The Bits and Bytes of Computer Networking

What are the 5 Networking Layers in order?

5. Application layer

6. Transport layer

7. Network layer

8. data link layer

9. Physical layer

Physical Layer

This layer has devices that interconnect computers with cabling connectors. It sends and receives signals on the physical wire or antenna to transmit the bits found in frames.

Data Link layer

Responsible for defining a common way of interpreting signals, so network deices can communicate.

Network Layer

Allows different networks to communicate with each other through networks, such as the internet.

Transport Layer

This layer sorts out which client and server programs are supposed to get that data.

Application Layer

Software that we use, the part of the model that is closest to the user (gmail, browser, etc.). Permits applications to request access to the network services.

Layer 1
Cable, Ethernet, hubs

Physical Layer

Layer 2
Switch, Ethernet Protocol

Data Link layer

Layer 3
Internet Protocol, Router, Logical Addressing

Network Layer

Layer 4
Transport Control Protocol, Client Server, Server, User Datagram Protocol

Transport Layer

Layer 5
Web Browser, HTTP , SMTP - send receive email

Application Layer

UDP or User Datagram Protocol

This is an alternative communications protocol to Transmission Control Protocol. It is part of the transport layer protocol. UDP is connectionless. This means there is no setup or teardown of a connection.

What is the difference between UDP & TCP?

The UDP protocol works similarly to TCP, but it throws out all the error-checking stuff. All the back-and-forth communication introduces latency, slowing things down. TCP provides mechanisms to ensure that data is reliably delivered while UDP does not.

Crosstalk

Caused by the electrical signals of one wire disrupting the signals of another wire.

TCP or Transmission Control Protocol

A protocol developed for the internet to get data from one network device to another

IP or Internet Protocol

A set of rules governing the format of data sent over the internet or other network.

Cat 5

Type of cable that has the ability to transfer information from one computer to another

Cat 5e

Enhanced cat 5 cable used for gigabit speeds and minimum for Voice over IP

Cat 6e

This cable has shorter distance at higher speeds.

Fiber cable

Contain individual optical fibers that uses light to transmit data.

Which cable supports the longest distance to transmit data - Cat5, Fiber Optic, Cat5e, Cat6e?

Fiber Optic

Hub

This is a physical layer device used to connect network components. All the devices connected to a hub will end up talking to all other devices at the same time.

Switch

A Data Link Layer device that connects network segments. A switch can inspect the contents of the Ethernet protocol data being sent around the network, determine which system the data is intended for and then only send data to that one system.

Collision Domain

This is a network segment where only one device can communicate at a time,

Hubs/Switches

primary devices used to connect computers on a single local area network (LAN)

Router

A Network layer device that routes packets of data between two or more networks.

BGP or Border Gateway Protocol

Protocol where routers share data with each other, allowing them to determine the most optimal path to forward traffic

Modulation

This is a way of varying the voltage of an electric charge moving across the Ethernet cable to represent 1's and 0's. Also known as line coding.

Twisted Pair Cabling

This is a cable consisting of two wires twisted around each other.

Duplex Communication

The concept that information can flow in both directions across the cable.

Simplex Communication

The concept that information can flow in one direction across the cable.

Communication on a phone line is Duplex or Simplex Communication?

Duplex Communication

A baby monitor transmits data in one direction is Duplex or Simplex Communication?

Simplex Communication

Full Duplex

The concept that devices can both communicate with each other at the exact same time.

Half Duplex

Only one device can be communicating at a time.

Vlan

It's a technique that lets you have multiple logical LANs operating on the same physical equipment. An example would be video calls and phone calls on the same LAN

RJ-45 or Registered Jack 45

A type of connector on the end of a cable.

Link Light

Located on the network port. It will be lit when a cable is properly connected to two devices that are both powered on.

Activity Light

Located on the network port. This light will flash when data is actively transmitted across the cable.

Patch Panel

A device containing many network ports but it does no other work.

Media Access Control or MAC

An address for communications on the physical network segment.

MAC

Uses 48-bit number normally represented by six groupings of two hexadecimal numbers.

Hexadecimal Numbers

This number system has 16 numerals 0 - 9 and uses A, B, C, D, E, and F to represent the numbers 10, 11, 12, 13, 14, and 15.

Octet

In computer networking, any number that can be represented by 8 bits.

Organizationally Unique Identifier or OIU

The first three octets in MAC address- Indicate a network card's manufacturer and is assigned by IEE. Institute of Electrical and Electronics Engineers.

