000, you can connect your computer to: 

Another computer using a direct cable connection.



A private network using a modem or an integrated service digital network (ISDN) adapter or a network adopter card.



A network using a virtual private network (VPN) connection.



Another computer by having another computer call your computer.

The interconnected collection of autonomous computers is called computer network. Two computers are said to be interconnected if they are able to exchange information. The connection need not be via a copper wire; fiber optics, microwaves and communication satellites can be used.

1.2 Types of Networking: Page 1 of 45

 Wired network  Wireless network

Wired networks: Wired networks are almost always faster and less expensive than wireless networks. Once connected, there is little that can disrupt a good-wired connection. Wired networks come in many forms, but the most popular are HomePNA and Ethernet. HomePNA uses the existing phone line wires in your home and Ethernet needs special network cabling.

Fig1.2: Wired network

Wireless Networks: Mobile computers, such as notebook computers and personal digital assistants (PDAs) are the fastest- growing segment of the computer industry. Many of the owner of these computers have desktop machines on LANs and WANs back at the office and want to be connected to their home base even when away from home or en route. Since having a wired connection is impossible in cars and airplanes, there is a lot of interest in wireless networks.

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Fig1.3: Wireless network

1.3 Models of Networking Model means the connectivity of two computers. We have many types of networking models.

(i)

(i)

Client – Server Model

(ii)

Peer to Peer Model (Workgroup Model)

(iii)

Domain Model

Client –Server Model

In a Client server model we have one server and many clients. A Client can share the resources of server, but a server cannot share the resources on clients. On the point of view of it’s very easy to control the network because we combine with the server also at security point of view. It is very useful because it uses level security in which s have to only one to share the resources.

(ii) Peer to Peer Model (Workgroup Model) In Peer to Peer networking model all computers are in equal status, that is we cannot manage centralization, istration security. In Peer to Peer networking client use operating system like Window 98, Window XP, Window 2000, Window Vista.

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(iii) Domain Model It is a mixture of client server and peer-to-peer model. In this clients can share their resources as peer-to-peer but with the permission of the server as in client server model therefore it is commonly used model because in this security is more as we can put restriction on both server and clients.

1.4 Categories of Network Local Area Network (LAN) LAN is a computer network that is used to connect computers and work station to share data and resources such as printers or faxes. LAN is restricted to a small area such as home, office or college. Devices used in LAN are: HUB and switch. Media for LAN is UTP cables.

Fig1.4: Local Area network

Campus Area Network (CAN) Campus Area Network is a computer network made up of two or more LANs within a limited area. It can cover many buildings in an area. The main feature of CAN is that all of the computers which are connected together have some relationship to each other. It Page 4 of 45

will help to interconnect academic departments, library and computer laboratories. CAN is larger than LAN but smaller than WAN. Devices used in CAN are: HUB, Switch, Layer-3 switch, Access Point.

Metropolitan Area Network (MAN) MAN is the interconnection of networks in a city. MAN is not owned by a single organization. MAN can also be formed by connecting remote LANs through telephone lines or radio links. MAN s data and voice transmission. The best example of MAN is cable T.V network in a city.

Fig1.5 Metropolitan area network

Wide Area Network (WAN) WAN covers a wide geographical area which includes multiple computers or LANs. It connects computer networks through public networks like, telephone system, microwave, satellite link or leased line. Most of the WANs use leased lines for internet access as they provide faster data transfer. WAN helps an organization to establish network between all its departments and offices Page 5 of 45

located in the same or different cities. It also enables communication between the organization and rest world. Devices used in WAN is only Router

Fig1.6: Wide area network

Chapter-2 PROBLEM FORMULATION 2.1 Problem Overview:

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It is difficult to manage communication between far away branches and absence of networking results in higher cost and low efficiency communication among organization and outside environment.

2.2 Objective of the project: Objective of project is to make communication possible between far away branches, head-offices of any organization with lower cost and higher efficiency. In this project we use routing protocols to have communication of an organization with it’s far away branches.

2.3 Networking components: When a computer or device A is requesting a resource from another computer or device B, the item A is referred to as a client. Because all or most items that are part of a network live in association or cooperation, almost any one of them can be referred to as a client. Based on this, there can be different types of clients. The most regularly used of them is referred to as a workstation. If you already have one or more computers that you plan to use as workstations, you can start by checking the hardware parts installed in the computer. The computer must meet the following requirements:

Processor: An Intel Pentium or Celeron family of processors or an AMD K6/Athlon/Duron family of processors. The processor should have a 300 megahertz clock speed. A higher speed is recommended.

RAM: The computer must have a memory of at least 64 megabytes (MB). As memory is not particularly expensive nowadays, you should upgrade the computer's memory to at least 512MB. Page 7 of 45

Hard Drive: Before installing Microsoft Windows XP Professional on an existing computer, make sure the hard drive has the appropriate capacity to handle the OS. To find out how much space your hard drive has, you can open Windows Explorer or My Computer, right-click the C:\ drive and click Properties.

