#‎DNS_and_Domain_Names‬
Have you ever wondered how your computer knows how to find the correct web server when you type in a web address?

When you type in a website, e.g. www.example.org your computer has to perform a lookup to translate that address into something it understands. The computer looks up “www.example.org” in a big list, and translates the address into an IP

Address.
An IP Address is a list of numbers which tells the computer how to find the correct web server for the web site you asked for. An IP address is usually in the form of four numbers separated by dots, for example 127.0.0.1. The maximum for each number is 255, so IP address range from 0.0.0.0 to 255.255.255.255.

(Note: There is a new form of IP addresses known as IPv6 which is six numbers separated by “:” characters. You can think of them as being basically the same idea but longer numbers! So don’t be confused if you see an IP address that doesn’t look like 0.0.0.0 – it’s just an IPv6 address.)
This ‘big list’ where the computer looks up the IP address is called the Domain Name System, which is often shortened to DNS.

When you register a domain name, you have ownership of that address. You can point it at any IP address you like.

The domain name is just a name – it doesn’t come with a web host… for that you have to get a web host! See our earlier lessons on web hosting to understand how to do this.
There are a number of companies which provide access to registering new domain names. When you buy a domain name you can log into the portal the company provides and edit the DNS records for your domain name.

So, perhaps when you register the domain name you have already purchased a web host. And you know that your web host has assigned you the IP address 127.0.0.1. So you can log into your DNS service and change the IP address associated with your domain name to 127.0.0.1.

This causes the DNS changes to ‘propagate’. This means that the big list of DNS addresses is updated all around the world. Sometimes this takes a few hours.

Then, whenever you type into a browser your domain name, e.g. www.example.org the computer will look up your domain name, find the IP address (127.0.0.1) and then it will ask your web host for your website.

At this point the web server software on your host will respond. And you already understand something about how this works from our earlier lessons!

Now you are beginning to get an idea of the entire workings of the internet and web browsers in more detail. This knowledge will help you greatly as you learn to create websites.

#‎How_to_Choose_a_Web_Host‬

Now you understand what web hosting is, you may be wondering how to choose a web host.

If you search for web hosting you will see there are hundreds or thousands of companies who are offering web hosting services. How do we decide which is best?

 

There are a number of important considerations.

Do we want their specific platform, or do we want a generic web host?

What technology do we require from our web host?

Some web hosts offer a complete package including specialised software to create websites using their platform. For example they might have created a particular blogging engine, and if we get hosting from them it must use their blogging engine. This can be very useful as it saves us the effort of creating our own blog!

However, these platforms may not be very flexible. Perhaps they can only be used in a certain way, or for a certain kind of website. Later we may be frustrated that we cannot do exactly what we want using this platform.

The alternative approach to this is a more generic web host. For example, a web host that offers simply basic Windows machines running IIS (or Apache on Linux) gives us the complete technical freedom to do whatever we want. We can put up our own HTML files for simple websites, or we can write complex websites in a server-side language such as ASP.NET or PHP or Ruby.

The downside of this generic approach is that we have to write our own software, which is difficult and time-consuming.

Of course if you want to write a website in ASP.NET then you must choose a host which provides a web server that runs ASP.NET. And the same goes for PHP or Ruby or other server-side languages.

Sometimes there is a tradeoff – perhaps we can use a web host which provides their platform, but they allow us to customise the code for our own needs, or to run other sites alongside it for additional functionality.

Technology is the most important initial consideration, as you need to ensure your web host is capable of doing everything your website requires.

‪#‎Support_and_Reputation‬

Does the hosting company you are looking at have strong support systems? Do they respond to support tickets rapidly? Hopefully you will not need much support, but it is inevitable that you will encounter problems and it is useful to have support.

It is worth noting that the hosting company is not responsible for everything to do with your site. They are responsible for ensuring the physical machine your site runs on is available and accessible, and for any software on it that they agree to install (for example the web server software). However if your site has bugs or problems they are usually not your line of support!

Sometimes it is difficult to tell whether a problem is to do with your site or to do with the web host not working correctly – in this instance you want to know that your web host is responsive to support requests so you can find out and get to fixing it!

