CNE Unit 5 Notes


UNIT –5 tcp/ip suite



1) Define protocol. (Any one Definition-2 Marks)


Protocol: –

  • It is set of rules and conventions .
  • Sender and receiver in data communication must agree on common set of rules before they can communicate with each other.


Protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems.

Protocol defines:

  1. a) Syntax (what is to be communicated)
  2. b) Semantics (how is it to be communicated
  3. c) Timing (When it should be communicated)


2) Define “Protocol” with reference to computer network. What is the function of IP? (Definition of protocol – 1 Mark, Function of IP – 1 Mark)


Protocol: –

Protocol is set of rules and conventions. Sender and receiver in data communication must agree on common set of rules before they can communicate with each other. Protocol defines.

  1. a) Syntax (what is to be communicated)
  2. b) Semantics (how is it to be communicated
  3. c) Timing (When it should be communicated)

Function of IP:

  1. Addressing
  2. Routing
  3. Data encapsulation
  4. Fragmentation & reassembly


3) Define protocol. Give the name of any two protocols (Definition -1 mark, any two examples- 1 mark)


Define protocol:

There are certain rules that must be followed to ensure proper communication & a set of such rules is known as protocol.

Example: UDP, TCP/IP, SMTP, HTTP, SSL, FTP etc


4) What is IP address? State the IP address classes. (Definition of IP address 1 mark, List of IP address classes 1 mark)

Ans: IP (internet protocol address):-

  • IP address is a logical address, 32 bit address having net-id & host-id that uniquely & universally identified over TCP/IP network or local network or to internet.
  • Messages are routed in a TCP/IP network based on destination IP address.

IP address classes:- Class A, Class B, Class C, Class D, Class E


5) List different classes of IP Address. ( ½ mark for each class, Any four classes)


Different classes of IP address:

  • Class A
  • Class B
  • Class C
  • Class D
  • Class E


6) Enlist any four problems with SLIP protocol.(Any four problems ½ Mark for each problem)


i)It only supports Internet Protocol (IP).

  1. i) It does not allow to the IP address to be assigned dynamically.
  2. ii) Lack of Security because it does not allow authentication.

ii) No Control Messaging.

  1. iv) It does not provide error detection.
  2. v) It does not provide Type identification.
  3. vi) It does not compress any packet data.


7) What is PPP? (Explanation-2 Marks)


7)Explain the following terms (2 marks each )

    1)PPP                       2) SLIP


PPP means Point to Point Protocol.

  • It is a much more developed protocol than SLIP (which is why it is replacing it), in so far as it transfers additional data, better suited to data transmission over the Internet (the addition of data in a frame is mainly due to the increase in bandwidth).
  • In reality, PPP is a collection of three protocols:
  • A datagram encapsulation protocol an LCP, Link Control Protocol,
  • Enabling testing and communication configuration a collection of NCPs, Network Control Protocols allowing integration control of PPP within the protocols of the upper layers
  • Data encapsulated in a PPP frame is called a packet.
  • These packets are generally datagrams, but can also be different (hence the specific designation of packet instead of datagram).
  • So, one field of the frame is reserved for the type of protocol to which the packet belongs. A PPP frame looks like this:


Data to be transmitted Padding data


2) SLIP ( Explanation-2 marks)

SLIP means Serial Line Internet Protocol.

SLIP is the result of the integration of modem protocols prior to the suite of TCP/IP protocols.

It is a simple Internet link protocol conducting neither address or error control, this is the

reason that it is quickly becoming obsolete in comparison to PPP.

Data transmission with SLIP is very simple:

This protocol sends a frame composed only of data to be sent followed by an end of transmission character (the END character, the ASCII code of which is 192).

A SLIP frame looks like this:

Data to be transmitted END


8) State and explain in brief at which layer the following protocol works?

  1. ICMP ii. ARP iii. IP           iv. SMTP             (1 Mark each point)


1) ICMP : Network layer

  • ICMP allows IP to inform a sender if a datagram is undeliverable.
  • A datagram travels from router to router until it reaches one that can deliver it to its final destination.

