Follow the submission instructions for each exercise and ensure that you meet the deadline, use the correct submission process and submit your work to the correct place. For some laboratory tasks you will be instructed by the lab instructor to submit hardcopy work. To avoid disappointment, you should carefully follow the instructions of the course unit lecturer, and ensure that you submit the work:

by the required deadline

to the designated hand-in place

in the required format

Electronically as well, if required, again in the required format.

This course looks into Computer Communication and Networks. This course introduces basic concepts in networking, the OSI model, TCP/IP protocol suit, Switching Strategies, Multiplexing, error detection and correction codes, flow control, , medium access control, IPv4 Addressing, routing, Transport layer protocols (TCP,UDP) and brief description of Application layer protocols. The course also includes a few lab sessions on Packet tracer in order to familiarize the students with practical networking aspects.

Objective

The objective of this course is:-

To familiarize students with challenges and basics of computer/network communication

To teach students IP address version 4.

To enable students understanding error detection and troubleshooting of networks.

To teach about the operations and configuration of the protocols being used inside the Internet.

To teach students how to design and administer and configure the networks using different routing protocols.

Lab-1

Basic Commands

Ping explained

pingis perhaps the most commonly used tool to troubleshoot a network.Ping (Packet Internet Groper)is included with most operating systems. It is invoked using a ping command and usesICMP (Internet Control Message Protocol)to reports errors and provides information related to IP packet processing. Ping works by sending an ICMP echo request message to the specified IP address. If the computer with the destination IP address is reachable, it responds with an ICMP echo reply message.

A ping command usually outputs some other information about a network performance, e.g. a round-trip time, a time to send an ICMP request packetand receive an ICMP reply packet.

Here is an output of the ping command from Windows 7:

In the example above we have pinged the ip address10.10.100.1. By default, ping on Windows sends four ICMP request packets. As you can see from the output above, the host with the IP address of 10.10.100.1 is reachable and has replied with four ICMP reply packets. You can also see that the remote host has replied within 1 ms (time<1ms), which indicates that the network is not congested.

Traceroute explained

Tracerouteis a command-line interface based tool used to identify the path used by a packet to reach its target. This tool also uses ICMP messages, but unlike ping, it identifies every router in a path taken by the packets. Traceroute is useful when troubleshooting network problems because it can help identify where exactly the problem is.You can figure out which router in the path to an unreachable target should be examined more closely as the probable cause of the network's failure.

Traceroute sends a series of ICMP echo request packets to a destination. First series of messages has a Time to Live (TTL) parameter set to 1, which means that the first router in a path will discard the packet and send an ICMP Time Exceeded message. TTL is then increased by one until the destination host is reached and an ICMP echo reply message is received. Originating host can then use received ICMP messages to identify all routers in a path.

NOTE The traceroute command on Windows is namedtracert. On Unix and Cisco IOS traceroute it is invoked using thetraceroutecommand.

Here is an example of using thetracertcommand in Windows:

In the output above you can see that thetraceroutecommand has listed the IP addresses of all of the routers in the path.

Traceroute on Unix-like operating systems

Traceroute command on Unix works slighty different than the Windows version. It uses UDP packets with a large destination port number (33434 to 33534) that is unlikely to be used by any application at the destination host. Like the Windows version of the command, traceroute on Unix uses TTL to get the IP addresses of the intermediary routers. When a destination host is reached, it replies with an ICMP port unreachable message.

Tasks:

Task 1:Type ipconfig command on CMD and find IP address and subnet mask.

Task 2:ping host IP address and take screen shot.

Task 3:ping Yahoo.com and Google.com also find IP address of both sites.

Task 4: type exit command on CMD prompt and write note down output.

Task 5: find system mac address.

Solution 1:

Solution 2:

Solution 3:

Yahoo.com = [98.137.246.8]

Google.com = [216.58.207.14]

Solution 4:

Use to exit the command prompt.

Solution 5:

Use command ipconfig/all or getmac for mac address.

Lab-2

Networking Basics

What is a network?

A computer network can be described as a system of interconnected devices that can communicate using some common standards (calledprotocols). These devices communicate to exchange resources (e.g. files and printers) and services.

Here is an example network consisting of two computers connected together:

In the example above, the two computers are directly connected using a cable. This small network can be used to exchange data between just these two computers.

What if we want to expand our network? Then we can use a network device, either a switch or a hub, to connect more than two computers together:

Now all of the devices on the network can communicate with each other.

