TCP/IP Basics Flashcards
IP Packet
Composed at Layer 3, includes IP info and payload from Layer 4
Gets encapsulated at Layer 2
Internet Control Message Protocol
ICMP
Important role in error reporting and diagnostics
Operates at Layer 3
Transmission Control Protocol
TCP
Connection-oriented protocol
User Datagram Protocol
UDP
Connectionless protocol
Three way handshake
Part of TCP
SYN - SYN-ACK, ACK
Sender sends syn, receiver responds with syn-ack, sender sends final ack
Main TCP Header parts
Source Port - Destination Port - Sequence Number - Acknowledgement Number
Will also include:
Flags: individual bits that give info on state of connection
Checksum - recipient can use this to validate data
User Datagram Protocol
UDP
Unlike with TCP, data does not get segmented in Layer 4.
UDP Datagram Header
Source port - destination port - length - checksum
Universal Broadcast MAC Address
FF-FF-FF-FF-FF-FF
CLI terms to get IP and MAC on:
MacOS
WinOS
Linux
ifconfig
ipconfig /all
ip (or ifconfig, but that is depreciated)
Bits in an IP(v4) address?
32
4 octets
Network ID
The shared portion of clients on a LAN
client unique portions will be written as a 0
Default Gateway
IP address of the router for a LAN
Frequently will be given the lowest or highest possible IP address within the network ID range
Subnet mask
Series of ones followed by zeroes
The ones stop where the network ID stops in dotted decimal, generally.
Computers can compare their IP with another against the subnet mask - if they are identical up to where the ones stop, they share the same subnet.
Address Resolution Protocol
ARP
An ARP request broadcasts to all MAC addresses on LAN. Sends destination IP, gets a response from destination IP with corresponding destination MAC, allows NIC to create frame with destination now
CIDR notation
/[NUMBER]
Number = the number of ones in the subnet mask
Automatically know the subnet mask from CIDR notation