Application Layer

Question 1

What are the characteristics of a client vs a server?

Answer 1

Dynamic vs permanent IP address, location, communication etc etc

Question 2

What is a process?

Answer 2

A program running within a host

Question 3

Client vs server process.

Answer 3

Process that initiates communication vs a process that waits to be contacted

Question 4

How do processes communicate within the same host vs in different hosts?

Answer 4

Inter-process communication vs exchanging messages

Question 5

What does a process use to send/receive messages?

Answer 5

A socket

Question 6

What is the relationship between the host, processes, sockets, ip addresses and port numbers

Answer 6

Within a host, there are processes.
And processes send messages from client to server through sockets. Each host has an IP address, and each process within the host has a port number. This port number is an identifier, and each process must have on in order to receive messages

Question 7

Does the IP address of the host on which a process runs suffice for identifying the process?

Answer 7

No, many processes can be running on the same host

Question 8

What are the port numbers for the following servers?
Http (TCP)
Https (TCP)
Telnet (TCP)
DNS (UDP)
SSH (TCP)
mail server

Answer 8

Http (TCP) - 80
Https (TCP) - 443
Telnet (TCP) - 23
DNS (UDP) - 53
SSH (TCP) - 22
mail server - 25

Question 9

What does an application layer protocol define?

Answer 9

Types of messages exchanged; message syntax; message semantics; rules for how processes send and respond to messages; open protocols, proprietary protocols.

Question 10

What does reliable data transfer entail?

Answer 10

All bytes sent get to the other side in the same order with no gaps.

Question 11

What transport service does an app need?

Answer 11

Data integrity which includes reliable data transfer; Timing, which refers to low delay, Throughput whether elastic or a minimum amount, And security, encryption and data integrity.

Question 12

TCP vs UDP go.

Answer 12

Reliable transport, flow control, congestion control, connection oriented.
Vs
Unreliable data transfer.

Question 13

What do neither TCP nor UDP have?

Answer 13

Timing, minimum throughput guarantee, and security.

Question 14

How can TCP be made more secure?

Answer 14

Transport layer security (TLS) encrypts TCP connections and allow for data integrity and end point authentication.

Question 15

What does a web page consist of?

Answer 15

Objects, a base html file which contains several referenced objects, each addressable by a URL.

Question 16

What is a url comprised of?

Answer 16

A host name and a path name

Question 17

In hypertext transfer protocol (HTTP), what is a client/server?

Answer 17

A client is a browser that requests receives and displays objects.
A server sends objects in response to requests.

Question 18

What does it mean to say HTTP is stateless?

Answer 18

The server maintains no information about past client requests.

Question 19

Non-persistent HTTP vs persistent HTTP.

Answer 19

For non persistent HTTP, only one object can be sent over TCP connection.
for persistent HTTP, multiple objects can be sent over one TCP connection.

Question 20

What is round-trip time (RTT)?

Answer 20

The time for a small packet to travel from client to server and back.

Question 21

Non-persistent HTTP response time =

Answer 21

2RTT + file transmission time

Question 22

How does persistent HTTP address non persistent HTTP issues?

Question 23

What are the two types of http messages?

Answer 23

Request and response

Question 24

Name four http request methods

Answer 24

Get, post, head, put

Question 25

List 5 http status response codes

Answer 25

200 OK
301 Moved Permanently
400 Bad Request
404 not found
505 http version not supported

Question 26

Which http request-response interaction is stateless?

Answer 26

Get.