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Networking and IP Addressing

Networking is the communication between computer systems or devices. A computer network is any set of computers or devices connected to each other with the ability to exchange data. The three types of networks are: 

• the Internet: The network formed by the co-operative interconnection of millions of computers, linked together is called Internet

• intranet: Internal private networks built within an organization using Internet and World Wide Web standards and products that allows employees of an organization to gain access to corporate information

• extranet:It is the type of network that allows users from outside to access the Intranet of an organization

The main difference between extranets and intranets is that intranets are internal networks that are accessible only to employees, while extranets are extended networks that allow external parties to access certain parts of an organization's intranet. Intranets are used for internal communication, collaboration, and operations management, while extranets are used for external communication and collaboration with customers, suppliers, and partners. Having an extranet makes an organization vulnerable

• Examples of different network methods are:

• Personal area network (PAN): short range small networks. Typically wireless and allows transfer of data between devices (e.g. cellphone to tablet)

• Local area network (LAN), which is usually a small network constrained to a small geographic area. An example of a LAN would be a computer network within a building. The group of computers and devices are connected together by a switch, or stack of switches, using a private addressing scheme as defined by the TCP/IP protocol

• Wireless LANs and WANs (WLAN & WWAN) are the wireless equivalent of the LAN and WAN.

• Metropolitan area network (MAN), which is used for medium size area. examples for a city or a state. ISP-level networks

• Wide area network (WAN) that is usually a larger network that covers a large geographic area.

All networks are interconnected to allow communication with a variety of different kinds of media, including twisted-pair copper wire cable, coaxial cable, optical fiber, power lines and various wireless technologies. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the interconnections of the Internet). Networking, routers, routing protocols, and networking over the public Internet have their specifications defined in documents called RFCs.

source

So how does this networking thing work?

All computers on a network have to know how to talk to each other. This requires a 'protocol' (which is a set of rules that dictate how computers can talk to each other). Think of a protocol being like a language. Both computers have to speak the same language. The model used in networking is known as the OSI model which will be discussed in a future topic in the course.

Essentially the way your computer (phone/console/computer/'smart refrigerator' etc...) talks to another computer is that packets of information are created by the computer. They move to the network interface, then across a medium (copper/glass/air) to a receiving network interface that then hands the information 'up' to the relevant application on the next computer.

 ADDRESSING (IPv4)

Implemented in 1998, Internet Protocol version 4 addressing was/is a connectionless protocol (a message can be sent from one location to another without a prior connection being formed) for use on packet-switched networks (e.g., Ethernet). It operates on a best effort delivery model, in that it does not guarantee delivery, nor does it assure proper sequencing or avoidance of duplicate delivery. These aspects, including data integrity, are addressed by an upper layer transport protocol (e.g., Transmission Control Protocol). All that to say, 'Information A' goes from one address to another by being broken down into packets, which make their way to the end-address the best they can, then get reassembled into 'Information A' once more.

Interestingly enough, the backbone of the internet, IPv4 is currently being replaced by IPv6 as a default protocol (e.g. Windows 10 by defaults assigns IPv4 and IPv6 address). The top-level IPv4 'exhaustion' occurred in 2011. Reserve addresses were exhausted between 2011 and 2019 depending on the area of the world you were in. Individual ISPs still have pools of unassigned IP addresses, and reclaim them as they are no longer needed by subscribers. Switching equipment to enable IPv6 was no easy task since there was cost associated with it.

An understanding of the way that IPv4 addressing works will help us to understand IPv6 addressing, so let's start there. In IPv4 addressing (let's just refer to it as IP addressing), an IP address is a 32 bit, 4 octet address which is assigned (by who?) to every computer on an IP (ethernet protocol) network.

For example, the host address 192.168.1.1 (which is a very common router address for most home networks) resolves to:

IP address is a 32 bit, 4 octet address assigned to every computer on an IP (Internet Protocol) network.

reminder:

111111112 = 25510

so:
00001010.10111100.00011100.00010000

10.190.28.17

There are major IP Address classes used in the wild:

Network and host addresses are like a real-world analogy: street address (ie I live on River Road) vs. street number (I'm at 1633 River Road)

1) Class A: Used by countries or VERY large companies (e.g. Cisco, Microsoft, Dell etc...). These are unique 1st octet ranges (1-> 127). They take the form of:

• network.host.host.host

• octet1.octet2.octet3.octet4

• street address.housenumber.housenumber.housenumber

• 255^3 bits so about 16.5million host addresses

• the default subnet mask (which creates subnets, or private addresses within the host network) for these is 255.0.0.0

2) Class B: Used by somewhat large companies (Bell, Videotron). The first octet is in the range of 128-191 and has the pattern:

• network.network.host.host

• 63*255 class B networks which about 16k addresses 

• subnet mask is 255.255.0.0 so about (255x255) 65k host addresses inside

3) Class C: Used by small companies and individuals. The first octet is in the range 192-223 and has the pattern:

• network.network.network.host

• 254 hosts per network

• subnet mask is 255.255.255.0

4) Class D/E: are experimental networks used to multicast

Tools we use in IP networking are:

• ipconfig: which gives information about the host computer's network adapters as well as the details of the connection to the ethernet network.

