TCP/IP

Question 1

What is a client program?

Answer 1

Running on end host
Does not communicate directly with other clients
Needs to know address of server

Question 2

Can a client program communicate with other clients?

Answer 2

Not directly.

Question 3

What is a server program?

Answer 3

Running on end host
Does not initiate contact with clients
Needs fixed, known address

Question 4

How does the network layer deliver data?

Answer 4

Delivers data packet to destination host based on destination IP

Question 5

How does the OS deliver data?

Answer 5

Delivers data to destination socket based on destination port number

Question 6

How does the application layer deliver data?

Answer 6

Read data from and write data to socket (then interpret data - eg. read a webpage)

Question 7

What is a socket?

Answer 7

Essentially a doorway leading in and out of an application. In order for a process to send a message to another, the underlying network must be traversed. This process sends and receives messages through the socket.

Question 8

How does a process send a message to another process?

Answer 8

In order for a process to send a message to another, the underlying network must be traversed. This process sends and receives messages through the socket.

Question 9

What level is TCP/IP?

Answer 9

Kernel

Question 10

What does socket API allow us to do?

Answer 10

Supports creation of network applications

Question 11

What must exist to develop ICP using a network application?

Answer 11

An association

Question 12

How do we represent a socket?

Answer 12

As a 5 tuple consisting of protocol, source IP, source port number, destination IP and destination port number

Question 13

What do port numbers do?

Answer 13

Uniquely identify a socket.

Question 14

Can same port number be used twice with the same address?

Answer 14

negative.

Question 15

What ensures a port number isn’t used twice in the same address?

Answer 15

OS

Question 16

What are some common port numbers?

Answer 16

80 - standard for web servers

25 - mail

Question 17

How to use sockets server side

Answer 17

socket()
bind() - binds socket to IP address 
listen() - listen for client
accept() - if client does connect, you accept it
read()
write()

Question 18

How to use sockets client side

Answer 18

socket()
connect()
write()
read()

Question 19

What are well known port numbers?

Answer 19

0 - 1023

These require root to use

Question 20

What are ephemeral port numbers?

Answer 20

1024- 65535

these can be good temp ports

Question 21

What does accept() do?

Answer 21

Takes in a fd of the socket and returns a new fd for reading and writing

Question 22

What internet protocols do we use when creating a socket?

Answer 22

AF_INET for ipv4

AF_INET6 for ipv6

Question 23

What are the inputs to socket()?

Answer 23

family, type, protocol

fam: AF_INET or AF_INET6
type: SOCK_STREAM for TCP, SOCK_DGRAM for UDP
protocol: 0 (not used for internet sockets)

Question 24

What structs are useful for sockets? Examples.

Answer 24

sockaddr, sockaddr_in

Question 25

What do big endian and little endian refer to?

Answer 25

Little endian: little end comes first, low order byte stored at lowest memory location
Big endian: high order byte stored at lowest memory location

Question 26

How do we translate a server name into an address?

Answer 26

Using struct hostnet, gethostbyname()

Question 27

What’s the difference between stream and datagram sockets?

Answer 27

Stream: send long stream of characters, typically implemented on top of TCP
Datagram: send single packet, typically implemented on top of UDP

Question 28

What socket would you typically implement on top of UDP?

Answer 28

Datagram, SOCK_DGRAM

Question 29

What socket would you typically implement on top of TCP?

Answer 29

Stream, SOCK_STREAM

Question 30

What does sendto do?

Answer 30

Sends data to another UDP socket

Question 31

What does subnetting do?

Answer 31

Allows the address to act internally as multiple addresses and externally as one

Question 32

What is ICMP?

Answer 32

internet control message protocol is used for testing and monitoring ambient conditions between hosts and routers