Network Cables: Cable is used to connect computers. Although we are planning to use as much wireless as possible, you should always have one or more cables around. In our network, we will use Category 5 cable RJ-45. The ends of the cable appear as follows:

Figure 2.1: RJ connectors

Introduction to Network Distributors: We can connect one computer to another. This can be done using their serial ports:

Figure 2.2: connecting computers by serial port

Hub: A hub is rectangular box that is used as the central object on which computers and other devices are connected. To make this possible, a hub is equipped with small holes called ports. Here is an example of a hub: Page 8 of 45

Figure 2.3: Hub

Routers: Routers are networking devices that forward data packets between networks using headers and forwarding tables to determine the best path to forward the packets. Routers work at the network layer of the T/IP model or layer 3 of the OSI model. Routers also provide interconnectivity between like and unlike media. Here is an example of a router:

Figure 2.4: Router

Network Cards: In order to connect to a network, a computer must be equipped with a device called a network card. A network card, or a network adapter, also called a network interface card, or NIC, allows a computer to connect to the exterior. If you buy a computer from one of those popular stores or big companies on the Internet, most of their computers have a network card tested and already. You can reliably use it. If you go to a store that sells or manufactures computers, you can ask them to install or make sure that the computer has a network card. When it comes to their installation, there are roughly two categories of network cards: internal and external. An internal network card looks like a printed circuit board with some objects "attached" or "glued" to it and it appears as follows:

Switch:

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A network

switch or switching

hub is

a computer

networking

device that

connects network segments. A network switch is a small hardware device that s multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model. Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub.

Figure 2.5: Switch

Server: A network server is a computer designed to process requests and deliver data to other (client) computers over a local network or the Internet. Examples include Web servers, proxy servers, and FTP servers. Not only should you learn about servers on the Internet, private network servers for business and personal use are also becoming more common.

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Figure 2.6: Server

Access Point: In computer networking, a wireless access point (WAP) is a device that allows wireless devices to connect to a wired network using Wi-Fi, Bluetooth or related standards. The WAP usually connects to a router (via a wired network), and can relay data between the wireless devices (such as computers or printers) and wired devices on the network.

Figure 2.7: Access Point

Network Software: Operating Systems: A workstation is a computer that is a member of a network. At homes and small businesses, the most regular operating system, at the time of this writing, is probably Microsoft Windows XP Home Edition. Other regularly used operating systems from Microsoft are Microsoft Windows XP Professional, Microsoft Windows 9X, and Page 11 of 45

Microsoft Windows 2000 Professional. On this site, we will mostly cover Microsoft Windows XP Professional.

Packet Tracer: Packet Tracer is a Cisco router simulator that can be utilized in training and education, but also in research for simple computer network simulations. The tool is created by Cisco Systems and provided for free distribution to faculty, students, and alumni who are or have participated in the Cisco Networking Academy. The purpose of Packet Tracer is to offer students and teachers a tool to learn the principles of networking as well as develop Cisco technology specific skills. The current version of Packet Tracer s an array of simulated Application Layer protocols, as well as basic routing with RIP, OSPF, and EIGRP, to the extent required by the current CCNA curriculum. While Packet Tracer aims to provide a realistic simulation of functional networks, the application itself utilizes only a small number of features found within the actual hardware running a current Cisco IOS version.

Chapter 3 Page 12 of 45

PROJECT TECHNIQUES 3.1 IP Addressing: An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation. Example: 140.179.220.200 It is sometimes useful to view the values in their binary form. 140 .179 .220 .200 10001100.10110011.11011100.11001000 Every IP address consists of two parts, one identifying the network and one identifying the node. The Class of the address and the subnet mask determine which part belongs to the network address and which part belongs to the node address. The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32-bit numbers. Since each of the eight positions can have two different states (1 or 0) the total number of possible combinations per octet is 28 or 256. So each octet can contain any value between 0 and 255. Combine the four octets and you get 232 or a possible 4,294,967,296 unique values. Out of the almost 4.3 billion possible combinations, certain values are restricted from use as typical IP addresses. For example, the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts. Understanding IP Addresses An IP address is an address used in order to uniquely identify a device on an IP network. The address is made up of 32 binary bits, which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary. Here is how binary octets convert to decimal: The right most bit, or least significant bit, of an octet holds a value of 20. The bit just to the left of that holds a value of 21. This continues until the left-most bit, or most significant bit, which holds a value of 27. So if all binary bits are a one, the decimal equivalent would be 255 as shown here: 1 1 1 11 1 1 Page 13 of 45

128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255) Here is a sample octet conversion when not all of the bits are set to 1. 0 1 0 0 0 0 0 1 0 64 0 0 0 0 0 1 (0+64+0+0+0+0+0+1=65) And this is sample shows an IP address represented in both binary and decimal. 10. 1. 23. 19 (decimal) 00001010.00000001.00010111.00010011 (binary) There are five IP classes plus certain special addresses:

Default Network :The IP address of 0.0.0.0 is used for the default network.

Class A :This class is for very large networks, such as a major international company might have. IP addresses with a first octet from 1 to 126 are part of this class. The other three octets are used to identify each host. This means that there are 126 Class A networks each with 16,777,214 (224 -2) possible hosts for a total of 2,147,483,648 (231) unique IP addresses. Class A networks for half of the total available IP addresses. In Class A networks, the high order bit value (the very first binary number) in the first octet is always 0.

