CN LAB REPORT

Dept. of ISE, BVBCET
Department of Information Science & Engineering,
BVBCET Hubballi

COMPUTER NETWORKING
LAB
Mahantesh Patil 2BV14IS410

Mahantesh Patil 2BV14IS410

CN LAB REPORT

Dept. of ISE, BVBCET

LAB-01
List the hardware components
1) Difference between switch and Hub:
2) Difference between SWITCH and ROUTER
3) Differences between Router and Gateway
4) What is the Difference between Subnetting and Supernetting?

HARDWARE COMPONENTS

Cables:

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Cables: which are used to connect one or more devices to computer or network. Different types of network cables are available market they are Coaxial cable, Optical fiber cable,
Twisted pair cable.

RJ-45

The most common UTP connector is RJ45 (RJ stands for registered Jack), as shown in
Figure. The RJ45 is a keyed connector, meaning the connector, meaning the connector can be inserted in only one way.

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SWITCHES:

Switches contain many ports to connect different network segments. They are similar to hubs, but offer greater performance. When a network contains a large number of devices, switches are needed instead of hubs to make sure the communications between devices does not slow down. Contrary to hubs, switches send the data it receives only to specific ports.

NIC(NETWORK INTERFACE CARD)

A network card, network adapter, or NIC is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the MAC address Each network interface card has its unique id. This is written on a chip which is mounted on the card
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Hub:

A hub is a networking device used to connect multiple devices directly to the network using cables. Each connection is called a 'port.' The connections typically consist of a fiber optic
Ethernet cable. When the hub receives data at one of its ports, it distributes the data to the other ports in the network. Typically, a hub sends all the data it receives to all the other ports.

Routers:

A router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes – from the small, four-port broadband routers that are very popular right now to the large industrial strength devices that drive the internet itself. Includes a mainframe system will need a gateway since this type of network uses different communication protocols.

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GATEWAY:

A gateway interfaces networks that use different protocols. A gateway may contain devices such as protocol translator, impedance matching devices, rate converters, etc
Gateways, also called protocol converts, can operate at any network layer. The activities of a gateway are more complex than that of the router or switch as it communicates using more than one protocol.

Bridges:
Bridges are networking devices that divide up the network into different segments to manage the amount of traffic. This prevents unnecessary traffic from entering other parts of the network and reduces congestion. As a network becomes more complex, bridges make sure your network speed doesn't drop dramatically.

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SERVER:

Server: In information technology, a server is a computer program that provides services to other computer programs in the same or other computers. A server is both a running instance of some software capable of accepting requests from clients, and the computer such a server runs on. Servers operate within a client-server architecture where "servers" are computer programs running to serve the requests of other programs, the "clients"

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Difference between switch and Hub:
Hub: In a hub, a frame is passed along or "broadcast" to every one of its ports. It doesn't matter that the frame is only destined for one port. The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination. This places a lot of traffic on the network and can lead to poor network response times.
Additionally, a 10/100Mbps hub must share its bandwidth with each and every one of its ports. So when only one PC is broadcasting, it will have access to the maximum available bandwidth. If, however, multiple PCs are broadcasting, then that bandwidth will need to be divided among all of those systems, which will degrade performance
Switch: A switch, however, keeps a record of the MAC addresses of all the devices connected to it. With this information, a switch can identify which system is sitting on which port. So when a frame is received, it knows exactly which port to send it to, without significantly increasing network response times. And, unlike a hub, a 10/100Mbps switch will allocate a full 10/100Mbps to each of its ports. So regardless of the number of PCs transmitting, users will always have access to the maximum amount of bandwidth. It's for these reasons a switch is considered to be a much better choice than a hub.

Difference between SWITCH and HUB
Hub

Switch
Physical layer. Hubs are classified as Data Link Layer.
Layer 1 devices per the OSI model.
Network switches operate at Layer 2 of the OSI model.