Also always check the reputation of a company you are getting your hosting from. Hosting contracts can be cancelled at any time, but you should still ensure the business you are dealing with has a good reputation amongst its customers.

‪#‎Space_and_Bandwidth‬

How much storage space and bandwidth do you get with your web host?

If you are making a small site that you will access only every now and then (for example, creating a family album just for yourself… and you don’t want to use a large photo-sharing service because you like the challenge of making your own website!) then you do not need a lot of bandwidth.

However if you intend to create a website to rival Facebook then you will need thousands of web servers and a lot of bandwidth. Of course you wouldn’t begin by getting all that bandwidth in advance! And if you are getting millions of hits per day then you should probably start developing your own computing infrastructure..!

It is important to be realistic and realise you will not have massive bandwidth needs immediately.

But it is important to estimate your traffic accurately. Will you get 1 hit per day? Or 1000? Or 100,000? In each case you need to choose the right amount of bandwidth.

Which brings us to…

‪#‎Price‬

The more computing power and bandwidth we want the more our hosting will cost. For most sites we don’t expect a lot of traffic so we can afford to choose a lower amount of bandwidth or computing power. These days it is easy to scale up the power of a server if it starts getting more traffic than expected, so it is wise to begin with the minimum amount of power you think you will need.

You must budget wisely – can you afford the monthly cost of this host? Paying more than you need for hosting is not a good use of the money for your business or family – look carefully at the costs, compare to other hosting companies that have the same technology and choose one that appears reputable (check the reviews!), and affordable for you.

‪#‎Conclusion‬

There are a number of important considerations when choosing a web hosting company. On the technical side you must consider the platform and software they offer, and how customisable it is. It is important to estimate your bandwidth requirements realistically. And choose a package you can afford from a reputable company.

Good luck with your hosting!

#‎What_is_Web_Hosting‬?
Web Hosting is the name commonly given to the service which makes our websites available over the internet.

Websites are uploaded to a computer known as a ‘web host’ and from there the web site is accessed. If you recall our lesson on What Is The Internet you will realise that a web host is just another name for a server.

There is nothing particularly special about ‘web hosting’ computers – they are just computers like any other! They usually have more specialised hardware than home computers (for example more memory, or a faster harddisk) but they are essentially “just computers”.

Unlike our home computers web hosts are connected to the internet all the time. Of course this is because the website must be accessible at all times so people from all over the world can access it.

‪#‎Web_Host_Software‬
Servers used as a web host are commonly configured with different software to the home computers we are used to.

There are two main ‘flavours’ of web host software: Windows and Linux.
Web hosts running Windows usually use a business/server version of Windows. This is similar to the home versions of Windows we are used to, but has some extra features for server administrators to use.

Linux is a very popular free operating system which is very common in the world of servers and web hosting.

However, the operating system is not sufficient software to run a modern website. On top of the operating system the web hosting machine also has a ‘web server’ installed.
This is confusing terminology, as the term “web server” is used to refer to the physical machine, and also this particular bit of software that runs on the machine! However, it is usually obvious from context when we are referring to a physical machine and when we are referring to the web server software.

On Windows the most common web server software is known as IIS. This is the web server provided by Microsoft.

On Linux the most common web server is known as Apache.
Both Apache and IIS are capable of more or less the same tasks, though the way in which we administer each is different. Naturally there are multiple different versions of both Apache and IIS so there is a lot of detail to be learned when mastering either of these pieces of software
When a web request arrives at the web host the web server software intercepts it. At this point IIS or Apache (or some other web server software) decides how to respond to the request and creates the response. Depending on the nature of the web site the way in which this response is created can be very different.

For example, if a request comes in:
*Asking for an image. The web server simply responds with the image file.
*Asking for an HTML page. The web server simply responds with the contents of the HTML file.
*Asking for a page written in ASP.NET or PHP or some other server-side language. The web server calls yet another program (ASP.NET or PHP etc) and that program creates the response. This response is then returned by the web server.

There are many possible ways the web server may create a response, but these few examples hopefully give you the idea. Sometimes it is as clear as sending back an individual file. Sometimes the web server asks another program for what to send back.
This is known as a pipeline. More and more programs can be connected together in this pipeline to allow very complex responses to be created.

