2.1 Intro 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

– 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

Answer 2

A series of moving vans

Question 3

TCP and UDP

Answer 3

• 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 4

• 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

Answer 4

TCP and UDP

Question 5

TCP – Transmission Control Protocol

Answer 5

• 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 6

• 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

Answer 6

TCP – Transmission Control Protocol

Question 7

UDP – User Datagram Protocol

Answer 7

• Connectionless - No formal open/close to the connection
• “Unreliable” delivery
  – No error recovery
  – No reordering of data or retransmissions

Question 8

• Connectionless - No formal open/close to the connection
• “Unreliable” delivery
  – No error recovery
  – No reordering of data or retransmissions

Answer 8

UDP – User Datagram Protocol

Question 9

Why would you ever use UDP?

Answer 9

• Real-time communication
  – There’s no way to stop and resend the data
  – Time doesn’t stop for your network
• Connectionless protocols
  – DHCP (Dynamic Host Configuration Protocol)
  – TFTP (Trivial File Transfer Protocol)

Question 10

Communication using TCP

Answer 10

• Connection-oriented protocols prefer a “return receipt” – HTTPS (Hypertext Transfer Protocol Secure)
  – SSH (Secure Shell)
• The application doesn’t worry about out of order frames or missing data
  – TCP handles all of the communication overhead – The application has one job

Question 11

Speedy delivery

Answer 11

• 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 12

Lots of ports

Answer 12

• 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 13

Port numbers

Answer 13

• 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