Layer

4/12 ports

Switch is multi port Bridge. 24/48 ports Passive Device (Without Software)

Active
Device
(With Software) &
Networking device

Ports

Device Type

Data form Transmission

Electrical signal or bits

Frame (L2 Switch)
Frame
&Packet
(L3 switch)

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Difference between Switch and Router:
Switches contain many ports to connect different network segments. They are similar to hubs, but offer greater performance. When a network contains a large number of devices, switches are needed instead of hubs to make sure the communications between devices does not slow down. Contrary to hubs, switches send the data it receives only to specific ports
Router: A router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes – from the small, four-port broadband routers that are very popular right now to the large industrial strength devices that drive the internet itself. Includes a mainframe system will need a gateway since this type of network uses different communication protocols. Difference between Routers and Gateway:
Routers: are communication devices used to connect two different networks. A router sorts incoming data and distributes it to the correct destination. For example, if you have a network within a single office building, many different devices from within the network may access resources outside the network. The best example of this would be the Internet. A router ensures that requests from within the network for information over the Internet are distributed to the correct computer within the network.
The Internet itself uses numerous routers to direct all the traffic taking place. Such routers are typically very large and heavy-duty pieces of hardware, designed to handle huge amounts of data traffic. Routers can be used for wired connection, wireless connections or both. A router that provides a wireless connection is referred to as a 'wireless router.'
While routers are used to connect different networks, they only work if the network protocols are the same. A gateway interfaces networks that use different protocols. You can think of a gateway as a router that includes protocol translators. The terms 'router' and 'gateway' are often used interchangeably, but it is important to remember that only gateways make it possible to connect networks using different protocols.
Since the Internet and many other computer networks use the same TCP/IP protocols, routers are sometimes all that is needed for a particular network. However, any network that also

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What is Subnetting?
Process of dividing an IP network in to sub divisions is called subnetting. Subnetting divides an IP address in to two parts as the network (or routing prefix) and the rest field (which is used to identify a specific host). CIDR notation is used to write a routing prefix. This notation uses a slash (/) to separate the network starting address and the length of the network prefix
(in bits). For example, in IPv4, 192.60.128.0/22 indicates that 22 bits are allocated for the network prefix and the remaining 10 bits are reserved for the host address. In addition, routing prefix can also be represented using the subnet mask. 255.255.252.0
(11111111.11111111.11111100.00000000) is the subnet mask for 192.60.128.0/22.
Separating the network portion and the subnet portion of an IP address is done by performing a bitwise AND operation between the IP address and the subnet mask. This would result in identifying the network prefix and the host identifier.

What is Supernetting?
Supernetting is the process of combining several IP networks with a common network prefix.
Supernetting was introduced as a solution to the problem of increasing size in routing tables.
Supernetting also simplifies the routing process. For example, the subnetworks 192.60.2.0/24 and 192.60.3.0/24 can be combined in to the supernetwork denoted by 192.60.2.0/23. In the supernet, the first 23 bits are the network part of the address and the other 9 bits are used as the host identifier. So, one address will represent several small networks and this would reduce the number of entries that should be included in the routing table. Typically, supernetting is used for class C IP addresses (addresses beginning with 192 to 223 in decimal), and most of the routing protocols support supernetting. Examples of such protocols are Border Gateway Protocol (BGP) and Open Shortest Path First (OSPF). But, protocols such as Exterior Gateway Protocol (EGP) and the Routing Information Protocol (RIP) do not support supernetting.

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LAB-02
Work on all networking commands in command prompt
Commands:
ARP

Ipconfig

Ipconfig is an MS-DOS utility that can be used from MS-DOS and an MS-DOS shell to display the network settings currently assigned and given by a network. This command can be utilized to verify a network connection as well as to verify your network settings.

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Ipconfig\all

Ping

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Ping is one of the most commonly used network commands that allows you to ping another network IP address. Pinging another address helps determine if the network card can communicate within the local network or outside network.

telnet

Netstat

The netstat command is used to display the TCP/IP network protocol statistics and information. 12 | P a g e

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Ns lookup

The nslookup MS-DOS utility that enables a user to do a reverse lookup on an IP address of a domain or host on a network.