2) ARP : Network layer

  • ARP converts an Internet Protocol (IP) address to its corresponding physical network address.
  • ARP is a low-level protocol that operates at Network Layer of the OSI model.

3) IP : Network layer

  • Network Layer is responsible for communicating two different devices, and IP is used to define source address and destination address.

4) SMTP : Application layer

  • SMTP was developed to send E-mail message across internet.
  • It utilizes TCP as the transport protocol to transmit mail to a destination mail exchanger.


9) State the layers at which the following protocols works: (1 mark each point)


1) ARP : Network layer

2) PPP : Data link layer

3) SMTP : Application layer

4) ICMP : Network layer


10) What is meant by subnet? How to use subnet masking to create two subnets? (Explanation of subnet -2 Marks, Subnet masking explanation with any suitable example – 2 Marks)


  • A subnet is a logical grouping of connected network devices.
  • Nodes on a subnet tend to be located in close physical proximity to each other on a LAN. Network designers employ subnets as a way to partition networks into logical segments for greater ease of administration.
  • When subnets are properly implemented, both the performance and security of networks can be improved.
  • In Internet Protocol (IP) networking, devices on a subnet share contiguous ranges of IP address numbers.
  • A mask (known as the subnet mask or network mask) defines the boundaries of an IP subnet.
  • The correspondence between subnet masks and IP address ranges follows defined mathematical formulas.
  • IT professionals use subnet calculators to map between masks and addresses.

Subnet masking for 2 subnet:

To calculate the number of subnets or nodes, use the formula (2n-2)

where n = number of bits in either field,

and 2n represents 2 raised to the nth power.

Multiplying the number of subnets by the number of nodes available per subnet gives you the total number of nodes available for your class and subnet mask.

Also, note that although subnet masks with non-contiguous mask bits are allowed, they are not recommended.


10001100.10110011.11011100.11001000    IPAddress

11111111.11111111.11000000.00000000      SubnetMask


10001100.10110011.11000000.00000000 Subnet Address


Subnet number Address

11) Describe Subnet Mask with example. (Description: 2 Marks, Example: 2 Marks)


Subnet mask is a net mask with the only real difference being that we are breaking a larger organizational network into smaller parts, and each smaller section will use different set of address numbers.

The subnet mask is a 32-bit value that usually expressed in the same dotted-decimal notation used by IP addresses.

The purpose of the subnet mask is to let IP separate the network ID from the full IP address and thus determine whether source and destination are on the same network.

It is the combination of Net-ID and Host-ID. Default Subnet Mask: Net-ID+ Host-id Class A:

Class B:

Class C:

For example: Given site address:

201  70  64 0
11001001 01000110 01000000 00000000



12) What is subnet masking? Design the subnets, to find six subnet addresses for the site address (Definition of subnet masking 1 mark, solved any 6 subnet ids 3 marks)


Subnet masking:

mask is used to determine what subnet an Ip address belongs to that is it decides the class

of an IP address it is used to identify network address and host address in an IP address .

Subnet mask is made by setting network bits to all 1’s and setting host bits to all 0’s.


Given site address:

201  70  64 0
11001001 01000110 01000000 00000000


It is class C network

For finding 6 subnet addresses at least 3 subnet bits are used.

Subnet 1 : 11001001. 01000110. 01000000.00000000

Subnet id 1:

Subnet 2: 11001001. 01000110. 01000000.00100000

Subnet id 2:

Subnet 3: 11001001. 01000110. 01000000.01000000

Subnet id 3:

Subnet 4: 11001001. 01000110. 01000000.01100000

Subnet id 4:

Subnet 5: 11001001. 01000110. 01000000.10000000

Subnet id 5:

Subnet 6: 11001001. 01000110. 01000000.10100000

Subnet id 6:

Subnet 7: 11001001. 01000110. 01000000.11000000

Subnet id 7:

Subnet 8: 11001001. 01000110. 01000000.11100000

Subnet id 8:


13) Explain sub-netting and super-netting with example.(Sub-netting 2 marks, super-netting 2 marks)


Sub-netting: Subnet mask is a net mask with the only real difference being that breaking a larger network into smaller parts and each smaller section will use different sets of address numbers.

