The Bits and Bytes of Computer Networking

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.

IP ADDRESS SUBNET MASK GATEWAY FOR A HOST DNS SERVER

4 parts of the standard modern network configuration:

What are the 5 Networking Layers in order?

5. Application layer 4. Transport layer 3. Network layer 2. data link layer 1. Physical layer

Port

A 16-bit number that's used to direct traffic to specific services running on a networked computer.

Iidentification field

A 16-bit number that's used to group messages together.

Nslookup

A DNS resolver tool available on all major desktop operating systems is ___.

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.

Router

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

subnet mask

A binary number that has two sections (the part of the number with all the ones).

CalDAV

A calendar and scheduling service.

frequency band

A certain section of the radio spectrum that's been agreed upon to be used for certain communications.

Hardware virtualization

A core concept of how cloud computing technologies work. It allows the concept of a physical machine and a logical machine to be abstracted away from each other.

cloud storage

A customer contracts a cloud storage provider to keep their data secure, accessible, and available.

WPA2 (Wi-Fi Protected Access 2)

A data encryption standard compliant with the IEEE802.11i standard that uses the AES (Advanced Encryption Standard) protocol. WPA2 is currently the strongest wireless encryption standard.

protocol

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

Patch Panel

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

Firewall

A device that blocks traffic that meets certain criteria.

Wireless Access Point (WAP)

A device that bridges the wireless and wired portions of a network.

Host file

A flat file that contains on each line a network address followed by the host name it can be referred to as.

Header Length Field

A four bit field that declares how long the entire header is (usually 20 bytes).

Domain name system (DNS)

A global and highly distributed network service that resolves strings of letters into IP address.

Ethernet Frame

A highly structured collection of information presented in a specific order

IP Datagram

A highly structured series of fields that are strictly defined.

Private Cloud

A large cluster of machines run by another company entirely used by a single large corporation and generally physically hosted on its own premises.

Public Cloud

A large cluster of machines run by another company.

Baud rate

A measurement of how many bits could be passed across a phone line in a second.

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.

Cloud Computing

A new model in computing where large clusters of machines let us use the total resources available in a better way.

hypervisor

A piece of software that runs and manages virtual machines while also offering these guests a virtual operating platform that's indistinguishable from actual hardware.

TCP or Transmission Control Protocol

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

communicates on behalf of something else.

A proxy is something that _______________________.

DHCP dynamic allocation

A range of IP addresses is set aside for client devices and one of these IPs is issued to these devices when they request one.

proxy service

A server that acts on behalf of a client in order to access another service.

reverse proxy

A service that might appear to be a single server to external clients, but actually represents many servers living behind it.

IP or Internet Protocol

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

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.

Virtualization

A single physical machine called a host could run many individual virtual instances called guests.

Platform as a service, or PaaS

A subset of cloud computing where a platform is provided for customers to run their services.

Anycast

A technique that's used to route traffic to different destinations depending on factors like location, congestion, or link health.

port forwarding

A technique where a specific destination ports can be configured to always be delivered to specific nodes.

Two-factor authentication

A technique where more than just a username and password are required to authenticate.

Port preservation

A technique where the source port chosen by a client, is the same port used by the router.

Cloud Computing

A technological approach where computing resources are provisioned in a shareable way so that lots of users get what they need when they need it.

network address translation or NAT

A technology that allows a gateway, usually a router or a firewall, to rewrite the source IP of an outgoing IP datagram, while retaining the original IP in order to rewrite it into the response.

Virtual Private Networks or VPNs

A technology that allows for the extension of a private or local network, to a host that might not work on that same local network.

VPNs

A technology that use encrypted tunnels to allow for a remote computer or network, to act as if it's connected to a network that it's not actually physically connected to.

Hybrid Cloud

A term used to describe situations where companies might run things like their most sensitive proprietary technologies on a private cloud while entrusting their less sensitive servers to a public cloud.

RJ-45 or Registered Jack 45

A type of connector on the end of a cable.

Software as a service (Saas)

A way of licensing the use of software to others while keeping that software centrally hosted and managed.

Loopback address

A way of sending network traffic to yourself.

Wireless networking

A way to network without wires.

Wide area networks or WAN

Acts like a single network but spans across multiple physical locations.

Internet Corporation for Assigned Names and Numbers (ICANN)

Administration and definition of TLDs is handled by this non-profit organization.