Loopback:The IP address 127.0.0.1 is used as the loopback address. This means that it is used by the host computer to send a message back to itself. It is commonly used for troubleshooting and network testing.

Class B:Class B is used for medium-sized networks. A good example is a large college campus. IP addresses with a first octet from 128 to 191 are part of this class. Class B addresses also includes the second octet as part of the Net identifier. The other two octets are used to identify each host. This means that there are 16,384 (214) Class B networks each with 65,534 (216 -2) possible hosts for a total of 1,073,741,824 (230) unique IP addresses. Class B networks make up a quarter of the total available IP addresses. Class B networks have a first bit value of 1 and a second bit value of 0 in the first octet.

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Class C:– Class C addresses are commonly used for small to mid-size businesses. IP addresses with a first octet from 192 to 223 are part of this class. Class C addresses also include the second and third octets as part of the Net identifier. The last octet is used to identify each host. This means that there are 2,097,152 (221) Class C networks each with 254 (28 -2) possible hosts for a total of 536,870,912 (229) unique IP addresses. Class C networks make up an eighth of the total available IP addresses. Class C networks have a first bit value of 1, second bit value of 1 and a third bit value of 0 in the first octet.

Class D:– Used for multicasts, Class D is slightly different from the first three classes. It has a first bit value of 1, second bit value of 1, third bit value of 1 and fourth bit value of 0. The other 28 bits are used to identify the group of computers the multicast message is intended for. Class D s for 1/16th (268,435,456 or 228) of the available IP addresses.

Class E:– Class E is used for experimental purposes only. Like Class D, it is different from the first three classes. It has a first bit value of 1, second bit value of 1, third bit value of 1 and fourth bit value of 1. The other 28 bits are used to identify the group of computers the multicast message is intended for. Class E s for 1/16th (268,435,456 or 228) of the available IP addresses.

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Fig 3.1 IP address

Broadcast:Messages that are intended for all computers on a network are sent as broadcasts. These messages always use the IP address 255.255.255.255.

Address:The unique number ID assigned to one host or interface in a network.

Subnet:A portion of a network sharing a particular subnet address.

Subnet mask:A 32-bit combination used to describe which portion of an address refers to the subnet and which part refers to the host.

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IP addressing: Given an IP address, its class can be determined from the three high-order bits. Figure shows the significance in the three high order bits and the range of addresses that fall into each class. For informational purposes, Class D and Class E addresses are also shown.

Figure 3.2: IP Address Main features Of IP are  Packetization: Data from an upper layer protocol is encapsulated inside one or more packets/datagrams (the are basically synonymous in IP). No circuit setup is needed before a host tries to send packets to a host it has previously not communicated with (this is the point of a packet-switched network), thus IP (Internet protocol) is a connectionless protocol. Page 17 of 45

 IP Packet Format: An IP packet contains several types of information.  Version- Indicates the version of IP currently used.  IP Header Length (IHL)- Indicates the datagram header length in 32-bit words  Type-of-Service- Specifies how an upper-layer protocol would like a current datagram to be handled, and assigns datagrams various levels of importance.  Total Length Specifies the length, in bytes, of the entire IP packet, including the data and header.  Identification- Contains an integer that identifies the current datagram. This field is used to help piece together datagram fragments.  Flags- Consists of a 3-bit field of which the two low-order (least-significant) bits control fragmentation. The low-order bit specifies whether the packet can be fragmented. The middle bit specifies whether the packet is the last fragment in a series of fragmented packets. The third or high-order bit is not used.  Fragment Offset- Indicates the position of the fragment’s data relative to the beginning of the data in the original datagram, which allows the destination IP process to properly reconstruct the original datagram.  Time-to-Live- Maintains a counter that gradually decrements down to zero, at which point the datagram is discarded. This keeps packets from looping endlessly.  Protocol- Indicates which upper-layer protocol receives incoming packets after IP processing is complete. Page 18 of 45

 Header Checksum- Helps ensure IP header integrity.  Source Address- Specifies the sending node.  Destination Address- Specifies the receiving node.  Options- Allows IP to various options, such as security.

3.2 Subnetting: By extending the mask to be 255.255.255.224, you have taken three bits (indicated by "sub") from the original host portion of the address and used them to make subnets. With these three bits, it is possible to create eight subnets. With the remaining five host ID bits, each subnet can have up to 32 host addresses, 30 of which can actually be assigned to a device since host ids of all zeros or all ones are not allowed (it is very important to this). So, with this in mind, these subnets have been created. 204.17.5.0 255.255.255.224 host address range 1 to 30 204.17.5.32 255.255.255.224 host address range 33 to 62 204.17.5.64 255.255.255.224 host address range 65 to 94 204.17.5.96255.255.255.224 host address range 97 to 126 204.17.5.128 255.255.255.224 host address range 129 to 158 204.17.5.160255.255.255.224 host address range 161 to 190 204.17.5.192 255.255.255.224 host address range 193 to 222 204.17.5.224 255.255.255.224 host address range 225 to 254

Types of Subnetting: 

Fixed Length Subnet Mask (FLSM)



Variable Length Subnet Mask (VLSM)

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FLSM: Steps of Subnetting for FLSM For IP address 192.168.10.0 (Class C) 

Identify the total no. of subnets 2^n = no.of subnets



Where n are the no.s and borrowed bytes from host ID portion. Let we are given that we have to make 4 subnets. Therefore 2^n =4 i.e n=2



To idettify the total no. of the valid hosts for each subnet.