The subnet mask is 32 bit value that usually express in dotted decimal notation used by IP address. This is the combination of net-ID and host-ID.


Consider the subnet mask as convert the subnet mask to binary. = 11111111.11111111.00000000.00000000 (in binary)

add 1s right after the last 1 on the right (in the middle of the mask, between the 1s and 0s)

I add five 1s to make it look like this: 11111111.11111111.11111000.00000000

Using the subnet’s formula, this would give us 25 = 32 networks

Super-netting: To create a super network, the procedure is to be reversed.

The networks are combined by creating space for a larger number of hosts.

To accomplish this, we start with the default subnet mask of and use some of the bits reserved for the Net-id to identify the Host-id.

The following example shows we would create a new super network by combining four  separate subnetworks.


If a packet arrives at the router with the destination address,

the supernet mask is applied to the destination address.

11000000.10101000.01000000.00110000 (destination IP address)


11111111.11111111.11111100.00000000 (supernet mask)




14) What is ARP? What are the functions of ARP?  ( ARP purpose 1 mark, functions of ARP 3 marks)


ARP(Address resolution protocol):-

Address resolution: Process for obtaining physical address of a computer based on its IP in order to transfer data over the network to which the node belongs to.

Network hardware needs datagram to contain physical address of receiver.

ARP takes IP address of host as input & gives its corresponding physical address as output.


3 methods for getting physical address based on IP address:

1) Table lookup : Mapping information between IP address & physical address is stored in a table in memory.ARP software uses this table to find out physical address.

2) Closed from computation: By using algorithm, IP address can be transformed into physical address by performing arithmetic & Boolean operations.

3) Message exchange: It is very popular method.ARP request is broadcasted to all computers on network. The host on network that has IP address in the request then replies with its physical address.

ARP Caching :-

Once physical address of corresponding IP address is known, it stores this information in a table. This is called as ARP Caching.

Next time if host wants to send data to same host, ARP request need not be broadcasted. Instead first it checks in ARP cache.

Only if IP address is not found in ARP cach, It broadcasts ARP query datagram.


15) Give the name of protocols used by different layers of TCP/IP. Discuss the function of ARP and RARP. (4 marks for protocols, 2 marks of ARP, 2 marks of RARP)


TCP/IP Model contains following layer.

1) Host-to-Network Layer –

It defines characteristics of transmission media.

It also concern with delivery of data when two systems are attached to same network  SLIP, PPP

2) Internet Layer –

This layer permits host to inject packets into network and packet travels independently to destination.

This layer defines packet format and protocol called IP (internet Protocol)




3) Transport Layer –

It has TCP and UDP.

TCP (Transmission Control Protocol) –it is Reliable & connection oriented protocol.

UDP (User Datagram Protocol)- it is Unreliable & connectionless protocol.

4) Application Layer –

It includes virtual Terminal (TELNET), file transfer Protocol (FTP), simple Mail Transfer Protocol (SMTP) and other protocols like HTTP, WWW, DNS.

ARP:(Address resolution protocol)

  • Networking H/W demands that a datagram contain the physical address of the intended recipient.
  • If problem Address Resolution protocol (ARP) was developed.
  • ARP takes the IP address of a host as input & gives its corresponding physical address as the output.
  • As if doesn’t know who must be having address if sends the broadcast message to all the computer on the network.
  • The computer whose IP address matches the broadcast IP address sends a reply and along with if, its physical address to the broadcasting computer.
  • All other computers lignose the broadcast message as IP address is different Now, when it is responding whose IP address gets match is aware of the sender.
  • So it doesn’t require sending broadcast message.
  • As it knows sender hardware as well as IP address that the reason it uncast the reply so that senders only receive it.

 RARP: (Reverse Address Resolution protocol)

  • ARP is used for solving the problem of finding out which Ethernet address corresponding to a given IP address.
  • But sometimes we have to solve a reverse problem.
  • That means we have to obtain the IP address corresponding to the given Ethernet address.
  • Such a problem can occur when booting a diskless workstation.
  • The problem of obtaining the IP address when an Ethernet address is given, can be solved by using RARP (Reverse Address Resolution protocol)
  • The newly booted workstation is allowed to broadcast its Ethernet address.
  • The RARP server looks at this request.
  • Then it looks up the Ethernet address in its configuration files and sends back the corresponding IP address.
  • Using RARP is actually better than embedding an IP address in the memory image because it allows the same image to be used on all machines.
  • If the IP address were buried inside the image, each workstation would need its own image.