We'll talk more about hubs and switches in just a moment. For now, just remember that these devices serve as a central point to which all of the computers connect to.

OSI & TCP/IP models

OSI model

OSI(Open Systems Interconnection) model was created by theInternational Organization for Standardization (ISO), an international standard-setting body. It was designed to be a reference model for describing the functions of a communication system. The OSI model provides a framework for creating and implementing networking standards and devices and describes how network applications on different computers can communicate through the network media.

The OSI model has seven layers, with each layer describing a different function of data traveling through a network. Here is the graphical representation of these layers:

The layers are usually numbered from the last one, meaning that the Physical layer is considered to be the first layer. It is useful to remember these layers, since there will certainly be a couple of questions on the CCNA exam regarding them. Most people learn the mnemonic Please Do Not Throw Sausage Pizza Away":

So, what is the purpose of these layers? They are most commonly used by vendors. They enable them to implement some functionality into a networking device, which then enables easier interoperability with devices from other vendors.

Here is a brief description of each of the layers of the OSI model.

Physical- defines how to move bits from one device to another. It details how cables, connectors and network interface cards are supposed to work and how to send and receive bits.

Data Link- encapsulates a packet in a frame. A frame contains a header and a trailer that enable devices to communicate. A header (most commonly) contains a source and destination MAC address. A trailer contains the Frame Check Sequence field, which is used to detect transmission errors. The data link layer has two sublayers:

1.Logical Link Control- used for flow control and error detection.

2.Media Access Control- used for hardware addressing and for controlling the access method.

Network- defines device addressing, routing, and path determination. Device (logical) addressing is used to identify a host on a network (e.g. by its IP address).

Transport- segments big chunks of data received from the upper layer protocols. Establishes and terminates connections between two computers. Used for flow control and data recovery.

Session- defines how to establish and terminate a session between the two systems.

Presentation- defines data formats. Compression and encryption are defined at this layer.

Application- this layer is the closest to the user. It enables network applications to communicate with other network applications.

It is a common practice to reference a protocol by the layer number or layer name. For example, HTTPS is referred to as an application (or Layer 7) protocol. Network devices are also sometimes described according to the OSI layer on which they operate - e.g. a Layer 2 switch or a Layer 7 firewall.

The following table shows which protocols reside on which layer of the OSI model:

TCP/IP model

The TCP/IP model was created in the 1970s by theDefense Advance Research Project Agency (DARPA)as an open, vendor-neutral, public networking model. Just like the OSI model, it describes general guidelines for designing and implementing computer protocols. It consists of four layers: Network Access, Internet, Transport, and Application:

The following picture show the comparison between the TCP/IP model and OSI model:

As you can see from the picture above, the TCP/IP model has fewer layers than the OSI model. The Application, Presentation, and Session layers of the OSI model are merged into a single layer in the TCP/IP model. Also, Physical and Data Link layers are called Network Access layer in the TCP/IP model. Here is a brief description of each layer:

Link- defines the protocols and hardware required to deliver data across a physical network.

Internet- defines the protocols for the logical transmission of packets over the network.

Transport- defines protocols for setting up the level of transmission service for applications. This layer is responsible for reliable transmission of data and the the error-free delivery of packets.

Application- defines protocols for node-to-node application communication and provides services to the application software running on a computer.

Differences between OSI and TCP/IP model

There are some other differences between these two models, besides the obvious difference in the number of layers. OSI model prescribes the steps needed to transfer data over a network and it is very specific in it, defining which protocol is used at each layer and how. The TCP/IP model is not that specific. It can be said that the OSI model prescribes and TCP/IP model describes.

Tasks:

Task 1: Verify internet connectivity.

Task 2: use tracert /? Command and display output.

Task 3: write down tracert google.com and tracert host_ip and note output.

Task 4: write down netstat command and explain output in detail.

Solution 1:

Click on Start > All Programs > Accessories > Command Prompt

OR

Click on Start > Run, type cmd and click on ok.

Use ping command to ping any other system.

Solution 2:

Solution 3:

Solution 4:

Netstat:netstat (network statistics) is a command line diagnostic tool that displays network connections (both incoming and outgoing), port numbers, connection state and protocol type etc. It can help find you any malicious or illegitimate connections established with your machine and also help finding installed rootkits.

Lab-3

Cisco Packet Tracer

Packet Tracer is a cross-platform visual simulation tool designed by Cisco Systems that allows users to create network topologies and imitate modern computer networks. The software allows users to simulate the configuration of Cisco routers and switches using a simulated command line interface. Packet Tracer makes use of a drag and drop user interface, allowing users to add and remove simulated network devices as they see fit.