Tracert
The tracert command in MS-DOS and Windows (known as traceroute in Unix-like operating systems) is a useful tool for diagnosing network issues. It allows you to view a listing of how a network packet travels through the network and where it may fail or slow down. Using this information you can determine the computer, router, switch or other network device possibly causing your network issues.

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After connecting a two pc’s
Ipconfig

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Netstat

Ns lookup

Tracert

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LAB-03
Study the different header formats

Protocol Header Format
TCP

TCP segments are sent as internet datagrams. The Internet Protocol header carries several information fields, including the source and destination host addresses. A TCP header follows the internet header, supplying information specific to the TCP protocol. This division allows for the existence of host level protocols other than TCP.

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Table 156: TCP Segment Format
Field Name

Size
Description
(bytes)

2

Source Port: The 16-bit port number of the process that originated the TCP segment on the source device. This will normally be an ephemeral (client) port number for a request sent by a client to a server, or a wellknown/registered (server) port number for a reply from a server to a client.

2

Destination Port: The 16-bit port number of the process that is the ultimate intended recipient of the message on the destination device. This will usually be a wellknown/registered (server) port number for a client request, or an ephemeral (client) port numberfor a server reply. 4

Sequence Number: For normal transmissions, the sequence number of the first byte of data in this segment. In a connection request (SYN) message, this carries the initial sequence number (ISN) of the source
TCP. The first byte of data will be given the next sequence number after the contents of this field

Acknowledgme
4
nt Number

Acknowledgment Number: When the ACK bit is set, this segment is serving as an acknowledgment (in addition to other possible duties) and this field contains the sequence number the source is next expecting the destination to send.

Source Port

Destination
Port

Sequence
Number

Data Offset

1/2
(4 bits)

Data Offset: Specifies the number of 32-bit words of data in the TCP header. In other words, this value times four equals the number of bytes in the header, which must always be a multiple of four. It is called a “data offset” since it indicates by how many 32-bit words the start of the data is offset from the beginning of the TCP segment. Reserved

3/4
(6 bits)

Reserved: 6 bits reserved for future use; sent as zero.

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Control Bits

Window

Checksum

Urgent Pointer

Dept. of ISE, BVBCET

3/4
(6 bits)

2

Window: Indicates the number of octets of data the sender of this segment is willing to accept from the receiver at one time. This normally corresponds to the current size of the buffer allocated to accept data for this connection. This field is, in other words, the current receive window size for the device sending this segment, which is also the send window for the recipient of the segment. 2

Checksum: A 16-bit checksum for data integrity protection, computed over the entire TCP datagram plus a special “pseudo header” of fields. It is used to protect the entire TCP segment against not just errors in transmission, but also errors in delivery. Optional alternate checksum methods are also supported.

2

Urgent
Pointer: Used in conjunction with the URG control bit for priority data transfer. This field contains the sequence number of the last byte of urgent data. 18 | P a g e

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Options

Variabl e Padding

Padding: If the Options field is not a multiple of 32 bits
Variabl
in length, enough zeroes are added to pad the header so e it is a multiple of 32 bits.

Data

Variabl
Data: The bytes of data being sent in the segment. e UDP HEADER FORMAT

The User Datagram Protocol offers only a minimal transport service -- non-guaranteed datagram delivery -- and gives applications direct access to the datagram service of the IP layer. UDP is used by applications that do not require the level of service of TCP or that wish to use communications services (e.g., multicast or broadcast delivery) not available from
TCP.
UDP is almost a null protocol; the only services it provides over IP are check summing of data and multiplexing by port number. Therefore, an application program running over UDP
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must deal directly with end-to-end communication problems that a connection-oriented protocol would have handled -- e.g., retransmission for reliable delivery, packetization and reassembly, flow control, congestion avoidance, etc., when these are required. The fairly complex coupling between IP and TCP will be mirrored in the coupling between UDP and many applications using UDP.
DHCP