The disadvantage of RARP is that it uses a destination address of all l’s (limited broadcasting) to reach the RARP server.

But such broadcasts are not forwarded by routers, so a RARP server is needed on each network.


 16) Describe any four IP address classes. (Any four IP address classes-1 Mark each)


An IPv4 address is 32-bit address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet

IP address classes: IP addresses are classified into 5 types:

1) class A    2) class B    3) class C    4) class D    5) class E


IP Address Classes and Parameters:

class First bits First byte values Network ID bits Host ID bits No. of networks No.of hosts
A 0 1-127 8 24 126 16,777,214
B 10 128-191 16 16 16,384 65,534
C 110 192-223 24 8 2,097,152 254


Class A format: (For first byte) In the first field the first bit ‘0’ indicates that it is class A network address.

The next 7 bits are used indicate network id .

Rest of the 3 bytes are used to indicate host id.

Class A: Minimum value is and maximum value

 Class B format: Minimum value is to maximum value

 Class C format: Minimum value to maximum value

 Class D format: If first 4 bits are 1110 the IP address belongs to class D

The IPv4 networking standard defines Class D addresses as reserved for multicast. Multicast is a mechanism for defining groups of nodes and sending IP messages to that group rather than to every node on the LAN (broadcast) or just one other node (unicast).

Multicast is mainly used on research networks.

As with Class E, Class D addresses should not be used by ordinary nodes on the Internet.

For class D minimum value for multi cast address is and maximum multi class address is

Class E format: For class E minimum value for reserved address is to


17) Explain Connection oriented and connectionless services.(Connection oriented services: 2 marks, connection less services: 2 marks)


 Connection –oriented services: is modeled after telephone system.

Connection-oriented communication includes the steps of setting up a call from one computer to another, transmitting/receiving data, and then releasing the call, just like a voice phone call.

However, the network connecting the computers is a packet switched network, unlike the phone system’s circuit switched network.

Connection-oriented communication is done in one of two ways over a packet switched network: with and without virtual circuits.

To use connection oriented service , the service user first establishes a connection, uses the connection, and then releases the connection.


 Connectionless service: is modeled after postal system.

Connectionless communication is just packet switching where no call establishment and release occur.

A message is broken into packets, and each packet is transferred separately. Moreover, the packets can travel different route to the destination since there is no connection.

Connectionless service is typically provided by the UDP (User Datagram Protocol), which we will examine later.

The packets transferred using UDP are also called datagrams:

Feature Connectionless Connection-oriented
How is data sent? one packet at a time as continuous stream of packets
Do packets follow same route? No virtual circuit: yes without virtual circuit: no
Are resources reserved in network? No virtual circuit: yes without virtual circuit: no
Are resources reserved in communicating hosts? No yes
Can data sent can experience variable latency? Yes yes
Is connection establishment done? No yes
Is state information stored at network nodes? No virtual circuit: yes without virtual circuit: no


18) Explain connectionless and connection oriented protocol. Give the example for each type. (Explanation 1 mark each, any one example 1 mark for each type)


18) Describe any two connectionless and connection oriented protocols. (Any 2 Connectionless protocol- 4 Marks, Any 2 connection oriented protocols – 4 Marks)

 Connection less protocol:

These protocols do not establish a connection between devices.

It is manually achieved by transmitting information in one direction, from source to destination without checking to see if the destination is still there or if it is prepared to receive the information.

 Connection-oriented protocol:

It means that when devices communication they perform hand sharing to set up on end to end connection.

Usually one device begins by sending a request to open a connection, and the other responds.

