Introduction to Networking

What is Networking?

Basics of Networking

Network

An interconnection of Computers.

The Internet

The physical connection of computers and wires around the world.

The Web

The information present on the Internet.

Networking

In an IT field, managing, building, and designing networks.

Networking Hardware

• Ethernet Cables
• Wi-Fi
• Fiber Optics
• Router
• ISP Network
• Switches and Hubs

Network Stack

A set of hardware or software that provides the infrastructure for a computer.

Language of the Internet

IP

Delivers packets to right computers.

TCP

Delivers information from one network to another.

The Web

• URL
• Domain Name (registered with ICANN: internet corporation for assigned names and numbers)
• DNS

Limitations of the Internet

History of the Internet

• 1960s DARPA project introduced with the earliest form of Internet called ARPANET.
• 1970s invention of TCP/IP made possible the interconnection of computers and different networks.
• 1990s was the start of World Wide Web (WWW).

Limitations of the Internet

• IPV4 addresses are limited, only >4 billion.
• IPV6 addresses solve this problem with 2¹²⁸ addresses, but adaptation is slow and expensive.

Network Address Translation (NAT)

Lets an organization use one public IP address and many private IP addresses within the network.

Impact of the Internet

Globalization

The movement that lets governments, businesses, and organizations communicate and integrate together on an international scale.

Internet of Things (IOT)

Smart devices like thermostat, refrigerators, and other home appliances as well as every day smart devices which are being connected to the internet thanks to the IOT.

Privacy and Security

• GDPR (General Data Protection Regulation)
• COPPA (Children Online Privacy Protection Act)
• Copyright Laws

Introduction to Computer Networking

Protocol

A defined set of standards that computers must follow in order to communicate properly.

Computer Networking

The name we’ve given to the full scope of how computer communicate with each other.

• TCP/IP five layered network model

The Basics of Networking Devices

Cables

“Connect different devices to each other, allowing data to be transmitted over them.”

• Copper Cables
  • Change voltage to get binary data
  • The most common forms of copper twisted-pair cables used in networking are Cat5, Cat5e, and Cat6 cables

  

  Crosstalk: “When an electrical pulse on one wire is accidentally detected on another wire.”

• Fiber Optic Cables

  Contain individual optical fibers, which are tiny tubes made out of glass about the width of a human hair.

• Unlike copper cables, fibers use light pulses to send 1s and 0s

Hubs and Switches

Hub

A physical layer device that allows for connections from many computers at once.

• Layer 1 device
• Collision domain: A network segment where only one device can communicate at a time.

• If multiple systems try sending data at the same time, the electrical pulses sent across the cable can interfere with each other.

  

Network Switch

• Layer 2 device
• Can direct traffic to a particular node on network, so reduces Collision Domain

Routers

• The primary devices used to connect computers on a single network, usually referred to as a LAN or local area network

  A device that knows how to forward data between independent networks

• Layer 3 (network) device
• Core ISP routers (More complex than home routers) form the backbone of the internet.

Servers and Clients

Server Provide data to some client, requesting it

• Vague definition, as individual programs running on the computer can also act a server

The TCP/IP Five-Layer Network Model

1) Physical Layer

Represents the physical devices that interconnect computers.

• 10 Base T, 802.11
• Bits

  The smallest representation of data that a computer can understand; it’s a one or zero

• 1s and 0s are sent across the network using modulation

  Modulation: A way of varying the voltage of charge moving across the cables

• When using modulation in computer networks, it’s called Line coding

Twisted-Pair Cabling and Duplexing

• Most common
• Twisted-Pair to avoid interference & crosstalk

Duplex Communication: The concept that information can flow in both directions across the globe

Simplex Communication: This is unidirectional

Network Ports and Patch Panels

• Twisted-Pair Cables end with the plug which takes the wires and act as a connector

• The most common plug RJ45

  

  Network Ports: They are generally directly attached to the devices that make up a computer network

• Most network ports have two small LEDs

  Activity LED: Would flash when data actively transmitted across the cable

  Link LED: Lit when cable properly connected to two devices that are both powered on

• Sometimes a network port isn’t connected directly to a device. Instead, there might be network ports mounted on a wall or underneath your desk. These ports are generally connected to the network via cables, run through the walls, that eventually end at a patch panel.

