Introduction to IP - CompTIA A+ 220-1201 - 2.1

A Series of Moving Vans

•Efficiently move large amounts of data

- use a shipping truck

•The network topology is the road

- ethernet, DSL, coax cable

•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

IP - Internet Protocol

*Routing protocol that is in charge of forwarding packets on the Internet from the Client to the Server

- Ethernet Header -> Ethernet Payload -> Ethernet Trailer

- Ethernet Header -> IP -> IP Payload -> Ethernet Trailer

- Ethernet Header -> IP -> TCP -> TCP Payload -> Ethernet Trailer

- Ethernet Header -> IP -> TCP -> HTTP data -> Ethernet Trailer

TCP and UDP

*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

TCP (Transmission Control Protocol)

•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

UDP (User Datagram Protocol)

•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

Why would you ever use UDP?

*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)

*The data might not get through

- the application keeps track and decides what to do

- it might not do anything

Communication using TCP

•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

Speedy Delivery

•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

Lots of Ports

•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

Port Numbers

•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

Ports on the Network

*Web server - tcp/80

*VoIP server - udp/5004

*Email server - tcp/143