#‎introduction_to_hardware_continue‬

 

Motherboard Slots

To add more functionality to a computer, cards such as network or video cards can be added. Sometimes these functions are built into the motherboard. There are several types of expansion slots:

The PCI (Peripheral Component Interconnect) The PCI bus is common in modern PCs, where it has displaced ISA as the standard expansion bus, but it also appears in many other computer types.

PCI 2 33.33 MHz clock with synchronous transfers peak transfer rate of 133 MB per second for 32-bit bus
PCI 2.2 allows for 66 MHz signalling (requires 3.3 volt signalling) (peak transfer rate of 503 MB/s) PCI 2.3 permitted use of 3.3 volt and universal keying, but did not support 5 volt keyed add in cards.
PCI 3.0 is the final official standard of the bus, completely removing 5 volt support.

ISA/EISA; Industry Standard Architecture and Extended Industry Standard Architecture An older type of bus connector. Considered obsolete

PCI Express, PCIe, or PCI-E is an implementation of the PCI computer bus that uses existing PCI programming concepts, but bases it on a completely different and much faster serial physical-layer communications protocol. PCIe transfers data at 250 MB/s (238 MiB/s), per channel to a maximum of 16 channels, a total combined transfer rate of 4GB/s (3.7 GiB/s). Almost all of the high end graphics cards pbeing released today use PCI Express. NVIDIA uses the high-speed data transfer of PCIe for its newly developed Scalable Link Interface (SLI) technology, which allows two graphics cards of the same chipset and model number to be run at the same time, allowing increased performance.

The Accelerated Graphics Port (also called Advanced Graphics Port) is a high-speed point-to-point channel for attaching a graphics card to a computer’s motherboard, primarily to assist in the acceleration of 3D computer graphics. Some motherboards have been built with multiple independent 

AGP slots. AGP is slowly being phased out in favour of PCI Express.

AGP 1x, using a 32-bit channel operating at 66 MHz resulting in a maximum data rate of 266 megabytes per second (MB/s), doubled from the 133 MB/s transfer rate of PCI bus 33 MHz / 32-bit; 3.3 V signaling.
 

AGP 2x, using a 32-bit channel operating at 66 MHz double pumped to an effective 133 MHz resulting in a maximum data rate of 533 MB/s; signaling voltages the same as AGP 1x;
 

AGP 4x, using a 32-bit channel operating at 66 MHz quad pumped to an effective 266 MHz resulting in a maximum data rate of 1066 MB/s (1 GB/s); 1.5 V signaling;
 

AGP 8x, using a 32-bit channel operating at 66 MHz, strobing eight times per clock, delivering an effective 533 MHz resulting in a maximum data rate of 2133 MB/s (2 GB/s); 0.8 V signaling.

Peripheral Connections
There are a number of ports on the motherboard for the connection of additional devices:.

Serial ports connected the computer to devices such as terminals or modems. Mice, keyboards, and other peripheral devices also connected in this way.

Parallel ports are most often used to communicate with peripheral devices. The most common kind of parallel port is a printer port, such as a Centronics connector based port which transfers eight bits at a time. Disk drives are also connected via special parallel ports, such as those used by the SCSI and 

ATA
technlogies. However, when people refer to a parallel port, they are usually referring to a printer port, either on a printer or a PC.

A USB system has an asymmetric design, consisting of a host controller and multiple daisy-chained devices. Additional USB hubs may be included in the chain, allowing branching into a tree structure, subject to a limit of 5 levels of branching per controller. No more than 127 devices, including the bus devices, may be connected to a single host controller. Modern computers often have several host controllers, allowing a very large number of USB devices to be connected. USB cables do not need to be terminated.

USB supports three data rates.

A Low Speed rate of 1.5 Mbit/s (183 KiB/s) that is mostly used for Human Interface Devices (HID) such as keyboards, mice, and joysticks.
 

A Full Speed rate of 12 Mbit/s (1.5 MiB/s). Full Speed was the fastest rate before the USB 2.0 specification and many devices fall back to Full Speed. Full Speed devices divide the USB bandwidth between them in a first-come first-served basis and it is not uncommon to run out of bandwidth with several isochronous devices. All USB Hubs support Full Speed.
A Hi-Speed rate of 480 Mbit/s (57 MiB/s).

