January 18, 2017

[Notorious] Networking for Beginners – Indepth Networking Guide

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This tutorial is for those that want to learn about networking. I will be sharing what I have learned through my career in networking so far, for everyone else. Everything in this tutorial is to get you started on your networking career. I will start off basic, and progress through stages, levels, categories and many other topics to do with networking, starting with the basic stuff first.

I know there are already tutorials/guides out there, I just thought I would work on a huge one myself. Please correct me if you feel I am wrong in any part of this guide and I will gladly correct the changes.

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Contents

1. Network Components
2. Types of networks
3. Internet Connections
4. Converged Networks
5. Network Reliability
6. Network Environment
7. OSI Model
8. Conclusion

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1. Network Components

End Devices

End devices are probably the devices that most people would use and be aware of within a network.

End devices can be either the source or destination of the communication. Each end device has a specific addresses identifier, which is used by the source end device to determine where the message should be sent to. You can see some examples of end devices below.

1. Desktop Computer
2. Laptop
3. IP Phone
4. Wireless Tablet
5. Printer

Intermediary Network Devices

Intermediary devices are used to connect end devices to a network. They can also connect individual networks together and form an internetwork. They provide connectivity and flow for the data across the network. You can see some examples of end devices below.

1. Wireless Router
2. LAN Switch
3. Router
4. Multilayer Switch
5. Firewall

Network Media

Also referred to by the name ‘medium’, the medium of a network is used to provide a channel for the data within the network. All messages use different types of network media to communicate across a network, or multiple networks. The three types of common network media are:

Cables with metallic wires
Glass/Plastic fibres (fibre optic cable)
Wireless

All three of these mediums are different in the way data is encoded. Cables with metallic wires use electrical impulses to encode the data, the fibre medium uses pulses of light, and the wireless uses wavelengths from the electromagnetic spectrum.

Network Representations

When designing a network, there are certain symbols that may represent a certain device for the network. This could be a printer, to a layer 3 switch etc. There are loads of representations. Here are a few below:

Topology Diagrams

Physical Diagrams

A physical diagram is used to identify the location of the devices and cable installation for a network.

Logical Diagrams

A logical diagram is used to identify the devices, ports and addressing scheme. I made an example for everyone to see. The software I am using is called Cisco Packet Tracer. Normally you wouldn’t use Packet Tracer for topology diagrams, but this is just to give you an idea.

The example above is more of a logical diagram, as I have listed the ports and IP addresses. A physical topology often requires a network engineer to build a network over a form of blueprint / birds eye view of offices etc.

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2. Types of networks

LAN

LAN stands for Local Area Network. A LAN network is one of the two most common network types, as LAN networks are a network infrastructure that is based around a geographical area. Examples of LAN networks often include: Offices, home, school or campus. You will find that within LANs comes high speed bandwidth to internal devices, such as end and intermediary devices.

WAN

WAN stands for Wide Area Network. You can probably guess by the transition between “Local” to “Wide” Area Network, that a WAN supports a much larger location for networks. A WAN is commonly managed by service providers or internet service providers (SP & ISP). WANs are used to interconnect LAN networks over a much larger geographical range, such as connecting cities, states, countries or continents. As WANs have a much bigger area to cover, the speed links are typically a lot slower than those of LAN networks.

MAN

A MAN network is not as popular, but it’s good to have some sort of understanding about them. They can be small or tall, and many females say they’re useless.

Enough of the cringe, MAN stands for Metropolitan Area Network. The size of a MAN is larger than a LAN , but smaller than a WAN. MANs often cover cities or towns.

WLAN

WLAN stands for Wireless Local Area Network. It’s pretty self explanatory. WLANs give you the ability to connect to a LAN wirelessly. This could be a hotspot while you’re out and about, or at home etc.

SAN

SANs aka Storage Area Networks, are high-speed networks that provide services to support files servers and provide data storage to users on the network.

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3. Internet Connections

Home and Small Office

Cable

When using cable for the connectivity of your network, you will find that this type of medium is typically offered by cable television service providers. It is always on, provides high bandwidth and connection to the internet. The Internet data signal that that travels on this medium is the same as the on used for cable television.

DSL

DSL stands for Digital Subscriber Lines. As opposed to connecting via television cable, DSL used a telephone line for connectivity, and offers an always on support, connectivity to the internet and high bandwidth. Typically small offices will connect via ADSL, which stands for Asymmetrical DSL, and this allows the download speed to be faster than the upload speed on the network.

Cellular

Cellular is used to connect to the internet with your cellular device. The performance may be limited because of the specifications/capabilities on the device, and/or the cell tower of which it is connected to.

Satellite

Satellite requires a clear line of sight for connectivity, so if anything was to interfere this line of site, the connectivity would be poor. Satellite is useful for areas that lack resources of other ways to connect to the Internet.

Dial-up Telephone

Access to dial-up is only really useful for mobile access when traveling if anything. Dial-up is a lot slower than other methods of connectivity, and would usually not be used for large data transfer because of its low bandwidth. It is the inexpensive option, and uses any phone line and a modem.