2^m-2= no.of valid hosts. Where m are the remaining no. of bits in host ID 2^62=62



Calculate the subnet mask and range



Subnet

mask

for

n/w

192.168.10.0/26

is

11111111.11111111.11111111.1100000000 ie 255.255.255.192 

range=> 256-192=64



Identify the total no of subnets, no. of valid hosts and the broadcast address.

VLSM In VLSM to allocate IP addresses to subnets depending upon the no. of hosts. The network having more no of hosts is given priority and the one having least no of host comes at last and for each network the subnet is assigned separately.

Fig 3.3: variable subnet mask Page 20 of 45

VLSM Example: Given the same network and requirements as in develop a sub-netting scheme using VLSM, given: netA: must 14 hosts netB: must 28 hosts netC: must 2 hosts netD: must 7 hosts netE: must 28 host Determine what mask allows the required number of hosts. netA: requires a /28 (255.255.255.240) mask to 14 hosts netB: requires a /27 (255.255.255.224) mask to 28 hosts netC: requires a /30 (255.255.255.252) mask to 2 hosts netD*: requires a /28 (255.255.255.240) mask to 7 hosts netE: requires a /27 (255.255.255.224) mask to 28 hosts A /29 (255.255.255.248) would only allow 6 usable host addresses Therefore netD requires a /28 mask. The easiest way to assign the subnets is to assign the largest first. For example, you can assign in this manner: netB: 204.15.5.0/27 host address range 1 to 30 netE: 204.15.5.32/27 host address range 33 to 62 netA: 204.15.5.64/28 host address range 65 to 78 netD: 204.15.5.80/28 host address range 81 to 94 netC: 204.15.5.96/30 host address range 97 to 98

3.3 Frame Relay: Frame Relay is still one of the most popular WAN services deployed over the past decade, and there’s a good reason for this—cost. By default, Frame Relay is classified as a non-broadcast multi-access (NBMA) network, meaning it doesn’t send any broadcasts like RIP updates across the network. Frame Relay has at its roots a technology called X.25, and it essentially incorporates the components of X.25 that are still relevant to today’s reliable and relatively “clean” telecommunications networks while leaving out the no-longer-needed error-correction components. It’s substantially more complex than the simple leased-line networks you learned about when I discussed the HDLC and PPP protocols, but is still relevant when looking at event the most commonly used networks Page 21 of 45

from providers such as o2, or other similar companies. The leased-line networks are easy to conceptualize - but not so much when it comes to Frame Relay. It can be significantly more complex and versatile, which is why it’s often represented as a “cloud” in networking graphics. You won’t be using the encapsulation HDLC or encapsulation PPP command to configure it.Frame Relay doesn’t work like a point-to-point leased line (although it can be made to look and act like one).Frame Relay is usually less expensive than leased lines are, but there are some sacrifices to make to get that savings. If, for example, you had to add seven remote sites to the corporate office and had only one free serial port on your router—it’s Frame Relay to the rescue! Of course, I should probably mention that you now also have one single point of failure, which is not so good. But Frame Relay is used to save money, not to make a network more resilient. Take a look at Fig. 43 to get an idea of what a network looked like before and after Frame Relay.

Fig 3.4: Frame Relay

3.4 VLAN: As networks have grown in size and complexity, many companies have turned to virtual local area networks (VLANs) to provide some way of structuring this growth logically. Basically, a VLAN is a collection of nodes that are grouped together in a single broadcast domain that is based on something other than physical location. Here are some common reasons why a company might have VLANs: Page 22 of 45



Security - Separating systems that have sensitive data from the rest of the network decreases the chances that people will gain access to information they are not authorized to see.



Projects/Special applications - Managing a project or working with a specialized application can be simplified by the use of a VLAN that brings all of the required nodes together.



Performance/Bandwidth - Careful monitoring of network use allows the network to create VLANs that reduce the number of router hops and increase the apparent bandwidth for network s.



Broadcasts/Traffic flow - Since a principle element of a VLAN is the fact that it does not broadcast traffic to nodes that are not part of the VLAN, it automatically reduces broadcasts. Access lists provide the network with a way to control who sees what network traffic. An access list is a table the network creates that lists which addresses have access to that network.



Departments/Specific job types - Companies may want VLANs set up for departments that are heavy network s (such as multimedia or engineering), or a VLAN across departments that is dedicated to specific types of employees (such as managers or sales people).

3.5 Spanning Tree Protocol (STP) A robust network design not only includes efficient transfer of packets or frames, but also considers how to recover quickly from faults in the network. In a Layer 3 environment, the routing protocols in use keep track of redundant paths to a destination network so that a secondary path can be used quickly if the primary path fails. Layer 3 routing allows many paths to a destination to remain up and active, and allows load sharing across multiple paths.