‪#‎Diagram_showing_motherboard_slot‬

Continuation of introduction to hardware....
BIOS Chips

The [[BIOS( Basic Input Output System)]] refers to the software code run by a computer when first powered on. The primary function of BIOS is to prepare the machine so other software programs stored on various media (such as hard drives, floppies, and CDs) can load, execute, and assume control of the computer. This process is known as booting up.

The BIOS is stored as a ROM (Read-Only Memory) program and is retained when the machine is turned off. Settings within the BIOS may be changed by the user and these changes are stored in the BIOS memory this is maintained by a trickle of charge from the BIOS battery.

Memory
SIMMS- Single Inline Memory Modules. An older type of memory only seen on very old motherboards came in 30 pin modules and 72 pin modules.

SDRAM chips are rated according to their maximum clock rate and their read cycle time. Common clock ratings include 66MHz, 100MHz, and 133MHz. Common read cycle times include 50ns and 60ns.

DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. It achieves greater bandwidth than ordinary SDRAM by transferring data on both the rising and falling edges of the clock signal (double pumped). This effectively nearly doubles the transfer rate without increasing the frequency of the front side bus.
Stick/module specification

PC-1600: DDR-SDRAM memory module specified to operate at 100 MHz using DDR-200 chips,
1.600 GByte/s bandwidth
PC-2100: DDR-SDRAM memory module specified to operate at 133 MHz using DDR-266 chips, 2.133 GByte/s bandwidth
PC-2700: DDR-SDRAM memory module specified to operate at 166 MHz using DDR-333 chips, 2.667 GByte/s bandwidth
PC-3200: DDR-SDRAM memory module specified to operate at 200 MHz using DDR-400 chips, 3.200 GByte/s bandwidth
 
Drive Connectors
Integrated Device Electronic (IDE)
[Integrated Device Electronic (IDE)]] connectors connect the motherboard, via a ribbon cable to various peripherals, the most common being hard drives and CD ROMs. On most boards there are 2 channels/connectors, each can have 2 devices attached giving a total of four IDE devices.
If one device is attached to a cable, it should be configured as the master.
If two devices are attached to the same cable then one must be the master device and one the slave. Master and slave are configured by the use of jumpers. Jumpers are small, insulated sleeves with a contact inside used to complete a circuit.

Hard Disks
Hard disks are used to store data in a non-volatile form within the machine. I.e. the data remains intact even if the power to the device is cut off. Data is stored as magnetic ones and zeros on a steel platen and is read by pickup arms that scan the drive as the platens spin.
Most major hard drive and motherboard vendors now support self-monitoring, analysis, and reporting technology (S.M.A.R.T.), by which impending failures can be predicted, allowing the user to be alerted to prevent data loss.The mostly sealed enclosure protects the drive internals from dust, condensation, and other sources of contamination. The hard disk’s read-write heads fly on an air bearing which is a cushion of air only nanometers above the disk surface. The disk surface and the drive’s internal environment must therefore be kept immaculate to prevent damage from fingerprints, hair, dust, smoke particles, etc., given the submicroscopic gap between the heads and disk.

Floppy Disks
The floppy disc controller is generally situated near the IDE controllers and in fact looks like a small

IDE slot
The ribbon has a twist and the first floppy drive (A: drive) should be placed after the twist if the cable has more than three connectors. If the cable is really old it may have a connector for a 5 1/4 Floppy drive.

SCSI
SCSI stands for “Small Computer System Interface”, and is a standard interface and command set for transferring data between devices on both internal and external computer buses. SCSI is most commonly used for hard disks and tape storage devices, but also connects a wide range of other devices, including scanners, printers, CD-ROM drives, CD recorders, and DVD drives. In fact, the entire SCSI standard promotes device independence, which means that theoretically SCSI can be used with any type of computer hardware.

On a parallel SCSI bus, a device (e.g. host adapter, disk drive) is identified by a “SCSI ID”, which is a number in the range 0-7 on a narrow bus and in the range 0-15 on a wide bus.

SATA
Serial ATA (SATA) is a computer bus technology primarily designed for transfer of data to and from a hard disk. It is the successor to the legacy AT Attachment standard (ATA). This older technology was retroactively renamed Parallel ATA (PATA) to distinguish it from Serial ATA. Both SATA and PATA drives are IDE (Integrated Drive Electronics) drives, although IDE is often misused to indicate PATA drives.