• ping: which is a way in which to test the reachability of a host or IP address on a network.

• traceroute: is a diagnostic tool for displaying the route (path) and measuring transit delays of packets across an Internet Protocol (IP) network.

There are several network IP addresses that reserved, they are:

• 10.host.host.host

• 127.host.host.host

• 169.host.host.host

• 192.host.host.host (chances are your home network is something like 192.168.X.X where the subnet IP addresses are likely 192.168.1.X or 192.168.2.X)

Model for computer networking

Network addresses, broadcast addresses & subnet masks

1. Network Address: The network bits stay the same. Host bits all resolve to 0

2. Broadcast Address: Network bits stay the same, host bits all are 1s

3. Subnet Mask: Network bits binary 1's, Host bits binary 0's

4. First available address: the first host bit will be 1

Case 1: 172.168.14.11 (Class B: Network Network Host Host)

1. 172.168.0.0

2. 172.168.255.255

3. 255.255.0.0

4. 172.168.0.1

Case 2: 203.200.0.42 (Class C: Network Network Network Host)

1. 203.200.0.0

2. 203.200.0.255

3. 255.255.255.0

4. 203.200.0.1

Subnetting

Where grade 11 starts:
Subnetting is where you divide a network into smaller networks. To do that you borrow host bits and make them into network bits. Why?

• bandwidth control

• security

Example. South Carleton wants to subnet its network for teachers, students, guests, caf and the library. (5 separate networks).

IP address is 10.0.0.0 (which is in the class A range though is protected)

a) class A means Network.Host.Host.Host

b) How many do we want to make? What is the # of host bits to borrow to accommodate this?

Take the following octet. You'll see what I put a line after the first 3 ones.

Calculating hosts is done by  2H-2 where H is the number of host bits left in the range. In this case 10.X.X.X we're borrowing 3 bits from octet #2 for the network, that leaves 5 for the host (and the last 2 octets would be an additional 8+8). So the number of hosts would be 5 + 8 + 8 bits = 21 bits so 221-2 = 2,097,150 hosts per subnet (-2 because the broadcast and network addresses per subnet)

c) Default subnet mask for a class A is 255.0.0.0. Our new subnet mask for 3 borrowed bits would be:

11111111.11100000.00000000.00000000

or 255.224.0.0 

A vanilla class A has 8 network bits and since we're borrowing 3 MORE bits from octet 2, that's 8 original network bits, and 3 more so /11

255.224.0.0 /11

What about this case?

150.3.7.9 /20

A vanilla class B would have /16, so this is borrowing 4 bits from the 3rd octet.

2N = 4 = 16 subnets

The number of hosts would be 4 host bits left in the 3rd octet, and all 8 bits in the 4th octet, so a total of 12 host bits

2H = 212 -2 = 4096-2 = 4094 hosts per subnet

c) Default subnet mask for a class B is 255.255.0.0. Our new subnet mask for 4 borrowed bits would be:

11111111.11111111.11110000.00000000

or 255.255.224.0.

Subnetting (dividing larger networks into smaller networks by borrowing host bits)

To understand how a router works, we need an IP address, a Subnet Mask and we need to use Boolean Logic.

Eg. 192.168.1.23 255.255.255.0

Routers only care about the Network bits. The Subnet Mask masks out the Host bits using Boolean Logic operation AND.

AND - both elements have to be True (1) for the end result to be True (1).

1 AND 1 = 1 (True)

1 AND 0 = 0 (False)

0 AND 1 = 0 (False)

0 AND 0 = 0 (False)

Eg.   1 0 1 0 1 0 0 0 

    AND  1 1 1 1 0 0 0 0

  1 0 1 0 0 0 0 0

Example with a default subnet mask:

      192.168.001.23

AND 255.255.255.0

 11000000.10101000.00000001.00010111 ← 192.168.1.23

AND   11111111.11111111.11111111.00000000 ← 255.255.255.0

      11000000.10101000.00000001.00000000 → 192.168.1.0

Example with a subnetted subnet mask:  172.172.33.4    255.255.240.0

172.172.33.4 →  10101100.10101100.00100001.00000100 

255.255.240.0 → 11111111.11111111.11110000.00000000

172.172.32.0  ← 10101100.10101100.00100000.00000000

^^^^^

Subnet Address

More examples:

State the network address of the following subnetted networks (use Boolean Logic):

1.  200.200.23.42 255.255.255.224

2. 13.14.15.67 255.248.0.0

3. 150.132.128.7 255.255.240.0 

Example 1 - Subnet Mask - 255.240.0.0 - Class A subnet mask

• Binary - 11111111.11110000.00000000.00000000

  • 4 bits borrowed from the 2nd octet (240)

Example 2 - Subnet Mask - 255.255.255.224 - Class C subnet mask

• Binary - 11111111.11111111.11111111.11100000

  • 3 bits borrowed from the 4th octet (224)

Example 3 - What would the Subnet Mask be for a Class B IP Address with 4 borrowed bits?