FE80:: (Link-local unicast addresses)

Allow for local network segment communications and are configured based upon a host's MAC address.

Network Layer

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

NAT or Network Address Translation.

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

Protocol field

An 8-bit field that contains data about what transport layer protocol is being used.

Media Access Control or MAC

An address for communications on the physical network segment.

DHCP, or Dynamic Host Configuration Protocol

An application layer protocol that automates the configuration process of hosts on a network.

WEP-Wired Equivalent Privacy

An encryption technology that provides a very low level of privacy.

CRC or cyclical redundancy check

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

Internet Engineering Task Force (IETF)

An open community charged with developing and maintaining the standards required for the Internet

Registrar

An organization responsible for assigning individual domain names to other organizations or individuals.

proxies

Any server that act as a intermediary between a client and another server.

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

Application Layer

IPv6 tunnel broker

Companies that provide IPv6 tunneling endpoints for you, so you don't have to introduce additional equipment to your network.

Fiber cable

Contain individual optical fibers that uses light to transmit data.

fragmentation offset field

Contains values used by the receiving end to take all the parts of a fragmented packet and put them back together in the correct order.

Optical Network Terminator, or ONT

Converts data from protocols the fiber network can understand to those that are more traditional twisted pair copper networks can understand.

DSLAMs or Digital Subscriber Line Access Multiplexers

DSL modems; establish data connections across phone lines.

HDSL, or High Bit-rate Digital Subscriber Lines.

DSL technologies that provision speeds above 1.544 megabits per second.

Layer 2 Switch, Ethernet Protocol

Data Link layer

SOA record

Declares the zone and the name of the name server that is authoritative for it.

802.11 protocols

Defines how we operate at both the physical and the data link layers

Communication on a phone line is Duplex or Simplex Communication?

Duplex Communication

Cat 5e

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

Subnet mask, gateway, DNS server, IP address

Every single computer on a modern TCP/IP based network needs to have at least four things specifically configured.

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

Fiber Optic

FTTB

Fiber to the Building

FTTN

Fiber to the Neighborhood

FTTX

Fiber to the X.

FTTH

Fiber to the home

FIN

Finish

caching name servers recursive name servers root name servers TLD name servers authoritative name servers

Five primary types of DNS servers

T-carrier technologies, digital subscriber lines or DSL, cable broadband, and fiber connections.

Four of the most common broadband solutions available today.

Destination network, net mask, next hop, total hops

Four possible columns of a routing table.

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.

IP masquerading

Hiding the IP of computer one from computer two. No one can establish a connection to your computer if they don't know what IP address it has.

1.544 Mb/sec

How fast is a T1 line?

network ID, and host ID

IP addresses can be split into two sections

the network ID, and the host ID

IP addresses can be split into two sections

Echo Reply

If the destination is up and running and able to communicate on the network, it will send back an ICMP ___ message type.

Octet

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

NS records

Indicate other name servers that may also be responsible for this zone.

Total Length

Indicates the total length of the IP datagram it's attached to.

Channels

Individual, smaller sections of the overall frequency band used by a wireless network.

Broadcast

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

Cable Broadband

Instead of using the existing telephone lines, special cabling has been laid which allows signals to travel at speeds up to 1000Mb

Round robin

Iterating over a list of items one by one in an orderly fashion.

Reverse lookup zone files.

Let DNS resolvers ask for an IP, and get the FQDN associated with it returned.

Ping

Lets you send a special type of ICMP message called an Echo Request.

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.

Mesh networks

Lots of the devices communicate with each other wirelessly forming a mesh if you were to draw lines for all the links between all the nodes.

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

MAC

allowing computers using non-routable address space to communicate with the Internet.

NAT addresses concerns over the dwindling IPv4 address space by ___________________.

public DNS servers

Name servers specifically set up so that anyone can use them for free.

Ad-hoc networks

Nodes all speak directly to each other.

Test-NetConnection

On Windows, one of the tools you can use to verify connectivity to a specific port is ___.

4.2.2.3

One of Level 3's public DNS servers is __.

Wireless LANS or WLANS

One or more access points act as a bridge between a wireless and a wired network.

Connection-oriented protocol

One that establishes a connection, and uses this to ensure that all data has been properly transmitted.

