The first steps from “Breaking into InfoSec” is to learn or at least catch up on Network Fundamentals. While I worked as a network admin for a couple years, it was with a smaller company and there are things you learn on the job and then there are things that you just didn’t need to learn to keep the network going. With the coming videos, I’ll dive into the easy.. IP information to the, probably not hard but I’ve always ignored the OSI model, why? who knows. but here I go.
The first video is Introduction to IP
Most of this was refreasher for me but there were some take-aways and deeper information that I thought was worth taking note of.
TCP/UDP Multiplexing
Use many differnet applications at the same time
TCP = Transmission Control Protocol
TCP numbers packets
Receiving device can slowdown transmissio
UDP = User Datagram Protocal
Connectionless
Sender determines transmission speed
Non-ephemeral ports = Permanent port numbers
Ports 0 through 1023
On a server or service
Ephemeral Ports = Temp port numbers
Ports 1024 through 65,535
Usually determined by client (real time), could be random
Port numbers are for communication, not security
UDP :80 and TCP:80 are different ports
Not conflict
Most applications have well know ports
Webservices tcp/80
Voip udp/5004
Email server tcp/143
ICMP = Internet Control Message Protocol
Checkin for devices
Not for data transfer
Checks on a device
Devices can also send ICMP message
(like time to live has expired)