Network+ Chapter 7: TCP/IP Basics pg 177 - 183

The TCP/IP Protocol Suite
- TCP/IP Model: Link, Internet, Transport, and Application layers

Internet Layer Protocols
- takes data chunks from the transport layer, adds an address, and creates the final IP packet
- IP then hands the IP packet to layer 2 for encapsulation into a frame
- ICMP: Internet Control Message Protocol
- full IP packet has 14 different fields

• Version (Ver): defines the type of IP address
• Header Length: total size of the IP portion of the packet in words
• Differentiated Services code Point (DSCP): contains data used by bandwidth sensitive applications 
• Time to Live (TTL): prevents an IP packet from indefinitely spinning through the internet 
• Protocol: Either TCP or UDP 

Transport Layer Protocols
- Transmission Control Protocol (TCP)
- User Datagram Protocol (UDP)

TCP
- 95% of all TCP/IP applications use TCP
- requires both the sending and the receiving machines to acknowledge the other's presence and readiness to send and receive data
- ACK/NACK or just ACK
- chops up data into segments, gives the segments a sequencing number, and verifies that all segments were received
- each application is designed a specific port number
- web servers use port 80 (HTTP)
- e-mail uses port 110 (POP3)
- TCP Headers

• Sequence Number: used to assemble/disassemble data
• ACK Number: tracks the readiness of the two communicating systems 
• Flags: give sending an receiving ends detailed information on state of connection
• Checksum: checks the TCP header for errors
• Source Port
• Destination Port 

 - UDP works best when transferring large amounts of data