Create the topologies in Packet tracer tool and take their screen shots. Assign IP addresses and subnet mask. Connect them with ports. Using Place Notefeature in packet tracer, write the IP address and connected port number on each device. Include the snapshots of ping result also in both topologies. Save the topologies.

1.Connect two system without any devices

2.Connect more than two system by suing hub

3.Connect more than two system by using switch

Lab-4

Topologies

Network topology is the arrangement of the elements of a communication network.

Types of Network Topology

Network Topology is the schematic description of a network arrangement, connecting various nodes (sender and receiver) through lines of connection.

BUS Topology

Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is calledLinear Bus topology.

Features of Bus Topology

1.It transmits data only in one direction.

2.Every device is connected to a single cable

Advantages of Bus Topology

1.It is cost effective.

2.Cable required is least compared to other network topology.

3.Used in small networks.

4.It is easy to understand.

5.Easy to expand joining two cables together.

Disadvantages of Bus Topology

1.Cables fails then whole network fails.

2.If network traffic is heavy or nodes are more the performance of the network decreases.

3.Cable has a limited length.

4.It is slower than the ring topology.

RING Topology

It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.

Features of Ring Topology

1.A number of repeaters are used for Ring topology with large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.

2.The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is calledDual Ring Topology.

3.In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.

4.Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node.

Advantages of Ring Topology

1.Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.

2.Cheap to install and expand

Disadvantages of Ring Topology

1.Troubleshooting is difficult in ring topology.

2.Adding or deleting the computers disturbs the network activity.

3.Failure of one computer disturbs the whole network.

STAR Topology

In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

Features of Star Topology

1.Every node has its own dedicated connection to the hub.

2.Hub acts as a repeater for data flow.

3.Can be used with twisted pair, Optical Fibre or coaxial cable.

Advantages of Star Topology

1.Fast performance with few nodes and low network traffic.

2.Hub can be upgraded easily.

3.Easy to troubleshoot.

4.Easy to setup and modify.

5.Only that node is affected which has failed, rest of the nodes can work smoothly.

Disadvantages of Star Topology

1.Cost of installation is high.

2.Expensive to use.

3.If the hub fails then the whole network is stopped because all the nodes depend on the hub.

4.Performance is based on the hub that is it depends on its capacity

MESH Topology

It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh hasn(n-1)/2physical channels to linkndevices.

There are two techniques to transmit data over the Mesh topology, they are :

1.Routing

2.Flooding

MESH Topology: Routing

In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance. Or, routing logic which has information about the broken links, and it avoids those node etc. We can even have routing logic, to re-configure the failed nodes.

MESH Topology: Flooding

In flooding, the same data is transmitted to all the network nodes, hence no routing logic is required. The network is robust, and the its very unlikely to lose the data. But it leads to unwanted load over the network.

Types of Mesh Topology

1.Partial Mesh Topology :In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.

2.Full Mesh Topology :Each and every nodes or devices are connected to each other.

Features of Mesh Topology

1.Fully connected.

2.Robust.

3.Not flexible.

Advantages of Mesh Topology

1.Each connection can carry its own data load.

2.It is robust.

3.Fault is diagnosed easily.

4.Provides security and privacy.

Disadvantages of Mesh Topology

1.Installation and configuration is difficult.

2.Cabling cost is more.

3.Bulk wiring is required.

TREE Topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

Features of Tree Topology

1.Ideal if workstations are located in groups.

2.Used in Wide Area Network.

Advantages of Tree Topology

1.Extension of bus and star topologies.

2.Expansion of nodes is possible and easy.

3.Easily managed and maintained.

4.Error detection is easily done.

Disadvantages of Tree Topology

1.Heavily cabled.

2.Costly.

3.If more nodes are added maintenance is difficult.

4.Central hub fails, network fails.

HYBRID Topology

It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).

Features of Hybrid Topology

1.It is a combination of two or topologies

2.Inherits the advantages and disadvantages of the topologies included

Advantages of Hybrid Topology

1.Reliable as Error detecting and troubleshooting is easy.

2.Effective.

3.Scalable as size can be increased easily.

4.Flexible.

Disadvantages of Hybrid Topology

1.Complex in design.

2.Costly.

Task:Create following topologies using Cisco Packet Tracer.

1.Bus, Ring, Star, Mesh

Solution:

Bust Topology

Ring Topology

Start Topology

Mesh Topology