Week3

Question 1

How Check-sum works?

Answer 1

Adds one more bit at the end to check if some bit flipped. Odd is 1 and even is 0.

Question 2

Media Access Control (MAC)

Answer 2

First 3 groups: vendor

Last are the address.

Question 3

Layer 2 switch

Answer 3

Every port on the switch is mapped to the MAC address of the computer.

Question 4

VLAN

Answer 4

A group of computers are configured as if they are in the same LAN.
Also, it can also keep network apps separate despite connected to the same physical network.

Question 5

Layer 3 - Network Layer

Answer 5

Dedicated to routing information to different networks;
Logical addressing hosts.
Instead MAC, the addressing system is made by IP for example.
Unit of measurement is packets

Question 6

Layer 3 switches

Answer 6

Layer 3 switches forward packets, whereas layer 2 switches forward frames.
Instead MAC, the addressing system is made by IP for example.

Question 7

Layer 4 - Transport Layer

Answer 7

This layer transmits messages between hosts through logical addressing.
It shields the upper layers from transport implementations details.
The protocols provide services such as break up messages, and send them through the subnet.
It informs the order of the packets which were broken in small packets.

Question 8

Connection Oriented Communications

Answer 8

CO Mode require that both devices or computers involved in the communication establish an end-to-end logical connection before data can be sent between the two.
If and individual packet is not delivered in a timely manner, it is resent; this can be done because the sending computer established the connection at the beginning of the session and knows where to to send.

Question 9

CL - Connectionless Communications

Answer 9

No end-to-end connection is necessary before data is sent.

Every packet that is sent has the destination address located in its header.

Question 10

Ports

Answer 10

Ports act as logical communications endpoints for computers.
65,536 (2^16). ports.
Internet Assigned Numbers Authority or IANA defines and divide in categories.
0-1023 = well known
1024 - 49151 = registered ports

Question 11

Inbound ports

Answer 11

Used by server to acccept incoming service requests

Question 12

Outbound ports

Answer 12

Used by client computers and are assigned dynamically by the OS

Question 13

Multiplexing / demultiplexing

Answer 13

Multiplexing is the process of combining two or more data streams into a single physical connection
TCP provides multiplexing

Question 14

Layer 5 - Session Layer

Answer 14

This layer governs the establishment, termination, and synchronization.

Question 15

Layer 6 - Presentation Layer

Answer 15

This layer translates the data format from sender to receiver that may be used.
Concepts include conversion (ex: ASCII), data compression (JPEG)

Question 16

Layer 7 - App Layer

Answer 16

This layer provides network services to user apps and is where message begins.
End-user protocols stand here.