Cellular Networking

Operates over radio waves, and there are specific frequency bands specifically reserved for cellular transmissions.

public Switched Telephone Network or PSTN

Plain Old Telephone Service or POTS; contains the basic infrastructure for connecting computers

web proxies

Proxies specifically built for web traffic.

PSH

Push

RFC 1918

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

Broadband

Refers to any connectivity technology that isn't dial-up Internet, faster than dial-up and always on connections.

Switches

Remember which computers live on which physical interfaces. So traffic is only sent to the node It's intended for.

Fixed allocation.

Requires a manually specified list of MAC address and the corresponding IPs.

RST

Reset

PTR, or Pointer Record

Resolves an IP to a name.

Authoritative name servers

Responsible for the last two parts of any domain name which is the resolution at which a single organization may be responsible for DNS lookups.

IPv6 tunnels

Servers take incoming IPv6 traffic and encapsulate it within traditional IPv4 datagrams.

SRV record

Service record; used to define the location of various specific services.

Zone files

Simple configuration files that declare all resource records for a particular zone.

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

Simplex Communication

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.

Ethernet Protocol

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

Caching name servers

Stores domain name lookups for a certain amount of time.

SYN

Synchronize

Transmission Control Protocol ( TCP)

TCP ensures that all data arrive accurately and 100% intact at the other end. This is the protocol most commonly used in the transport layer.

TXT

Text; used to convey additional data intended for other computers to process.

subdomain or hostname

That www portion of the domain name.

Automatic allocation

The DHCP server is asked to keep track of which IPs it's assigned to certain devices in the past.

Error-recovery

The ability for a protocol or program to attempt to fix something that went wrong.

Error-detection

The ability for a protocol or program to determine that something went wrong.

Fully Qualified Domain Name (FQDN)

The complete domain name for a specific computer (host) on the Internet.

data payload section

The entire contents of an IP datagram are encapsulated as the payload of an Ethernet frame.

Transmission System 1 (T1)

The first T-Carrier specification; carries up to 24 simultaneous phone calls across a single piece of twisted pair copper.

Version Field

The first field of an IP Datagram, is 4 bits long. Most common is IPv4.

2 rules for shortening IPv6 addresses.

The first is that you can remove any leading zeros from a group. The second is that any number of consecutive groups composed of just zeros can be replaced with two colons.

Preamble

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

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.

AFRINIC, ARIN, APNIC, LACNIC, RIPE

The five RIRs:

Socket

The instantiation of an endpoint in a potential TCP connection.

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.

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.

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

Ethernet

The most common data link layer protocol for wired connections.

IEEE 802.11 standards or 802.11 family

The most common specifications for how wireless networking devices should communicate, are defined by ___.

hexadecimal

The number system that has 16 numerals.

ICANN (Internet Corporation for Assigned Names and Numbers)

The organization responsible for DNS at a global level is __.

Hosts files

The original way that numbered network addresses were correlated with words; a popular way for computer viruses to disrupt and redirect user's traffic.

Echo Request

The ping utility sends what message type?

DHCP discovery

The process by which a client configured to use DHCP attempts to get network configuration information.

Name resolution.

The process of using DNS to turn a domain name into an IP address.

Domain

The second part of the domain name, example google.

Bit

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

USENET

The system two grad students built using a phone line to transmit data.

Top Level Domain (TLD)

The top of the hierarchical DNS name resolution system (.com).

4.2 billion possible

The total number of IPv4 addresses is approximately:

Header and payload

The two primary sections of an IP datagram.

SDSL stands for Symmetric Digital Subscriber Line.

The upload and download speeds are the same.

root named server

There are 13 total root name servers and they're responsible for directing queries toward the appropriate TLD name server.

Service Type field

These eight bits can be used to specify details about quality of service or QoS technologies.

NTP-Network Time Protocol

This Is used to keep all computers on a network synchronized in time.

header checksum field

This field is a checksum of the contents of the entire IP datagram header.

Time to Live or TTL field

This field is an 8-bit field that indicates how many router hops a datagram can traverse before it's thrown away.

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

FCS or Frame Check Sequence

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

Twisted Pair Cabling

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

IP options field

This is an optional field and is used to set special characteristics for datagrams primarily used for testing purposes.

padding field

This is just a series of zeros used to ensure the header is the correct total size.

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.