 Connectionless protocols: 1) IP       2) ICMP     3) UDP  


  • IP is internet Protocol.
  • It is unreliable protocol because it does not provide any error control and flow control.
  • Packets in IP are called “Datagram”


  • It is internet control message protocol.
  • It reports error and sends control messages.
  • Error reporting messages include – destination unreachable, source quench , time exceed, parameter problem , redirection etc.
  • Query message includes –echo request and reply, time stamp request and reply, router solicitation and advertisement. etc


  • UDP is user datagram protocol.
  • It is connectionless protocol because data is sent without establishing a connection between sender and receiver before sending the data.
  • UDP is unreliable because data is delivered without acknowledgement.
  • UDP does not perform Auto retransmission.
  • UDP does not use flow control.
  • UDP has high transmission speed.


Connection oriented protocol:

                   1) TCP     2) SLIP       3) PPP        4) SMTP  

1) TCP

  • TCP is transmission control protocol.
  • It is connection oriented protocol because connection must be establish prior to transmission of data.
  • TCP is reliable protocol because data is delivered with acknowledgement.
  • TCP perform Auto Retransmission if the data is lost.
  • TCP use flow control.
  • TCP has low speed of transmission.


  • SLIP is serial line internet protocol
  • SLIP does not perform error detection and correction.
  • SLIP does not provide any authentication.
  • SLIP is not approved internet standard.
  • SLIP supports only Internet protocol (IP)
  • SLIP supports static IP address assignment


  • PPP is point to point protocol.
  • PPP perform error detection
  • PPP provides authentication and security.
  • PPP is approved internet standard.
  • PPP supports IP and other protocols.
  • PPP supports Dynamic IP address assignment


  • SMTP is simple mail transfer protocol.
  • It is connection oriented text based protocol in which sender communicates with receiver using a command and supplying data over reliable TCP connection.
  • SMTP is standard application layer protocol for delivery of email over TCP/IP network.
  • SMTP establish a TCP connection between Sender And port number 25 of receiver


19) Describe meaning and function of:

  1. i) MAC address ii) IP address (MAC address explanation- 1 Mark, Example- 1 Mark)


i) MAC Address:

             The MAC address is a unique value associated with a network adapter.

MAC addresses are also known as hardware addresses or physical addresses.

They uniquely identify an adapter on a LAN.

MAC addresses are 12-digit hexadecimal numbers (48 bits in length).

By convention, MAC addresses are usually written in one of the following two formats:



The first half of a MAC address contains the ID number of the adapter manufacturer.

These IDs are regulated by an Internet standards body (see sidebar).

The second half of a MAC address represents the serial number assigned to the adapter

by the manufacturer.

Example:- 00:A0:C9:14:C8:29


  1. ii) IP Address: (IP address Explanation -1 Mark, Example – 1 Mark)


An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.

An IP address serves two principal functions: host or network interface identification and location addressing.

Its role has been characterized as follows: “A name indicates what we seek. An address indicates where it is. A route indicates how to get there.”

  1. The IP address consists of two parts namely a network identifier and a host identifier.
  2. All the computers on a particular subnet will have the same network identifier but different host identifiers
  1. The internet Assigned Number Authority (IANA) assigns network identifiers to avoid any duplication of addresses.
  1. An IPv4 address consists of two parts. The first part of the of the address, called the network number, identifies a network on the internet; the remainder, called the host ID, identifies an individual host on that network.

Classful Addressing: The IPv4 addresses are classified into 5 types as follows:

  1. Class A
  2. Class B
  3. Class C
  4. Class D
  5. Class E


20) Describe TCP used in computer communication. (Any 4 Services/ Relevant explanation – 1 Mark each)


Following are some of the services offered by TCP to the process at the application layer:

  1. Stream delivery service
  2. Sending and receiving buffers
  3. Bytes and segments
  4. Full duplex service
  5. Connection oriented service
  6. Reliable service.
  7. Process to process communication
  8. Stream delivery service:
  • TCP is a stream oriented protocol.
  • It allows the sending process to deliver data as a stream of bytes and the receiving process to obtain as a stream of bytes.
  • TCP creates a working environment in such a way that the sending and receiving processes seem to be connected by an imaginary “tube” This is called as stream delivery service.
  1. Sending and receiving buffers:
  • The sending and receiving process may not produce and receive data at the same speed.
  • Hence TCP needs buffers for storage.

There are two types of buffers used in each direction:

1) Sending buffer

    2) Receiving buffer.

