TCP/IP Flashcards
What is a client program?
Running on end host
Does not communicate directly with other clients
Needs to know address of server
Can a client program communicate with other clients?
Not directly.
What is a server program?
Running on end host
Does not initiate contact with clients
Needs fixed, known address
How does the network layer deliver data?
Delivers data packet to destination host based on destination IP
How does the OS deliver data?
Delivers data to destination socket based on destination port number
How does the application layer deliver data?
Read data from and write data to socket (then interpret data - eg. read a webpage)
What is a socket?
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.
How does a process send a message to another process?
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.
What level is TCP/IP?
Kernel
What does socket API allow us to do?
Supports creation of network applications
What must exist to develop ICP using a network application?
An association
How do we represent a socket?
As a 5 tuple consisting of protocol, source IP, source port number, destination IP and destination port number
What do port numbers do?
Uniquely identify a socket.
Can same port number be used twice with the same address?
negative.
What ensures a port number isn’t used twice in the same address?
OS
What are some common port numbers?
80 - standard for web servers
25 - mail
How to use sockets server side
socket() bind() - binds socket to IP address listen() - listen for client accept() - if client does connect, you accept it read() write()
How to use sockets client side
socket()
connect()
write()
read()
What are well known port numbers?
0 - 1023
These require root to use
What are ephemeral port numbers?
1024- 65535
these can be good temp ports
What does accept() do?
Takes in a fd of the socket and returns a new fd for reading and writing
What internet protocols do we use when creating a socket?
AF_INET for ipv4
AF_INET6 for ipv6
What are the inputs to socket()?
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)
What structs are useful for sockets? Examples.
sockaddr, sockaddr_in
What do big endian and little endian refer to?
Little endian: little end comes first, low order byte stored at lowest memory location
Big endian: high order byte stored at lowest memory location
How do we translate a server name into an address?
Using struct hostnet, gethostbyname()
What’s the difference between stream and datagram sockets?
Stream: send long stream of characters, typically implemented on top of TCP
Datagram: send single packet, typically implemented on top of UDP
What socket would you typically implement on top of UDP?
Datagram, SOCK_DGRAM
What socket would you typically implement on top of TCP?
Stream, SOCK_STREAM
What does sendto do?
Sends data to another UDP socket
What does subnetting do?
Allows the address to act internally as multiple addresses and externally as one
What is ICMP?
internet control message protocol is used for testing and monitoring ambient conditions between hosts and routers
