2.1 - Introduction to IP

Question 1

A series of moving vans

Answer 1

• Efficiently move large amounts of data
• Use a shipping truck
• The network topology is the road
• Ethernet, DSL, cable system
• The truck is the Internet Protocol (IP)
• We’ve designed the roads for this truck
• The boxes hold your data
• Boxes of TCP and UDP
• Inside the boxes are more things
• Application information

Question 2

TCP and UDP

Answer 2

• Transported inside of IP
• Encapsulated by the IP protocol
• Two ways to move data from place to place
• Different features for different applications
• OSI Layer 4
• The transport layer
• Multiplexing
• Use many different applications at the same time
• TCP and UDP

Question 3

TCP – Transmission Control Protocol

Answer 3

Connection-oriented
• A formal connection setup and close
• “Reliable” delivery
• Recovery from errors
• Can manage out-of-order messages or retransmissions
• Flow control
• The receiver can manage how much data is sent

Question 4

Port numbers

Answer 4

• TCP and UDP ports can be any number
between 0 and 65,535
• Most servers (services) use non-ephemeral
(not-temporary) port numbers
• This isn’t always the case
• It’s just a number.
• Port numbers are for
communication, not security
• Service port numbers need
to be “well known”
• TCP port numbers aren’t the same
as UDP port numbers

Question 5

Lots of ports

Answer 5

• IPv4 sockets - Server IP address, protocol,
server application port number
• Client IP address, protocol, client port number
• Non-ephemeral ports – permanent port numbers
• Ports 0 through 1,023
• Usually on a server or service
• Ephemeral ports – temporary port numbers
• Ports 1,024 through 65,535
• Determined in real-time by the client

Question 6

Speedy delivery

Answer 6

The IP delivery truck delivers from
one (IP) address to another (IP) address
• Every house has an address,
every computer has an IP address
• Boxes arrive at the house / IP address
• Where do the boxes go?
• Each box has a room name
• Port is written on the outside of the box
• Drop the box into the right room

Question 7

UDP – User Datagram Protocol

Answer 7

• Connectionless
• No formal open or close to the connection
• “Unreliable” delivery
• No error recovery
• No reordering of data or retransmissions
• No flow control
• Sender determines the amount of data transmitted