Network Technology

Question 1

What is Encapsulation/Decapsulation?

Answer 1

The process of adding (down) or removing (up) a Header from a layer when data is travelling through an OSI or TCP/IP model. Data is wrapped with protocol-specific headers and trailers e.g. Transport layer adds TCP segment, IP header packet then added at Network layer, etc.

Question 2

What is an OSI model?

Answer 2

OSI stands for Open System’s Interconnection Model and consists of the 7 layers computers use to communicate over a network.

Question 3

What does PDU stand for?

Answer 3

PDU stands for Protocol Data Unit. It is the unique names given to data on each layer of the OSI model. Includes Data (Physical, Presentation, Session), Segment (Transport), Packet (Network), Frame (Data Link) and Bits (Physical).

Question 4

What is the minimum length of each header?

Answer 4

20 octets (bytes)

Question 5

Define MTU.

Answer 5

MTU stands for Maximum Transmission Unit. It defines the maximum size of a frame in the data link layer. In case a packet exceeds the tolerated size, it is fragmentised.

Question 6

What is a Circuit-Switched Network?

Answer 6

A Circuit-Switched Network is when nodes between devices are predetermined and must be set up before they can communicate. It follows the same route.

Question 7

What is a Packet-Switched Network?

Answer 7

A Packet-Switched Network splits data into packets at the Network layer, and each packet may take different routes to others from the source.

Question 8

What is a MAC Address?

Answer 8

The Medium Access Control address. At the Data Link layer, devices use physical addresses to identify their neighbours.

Question 9

What is the ARP?

Answer 9

The ARP stands for Address Resolution Protocol. It is used to detect MAC addresses and find out the logical IP address associated to it.

Question 10

If two devices want to exchange data packets and the size of each unit is too big, how is this data transmitted between them?

Answer 10

A packet is fragmented in the network layer. An identifier is added to each fragment (sub-packet). The new fragment is treated as a standard packet.

Question 11

What is the maximum size of an IP packet?

Answer 11

65,535 octets.

Question 12

What is a Router?

Answer 12

A device that connects 2 or more networks together.

Question 13

What is a Hub?

Answer 13

A node that broadcasts data to every ethernet-based device or computer connected to it.

Question 14

What is a repeater?

Answer 14

Regenerates or amplifies signals to extend their reach in the network.

Question 15

What is a Switch?

Answer 15

Connects devices in a network enabling them to talk by exchanging data packets

Question 16

What is a Network Collision?

Answer 16

When two or more data packets try occupy the same network channel at the same time.

Question 17

List the PDUs

Answer 17

Data (Application, Presentation, Session), Segments (Transport), Packet (Network), Frame (Data Link), Bits (Physical)

Question 18

What’s the difference between upper layers and lower layers?

Answer 18

Upper layers are known as Application layers and are usually implemented only in software. Lower layers are known as Transport layers, and Physical and Data Link are implemented in hardware and software.

Question 19

What is the Physical layer?

Answer 19

Manages communication in the physical link (signal, voltage, physical data rates, recovery of link failure)

Question 20

What is the Link layer?

Answer 20

Provides reliable transit of data across physical network link (physical addressing, error notification, sequencing of frames, flow control, etc.)

Question 21

What is the Network layer?

Answer 21

Defines the network topology and the routing

Question 22

What is the Transport layer?

Answer 22

Segments data and ensures error-free transmission

Question 23

What is the Session layer?

Answer 23

Establishes, manages and terminates communication sessions (SCP, SIP, etc.)

Question 24

What is the Presentation layer?

Answer 24

Provides coding and conversion functions that are applied to Application layer data

Question 25

What is the Application layer?

Answer 25

Identifies communication partners, determines resource availability, and synchronises communication

Question 26

What is Control Communication (CI)?

Answer 26

It is how peer layers communicate, using headers and trailers.

Question 27

What are Bridges?

Answer 27

Filter, segment and connect 2 LANs. Extends the effective length of a LAN, reduces traffic, and acts as firewall for network errors. Can be local (using LAN switches) and remote (using WAN)

Question 28

What are Switches?

Answer 28

Found on Layer 2 (Data Link) of the OSI model. Forward and flood traffic based on MAC addresses. Segments large LAN into smaller segments. Have many ports compared to bridges. Reduces collision and supports cut-through switching.

Question 29

What are the three types of routers?

Answer 29

Access router, Core router and Edge router.

Question 30

What is an Access Router/Point?

Answer 30

A router that connects directly to end hosts. May be mobile or stationary.

Question 31

What is a Core Router?

Answer 31

Connects to multiple access routers (multiple LANs) and performs intra-domain routing.

Question 32

What is an Edge router?

Answer 32

Connects and performs routing between different AS. Ingress Router (traffic enters a domain) and Egress Router (traffic leave a domain)

Question 33

What is a Collision Domain?

Answer 33

When a device sends out a message to the network, all other devices included in its collision domain have to pay attention to it. This causes problems in situations where two devices send out their messages simultaneously. A collision will occur causing them to wait and re-transmit their messages one at a time. Only happens in half-duplex mode.

Question 34

Explain one way of reducing collisions

Answer 34

Switches reduce collisions by isolating each port to its own collision domain, typically by using full-duplex technology where each port can send and receive data at the same time, eliminating collisions.

Question 35

What is the Broadcast Domain?

Answer 35

The Broadcast Domain is the domain in which a broadcast is forwarded containing all the devices that can reach each-other at the Data Link layer via broadcast.

Question 36

What is a Collision Domain?

Answer 36

A Collision Domain is any part of the network where packet collisions can occur. When two devices send a packet at the same time on a shared network segment, they collide and must be resent.

Question 37

What is a Network Port?

Answer 37

A virtual port where network connections begin and end.

Question 38

What is Carrier Sense Multiple Access (CSMA)?

Answer 38

Carrier Sense Multiple Access (CSMA) is a protocol that operates on the Data Link layer of the OSI Model. It is when a node verifies the absence of other traffic before transmitting on a shared transmission medium.