The Basics.

What is a network?
A Network is two or more connected computers that can share resources such as data and applications, office machines, an internet connection, or some combination of all these.
Example of a Simple Network
A Workgroup is a set of devices with no centralized or connected security with one another.
Each device in a workgroup handles their own security.
Workgroups are typically seen in LANs — By splitting devices in their own logical zones, it makes administration easier to manage these devices.
What is a LAN?
LANs (Local Area Networks) are small networks that are restricted to a spanning particular geographic location such as an office building, a single department within an office building, or even a SOHO (Small Office/Home Office)
Workgroups are vey common in LANs.
To access the resources of a LAN you have to be physically connected to it (Ethernet Cables or through a network connectivity)
Ex. Any device that physically connects to the Marketing LAN will have access to the Marketing LAN’s resources.
This causes two problems though
You must be physically connected to a workgroup’s LAN to get the resources from it.
You can’t remotely connect to another LAN to use it’s resources.
A solution to this problem is a device called a Router.
Routers connect two LANs so any device connected to one of these LANs can use the resources of both of them. In the most basic definition, routers connect networks together!
They separate workgroups while still allowing access between them. This is better than just having one big workgroup.
Larger workgroups tend to be slow, have high latency, and are generally harder to administrate.
Network Devices 101.
Often powerful computers that a end-user utilizes on a daily basis
Its resources can be accessed by other workstations on the same network.
Servers are insanely powerful computers that specialize in providing one “service” to the entire network.
Servers serve the network and all the workstations that are on the network.
Because of this, they need to have very high CPUs, hard drive space, and RAM.
They serve many workstations on the network and must provide any resources they require.
They’re highly specialized and are there to handle one important labor-intensive job. This doesn’t mean that a server can’t do more than one job, it just means that ideally you’d only want them doing one job because you’ll get better performance and better results if you do!
Ex. of servers
File Server
stores and dispenses files
Mail Server
the network’s post office; handles email functions
Print Server
manages printers on the network
Web Server
manages web-based activities
Fax Server
handles any faxes sent over the network
Application Server
manages network applications
Telephony Server
handles the call center and call routing; a sophisticated network answering machine
Proxy Server
handles tasks in the place of other machines on the network; provides a gateway between users and the internet.
Hosts are networking devices, workstations, and servers that have IP addresses.
MPLS (Multiprotocol Label Switching)
A very popular WAN protocol being used today.
It acts a switching mechanism that imposes numbers to data and then uses those numbers to forward data when it arrives at the MPLS network.
Key Benefits
It has physical layout flexibility
You can rearrange data based on priority
Offer redundancy incase of link failure

Network Architecture: Peer-to-Peer or Client Server
We’ve developed networking as a way to share resources and information, and how that’s achieved directly maps to the particular architecture of the network operating system software.
There are 2 main types of Networks
Computers connected together in peer-to-peer networks do not have any central, or special authority— they’re all peers, meaning that when it comes to authority , they’re all equals!
Security checks occur on an individual PC basis — meaning that each PC has the individual right to do a security check on any other computer that tries to access resources from it.
Because it’s every man for himself, or should I say “every PC for itself”, there is no centralized security administration. Meaning that every computer has to remember and maintain a list of all the users and passwords on each and every machine.
Client-Server Networks
These are pretty much the exact opposite of peer-to-peer networks.
Zero client-to-client communication.
A single server uses a network operating system for managing the whole network.
Here’s how it works:
1.) A client machine’s request for a resource goes to the main server first.
2.) The main server responds by handling security and directing the client to the PC with the desired resource.
This happens instead of the request going directly to the machine!
Organization: because the network is much better organized and doesn’t depend on users remembering where the needed resources are, it’s way easier to find the files you need because every file is one spot; and not spread out all over the network.
Security: is a whole lot tighter because all the usernames and passwords are on that specific server, which is never used by a workstation.
Scalability: Client-Server networks can have armies of workstations on them thanks to having highly specialized computers (servers) perform highly specialized services!
Network Topologies
Type of network where all the devices on the network are connected by a single ethernet cable or coaxial cable; Mainly used in 802.3 Ethernet Networks.
The single cable where all the data is transmitted on, is called the bus!
Easy to install
Not very expensive
harder to troubleshoot because all of the devices are on one RJ-45 cable or coaxial cable.
Offers zero fault tolerance; meaning any one single fault in the cable would bring the whole network down.
Type of network where the computers are connected to a central point with their own individual cables or wireless connections.
The central point is often times inhabited by a connectivity device like a hub, switch, or an access point.
Star topologies offer a lot of advantage over bus topology, making it widely used even though it does require more physical media (cables).
New stations can be added or moved quickly
A single cable failure won’t bring the network down
Easy to troubleshoot
Centralized Connection Point.
Total installation cost can be higher because of the large number of cables you need.
It has a central single point of failure — the hub or other central connectivity device.