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In a Layer 2 environment (switching or bridging), however, no routing protocols are used, and active redundant paths are neither allowed nor desirable. Instead, some form of bridging provides data transport between networks or switch ports. The Spanning Tree Protocol (STP) provides network link redundancy so that a Layer 2 switched network can recover from failures without intervention in a timely manner. The STP is defined in the IEEE 802.1D standard. Preventing Loops with Spanning Tree Protocol Bridging loops form because parallel switches (or bridges) are unaware of each other. STP was developed to overcome the possibility of bridging loops so that redundant switches and switch paths could be used for their benefits. Basically, the protocol enables switches to become aware of each other so they can negotiate a loop-free path through the network. Loops are discovered before they are made available for use, and redundant links are effect shut down to prevent the loops from forming. In the case of redundant links, switches can be made aware that a link shut down for loop prevention should be brought up quickly in case of a link failure. STP is communicated among all connected switches on a network. Each switch executes the spanning-tree algorithm based on information received from other neighbouring switches. The algorithm chooses a reference point in the network and calculates all the reduct paths to that reference point. When redundant paths are found, the spanning-tree algorithm picks one path by which to forward frames and disables, or blocks, forwarding on the other redundant paths. As its name implies, STP computes a tree structure that spans all switches in a subnet or network. Redundant paths are placed in a Blocking or Standby state to prevent frame forwarding. Page 24 of 45

The switched network is then in a loop-free condition. However, if a forwarding port fails or becomes disconnected, the spanning-tree algorithm re computes the spanning tree topology so that the appropriate blocked links can be reactivated. How STP Works? Electing a Root Bridge For all switches in a network to agree on a loop-free topology, a common frame of reference must exist to use as a guide. This reference point is called the root bridge. (The term bridge continues to be used even in a switched environment because STP was developed for use in bridges. Therefore, when you see bridge, think switch.) An election process among all connected switches chooses the root bridge. Each switch has a unique bridge ID that identifies it to other switches. The bridge ID is an 8-byte value consisting of the following fields: Bridge Priority (2 bytes)—The priority or weight of a switch in relation to all other switches. The Priority field can have a value of 0 to 65,535 and defaults to 32,768 (or 0x8000) on every Catalyst switch. MAC Address (6 bytes)—The MAC address used by a switch can come from the Supervisor module, the backplane, or a pool of 1,024 addresses that are assigned to every supervisor or backplane, depending on the switch model. In any event, this address is hard-coded and unique, and the cannot change it. As an example, consider the small network shown in Figure. For simplicity, assume that each Catalyst switch has a MAC address of all 0s, with the last hex digit equal to the switch label.

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Fig 3.5: MAC address In this network, each switch has the default bridge priority of 32,768. The switches are interconnected Fast Ethernet links. All three switches try to elect themselves as the root, but all of them have equal Bridge Priority values. The election outcome produces the root bridge, determined by the lowest MAC address—that of Catalyst A. Electing Root Ports Now that a reference point has been nominated and elected for the entire switched network, each non root switch must figure out where it is in relation to the root bridge. This action can be performed by selecting only one root port on each non root switch. The root port always points toward the current root bridge. STP uses the concept of cost to determine many things. Selecting a root port involves evaluating the root path cost. This value is the cumulative cost of all the links leading to the root bridge. A particular switch link also has a cost associated with it, called the path cost. To understand the difference between these values, that only the root path cost is carried inside the BPDU. As the root path cost travels along, other switches can modify its value to make it cumulative. The path cost, however, is not contained in the

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BPDU. It is known only to the local switch where the port (or “path” to a neighboring switch) resides. The original IEEE 802.1D standard defined path cost as 1000 Mbps divided by the link bandwidth in megabits per second. These values are shown in the center column of the table. Modern networks commonly use Gigabit Ethernet and OC-48 ATM, which are both either too close to or greater than the maximum scale of 1000 Mbps. The IEEE now use sa nonlinear scale for path cost The root path cost value is determined in the following manner: 1. The root bridge sends out a BPDU with a root path cost value of 0 because its ports sit directly on the root bridge. 2. When the next-closest neighbor receives the BPDU, it adds the path cost of its own port where the BPDU arrived. (This is done as the BPDU is received.) 3. The neighbor sends out BPDUs with this new cumulative value as the root path cost. 4. The root path cost is incremented by the ingress port path cost as the BPDU is received at each switch down the line. 5. Notice the emphasis on incrementing the root path cost as BPDUs are received. When computing the spanning-tree algorithm manually, to compute a newroot path cost as BPDUs come in to a switch port, not as they go out.