The two SATA interfaces, SATA/150, runs at 1.5 GHz resulting in an actual data transfer rate of 1.2 Gigabits per second (Gb/s), or 150 megabytes per second (MB/s). SATA II 3Gb/s resulting in an actual data transfer rate of 2.4 Gb/s, or 300 MB/s.
‪#‎to_be_continued‬

Introduction To Hardware
The interior of a computer looks very complicated at first glance. When the case is removed there is a mass of bits, cables and components that can intimidate the uninitiated. This lesson will seek to dispense some of the mist that may surround the hardware of a computer.

Motherboards
The most important part of any computer is the motherboard. As the name implies a motherboard is the mother of all other components in a computer.

The motherboard brings all the core components together such as the Central Processing Unit (CPU), Memory and Hard Disks. In short, the motherboard connects and allows all of the components in the computer to work together.

There are two different types of Motherboard: AT style and ATX style.

AT Motherboards
The AT-style motherboards represent the classic approach to component placement. AT-motherboards are available in two variations, the baby AT and the full AT. Both variations simply refer to the overall dimensions of the board.

AT Boards are generally found in older systems, typically those that use the now aged Pentium Processor. The Majority of AT motherboards had a single keyboard port soldered to the motherboard
The I/O ports (e.g. USB, COM and PS/2 ports) are separate from the motherboard and are placed on a riser card or separate headers.

To identify an AT motherboard first check the power connectors. AT Motherboards use two sets of 6-pin inline power connectors

Caution it is possible to plug these connectors in the wrong order and fuse the motherboard.

ATX Motherboards
The ATX-style motherboards are a result of the industry’s push for standardization and are found in most systems today. Most modern computers contain an ATX motherboard. ATX boards can use

Advanced Power Management.
Distinguished by having more than just one external connector ATX boards have Keyboard, Mouse, Serial, Parallel and USB connectors.

ATX boards can also be distinguished by the monoblock power connectors. Also available in micro ATX enabling the use of smaller cases.

Motherboard Components
There are two types of receivers for CPU’s

Zero insertion force or ZIF sockets. With a ZIF socket, before the CPU is inserted, a lever or slider on the side of the socket is moved, pushing all the sprung contacts apart so that the CPU can be inserted with very little force (generally the weight of the CPU itself is sufficient with no external downward force required). The lever is then moved back, allowing the contacts to close and grip the pins of the CPU, often with a fan attached for cooling.

Single Edged Contact (SEC) cartridge slot or Slot 1 seen on PII and PIIIs. Developed by Intel to add Cache memory for the processor cheaply. The processor is mounted on a Single Edge Connector Cartridge (SECC), much like a PCI slot, but with a 242-lead edge-connector.

Bridges
There are two main bridges on a motherboard the Northbridge and the Southbridge. Bridges control access to the processor from the peripherals.

The Northbridge, also known as the Memory Controller Hub (MCH), is traditionally one of the two chips in the core logic chipset on a PC motherboard. The Northbridge typically controls communications between the CPU, RAM, AGP or PCI Express, and the Southbridge.. A Northbridge will typically work with only one or two classes of CPUs and generally only one type of RAM. There are a few chipsets that support two types of RAM (generally these are available when there is a shift to a new standard).

The Southbridge, also known as the I/O Controller Hub (ICH), is a chip that implements the “slower” capabilities of the motherboard in a Northbridge Southbridge chipset computer architecture. The Southbridge can usually be distinguished from the Northbridge by not being directly connected to the CPU. Rather, the Northbridge ties the Southbridge to the CPU. The functionality found on a contemporary Southbridge includes:PCI bus, ISA bus, SMBus, DMA controller, Interrupt controller, IDE, (SATA or PATA) controller ,LPC Bridge, Real Time Clock, Power management (APM and ACPI) and Nonvolatile BIOS memory.

To be continued from here in the next lesson......‪#‎StayFocussed‬
Diagram showing an ATX MotherBoard

Cloud Computing

Don’t be confused by the expression “cloud services, you are probably already using them if you use Amazon, Gmail, Hotmail, or Facebook. All it means is that your data is stored virtually.