Last three octets

Can be assigned in any way that the manufacturer would like with the condition that they only assign each possible address once to keep all MAC addresses globally unique.

Unicast

A message that goes from one single computer to another single computer. It is communication between a single sender and a single receiver over a network.

How do you know if the information sent is a Unicast?

The least significant bit in the first octet of a destination address is set to zero

How do you know if the information sent is a Multicast?

The least significant bit in the first octet of a destination address is set to one.

Broadcast

Information is sent to every single device on a LAN. The Ethernet broadcast address is all F's.

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

Preamble

The first part of an Ethernet frame. 8 bytes or 64 bits long and can itself be split into two

SFD or Start Frame Delimiter

The last byte in the preamble. Signals to a receiving device that the preamble is over and that the actual frame contents will now follow.

This type of address is 48 bits or 6 bytes long.

MAC

MAC Adress

In the Ethernet frame the destination and source address is listed after the SFD.

Ether type Field

This frame comes after MAC address and is 16 bits long. It is used to indicate which protocol is encapsulated in the payload of the frame

Payload

The actual data being transported, which is everything that isn't a header.

Data Payload

This Ethernet frame is anywhere from 46 to 1500 bytes long and is the actual data being transported.

FCS or Frame Check Sequence

This is a 4-byte or 32-bit number that represents a checksum value for the entire frame.

CRC or cyclical redundancy check

An error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data.

Server

Provides data to something requesting data.

Client

The thing receiving the data.

CSMA/CD

Used to determine when the communications channels are clear and when the device is free to transmit data.

hexadecimal

The number system that has 16 numerals.

Ethernet

The most common data link layer protocol for wired connections.

protocol

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

IP addresses

32-bit long numbers made up of 4 octets, and each octet is normally described in decimal numbers. This format is known as dotted decimal notation.

Fragmentation

The process of taking a single IP datagram and splitting it up into several smaller datagrams.

network ID, and host ID

IP addresses can be split into two sections

Class A, class B, and class C

three primary types of address classes

Class A addresses

the first octet is used for the network ID, and the last three are used for the host ID.

Class B addresses

the first two octets are used for the network ID, and the second two, are used for the host ID.

Class C addresses

the first three octets are used for the network ID, and only the final octet is used for the host ID.

Address Resolution Protocol or ARP

a protocol used to discover the hardware address of a node with a certain IP address.

subnetting

the process of taking a large network and splitting it up into many individual smaller subnetworks or subnets.

CIDR

classless inter-domain routing. It expands on the concept of subnetting by using subnet masks to demarcate networks.

demarcation point

where one network or system ends and another one begins.

CIDR notation

uses a forward slash and then lists the numbers of bits in the subnet mask. 192.168.1.0/24

4

How many octets does a subnet mask have?

binary or base two

uses a zero and one

router

a network device that forwards traffic depending on the destination address of that traffic

routing table

A set of rules, often viewed in table format, that is used to determine where data packets traveling over an Internet Protocol (IP) network will be directed.

Interior gateway protocols

Used by routers to share information within a single autonomous system.

autonomous system

a collection of networks that all fall under the control of a single network operator.

exterior gateway protocols

used for the exchange of information between independent autonomous systems.

state routing protocols and distance-vector protocols

The two main types of interior gateway protocols

link state protocol

A complex routing protocol that shares information with other routers in order to determine the best path.

Exterior gateway protocol

A broad category of routing protocols that are designed to span different autonomous systems.

IANA the Internet Assigned Numbers Authority

a non-profit organization that helps manage things like IP address allocation.

ASN, or Autonomous System Number allocation

ASNs are numbers assigned to individual autonomous systems.

Internet Protocol

The communication technology used worldwide in LANS, WANS and the Internet.

Ethernet Protocol

Specifies physical layer attributes and define a protocol responsible for getting data to the same network or link.

RFC 1918

RFC or Request for Comments, is a publication that helps keep the internet running.

Non-Routable Address Space

Ranges of IPs set aside for use by anyone that cannot be routed to.

NAT or Network Address Translation.

Allows for computers on non-routable address space to communicate with other devices on the internet.

Bit

The smallest representation of data that a computer can understand. It's a one or a zero.

Network ports

Generally directly attached to the devices that make up a computer network. Switches would have many network ports because their purpose is to connect many devices.

Multicast

To transmit data to multiple recipients on the network at the same time using one transmission stream to the switches, at which point data are distributed out to the end users on separate lines.

IP Datagram

A highly structured series of fields that are strictly defined.