Transport Layer

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

The purpose of DNS zones.

To allow for easier control over multiple levels of a domain.

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.

Modems (modulator/demodulator)

Transferring data across a dial-up connection is done through devices called ______.

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

Transport Layer

mtr on Linux and MacOS and pathping on Windows

Two tools that are similar to traceroute.

Cat 5

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

URG

Urgent

IPv6 addresses

Use 128 bits and are displayed in hexadecimal format separated by colons. IPv6 addresses are usually written out as 8 groups of 16 bits each. Each one of these groups is further made up of four hexadecimal numbers.

ICMP or internet control message protocol

Used by router or remote hosts to communicate while transmission has failed back to the origin of the transmission.

Interior gateway protocols

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

FF00::

Used for multicast, which is a way of addressing groups of hosts all at once.

MX record

Used in order to deliver e-mail to the correct mail exchange server.

CSMA/CD

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

flag field

Used to indicate if a datagram is allowed to be fragmented, or to indicate that the datagram has already been fragmented.

A record

Used to point a certain domain name at a certain IPv4 IP address.

Quad A record

Used to point a certain domain name at a certain IPv6 IP address.

CNAME record

Used to redirect traffic from one domain to another (canonical name).

MAC

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

WPA or Wi-Fi Protected Access

Uses a 128-bit key, making it a whole lot more difficult to crack than WEP.

ADSL stands for Asymmetric Digital Subscriber Line.

Uses different speeds for outbound and incoming data.

Traceroute

Utility that lets you discover the paths between two nodes, and gives you information about each hop along the way.

Tunneling

VPNs are known as a _____ protocol.

One to many NAT

We could actually have hundreds of computers on network A, all of their IPs being translated by the router to its own. To the outside world, the entire address space of network A is protected and invisible.

Port forwarding

What technique allows for inbound traffic through a NAT?

A MAC Address

When using Fixed Allocation DHCP, what's used to determine a computer's IP?

2.4 gigahertz and 5 gigahertz bands

WiFi networks operate on a few different frequency bands.

NAT and non-routable address space.

Workaround for lack of IPv4 IP addresses.

MAC filtering

You configure your access points to only allow for connections from a specific set of MAC addresses belonging to devices you trust.

Infrastructure as a service or IaaS

You shouldn't have to worry about building your own network or your own servers.

autonomous system

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

router

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

IANA the Internet Assigned Numbers Authority

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

Address Resolution Protocol or ARP

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

Digital subscriber line or DSL

able to send much more data across the wire than traditional dial-up technologies.

IPv4 addresses

are 32 bits, meaning there can be around 4.2 billion individual addresses

CIDR

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

Cable modem termination system, or CMTS.

connects lots of different cable connections to an ISP's core network.

IANA-Internet Assigned Numbers Authority

has primarily been responsible with assigning address blocks to the five regional internet registries or RIRs.

Class A, class B, and class C

three primary types of address classes

exterior gateway protocols

used for the exchange of information between independent autonomous systems.

CIDR notation

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

binary or base two

uses a zero and one

T-carrier technologies

Originally invented by AT&T in order to transmit multiple phone calls over a single link.

Recursive name servers

Perform full DNS resolution requests.

ACK

Acknowledge

ICMP

The protocol used to communicate network errors is known as ___.

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.

Layer 1 Cable, Ethernet, hubs

Physical Layer

Class A addresses

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

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.

MAC Adress

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

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

Activity Light

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

Layer 3 Internet Protocol, Router, Logical Addressing

Network Layer

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.

Payload

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

Internet Protocol

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

Full Duplex

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

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.

Fragmentation

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

Client

The thing receiving the data.

state routing protocols and distance-vector protocols

The two main types of interior gateway protocols

Data Payload

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

Cat 6e

This cable has shorter distance at higher speeds.

Hubs/Switches

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

Class B addresses

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

subnetting

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

demarcation point

where one network or system ends and another one begins.

Half Duplex

Only one device can be communicating at a time.

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.

BGP or Border Gateway Protocol

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

Server

Provides data to something requesting data.

Collision Domain

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

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.

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.

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.

ASN, or Autonomous System Number allocation

ASNs are numbers assigned to individual autonomous systems.

data packet

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

Crosstalk

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

4

How many octets does a subnet mask have?

Non-Routable Address Space

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

Data Link layer

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