  Patch Panel: A device containing many network ports. But it does no other work.

2) Data Link Layer

Responsible for defining a common way of interpreting these signals so network devices can communicate.

• Ethernet: The Ethernet standards also define a protocol responsible for getting data to nodes on the same network.
• WI-FI
• Frames
• Mac-Address

Ethernet and MAC Addresses

• Ethernet is the most common means of sending data

• Ethernet solves Collision domain by using a technique known as carrier sense multiple access with collision detection (CSMA/CD).

  CSMA/CD: Used to determine when the communications channels are clear, and when device is free to transmit data

  MAC Address: A globally unique identifier attached to an individual network interface

  • It’s a 48- bit number normally represented by six groupings of two hexadecimal numbers
  • Hexadecimal: A way to represent numbers using 16 digits

  

  • Another way to represent MAC Address is Octet
  • Octet: In computer networking, any number can be represented by 8 bits
  • MAC-Address is split in two categories

  1) Organizationally Unique Identifier(OUI): The first three octets of a MAC address

  2) Vendor Assigned(NIC Cards, Interfaces): Last three octets are assigned by the vendor, depending upon their preferences.

  

  • Ethernet uses MAC addresses to ensure that the data it sends has both an address for the machine that sent the transmission, and the one the transmission was intended for.

Uni-cast, Multicast and Broadcast

• Uni-cast

  A uni-cast transmission is always meant for just one receiving address

  

  • It’s done by looking at a specific bit in the destination MAC address
  • If the least significant bit in the first octet of a destination address is set to zero, it means that an Ethernet frame is intended for only the destination address.
  • If the least significant bit in the first octet of a destination address is set to one, it means you’re dealing with a Multicast frame.

  

• Broadcast

  An Ethernet Broadcast is sent to every single device on a LAN

  • This is accomplished by a special address known as Broadcast address
  • Ethernet broadcast are used, so devices can learn more about each other
  • Ethernet broadcast address used is FF:FF:FF:FF:FF:FF:FF

  

Dissecting an Ethernet Frame

• Data Packet

  An all-encompassing term that represents any single set of binary data being sent across a network link

• Ethernet Frame

  A highly structured collection of information presented in a specific order

  

  • The first part of an Ethernet frame is called a preamble.

  Preamble: 8 bytes (or 64 bits) long, and can itself split into two sections

  • Preamble can split into two part of 1 byte of series of 1s and 0s
  • Last frame in preamble is called Start frame delimiter (SFD)

  Signals to a receiving device that the preamble is over and that the actual frame contents will now follow

  • Next is Destination MAC address

  The hardware address of the intended recipient

  • Followed by Source Address
  • The next part of Ethernet Frame is EtherType field

  16 bits long and used to describe the protocol of the contents of the frame

  • WE can use VLAN header in place of EtherType field

  Indicates that the frame itself is what’s called a VLAN frame

  • If a VLAN header is present, the EtherType field follows it.

    Virtual LAN (VLAN): A technique that lets you have multiple logical LANs operating on the same physical equipment

  • VLANs, use to segregate different type of network traffic

  

  • The next part of Ether frame is payload

  In networking terms, is the actual data being transported, which is everything that isn’t a header.

  • Following payload is, Frame Check Sequence (FCS)

  A 4-byte (or 32-bit) number that represents a checksum value for the entire frame

  • This checksum value is calculated by performing what’s known as a cyclical redundancy check against the frame.

  Cyclic Redundancy Check (CRC): An important concept for data integrity, and is used all over computing, not just network transmissions

3) Network Layer

Allows different networks to communicate with each other through devices known as routers.

• IP: IP is the heart of the Internet and smaller networks around the world.
• Datagram
• IP Address

Inter-network

A collection of networks connected together through routers, the most famous of these being the Internet.

4) Transport Layer

Sorts out which client and server programs are supposed to get that data.

• TCP/UDP
• Segment
• Ports

5) Application Layer

There are lots of different protocols at this layer, and as you might have guessed from the name, they are application-specific. Protocols used to allow you to browse the web or send, receive email are some common ones.

• HTTP, SMTP etc.
• Messages