OSI LAYERS AND FUNCTIONS - [Part 2] - INTERVIEW QUESTIONS

Question - 1 Explain three way handshake process.

Establishing a connection oriented communication

Figure: Three way handshake

  The three-way handshake is connection oriented process and follow these steps.

• Sender wants to initiate a connection with receiver, So Sender sends a TCP segment with SYN(Synchronize Sequence Number). This segment will inform the receiver that Sender would like to start a communication with receiver and informs receiver what sequence number it will start its segments with.
• Receiver will respond to Sender with "Acknowledgment" (ACK) and SYN bits set. Now receiver's ACK segment does two things; It acknowledges Sender's SYN segment. It informs Sender what sequence number it will start its data with.
• Now finally Sender Acknowledges Receiver's initial sequence Number and its ACK signal. And then Sender will start the actual data transfer.

Question - 2 Explain the flow control, acknowledgments and widowing in Transport Layer.

Flow Control

Figure : Transmitting The  Segment With Flow Control

• Flow control prevents overflowing of buffers in the receiving host - when a sending host is sending the segment to receiving host continuously and buffer on the receiver side has filled then in this situation receiving host will notify the sending host about this event after that receiving host will stop transmission and wait for permission to start transmission again. Overflowing of buffer can result in lost data. 

Acknowledgement - 

• It guarantees that the data will not be duplicated or lost. It will be accomplished with positive acknowledgment with re-transmission
• Receiver communicates with the sender by sending an acknowledgment, actually receiver will send acknowledgement  back to the sender when it will receive data.

 Windowing -

Figure : Windowing

Windows are used to control the amount of outstanding, unacknowledged data segments. In windowing user can increase or decrease the size of window anytime.

Question - 3 Which type packets are used at the Network Layer ?

Two types of packets are used at the Network layer: data and route updates.
Data packets -

• Used to transport user data through the inter-network. 
• Protocols used to support data traffic are called routed protocols; examples of routed protocols are IP and IPv6.

Route update packets -

• Used to update neighboring routers about the networks connected to all routers within the inter-network. 
• Protocols that send route update packets are called routing protocols; examples of some common ones are RIP, RIPv2, EIGRP, and OSPF. 
• Route update packets are used to help build and maintain routing tables on each router

Question - 4 What is Routing Table ?

Routing table is also known as Map of inter-network, basically it used to find the remote network and to forward the packets to remote networks. Routing table containing the following information.

• Network addresses A router maintain a routing table for individual routed protocol because each routed protocol keeps track of a network with a different addresses like IPv4, IPv6, IPX
• Interface The exit interface used by a packet when packet destined for a specific network.  
• Metric Metric is basically used to calculate the best path. Different routing protocols use different method to calculate the distance like hop count, delay, bandwidth.

Question - 5 Differentiate connection-oriented and connection-less network services and describe how each is handled during network communications.

• Connection-oriented - Connection oriented means reliable delivery, connection oriented services use acknowledgments, sequencing, windowing and flow control to provide a reliable session. Telephone and mobile conversation are very good example of connection oriented communication.
• Connection-less - Connection-less means unreliable delivery where acknowledgments, sequencing, windowing and flow control do not take place, connection-less services are used to send data with no acknowledgments or flow control. This is considered unreliable.

Question - 6 Identify the possible causes of LAN traffic congestion.

• Too many hosts in a broadcast or collision domain
• Broadcast storms
• Too much multicast traffic
• Low bandwidth
• Adding hubs for connectivity to the network

Question - 7 Describe the difference between a collision domain and a broadcast domain.

• Collision domain is the network segment with the two or more host sharing the same bandwidth. 
• Broadcast domain refers to a group of devices on a network segment that hear all broadcast sent on that network segment. 

Question - 8 Differentiate a MAC address and an IP address and describe how and when each address type is used in a network.

MAC Address

• A MAC address is represented in hexadecimal number and identifying the physical connection of a host.
• MAC addresses are  operate on layer 2 (Data Link Layer) of the OSI model.
• Hosts on the same physical segment locate one another with MAC addresses.

IP Address

• IP addresses can be represented in binary or decimal format,  IP addresses are logical identifiers
• IP address are operate on layer 3 (Network Layer) of the OSI model.
• IP addresses are used when they reside on different LAN segments or subnets. 
• Even when the hosts are in different subnets, a destination IP address will be converted to a MAC address when the packet reaches the destination network via routing. 

Question - 9 What is data-gram ?

Data-gram is the basic transfer unit associated with the packet switched network

Question - 10 What is bandwidth ?

Bandwidth is the bit rate of available or consumed information capacity expressed typically in metric multiple of bits per second.

Question - 11 Differentiate Analog Signal and Digital Signal.  

• Analog Signal - In analog signal information translated into electric pulsed of varying amplitude 
• Digital Signal - In digital signal information translated into binary format (0,1) and each bit representative of two distinct amplitude 
• Amplitude - It is measurement of degree of change

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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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