TCP/IP - [Part 1] - INTERVIEW QUESTIONS

Question - 1 What is the TCP/IP model ?

• Basically TCP/IP model came to overcome the drawbacks of general OSI model. TCP/IP determine how computers transfer data from one device to another.
• TCP/IP is two separate computer network protocols. IP is responsible to deliver the packet from the source host to the destination host based on their addresses.. TCP is responsible for reliable data delivery once that IP address has been found, it has the functionality of error checking, Windowing, Sequencing, Flow Control and Error Checking.
• TCP/IP has only four layers as compared to seven layers of OSI Model. The purpose of these layers is to keep things standardized.
• These four layers are generated by combining the layers of OSI model internally, so that protocols can be implemented.

Question - 2 TCP/IP architecture ?

TCP/IP has only four layers as compared to seven layers of OSI Model.

Question - 3 Explain each layer of TCP/IP model.

Layer - 1 (Network Access Layer) 

Network Access Layer = Data Link Layer + Physical Layer [OSI Model]

Network Access Layer is combination of Data Link and Physical Layer of OSI Model.

Data Link Layer

• Data Link layer is responsible for physical transmission of the data and for successful data synchronization.
• It handles error notification, network topology, and flow control. 
• Data Link layer ensure that messages are delivered to the proper device on a LAN using physical address(MAC) 
• It translate messages from the Network layer into bits for the Physical layer to transmit.
• It reassembles the packet into data frames. Frames are containing the source address field, destination address field, packet, ether field and FCS.
• Data Link Layer is divided into two fields -Logical Link Control and Media Access Control.

Physical Layer

• Physical layers sends bits and receives bits. Bits is represented in only format of 1 or 0.
• It specifies the electrical, mechanical, procedural, and functional requirements for activating, maintaining, and deactivating a physical link between end systems.
• It identify the interface between the data terminal equipment (DTE) and the data communication equipment (DCE).

Layer - 2 (Internet Layer)

Internet Layer = Network Layer [OSI Model]

Internet Layer is similar to Network Layer of OSI Model:

Internet Layer

• Internet layer is responsible to manages device addressing and it tracks the location of devices on the network.
• Internet Layer is responsible for establishing data communication channel between multiple networks or nodes or devices or hosts.
• It determines the best path to move data, which means that the Internet layer must act as a transport traffic between devices that are not locally attached.
• Internet-Layer is used when a connection needs to establish between two or more different networks. If two or more nodes or devices are connected locally, then there is no any requirement of Internet layer.
• Router is a layer 3 devices, which is specified at the Internet layer and provide the routing services within an inter-network.

Layer - 3 (Transport Layer/Host To Host Layer)

Transport Layer = Transport Layer [OSI Model]

Transport Layer has same function as Transport Layer of OSI Model, it is also known as Host To Host Layer:

Transport Layer

• The Transport layer is responsible to reassembles segments into a data stream.
• Transport layer provide end to end data transport services.
• It can establish a logical connection between the sending host and destination host on an inter-network.
• It is also responsible to hide sensitive details of data from networks and to providing data transmission in a transparent mode.
• Transport layer can be connection-less or connection oriented. Because TCP and UDP both work at the Transport layer. Where TCP is a connection oriented means provide reliable communication and UDP is connection-less means provide unreliable communication.
• Because Transport layer can be connection oriented, so it also will be use acknowledgments, sequencing, windowing, error control and flow control.

Layer - 4 (Application Layer)

Application Layer = Transport Layer + Presentation Layer + Session Layer [OSI Model]

Application Layer is combination of Transport, Presentation and Session Layer of OSI Model:

Application Layer

• Provide a user interface and allow to access network resources.
• Application Layer is the first layer of the OSI Model and this layer is responsible to provide interface among users and the software application.
• It plays a role of intermediates between actual software application and the users.
• We can say that, application layer plays a front-end role, where user actually communicate or interact, other remaining layers play a back-end role.
• File transfer, emails etc. are the example of application layer where users interact.

Presentation Layer

• It is responsible to present data to the Application layer 
• Presentation Layer is responsible for data translation, conversion and code formatting like 

1. Data compression/Decompression
2. Data Encryption/Decryption
3. Graphic handling
4. Character/string conversion

• A data-transfer technique -  Data will be in standard format before transmission. After that computers will receive generically formatted data and then convert the data back into its native format for actual reading. 
• This layer ensures that data transferred from the Application layer of one system can be read by the Application layer of another system.
• So presentation layer is responsible for integrating all data formats into a standard format for efficient and effective communication. Best example is  EBCDIC (Extended Binary Coded Decimal Interchange Code) to ASCII (American Standard Code for Information Interchange) conversion. 

Session Layer

• Session Layer provides appropriate sessions between users and software, actually where users interacts.
• It is responsible for sessions establishment, session management, session termination and synchronization. Example : Online payment session and IRCTC login session
• It is also provides dialog control between devices, or nodes.

Question - 4 Which protocols come under these layers ?

Layer 1 - Network Access Layer Protocols

• Ethernet
• Fast Ethernet
• Token Ring
• FDDI

Layer 2 - Internet Layer Protocols

• Internet Protocol (IP) 
• Internet Control Message Protocol (ICMP)
• Address Resolution Protocol (ARP)
• Reverse Address Resolution Protocol (RARP)
• Proxy Address Resolution Protocol (Proxy ARP)
• Gratuitous Address Resolution Protocol (Gratuitous ARP)

Note:- To know more about Internet Layer Protocols, go to TCP/IP - [Part 4] - INTERNET LAYER PROTOCOLS 

Layer 3 - Transport Layer/Host To Host Layer Protocols

• Transmission Control Protocol (TCP)
• User Datagram Protocol (UDP)

Note:- To know more about Transport Layer Protocols, go to TCP/IP - [Part 3] - TRANSPORT LAYER PROTOCOLS

Layer 4 - Process/Application Layer Protocols

• Telnet (Teletype Network Protocol)
• File Transfer Protocol (FTP)
• Trivial File Transfer Protocol (TFTP)
• Network File System (NFS)
• Simple Mail Transfer Protocol (SMTP)
• Post Office Protocol (POP)
• Internet Message Access Protocol (IMAP)
• Transport Layer Security (TLS)
• Session Initiation Protocol (SIP)
• Real-time Transport Protocol (RTP)
• Line Printer Daemon (LPD)
• Line Printer Remote (LPR)
• Domain Name Service (DNS)
• X Window
• Simple Network Management Protocol (SNMP)
• Secure Shell (SSH)
• Hypertext Transfer Protocol (HTTP)
• Hypertext Transfer Protocol Secure (HTTPS)
• Network Time Protocol (NTP)
• Network News Transfer Protocol (NNTP)
• Secure Copy Protocol (SCP)
• Lightweight Directory Access Protocol (LDAP)
• Internet Group Management Protocol (IGMP)
• Dynamic Host Configuration Protocol (DHCP)
• Automatic Private IP Addressing (APIPA)

Note:- To know more about Application Layer Protocols, go to TCP/IP - [Part 2] - APPLICATION LAYER PROTOCOLS

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Anubhav Upadhyay

Hello and welcome to networktopic Blog. My name is Anubhav. I am a Senior Network Egineer. I have created this blog specially to serve interview questions and answer on Network Routing and Switching, I will try my best to serve correct and updated networking knowledge for you as per my corporate experience.

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