  • A buffer can be implemented by using a circular array of 1 byte locations as shown
  • The movement of data in one direction on the sending side the buffer has there types of locations:

                              1)Empty Locations

                              2)  Location containing the bytes which  have been sent but not acknowledgement. These bytes are kept in the buffer till an acknowledgement is received.

                              3)The locations containing the bytes to be sent by the sending TCP.

  1. Bytes and segments:
  • Buffering is used to handle the difference between the speed of data transmission and data consumption. But only buffering is not enough. We need one more step before sending the data.
  • The IP layer, as a service provider for TCP, need to send data in the form of packets and as a stream of bytes.
  • At the transport layer, TCP groups a number of bytes together into a packet called a segment.
  • A header is added to each segment for the purpose of exercising control.
  • The segments are encapsulated in an IP datagram and then transmitted. The entire operation is transparent to the receiving process.
  • The segments may be receiver out of order, lost or corrupted when it reaches the receiving end.
  1. Full duplex service:
  •  TCP offers full duplex service where the data can flow in both the direction simultaneously.
  • Each TCP will then have a sending buffer and receiving buffer.
  • The TCP segments are sent both the directions.
  1. Connection oriented service:
  •  TCP is a connection oriented protocol.
  • When process –1 wants to communicate (send and receive) with another process (process-2), the sequence of operations is as follows: TCP of process -1 informs TCP of process -2 and gets its approval.
  • TCP of process -1 and TCP of process -2 exchange data in both the directions.
  • After completing the data exchange, when buffers on both sides are empty, the two TCPs destroy their buffers.
  1. The type of connection in TCP is not physical, it is virtual.

The TCP segment is encapsulated in an IP datagram and can be sent out of order.

  1. These segments can get lost or corrupted and have to be resent.
  2. Each segment may take a different path to reach the destination. 
  1. Reliable services:
  • TCP is a reliable transport protocol.
  • It uses an acknowledgment mechanism for checking the safe and sound arrival of data.
  1. Process to process communication:
  • The TCP user port numbers a transport layer addresses.
  • Show some well known port number used by TCP.
  • Note that if an application can use both UDP and TCP, the same port number is
  • assigned to this application.

21) Compare IPV6 and IPV4 protocol (4 points). (Any four points-1 Mark each)


Comparison of IPv4 and IPv6

IPv4 IPv6
Source and destination addresses are 32 bits (4 bytes) in length. Source and destination addresses are 128 bits (16 bytes) in length. For more information.
Uses broadcast addresses to send traffic to all nodes on a subnet. There are no IPv6 broadcast addresses. Instead, multicast scoped addresses are used.
Fragmentation is supported at originating hosts and intermediate routers. Fragmentation is not supported at routers. It is only supported at the originating host.
IP header includes a checksum. IP header does not include a checksum.
IP header includes options. All optional data is moved to IPv6 extension headers.
IPSec support is optional. IPSec support is required in a full IPv6 implementation.
No identification of payload for QOS handling by routers is present within the IPv4 header. Payload identification for QOS handling by routers is included in the IPv6 header using the Flow Label field..
Addresses must be configured either manually or through DHCP. Addresses can be automatically assigned using stateless address auto configuration, assigned using DHCPv6, or manually configured.
Uses host address (A) resource records in the Domain Name System (DNS) to map host names to IPv4 addresses. Uses host address (AAAA) resource records in the Domain Name System (DNS) to map host names to IPv6 addresses.


22) Compare the OSI reference model with TCP/IP network model. (Any four points one mark each)


 OSI reference model TCP/IP network model
1)It has 7 layers 1)Has 4 layers
2)Transport layer guarantees delivery of packets 2)Transport layer does not guarantees delivery of packets
3)Horizontal approach 3)Vertical approach
4)Separate presentation layer 4)No session layer, characteristics are provided by transport layer
5)Separate session layer 5)No presentation layer, characteristics are provided by application layer
6)Network layer provides both connectionless and connection oriented services 6)Network layer provides only connection less services
7)It defines the services, interfaces and protocols very clearly and makes a clear distinction between them 7)It does not clearly distinguishes between service interface and protocols
8)The protocol are better hidden and can be easily replaced as the technology changes 8)It is not easy to replace the protocols
9)OSI truly is a general model 9)TCP/IP can not be used for any other application
10)It has a problem of protocol filtering into a model 10)The model does not fit any protocol stack.


