Nätverksprotokoll

Question 1

Communication methods: three elements in common?

Answer 1

Source-Channel-Destination

Question 2

What does protocols include?

Answer 2

• Identified sender and receiver
• Common language and grammar
• Speed and timing of delivery
• Confirmation (ACK)

Question 3

What does protocols define?

Answer 3

Message encoding, delivery options, formatting and encapsulation, timing and size.

Question 4

Message encoding process?

Answer 4

Message is converted into bits by the sending host → Each bit is encoded into a pattern of sounds, light waves or electrical impulses (depends on media) → Destination host receives and decodes the signals.

Question 5

What is a frame?

Answer 5

A frame works as an envelope providing destination address and source address

Question 6

What happens with messages that are too big?

Answer 6

Broken down to smaller pieces → each piece is sent in separate frames.
Each frame has its own addressing info.

Question 7

Describe Access Method?

Answer 7

Hosts on a network need to know when to begin sending messages and how to respond when collisions occur.

Question 8

What is flow control?

Answer 8

Source and destination host use it to negotiate correct timing to avoid overwhelming the destination and ensure information is received.

Question 9

What is response timeout?

Answer 9

How long to wait for response and what action to take if a response timeout occurs.

Question 10

What are the 3 common networking protocols

Answer 10

HTTP, TCP, IP

Question 11

Here is a protocol interaction example

Answer 11

PC and web server communication

• HTTP → app protocol that control the way a web server and a client interact
• TCP → transport protocol that manages the individual conversations
• IP → encapsulates the TCP segments into packets, assign addresses and delivers to destination
• Ethernet → allow communication over a data link

Question 12

What happens when a router receives a frame from another router?

Answer 12

The router adds new data link information (MAC source) before forwarding the packet.

Question 13

What happens when a client receives the frames?

Answer 13

The client removes each protocol header in the opposite order it was added: Ethernet → IP header → TCP header → HTTP info.

Question 14

What does Open standard protocols mean?

Answer 14

The protocols are freely available, and any vendor is
able to implement these protocols on their hardware
or in their software.

Question 15

What is Multiplexing?

Answer 15

By sending smaller pieces, many different conversations can be interleaved on the network, called multiplexing.

Vilket innebär att flera kan kommunicera samtidigt, vi delar på tillgänglig bandbredd.

Question 16

What happens if a part of a message fails to reach destination?

Answer 16

The missing part is retransmitted. This is one of the advantages of message segmentation.

Question 17

What is Encapsulation?

Answer 17

When information is added at each level of the protocol model.

Question 18

What is PDU and what are the names of the PDU at the different layer levels?

Answer 18

PDU stands for Protocol Data Unit. And is a significant term related to the initial four layers of the OSI model.
In Layer 1, PDU is a bit,
in Layer 2 it is a frame,
in Layer 3 it is a packet and,
in Layer 4 it is a segment.
In Layer 5 and above, PDU is referred to as data.

Question 19

An example of encapsulation.

Answer 19

1. Data is divided into segments
2. TCP segment is encapsulated in IP packet
3. IP packet is encapsulated in Ethernet Frame
4. The frame is encapsulated into bits.

Question 20

What is the responsibility of the network layer(Layer 3)?

Answer 20

The network layer is responsible for routing, Delivering the IP packet from source to destination. (IP source-destination). If the packets are too large for delivery, they are broken down into smaller frames.

Question 21

What is the purpose of the data link layer (Layer 2)

Answer 21

Deliver data link frame from one network interface to another on the same network (MAC address source-destination)