Fig 3.6: Electing Root Bridge Page 27 of 45

Electing Designated Ports A starting or reference point has been identified, and each switch “connects” itself toward the reference point with the single link that has the best path. A tree structure is beginning to emerge, but links have only been identified at this point. All links still are connected and could be active, leaving bridging loops. To remove the possibility of bridging loops, STP makes a final computation to identify one designated port on each network segment. Suppose that two or more switches have ports connected to a single common network segment. If a frame appears on that segment, all the bridges attempt to forward it to its destination. In each determination process discussed so far, two or more links might have identical root path costs. This results in a tie condition, unless other factors are considered. All tie STP decisions are based on the following sequence of four conditions: 1. Lowest root bridge ID 2. Lowest root path cost to root bridge 3. Lowest sender bridge ID 4. Lowest sender port ID

Fig 3.7: Electing Designated Ports Page 28 of 45

The three switches have chosen their designated ports (DP) for the following reasons: Catalyst A Because this switch is the root bridge, all its active ports are designated ports, by definition. At the root bridge, the root path cost of each port is 0. Catalyst B Catalyst A port 1/1 is the DP for the Segment A–B because it has the lowest root path cost (0). Catalyst B port 1/2 is the DP for segment B–C. The root path cost for each end of this segment is 19, determined from the incoming BPDU on port 1/1. Because the root path cost is equal on both ports of the segment, the DP must be chosen by the next criteria— the lowest sender bridge ID. When Catalyst B sends a BPDU to Catalyst C, it has the lowest MAC address in the bridge ID. Catalyst C also sends a BPDU to Catalyst B, but its sender bridge ID is higher. Therefore, Catalyst B port 1/2 is selected as the segment’s DP. Catalyst C Catalyst A port 1/2 is the DP for Segment A–C because it has the lowest root path cost (0). Catalyst B port 1/2 is the DP for Segment B–C. Therefore, Catalyst C port 1/2 will be neither a root port nor a designated port. As discussed in the next section, any port that is not elected to either position enters the Blocking state. STP States To participate in STP, each port of a switch must progress through several states. A port begins its life in a Disabled state, moving through several ive states and, finally, into an active state if allowed to forward traffic. The STP port states are as follows: Disabled—Ports that are istratively shut down by the network , or by the system because of a fault condition, are in the Disabled state. This state is special and is not part of the normal STP progression for a port.

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Blocking—After a port initializes, it begins in the Blocking state so that no bridging loops can form. In the Blocking state, a port cannot receive or transmit data and cannot add MAC addresses to its address table. Instead, a port is allowed to receive only BPDUs so that the switch can hear from other neighboring switches. In addition, ports that are put into standby mode to remove a bridging loop enter the Blocking state. Listening—A port is moved from Blocking to Listening if the switch thinks that the port can be selected as a root port or designated port. In other words, the port is on its way to begin forwarding traffic. In the Listening state, the port still cannot send or receive data frames. However, the port is allowed to receive and send BPDUs so that it can actively participate in the Spanning Tree topology process. Here, the port finally is allowed to become a root port or designated port because the switch can the port by sending BPDUs to other switches. If the port loses its root port or designated port status, it returns to the Blocking state. Learning—After a period of time called the Forward Delay in the Listening state, the port is allowed to move into the Learning state. The port still sends and receives BPDUs as before. In addition, the switch now can learn new MAC addresses to add to its address table. This gives the port an extra period of silent participation and allows the switch to assemble at least some address information. The port cannot yet send any data frames, however. Forwarding—After another Forward Delay period of time in the Learning state, the port is allowed to move into the Forwarding state. The port now can send and receive data frames, collect MAC addresses in its address table, and send and receive BPDUs. The port is now a fully functioning switch port within the spanning-tree topology. that a switch port is allowed into the Forwarding state only if no redundant links (or loops) are detected and if the port has the best path to the root bridge as the root port or designated port. Page 30 of 45

3.6 Routing: Routing is the process of directing packets from a source node to a destination node on a different network. It is of two types:

Static routing: The process of manually adding routes in each router's routing table. The configures the destination network, next hop, and appropriate metrics. The route doesn't change until the network changes it.

Advantages:

No overhead on router U.



No bandwidth usage between links.



Security (only adds routes).

Disadvantages:

must really understand internetwork and how each router is connected.



If a new network is added, must update all routers. Not practical on large networks as it is time intensive.

Dynamic routing: Dynamic routes adjust to changes within the internetwork environment automatically. When network changes occur, routers begin to converge by recalculating routes and distributing route updates. The route update messages spread through the network, which causes other routers to recalculate their routes. The process continues until all routes have converged. Uses protocols to find and update routes on a routing table. It uses U time and consumes bandwidth between links. The routing protocol defines the rules used by the routers when they communicate with each other. There are two types of routing protocols on internetworks, Interior Gateway Protocol (IGP) and Exterior Gateway Page 31 of 45

Protocol (EGP). IGP is used in networks in the same istrative domain. EGPs are used to communicate between the domains.