Cloud computing is the delivery of hosted services over the internet .The origin of the term cloud computing is not known but it may be based on practice of using drawings of clouds to denote networks in diagrams of computing and communications systems.

Cloud computing provides easy, scalable access to computing resources and IT services. It can be thought of as similar to a utility like an electricity grid, delivered over a network .It involves the sharing of resources, services and infrastructure and can often be very cost effective.
Amazon played a key role in the development of cloud computing by modernizing their data centers, which were using a fraction of their capacity . The new cloud architecture gave significant efficiency improvements and small, fast-moving teams could add new features faster and more easily. Amazon
then developed a product that could provide cloud computing to external customers, and launched Amazon Web Service on a utility computing basis in 2006.

There are three characteristics of cloud services that differentiate them from traditional hosting.
*They are sold on demand, typically by the minute or the hour;
*They are elastic — a user can have as much or as little of a service as they want at any given time;
*services are fully managed by the provider , so the consumer only needs a personal computer and Internet access

To be successful, Companies today need to compete in the global economy and keep up with the pace of innovation. Their IT departments must be agile when responding to changing business needs, and must optimise efficiency and manage costs while enabling their business to stay productive. Cloud computing is one of the key technology trends creating opportunities to address these needs.

Private or Public Cloud.
 
A public cloud sells services to anyone on the Internet. An example is Amazon Web Services which is thought to be currently the largest public cloud provider.

A private cloud is a privately owned network or a data centre that supplies hosted services to a limited number of clients. When a service provider uses public cloud resources to create their private
cloud, this is known as a virtual private cloud.

A hybrid cloud or hybrid IT is a composition of at least one private cloud and at least one public cloud. Some resources are managed in-house and others are provided externally. For example, an organization might use a public cloud service, such as Amazon Simple Storage Service (Amazon S3) for archived data but continue to maintain in-house storage for customer data that is still active. This hybrid approach takes advantage of the scalability and cost-effectiveness that a public cloud environment offers without exposing critical applications and data to third-party vulnerabilities.

Cloud services are broadly divided into three categories:
*Infrastructure-as-a-Service (IaaS),
*Platform-as-a-Service (PaaS)
*Software-as-a-Service (SaaS).

Infrastructure-as-a-Service allows users to start, stop, and access and configure their virtual servers and storage. An example is Amazon Web Services. A user will pay for only the capacity that is needed, and can bring more online when required. Because this pay-for-what-you-use model resembles the way electricity, fuel and water are consumed, it’s sometimes referred to as utility computing.

Platform-as-a-service is a set of software and product development tools hosted on the provider’s infrastructure. An example is GoogleApps. Developers create applications on the provider’s platform.

Software as a service providers manage the infrastructure and platforms on which the applications run. It is sometimes referred to as “on-demand software” and is usually priced on a pay-per-use basis, often using a subscription fee. Examples can be anything from Web-based email to inventory control and database processing. Because the service provider hosts both the application and the data, the end user is free to use the service from anywhere. SaaS can usually help business to reduce IT operational costs by outsourcing hardware and software maintenance and support to the cloud provider. This reduces their requirement for hardware/software spending and personnel expenses. Because applications are hosted centrally, updates can be released without users having to install new software. A potential downside is that the users’ data are stored on the cloud provider’s server,so there could be unauthorized access to the data.

Cloud backup or online backup
Cloud backup or online backup allows data to be backed up by sending a copy of the data over a network to an off-site server The server is often hosted by a third-party service provider, who charges the customer a fee based on capacity, bandwidth or number of users.

Online backup systems often run on a schedule determined by the level of service the customer has purchased. If the customer has purchased an option for daily backups then the application collects, compresses, encrypts and transfers data to the service provider’s servers every 24 hours. To reduce the amount of bandwidth consumed and the time it takes to transfer files, the service provider might only provide incremental backups after the initial full backup.

Third-party cloud backup is extremely popular with small offices and home users because of its convenience. There is no spend on additional hardware and backups run automatically without manual intervention.

Traditional backup is a better solution for critical data that requires a short recovery time because there are physical limits governing how much data can be moved over a network in a given amount of time. If a large amount of data needs to be recovered, it may need to be shipped on tape or some other portable storage media.