23) Explain following:

  1. Telnet II. FTP (2 Marks for each)
  2. Telnet:


  • TELNET is abbreviation for Terminal Network.
  • It is standard TCP/IP protocol for virtual terminal services proposed by ISO.
  • TELNET enables establishment of connection to a remote system in such a way that a local terminal appears to be terminal at remote system.
  • TELNET is general purpose client server application program.
  1. FTP:
  • FTP is a stranded mechanism provided by the Internet for copying a file from one host to the other.

Some of the problem in transferring files from one system to the other are as follows:

  • Two systems may use different file name conventions.
  • Two systems may represent text data in different types.
  • The directory structure of the two systems may be different.

FTP provides a simple solution to all these problems.

FTP established two connections between the client and server.

One is for data transfer and the other is for the control information.

The fact that FTP separates control and data makes it very efficient.

The control connection uses simple rules of communication.

Only one line of command or a line of response is transferred at a time.

But the data connection uses more complex rules due to the variety of data types being


FTP uses port 21 for the control connection and port 20 for the data connection.


24) Explain the working of “File Transfer Protocol” with a neat diagram. (Working – 3 Marks, Diagram 1 Mark)


FTP is a stranded mechanism provided by the Internet for copying a file from one host to the other.

  1. Some of the problem in transferring files from one system to the other are as follows:

Two systems may use different file name conventions.

Two systems may represent text data in different types.

The directory structure of the two systems may be different.

  1. FTP provides a simple solution to all these problems.
  2. The basic model of FTP is shown
  3. FTP established two connections between the client and server.

One is for data transfer and the other is for the control information.

  1. The fact that FTP separates control and data makes it very efficient.
  2. The control connection uses simple rules of communication.

Only one line of command or a line of response is transferred at a time.

  1. But the data connection uses more complex rules due to the variety of data types being


  1. FTP uses port 21 for the control connection and port 20 for the data connection.
  2. As shown in the figure client has three components namely:
  3. User interface
  4. Control process and

iii. Data transfer process.

  1. The Server has two components: the control process and data transfer process.
  2. The control connection is maintained during the entire interactive FTP session.

The data connection is first opened, file is transferred and data connection is closed. This is closed. This is done for transferring each file.



Control connection:

This connection is created in the same way as the other application programs described earlier.

Control connection remains alive during the entire process.

The IP uses minimize delay type services because this is an interactive connection between a user and server.

Data Connection:

This connection is opened when data to be transferred is ready and it is closed when transfer of data is over.

The service types used by IP is maximize throughput.


25) Explain the working of “TELNET” (Explanation – 4 Marks)



TELNET is abbreviation for Terminal Network. It is standard TCP/IP protocol for

virtual terminal services proposed by ISO.

TELNET enables establishment of connection to a remote system in such a way

that a local terminal appears to be terminal at remote system.

TELNET is general purpose client server application program.

locallogin Local Login

When user log in to local time sharing system it is called local login.

The keystrokes accepted by terminal driver. Terminal driver passes the character to the operating system.

Operating system, in tern interprets the combination of character and invoke the desired application or utility.

Remote login

When user wants to access the application or utility located at the remote machine, he or she performs remote login.

Here the telnet client and server program come into use.

The user sends the keystrokes to local operating system.

local operating system accept is, but do not interpret them.

The characters are send to TELNET client. TELNET client transform the character to a universal character set called Network Virtual Terminal Character and deliver them to the local TCP/IP stack.


As shown in above figure the command/text in NVT form travel through internet, and arrive at TCP/IP stack of remote Machine.

Here the characters are delivered to the operating system and Passed to the TELNET server. Which changes the characters to the understandable characters by the remote computer. However characters could not directly pass to the operating system because remote operating system is not designed to receive characters from TELNET server.

The solution is to add piece of software called Pseudo- terminal driver, which pretends that characters are coming from terminal.

The operating system passes the characters to appropriate ap

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