3.7 Routed protocols: Routed protocols are nothing more than data being transported across the networks. Routed protocols include: 

Internet Protocol



Telnet



Remote Procedure Call (RPC)



SNMP



SMTP



Novell IPX



Open Standards Institute networking protocol



DECnet



Appletalk



Banyan Vines



Xerox Network System (XNS)

3.8 Routing protocols: Routing Protocols are the software that allow routers to dynamically and learn routes, determine which routes are available and which are the most efficient routes to a destination. Routing protocols used by the Internet Protocol suite include: 

Routing Information Protocol (RIP and RIP II)



Open Shortest Path First (OSPF) Page 32 of 45



Intermediate System to Intermediate System (IS-IS)



Interior Gateway Routing Protocol (IGRP)



Enhanced Interior Gateway Routing Protocol (EIGRP)

RIP (Routing Information Protocol): RIP (Routing Information Protocol) is a widely-used protocol for managing router information within a self-contained network such as a corporate local area network (LAN) or an interconnected group of such LANs. RIP is classified by the Internet Engineering Task Force (IETF) as one of several internal gateway protocols (Interior Gateway Protocol). Using RIP, a gateway host (with a router) sends its entire routing table (which lists all the other hosts it knows about) to its closest neighbor host every 30 seconds. The neighbor host in turn will the information on to its next neighbor and so on until all hosts within the network have the same knowledge of routing paths, a state known as network convergence. RIP uses a hop count as a way to determine network distance. (Other protocols use more sophisticated algorithms that include timing as well.) Each host with a router in the network uses the routing table information to determine the next host to route a packet to for a specified destination. RIP is considered an effective solution for small homogeneous networks. For larger, more complicated networks, RIP's transmission of the entire routing table every 30 seconds may put a heavy amount of extra traffic in the network. The major alternative to RIP is the Open Shortest Path First Protocol (OSPF). OSPF (Open Shortest Path First): Open Shortest Path First is a true link state protocol developed as an open standard for routing IP across large multi-vendor networks. A link state protocol will send link state ments to all connected neighbors of the same area to communicate route information. Each OSPF enabled router, when started, will send hello packets to all directly connected OSPF routers. The hello packets contain information such as router Page 33 of 45

timers, router ID and subnet mask. If the routers agree on the information they become OSPF neighbors. Once routers become neighbors they establish adjacencies by exchanging link state databases. Routers on point-to-point and point-to-multipoint links (as specified with the OSPF interface typesetting) automatically establish adjacencies. EIGRP (Enhanced Interior Gateway Routing Protocol): Enhanced Interior Gateway Routing Protocol is a hybrid routing protocol developed by Cisco systems for routing many protocols across an enterprise Cisco network. It has characteristics of both distance vector routing protocols and link state routing protocols. It is proprietary which requires that you use Cisco routers. EIGRP will route the same protocols that IGRP routes (IP, IPX) and use the same composite metrics as IGRP to select a best path destination. As well there is the option to load balance traffic across equal or unequal metric cost paths. Summarization is automatic at a network class address however it can be configured to summarize at subnet boundaries as well. Redistribution between IGRP and EIGRP is automatic as well. There is for a hop count of 255 and variable length subnet masks.

3.9 TELNET: Telnet is a protocol which is part of the T/IP suite. It is quite similar to the UNIX r program. Telnet allows you to control a remote computer from your own one. It is terminal emulation software. In the old days hard drives were humongous and expensive and there were no personal computers. To make use of existing computers you had to lease hard rive space and use terminals to operate the system. For developers this was great because computing became lots cheaper. You needed a server and many connections could be made. With telnet u can emulate this type of distributed computing and for example operate a supercomputer from a distance.

3.10 DH (Dynamic Host Configuration Protocol): DH (Dynamic Host Configuration Protocol) is a communications protocol that lets network s centrally manage and automate the assignment of Internet Protocol (IP) addresses in an organization's network. Using the Internet Protocol, each Page 34 of 45

machine that can connect to the Internet needs a unique IP address, which is assigned when an Internet connection is created for a specific computer. Without DH, the IP address must be entered manually at each computer in an organization and a new IP address must be entered each time a computer moves to a new location on the network. DH lets a network supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network.

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Chapter no. 4 ABOUT OUR PROJECT 4.1 Introduction: The project is a communication model which represents a mesh of networking elements including routers, switches, servers (DH and DNS in this model), frame relay, access points, computers and different types of cables to connect them. The project is based on the technology of Hardware and Networking, typically on CCNA (Cisco Certified Network Associate). The essence of this project lies in the configuration of these network elements so that they can communicate with each other as required by the network . The kind of access rights given to each network element and the services each computer can use depends on the configuration done by the network . The project typically shows the communication model for an organization with its two branches and one headoffice. The objective of planning such a network model is to make easy the task of actual set up of a network. The communication model prepared (as in this project) acts as a guide while connecting the real computers and other network devices like routers, switches, and different types of servers. The detailed objectives are given as: 

Easy to set up actual network: It becomes so easy to set up an network that is

prepared in the model. It acts in similar way as a map of a building to be built. As it is so difficult job to construct a house whose map is not available, similarly it is very cumbersome job to start connecting a lot of networking devices available in absence of a model. 

IP addressing: Asg the IP addresses to the network is the first and the most

important task. IP addresses are actually unique addresses to each network element. It is Page 36 of 45

the unique code that identified the network element in the network. In the network model, we have all the elements visible to us at a time, so we can assign them IP addresses easily, but the same job will be difficult to do on a group of computers, at different locations. 

Easy to make changes and extend the network: It becomes easy to make further

changes in the network if is network model is available. We can have a look on the settings and the implementations already done on it and so can modify it. the same job is really hectic to be done on actual network and can result the introduction of errors in it. 