The Cloud OS
Microsoft has developed a platform named “the Cloud OS,” which addresses this technology. This delivers a platform of products and services that enables companies to;-
*transform their current infrastructure to an elastic, scalable, and reliable infrastructure;
*quickly and flexibly build and manage modern applications across platforms, locations, and devices;
*unlock insights from new and existing data;
*Support user productivity on whatever device they choose, wherever they use it.
The heart of the Microsoft Cloud OS is Windows Server 2012, which delivers in four ways:
*It goes beyond virtualization to provide maximum flexibility for delivering and connecting to cloud services.
*It delivers the power of many servers with the simplicity of one:
*It opens the door to every app on any cloud : it is a broad, scalable, and elastic server platform that gives organizations the flexibility to build and deploy applications and websites on-premises, in the cloud, and in a hybrid environment, using a consistent set of tools and frameworks.
*It enables a contemporary work style: provide users with flexible access to data and applications from virtually anywhere, on virtually any device, with a rich user experience, while simplifying management and helping maintain security, control, and compliance.

Microsoft Private Cloud Fast Track is a joint project between Microsoft and its hardware partners to deliver pre-configured solutions that reduce the complexity and risk of implementing a private cloud. It is Based on Windows Server, and delivers flexibility and choice across a range of hardware vendor options technologies.

#‎Introduction_to_networking_continue‬

‪#‎Cables‬

Cable Terminology
10BASE2 (also known as cheapernet or thinnet) is a variant of Ethernet that uses thin coaxial cable. The 10 comes from the maximum transmission speed of 10 Mbit/s (millions of bits per second). The BASE stands for baseband signaling, and the 2 represents a rounded up shorthand for the maximum segment length of 185 metres (607 feet).

10BASE5 (also known as thicknet) is the original “full spec” variant of Ethernet cable. The 10 refers to its transmission speed of 10 Mbit/s. The BASE is short for baseband signalling as opposed to broadband, and the 5 stands for the maximum segment length of 500 metres.

10BASE-T is an implementation of Ethernet which allows stations to be attached via twisted pair cable. The name 10BASE-T is derived from several aspects of the physical medium. The 10 refers to the transmission speed of 10 Mbit/s. The BASE is short for baseband.The T comes from twisted pair, which is the type of cable that is used

100BASE-T is any of several Fast Ethernet 100 Mbit/s CSMA/CD standards for twisted pair cables, including: 100BASE-TX (100 Mbit/s over two-pair Cat5 or better cable). The segment length for a 100BASE-T cable is limited to 100 metres

‪#‎Coaxial‬
Coaxial cable is an electrical cable consisting of a round conducting wire, surrounded by an insulating spacer, surrounded by a cylindrical conducting sheath, usually surrounded by a final insulating layer. It is used as a high- frequency transmission line to carry a high-frequency or broadband signal.

BNC connectors were commonly used on 10base2 thin Ethernet networks, both on cable interconnections and network cards, though these have largely been replaced by newer Ethernet devices whose wiring does not use coaxial cable.

‪#‎CAT_5‬
Category 5 cable, commonly known as Cat 5, is an unshielded twisted pair cable type designed for high signal integrity. Category 5 has been superseded by the Category 5e specification. This type of cable is often used in structured cabling for computer networks such as Gigabit Ethernet, although they are also used to carry many other signals such as basic voice services, token ring.

Category 5 cable included four twisted pairs in a single cable jacket. It was most commonly used for 100 Mbit/s networks, such as 100BASE-TX Ethernet.

Cat5 cable uses an RJ-45 (Registered Jack-45) connector at each end of the cable with a fixed wiring scheme. The ends are then crimped on to the cable.

‪#‎Wiring_Scheme‬
Patch or straight through cables have Wiring scheme 1 at both ends of the cable and are used to connect computers to network wall sockets or hubs.

Crossover cables have Wiring scheme 1 at one end of the cable and Wiring scheme 2 at the other. These cables are used to connect network hardware together e.g. PC to PC, hub to hub.