Op – the message type (see DHCP message types table below)
Htype – Hardware address type (see HTYPE codes table below)
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Hlen – Hardware address length
Hops – set to zero by a client – but can optionally be used when booting via a relay agent
Xid – Transaction ID, a random number choosen by the client, used by the client and server so that no-one get confused between messages.
Secs – The number in seconds since the address was allocated, the client fills this part
Flags – Exactly what it says on the tin
Ciaddr – The clients IP address, but only if they have one, basically if the client is BOUND,
RENEW or REBINDING.
Yiaddr – Your (client) IP address.
Siaddr – IP address of the next server to use in bootstrap. Is returned in DHCPOFFER and
DHCPACK messages by the DCHP server.
Giaddr – VPN server IP address used in booting via relay agents
Chaddr – Client Hardware address (should be unique – LOL)
Sname – Optional server host name, should be a null terminated string
File – Boot file name, it should be a null terminated string. For DHCPDISCOVER messages it should be a fully generic name or null, for DHCPOFFER messages it should be a fully qualified directory path name.
Options – For optional parameters.
ARP

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HTTP

DNS

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As we can see, the Type field (red circle) in the first answer of the Authoritative Name Servers section is set to NS, which means this part contains information about the Authoritative name servers of the queried domain.

Going to the first answer of the Additional records, we can see that the Type field here is set to A, which means the data contained in this part is an IP address for the particular host.
When requesting the name servers for a domain, it also also essential their IP address is also provided, so that the client can construct a DNS query and send it to the name servers for that domain. In this article we analysed the DNS response message format by looking into the details of a DNS response packet. We also covered the different DNS type field messages and explained the contents of the DNS Response message.

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LAB-04
Correlate Theory with TCP protocol
Using Netmon tool we are analysing TCP protocol with theory concepts. The following snaps will show the TCP protocol header formats.

In this below snap it shows TCP header format like,
Sorceport, destport, seqnumber, acknumber, etc

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Graph:

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LAB-05
Bit Stuffing:
Bit stuffing is the insertion of one or more bits into a transmission unit as a way to provide signalling information to a receiver. The receiver knows how to detect and remove or disregard the stuffed bits.
 Each frame begins and ends with a special bit pattern called a flag byte [01111110].
 Whenever sender data link layer encounters five consecutive ones in the data stream, it automatically stuffs a 0 bit into the outgoing stream.
 When the receiver sees five consecutive incoming ones followed by a 0 bit, it automatically de-stuffs the 0 bit before sending the data to the network layer.
Bit Stuffing:
Input Data: 0110111111100111110111111111100000
Stuffed data: 011011111 0 110011111 0 011111 0 11111 0 00000
Red colour highlighted bit is stuffed bit.
Unstuffed data: 0110111111100111110111111111100000

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Code:
Server:
#include
#include
#include
#pragma comment(lib,"ws2_32.lib") //Winsock Library int main(int argc , char *argv[])
{

WSADATA wsa ;
SOCKET s , new_socket; struct sockaddr_in server , client; int c, cnt; char msg [100],msg1[100]; char client_reply[2000]; int recv_size; int count=0,j,nl; int i,jl,a; char ar[60]; int flag = 0;

printf("\nInitialising Winsock..."); if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
{
printf("Failed. Error Code : %d",WSAGetLastError()); return 1;
}

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printf("Initialised.\n");

if((s = socket(AF_INET , SOCK_STREAM , 0 )) == INVALID_SOCKET)
{
printf("Could not create socket : %d" , WSAGetLastError());
}
printf("Socket created.\n"); server.sin_family = AF_INET; server.sin_addr.s_addr = inet_addr ("127.0.0.1"); server.sin_port = htons( 8888 );

if( bind(s ,(struct sockaddr *)&server , sizeof(server)) == SOCKET_ERROR)
{
printf("Bind failed with error code : %d" , WSAGetLastError());
}
puts("Bind done"); listen(s , 3);

puts("Waiting for incoming connections...");

c = sizeof(struct sockaddr_in); new_socket = accept(s , (struct sockaddr *)&client, &c); if (new_socket == INVALID_SOCKET)
{
printf("accept failed with error code : %d" , WSAGetLastError());
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}

puts("Connection accepted"); while(1){printf ("Server: "); printf("enter the bit string to be Stuffed::"); gets(ar); for (i=0;i