project report on computer networks

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:

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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) Client – Server Model

(ii) Peer to Peer Model (Workgroup Model)

(iii) Domain Model

(i) 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 administrator 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

user level security in which users have to remember only one password 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, administration security. In Peer to Peer networking client use

operating system like Window 98, Window XP, Window 2000, Window Vista.

(iii) Domain Model

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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

will help to interconnect academic departments, library and computer laboratories. CAN

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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 supports 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

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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.

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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:

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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 TCP/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 joins

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

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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 supports 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

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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

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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 account 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 accounts 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 accounts 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 terms 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.

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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.

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Header Checksum- Helps ensure IP header integrity.

Source Address- Specifies the sending node.

Destination Address- Specifies the receiving node.

Options- Allows IP to support 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

remember 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


204.17.5.96255.255.255.224 host address range 97 to 126


204.17.5.160255.255.255.224 host address range 161 to 190



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 2^6-

2=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

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VLSM Example:

Given the same network and requirements as in develop a sub-netting scheme using VLSM, given:netA: must support 14 hostsnetB: must support 28 hostsnetC: must support 2 hostsnetD: must support 7 hostsnetE: must support 28 hostDetermine what mask allows the required number of hosts.netA: requires a /28 (255.255.255.240) mask to support 14 hostsnetB: requires a /27 (255.255.255.224) mask to support 28 hostsnetC: requires a /30 (255.255.255.252) mask to support 2 hostsnetD*: requires a /28 (255.255.255.240) mask to support 7 hostsnetE: requires a /27 (255.255.255.224) mask to support 28 hosts

A /29 (255.255.255.248) would only allow 6 usable host addressesTherefore 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

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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:

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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 administrator to create VLANs that reduce the number of router hops and

increase the apparent bandwidth for network users.

Broadcasts/Traffic flow - Since a principle element of a VLAN is the fact that it

does not pass broadcast traffic to nodes that are not part of the VLAN, it

automatically reduces broadcasts. Access lists provide the network administrator

with a way to control who sees what network traffic. An access list is a table the

network administrator 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 users (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.

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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 user 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, remember 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, remember 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

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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

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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 passive states and, finally, into

an active state if allowed to forward traffic. The STP port states are as follows:

Disabled—Ports that are administratively shut down by the network administrator, 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 advertise 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.

Remember 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.

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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 administrator

configures the destination network, next hop, and appropriate metrics. The route doesn't

change until the network administrator changes it.

Advantages:-

No overhead on router CPU.

No bandwidth usage between links.

Security (only administrator adds routes).

Disadvantages:-

Administrator must really understand internetwork and how each router is

connected.

If a new network is added, administrator 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 CPU 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

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Protocol (EGP). IGP is used in networks in the same administrative 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 advertise 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)

Intermediate System to Intermediate System (IS-IS)

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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 pass 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

advertisements 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

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

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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 support for a hop

count of 255 and variable length subnet masks.

3.9 TELNET:

Telnet is a protocol which is part of the TCP/IP suite. It is quite similar to the UNIX

rlogin 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 DHCP (Dynamic Host Configuration Protocol):

DHCP (Dynamic Host Configuration Protocol) is a communications protocol that lets

network administrators centrally manage and automate the assignment of Internet

Protocol (IP) addresses in an organization's network. Using the Internet Protocol, each

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 DHCP, the IP

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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.

DHCP lets a network administrator 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 (DHCP 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

administrator.

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 administrator. 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:

Assigning 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

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.

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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

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

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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.

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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 designing will be consisting of routers, switches,

computers, servers, hubs. All the above elements together represent an organization. In

project, different technology of networking is implemented. These technologies are like

named below:

Routing protocol : OSPF (Open Shortest Path First Protocol)

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VLAN (Virtual Local Area Networks)

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

DNS (Domain Name Space)

HTTP

DNS

DHCP 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.

Fig 4.4: Project Outlay

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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.

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 user to share data, share folders and files with

other users 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/dhcp

http://www.cisco.com/web/IN/products/routers/index.html

http://www.webopedia.com/TERM/R/router.html

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project report on computer networks

Documents

computer network

peer networking model

client server model

networking networking

models of networking

peer networking client

resources of server

computer industry