Easy to understand: A network can be easily understood for its structure,

characteristics and configuration from the network model. In the absence of this, each network element will need to be visited at different locations and checked for its configuration. 

Estimation of the computers and hardware required: Any organization first prepares a

network model, before actual set up. The main things like number of departments, ad number of computers in each department etc. are taken care of while preparing the network model. After the network model is ready, the organization can easily estimate the cost required to have such network, the type of network elements required and the number of these, thereby avoiding the wastage. 

Cabling: Different network elements needed to be connected by different types of

cables. In actual, mistake can be done while connecting different elements with wrong type of cables and on the wrong interfaces as well. But a network model provides the types of cables and the detail of interfaces on which they should be connected, which helps a lot while its actual implementation. 

Configuration of network: A lot of computers, routers and switches connected together can’t

be called a network. Configuration is to be done on each network element that decides the Page 37 of 45

working of network. All that configuration is already done in the network model. It is easy to do the configuration on the model itself than to do the same on the actual network first time. This will cause a lot of time waste and errors as well. When we have a network model, we can easily see the configuration done in the model and can implement the same on the actual network. This reduces the errors and saves the time. 

Routing protocols: Whenever a group of elements are connected in a network, a routing

protocol must be used in order to tell each network element the way or path to use for transmitting a packet from a particular source to the destination. The routing protocols are also implemented in a communication model much easily. The software used for the development of the project is “cisco packet tracer” whose opening window is shown below in the figure. This work area is used to prepare the network model. Here we can select the necessary hardware needed to prepare the model and also can alter its properties such as, we can add interfaces to the routers, wireless LAN cards to the computers.

Fig 4.1: Cisco Packet Tracer Before coming to the project, here are some main points that demonstrate the features of packet tracer, which will be required later to operate the project. Whenever we place the cursor on the terminal, the packet tracer shows its IP address allocated, gateway, and all other properties which are assigned to it when it works within a network. Page 38 of 45

Same is the case, when the cursor is pointed on the router, which is also a networking element, its various interfaces, active interfaces, IP address, MAC address its hostname etc. are shown to enhance the understandability At the bottom of the packet tracer screen, various devices are available for constructing a communication model. When any device is selected, its corresponding models are available. Example, when a router is selected, its models in different series eg. 2500, 2600 are displayed. Same in the case of terminals, different kinds of computers like desktops, laptops, telephones that can be used as data terminal devices in a network are available.

Fig 4.2: The end devices available in Packet Tracer two similar kind of devices, eg both DTE or DCE, then a cross cable (shown with dotted lines) will be used. And when different types of devices are being connected, like one DTE and other DCE, the n serial cables will be used (with an exception of routers).

Figure 4.3: The connections available in the Packet Tracer

4.2 Project Details: The network model which we are deg will be consisting of routers, switches, computers, servers, hubs. All the above elements together represent an organization. In

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project, different technology of networking is implemented. These technologies are like named below: 

Routing protocol : OSPF (Open Shortest Path First Protocol)



VLAN (Virtual Local Area Networks)



ACL(Access Control List) both standard and extended ACL implementation



DNS (Domain Name Space)



HTTP



DNS



DH server



Configuration of routers, switches, servers, access points and PC’s.

Here in the figure, the complete model is shown which has been constructed in the project. Each part of the organization has been given a different background color and according to the configuration done on it.

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Fig 4.4: Project Outlay

When ever any computer in the communication model is selected, packet tracer shows the window, shown in the figure below. This window basically shows the options that any computer have. E.g. command prompt, option to allocate IP address etc. we can use any of the service to ensure that the terminal connected is working correctly in the network.

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Fig 4.5: The options available for a Laptop/ Terminal Below is the example given to check if one computer is communicating to another. This is done by using “ping” command in the command prompt. Typing the keyword “ping” and then the IP address shows the result. The reply is shown from the address to which we wanted to communicate, if they are connected in right manner, or not blocked explicitly, otherwise, failure is shown.

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Fig 4.6: Using Ping Command

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Chapter 5 Conclusion and Future Scope Computer Networking is a very vast project in the present developing era of electronics and communication. Now days, computers are used in a wider range. All the organizations are using multiple computers within their departments to perform their day to day work. Computer network allows the to share data, share folders and files with other s connected in a network. Computer Networking has bound the world in a very small area with it wide networking processes like LAN, MAN, WAN. Networking inside your organization is valuable also. In larger companies, many people never meet others in the organization that can facilitate solving problems or getting resources. This project is forward compatible as we can add more branches at low cost and high efficiency with effective communication between head office and various branches of an organization.

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References The following web links are visited for the theory reference: http://www.cisco.com/web/learning/netacad/course_catalog/PacketTracer.html http://www.cisco.com/web/learning/netacad/index.html http://www.cisco.com/en/US/docs/internetworking/technology/handbook/ito_doc.html http://netcert.tripod.com/ccna/routers/routeprotocols.html http://www.livinginternet.com/i/iw_route.htm http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol http://www.isc.org/software/dh http://www.cisco.com/web/IN/products/routers/index.html http://www.webopedia.com/TERM/R/router.html

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