Default Class B Subnet Mask - 255.255.0.0

We borrow 4 bits from the 3rd octet → 11110000 = 240

Therefore, the new Subnet Mask is 255.255.240.0

Example 4 - What would the Subnet Mask be for a Class C IP Address with 7 borrowed bits?

Default Class C Subnet Mask - 255.255.255.0

We borrow bits from the 4th octet → 111111102 = 25410

Therefore, the new Subnet Mask is 255.255.255.254

Example 5 - What would the Subnet Mask be for a Class A IP Address with 2 borrowed bits?

Default Class A Subnet Mask - 255.0.0.0

We borrow bits from the 2nd octet → 110000002 = 19210

Therefore, the new Subnet Mask is 255.192.0.0

THAT SAID: Things aren't as simple as you thought - you can borrow bits from octets to the right PAST the 'regular' subnet mask. E.g. you can have a "class C" mask on a "class A" address. Why? when you have to have more hosts per subnet than 255

E.g. 12.14.1.0

with a mask of

255.255.240.0 (class B mask)

or 12.14.1.0

255.255.255.240 (class C mask)

Typically borrowing bits from the right is ok, however, you CAN borrow bits from the left (e.g. use a class B subnet mask on a class C address) in what is called classless addressing. Feel free to look up CIDR and VLSM classless masks

Network Topology

Describes the physical and logical layout of a network

1. Physical Topology: the actual (scaled) network

2. Logical Topology: how the various computers are organized from a communications perspective (star topology being common)

Networking & IP addressing Quiz

Activity: How to make a network cable

Materials:

• length of cat6 UTP (unshielded twisted pair): has 4 pairs of copper wires which have colour coding

• RJ45 jack

Tools:

• scissors

• crimper

• tester

Steps:

1. measure cable and add 15% length and cut it

2. cut away outer coating to expose the twisted pairs. Don't nick the copper cables as you cut away the protective sheath

3. Put the cable colors in order (what is a straightthrough vs. crossover):

StraightThrough (A-A or B-B)

• WG/G/WO/Bl/WBl/O/WBr/Br

Crossover (A-B or B-A)

• WO/O/WG/Bl/WBl/G/WBr/Br

4. Flatten out the wires and trip them so about 2cm of wire are exposed

5. Slide the RJ45 jack onto the wires (gold side up). The jack should JUST slide down to the cable sheath

6. Check with your teacher

7. Crimp and test the cable

Cryptography and network Security

Cryptography is the study and practice of techniques for secure communication in the presence of third parties called adversaries. It deals with developing and analyzing protocols that prevents malicious third parties from retrieving information being shared between two entities thereby following the various aspects of information security. Secure Communication refers to the scenario where the message or data shared between two parties can’t be accessed by an adversary. In Cryptography, an Adversary is a malicious entity, which aims to retrieve precious information or data thereby undermining the principles of information security. Data Confidentiality, Data Integrity, Authentication and Non-repudiation are core principles of modern-day cryptography.

Network security on the other hand are activities designed to protect the integrity of your network and data. They include both hardware and software technologies. The aim is to stops threats from entering or spreading on your network. 

Functional Encryption

Hash Functions 

• A hash function takes an input (data of any size) and produces a fixed-size output (the hash or message digest). 

• Hash functions are designed to be one-way, meaning it's computationally infeasible to reverse the process and find the original input from the hash. 

• A good hash function should produce unique hashes for different inputs, and even a small change in the input should result in a drastically different hash. 

How CAs (Certificate Authorities) Use Hash Functions: 

• Digital Signatures: When a CA signs a certificate, it calculates the hash of the certificate's data (e.g., subject information, public key). 

• Private Key Encryption: The CA then encrypts this hash using its private key, creating a digital signature. 

Verification: Anyone can verify the signature by decrypting it with the CA's public key and recalculating the hash of the original data. If the decrypted hash matches the recalculated hash, the signature is valid, and the data is considered authentic and unaltered. 

The reason to use Hash Functions

• Data Integrity: Hash functions ensure that the data being signed hasn't been tampered with during transmission or storage. 

• Efficiency: Using a hash function allows the CA to sign a small, fixed-size hash instead of the entire data, which is more efficient. 

• Security: Hash functions are crucial for secure digital signatures, password storage, and other cryptographic applications. 

Examples: 

• SSL/TLS: Hash functions are used in the SSL/TLS handshake to authenticate parties and establish secure connections. 

• Password Storage: Instead of storing passwords in plain text, systems often store the hash of the password (often with a salt) to enhance security. 

• File Integrity Checks: Hash functions can be used to verify that a downloaded file hasn't been corrupted during the download process. 

CyberSecurity

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