Business

Dedicated Leased Line

Businesses would rent a dedicated leased line if they wanted to connect two or more locations together for private voice/data networking at a monthly or yearly rent.

Ethernet WAN

An Ethernet WAN is available for use then a company wants to extend an existing Ethernet LAN into the WAN.

DSL

DSL is commonly used for smaller businesses. DSL stands for Digital Subscriber Lines, and can come in several formats such as: ADSL, HDSL, IDSL, SDSL, VDSL and more.

Satellite

Similar to the satellite connection described on office and home users, this is useful when wired connection is not available for the business.

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4. Converged Networks

Converged networks are becoming more popular by the day. When it comes to things like Voice, Internet and Private Data, companies would often need a dedicated line for each of these. Each line would go to whoever they’re subscribed (ISP/Telecommunications Provider), which would most probably be at set bandwidths on each line, and even possibly different providers. The problem with this is that it’s time consuming, more complicated than it needs to be, and a lot more expensive; you also may be paying more than you need to, as you may not be using all the bandwidth for example the voice network.

This is where network convergence comes into play. Imagine if instead of having several lines for these types of networks in a business, they were all linked to one line going to one provider, that has them all setup in the same area. The benefits speak for themselves. Network technicians don’t have to monitor multiple networks running on different lines, more money is being saved and the setup is a lot more efficient and less complex.

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5. Network Reliability

When it comes to network architecture, there are four characteristics which need addressing in order to meet the expectations for the users of the network. These characteristics are: Fault Tolerance, Scalability, Quality of Service (QoS) and Security.

Fault Tolerance

The goal of a fault tolerant network is to try and limit the impact of a failure. This would be accomplished by simple redundancy techniques such as adding alternative paths in a network for data to travel across; if one path on the network goes down, then the data can switch to the other path which is still functioning. This is also known as redundancy. A good redundancy method would be to implement a packet-switched network. A packet-switched network breaks parts of data into packets. Each one of these packets will have the appropriate header information containing the address destination on the network. The routers within the network will determine the best path for the packet that arrives at that time, meaning that each one of those packets that were broken down (maybe from a video stream for example), will eventually all regroup to the destination as they could most definitely travel on different paths, so if a link is to fail, the message can still be delivered.

The discussion on packets will be included later in the tutorial, so that will be more clear soon.

Scalability

A scalable network is a network that supports the increase of users and applications on a network, without affecting the performance of the network for existing users. A scalable network can be obtained by network designers following simple protocols. This can also be done by buying decent hardware within the network to suit possible future software updates and upgrades that require more resources, so to save time in the future you will already meet the specifications and the performance of the network should not be affected.

Quality of Service

Quality of service is used in a network to ensure the correct services within the network have the sufficient bandwidth to operate correctly for the end users. QoS is based on priority. Web pages would often receive lower priority in the network as opposed to streaming media. You will probably know from experience how annoying a buffering streamed video can be, whereas you can load a webpage and that will be the only load it has to do for that page. QoS ensures that each service meets the expectations of the quality of these services.

Security

There are so many aspects to network security nowadays, the list goes on and on. It’s so much have good security, but companies nowadays focus on time a lot more than security. That may sound bad, but no matter how much security you put into a network, there can always be a breach. All it can take is some physical unauthorised access, to a possible 0day exploit.

Physical Security

Physical security within the company would start by the security of the network infrastructure. This would include securing the devices on the network that provide network connectivity, to making sure there is no unauthorised access to any network admin/management software that could do potential harm to the organisation.

Information Security

The second type of security would fall under information security, where the clue is in the name; to protect the information transmitted through the network, and to protect the information stored on the network. A called the CIA Triad which will be explained below is used in an organisation to assist polices that should be followed when it comes to information security.

CIA Triad

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Confidentiality, Integrity and Availability within information security.

Confidentiality

The confidentiality is in place so that the data can only be access by the person that has authentication to access it. This focuses on the security aspect of preventing unauthorised access.

Integrity

Data integrity is in place so that the data stays the same (not tampered with) from when it left the source to when it reaches its destination.

Availability

It is important to make sure that the appropriate data is available for authorised users. If for example someone was trying to prevent information being available on a website via a DDoS attack or whatnot, then people will look for alternative and competitor sources to get the information they need.

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6. Network Environment

Network Trends

BYOD

BYOD was the idea of giving end users the freedom on how to access resources within a network. Previously, to access a network, you had to use a standard issued computer by the company, workplace, or educational institute etc. Nowadays networks allow you connect to their network on personal devices such as: Tablets, Laptops, Smartphones etc. This allows users to have freedom when accessing resources, easier to access the network, reduces costs for businesses (although the company may want to buy the devices and offer them to employees).

Online Collaboration

Online collaboration is the way individuals on a network can interact with eachother on a network. They are applications that allow this. The whole idea of online collaboration is ideal for education, as it allows students to be able to interact with eachother and work on projects in a whole new efficient way. It also allows companies to discuss their different ways and strategic operations on a whole new level.