One of the best features about a star topology is that since each computer is connected to the central device via their own individual cable, if one PC’s cable goes down then the entire network can still operate normally!
This makes the network much more fault tolerant and a whole lot easier to troubleshoot.
Each computer is directly connected to other computers within the same network using a circular data path. The network’s data flows through the entire network from computer to computer.
Similar to a bus topology, because if you want to add to the network you’ll have to break the cable ring and essentially bring the entire network down!
Different from a bus topology in the sense that there is no single backbone cable that all of the workstations are connected.
Chances of Data collision are low.
Troubleshooting is easier compared to a bus network
In a ring topology, the data travels from one device to another until they reach their destination, so there is a high level of security.
If there is a point of failure, the data will simply keep looping data through the still connected devices in the network.
You’ll need several cables to connect the computers
Adding to the network requires you to break a cable, which in turns brings down the whole network
Zero Fault tolerance.
This network type includes a path from every machine to every other one in the network. This topology type wins the award for “Most Physical connections between machines”.
A network is only considered “Mesh” if there’s a connection between every device on the network.
Often used within WANs to create a hybrid version of an actual Mesh.
Not used in corporate settings anymore because they’re so complicated to manage, but they work great in smaller networks.
Mesh is a very robust fault tolerant network topology. Great for redundancy!
Awesome option for network fault redundancy because failure during a single device won’t break the network.
Collisions are uncommon in a full mesh network topology.
Collisions are when the data from two hosts trying to communicate simultaneously “collides” and gets lost.
Troubleshooting faults is pretty straightforward since each PC is physically connected to each other.
Provides multiple paths to travel to the destination.
No centralized authority.
Due to the sheer number of cables involved, this topology type can get very costly!
Installation can be very difficult and tedious.
Challenging to maintain
Type of network where you have a direct connection between two devices or two locations, using a layer 2 connection and in the process this creates a closed network.
Data on these connections don’t travel on the internet; this method avoids hackers and cyber criminals and is leaps + bounds more secure than the other network topologies
Extremely secure, so much that built-in encryption may not be needed
Mainly used when High-Bandwidth (the amount of data that can be transmitted in a particular window of time) and Low-Latency (the delay between the user’s action and the network’s response) are a main priority.
P2P can provide these two things because data always travels back and forth the same way when using a dedicated route (a single connection).
When businesses use the public internet, their data may be routed differently at different times or rerouted to reach its destination. With a point-to-point connection, data travels a predictable path, meeting customer expectations (and provider promises) for a high quality of service (QoS)
They’re most often used when establishing secure cloud or data center connections, facilitating large file transfers, or protecting data in transit to a disaster recovery backup solution.
Not scalable!
There’s only a max of two devices in the entire network.
There’s only one-point of failure: the single cable or wireless connection that’s connecting the two.
Really only applicable when the two devices are close to each other or you have a really long cable if the devices have some distance between them.
One point of connection (one router) to multiple points of connections (multiple routers). Every router involved in this type of network are apart of the same network.
Type of network that is a combination of two or more players of physical or logical network topologies working together within the same network.
When choosing the right network topology, consider:
Ease of Installation
Ease of Maintenance
Fault-Tolerance requirement
Security requirement
Today’s networks are complicated, so it’s important that we have a standard way of communicating with each other coherently about which part of the network we’re talking about.
To do this, we separate the network into the Backbone & Segments.
Network Backbone
A network backbone is very similar to our own in the way that it’s what all the network segments and servers connect to.
It gives the network a very transparent structure.
Backbones have to use very fast and robust connection technology to optimize network performance, speed, and efficiency.
Network Segments
Network segments can mean any small section of the network that may be connected indirectly to the backbone.
A CAN (Campus Area Network) refers to a network that encompasses several buildings.
It consists of the part of the network where data, services, and connectivity to the outside world is provided to those who work in the corporate office and headquarters.
SANs (Storage Area Networks) are compromised of high-capacity storage devices that are connected by a high-speed private network (separate from the LAN) using a switch built specifically for the storage.
SANs regulate the collection of data, management of data, and use of the data.
Normally ran on Fiber networks.
SD-WAN aka Software Defined - Wide Area Network is a virtual WAN architecture that uses software to manage connectivity, devices, and services — and can make changes in the network based on current operations.
The SD-WAN controller can make changes in real time to add or remove bandwidth or to route around failed circuits.
SD-WAN can simplify wide-area networking management and operations by decoupling the networking hardware from its control mechanism.
SD-WAN uses the cloud to get the job done.
Before the cloud, if a workstation wanted to access a particular resource, it had to go directly to the data center first.
Data center had all the servers; including email servers, SMTP servers, web servers, database servers, etc. All of the remote sites had to first connect to the datacenter to gain access to all of these resources.
SD-WAN uses cloud technology to take this “gatekeeper” (datacenter) out the mix, and have the remote sites connect directly to the resource itself.
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