Day 2

- Communication Servers
-
- Modems

Network media = Fiber, copper, wireless.
Copper, twisted pair: problem with copper electromagnetic interference.
Fiber, uses light pulses.
Wireless, electromagnetic waves for wireless.

Considerations:

1. How far you need to go.
2. Distance
3. What kind of bandwidth
4. Cost of installation, connectors, etc.
Types of networks:
1. LAN – a group of IN devices in control of a single administrator.
2. WAN – tend to connect geographically challenged locations.
3. Internetwork – collection of two more LAN’s.
4. Intranet – is a private web network that is closed to the public.
5. ISP
6. NIC – is a physical connection to the network. Network Internet Connection.
7. Port – physical port, where you can plug in a cable.
8. Protocols are rules.
Protocols define sharing, update message, starting/stopping communication.
IEEE - standardized the protocols that everyone agreed to.
IETF – Internet Engineering Task Force, the protocols they designed are provider independent.
A group of protocols can be grouped in a different Layer.
Protocol model, describes functions that occur.
Reference model, gives you a common reference for each layer.

TCP/IP suite PiPP:
- Application (httpd)
- Transport (communication between devices)
- Internet (path selection)
- Network (hardware and media)
OSI Model:
- Application layer. 7
- Presentation 6
- Session 5
- Transport 4
- Network 3
- Data Link 2
- Physical 1
Incapsulation: Take data and capsulate it as data goes as you go from layer 7 to layer 1.
Decapsulation: Data going from layer 1 to layer 7.

- Data Link, Layer 2 – FRAMES = Mac.addr
- Network, Layer 3 – Packets = IP ADDR
- Transport, Layer 4 = Port. Address

Chapter 3: Application Layer, first step on getting data off to the internet.

It has:
- Applications: software used to communicate over the internet. Not windows/excel/etc.
- Services: File transfer.
- Protocols: HTTP, FTP, DNS. Exchange data between source and destination.

APPLICATION LAYER (Layer 7) - first step on getting data off to the internet.

PRESENTATION LAYER (Layer 6) - coding and conversion of the application layer. Compression, encryption, etc.

SESSION LAYER (Layer 5) - establishes a session, mantains a session, and terminates a session.

Telnet, is an application, a service, a protocol. Telnet allows you to have remote access to another device

Client server model = a requesting device, "please send me some data"
Server model = is a responding device. Server can handle multiple clients at one time.

Daemon = service that is running on the background, it listens for a request and then respond.

PEER-TO-PEER = two or more computers connected to a network.

PORT NUMBERS::

-DNS can be TCP/UDP port 53.
-HTTP is TCP port 80
-SMTP is TCP port 25
-Telnet is TCP port 23
-DHCP