Open Systems Interconnection (OSI) model

2.1 – Ports and Protocols

Introduction to IP (18:48)
IP ——- Internet Protocol
UDP ——- User datagram protocol
TCP ——- Transmission Control Protocol
** Both UDP and TCP are designed for sending and transmitting information.
** TCP is a connection-oriented protocol, whereas UDP is a connectionless protocol.
** TCP and UDP works at Transport layer of network (Layer 4 of the OSI Model)

**Port Number ——— The port number is “tacked on” to the end of the IP address, for example, “192.168. 1.67:80” shows both the IP address and port number.

** Port 80: To send Unencrypted Data. Port 80 is the port number assigned to commonly used internet communication protocol, Hypertext Transfer Protocol (HTTP). It is the default network port used to send and receive unencrypted web pages.

** Port 443: To Send Encrypted Data. Port 443. The Internet Engineering Task Force (IETF) recognizes the TCP port number 443 as the default HTTPS protocol. It provides an encryption algorithm for exchanging information between web servers and browsers. HTTPS port 443 works by securing network traffic packets before the data transmission occurs.

** Port 123: For Time Server

** Port 25: Mail Server

Non-ephemeral Ports ———– Permanent Ports from Port 0 to Port 1023
Ephemeral Ports —————— Temporary Port Numbers from Port 1024 to Port 65535

** TCP and UDP ports can be any number between 0 and 65535.
** Port number are for communication, not security

HTTP ——- Hypertext Transfer Protocol
HTTPS ——- Hypertext Transfer Protocol Secure

Common Network Ports (13:18)
** IPv4 vs IPv6 ——- The main difference between IPv4 and IPv6 is the address size of IP addresses. The IPv4 is a 32-bit address, whereas IPv6 is a 128-bit hexadecimal address.

The Internet Protocol version 6 (IPv6) is more advanced and has better features compared to IPv4.

2.2 – Network Devices

** Routes traffic between IP subnets
** Make forwarding decisions based on IP address
** Routers inside of switches sometimes called “Layer 3 Switches”.
** A Router works at OSI Layer 3 (Network Layer)

** A subnet, or subnetwork, is a segmented piece of a larger network. More specifically, subnets are a logical partition of an IP network into multiple, smaller network segments.

A switch is a hardware component in network infrastructure that performs the switching process. The switch connects network devices, such as computers and servers, to one another. 
** Forwards traffic based on data link address
** ASIC: Application-Specific integrated circuit

**A network switch operates at Layer 2 (Data Link Layer) of the Open Systems Interconnection (OSI) model.

Unmanaged Switch:
** Very few configuration Options, Plug and Play
** Fixed Configuration, No VLANs
** Very Little integration with other devices, No Management Protocols
** Low Price Point, less expensive

Access Point:
Access point is bridge that extends the wired network onto the wireless network.

** Filters traffic by port number
** OSI layer 4 (TCP/UDP)

Cable Modem:
— Transmission across multiple frequencies
— Different Traffic types
** DOCSIS —— Data Over Cable Service Interface Specification.
** ADSL ——- Asymmetric Digital Subscriber Line.

How is a switch different from a hub? 

Before there were switches, there were network hubs. Hubs enable many devices to plug into a network through a single shared port on a router. The disadvantage of hubs is that when a hub receives a packet, it sends copies of the packet to every other device connected to it. This can cause problems with traffic congestion and data security.

Switches solve this problem by keeping tables of the MAC addresses of all devices sending packets to them and forwarding packets only to their destinations, instead of flooding all connected devices with the packets. 

How is a switch different from a router?

A switch connects devices within a LAN (local-area network) by using MAC addresses to identify where to send data packets. A router connects LANs to other area networks or to the internet. A router uses IP addresses to route data packets.

Software Defined Networking (4:38)

2.3 – Wireless Networks

2.4 – Network Services

2.5 – Network Configurations

2.6 – Network Connections

2.7 – Internet Connections

2.8 – Network Tools