Video Communication

Video communication within a network is being more critical by the day. This is due to being able to achieve video conferences at any chance of convenience, and allows you to collaborate with organisations and individuals that exceed across a geographic location.

Cloud Computing

Cloud computing is a very big trend in today’s day in age. Cloud computing allows you to store you own personal files on servers across the internet including full sized HDDs. Cloud storage also allows you to use word processor programs such as Microsoft Word online.

Security Threats

Viruses, Worms and Trojan Horses

Malicious code used to delete, edit, move or change files on the infected server.

Zero-day Attacks

A zero-day (0day) vulnerability is a fresh exploit that can be used to attack a system that has not been patched for that vulnerability. It can be seen as a fresh piece of code specifically written to exploit a target before it becomes known/detected and patched.

Denial of Service Attacks

Denial of Service (DoS) attacks are used to crash or slow down networks and applications. Hackers/attackers commonly use DoS/DDoS (Distributed Denial of Service) attacks for a distraction, so that the hacker can then focus on breaching the company when the security is focused on defending against the DoS attack.

Spyware and Adware

When a network/user is infected with spyware and or adware, they find themselves in a position where all their information will be collected.

Hacker Attacks

Attacks by an individual that focus on attacking network resources and/or devices.

Identity Theft

When identify theft is used, hackers will attempt to steal the private data of a person. This can be done by stealing logins so that the hacker can access the private information.

Data Theft

Data theft is used to try and capture the data and traffic on an organisations network.

Security Solutions

Antivirus/Antispyware

When it comes to facing malicious software, these programs are used to stop / defend the malicious software from access the end devices and/or network.

Firewall Filtering

Firewall can be implemented different ways. The main use of firewall filtering is to block unauthorized access to a network. This could be a host-based firewall system which is used to prevent unauthorized network to an end device, or a filtering system on a home network which prevents unauthorized access into the network from the outside world.

Dedicated Firewall Systems

Dedicated firewall systems are used to filter large amounts of traffic, but are also used to provide more advanced firewall capabilities.

Access Control Lists (ACL)

Access control lists are a table of information that contain the access rights information for a user on the system. Maybe one user is only allowed to read a file, whereas someone else is allowed to read and write a file; access control lists will contain this information.

Intrusion Prevention Systems (IPS)

Within a network, an IPS is implemented for fast acting scenarios when it comes to facing particular threats / unauthorised packets. An IPS will monitor all the traffic on the network. If a fast acting exploit enters the system, the IPS also has available options to fastly act on the matter, depending which rules have been set by the network administrator. Commonly if it acts fast against exploits and attacks, the IPS will drop the packets from that particular IP address or port, so when it comes to fast acting zero-day attacks, the IPS will try and work to prevent it.

Virtual Private Networks (VPN)

VPNs are used to provide secure access to remote workers from a remote location.

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7. OSI Model

The OSI model is something you should all familarise yourself with when it comes to networking. All the OSI model is, is a framework that allows us to understand more on how communication and interaction works within an individual area of a network. The OSI consists of 7 layers in total.

Layer 1 (Physical)

The last layer is the physical layer. Cables deal with the physical layer, where all the information is sent from one place to another. After all the information has traveled from the application layer, it ends up here for the last step. If a cable is unplugged, this would be a problem for the physical layer. If a cable was to be damaged, this would be problem for the physical layer too, etc.

Layer 2 (Data Link)

The data link layer is where all the switching happens. This protocol transfers data between two network nodes in a WAN, or between two nodes on a LAN. The data link layer can also provide information to why the physical layer could be broken, and can possibly find, provide, and apply appropriate fixes.

Layer 3 (Network)

The network layer is responsible for packet forwarding. This includes forwarding packets between two routers.

Layer 4 (Transport)

The transport layer ensures that the messages arrive correctly. The transport layer also provides the ability to check for errors and the controlling of data flow. It provides the services for both connection-mode and connectionless-mode transmissions. This means a transmission may arrive or send in packets, which need to be reconstructed into an overall structured message at the other end of the transmission.

Layer 5 (Session)

The session layer provides the needed opening and closing management of a session, which is used when connecting to something. An example would be a web-server. The session layer would create a session between the computer which is trying to contact and access the web server, and would determine whether it needs to be opened or closed based on the sender’s request. Session layer services are often found to be used in application environments that make use of RPCs (remote procedure calls).

Layer 6 (Presentation)

The presentation layer is responsible for delivering and formatting the information to the application later, so it can process or display further into the process. What it does, is it relieves the application later, and raises a concern regarding syntactical differences in data representation which is in the end-user systems. An example where this layer is useful / used would be a conversation of an EBCDIC-coded text computer files to an ASCII-coded file.

Layer 7 (Application)

The final layer is the application layer. This layer ensures that an effective communication with another application program in a network is possible.

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8. Conclusion
Thanks for reading and I hope you benefit from this somehow. These are only SOME basic things, there are a lot more, and I plan to cover more and go indepth with a lot of more in the future. Feel free to ask any questions.
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