‪#‎diagram_showing_wiring_scheme‬

Introduction to Networking

Why use a Network?
Quite simply explained we use networks for communication between computers, sharing of data and peripherals. In the business world we use networks for ease of administration and to cut costs.
Sharing data example imagine an office with 5 secretaries working on 5 different computers, one requires a file from another computer in a non networked office this file would have to be written to a portable media then loaded onto the computer. In a networked office the file could be accessed via the network from a shared folder.

Sharing peripherals example the same office with 5 secretaries working on 5 different computers, in order to print their work each computer would need to have a printer attached. In a networked office you could have one shared printer, cutting costs.
What do you need?

A common language or protocol (TCP/IP IPX/SPX, APPLE TALK) is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints.

A common language or protocol (TCP/IP IPX/SPX, APPLE TALK) is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints.

Cabling BNC,Cat5, fibre optic
Hardware NIC(Network Interface Card), router, switch, hub, modem wireless
access point.
Network Service (DNS, WINS, DHCP).
Network Hardware
Network Interface Card

A network card, network adapter, network interface card or NIC is a piece of computer hardware designed to allow computers to communicate over a computer network. It has a MAC address. Every network card has a unique 48- bit serial number called a MAC address, which is written to ROM carried on the card. Every computer on a network must have a card with a unique MAC.address. The IEEE is responsible for assigning MAC addresses to the vendors of network interface cards. No two cards ever manufactured should share the same address.

Hubs
An Ethernet hub or concentrator is a device for connecting multiple twisted pair or fibre optic Ethernet devices together, making them act as a single segment. It works at the physical layer of the OSI model, repeating the signal received at one port out each of the other ports (but not the original one). The device is thus a form of multiport repeater. Ethernet hubs are also responsible for forwarding a jam signal to all ports if it detects a collision. Hubs also often come with a BNC and/or AUI connector to allow connection to legacy 10BASE2 or 10BASE5 network segments. The availability of low-priced Ethernet switches has largely rendered hubs obsolete but they are still seen in older installations and more specialist applications.

Switches
A network switch or switch for short is a networking device that performs transparent bridging (connection of multiple network segments with forwarding based on MAC addresses) at full wire speed in hardware. As a frame comes into a switch, the switch saves the originating MAC address and the originating (hardware) port in the switch’s MAC address table. This table often uses content-addressable memory, so it is sometimes called the “CAM table”. The switch then selectively transmits the frame from specific ports based on the frame’s destination MAC address and previous entries in the MAC address table. If the destination MAC address is unknown, for instance, a broadcast address or (for simpler switches) a multicast address, the switch simply transmits the frame out of all of the connected interfaces except the incoming port. If the destination MAC address is known, the frame is forwarded only to the corresponding port in the MAC address table.

Hubs VS Switches
A hub, or repeater, is a fairly unsophisticated broadcast device. Any packet entering any port is broadcast out on every port and thus hubs do not manage any of the traffic that comes through their ports. Since every packet is constantly being sent out through every port, this results in packet collisions, which greatly impedes the smooth flow of traffic. A switch isolates ports, meaning that every received packet is sent out only to the port on which the target may be found (assuming the proper port can be found; if it is not, then the switch will broadcast the packet to all ports except the port the request originated from). Since the switch intelligently sends packets only where they need to go the performance of the network can be greatly increased.

Routers
A router is a computer networking device that forwards data packets across a network toward their destinations, through a process known as routing. A router acts as a junction between two or more networks to transfer data packets among them. A router is different from a switch. A switch connects
devices to form a Local area network (LAN).
One easy illustration for the different functions of routers and switches is to think of switches as local streets, and the router as the junctions with the street signs. Each house on the local street has an address within a range on the street. In the same way, a switch connects various devices each with their own IP address(es) on a LAN. Routers connect networks together the way that on-ramps or major junctions connect streets to both main roads and motorways. The street signs at the junctions the (routing table) show which way the packets need to flow.

Wireless
Wireless Access Point (WAP) A wireless access point (AP) connects a group of wireless stations to an adjacent wired local area network (LAN). An access point is similar to an Ethernet hub, but instead of relaying LAN data only to other LAN stations, an access point can relay wireless data to all other compatible wireless devices as well as to a single (usually) connected LAN device, in most cases an Ethernet hub or switch, allowing wireless devices to communicate with any other device on the LAN.
Wireless Routers A wireless router integrates a wireless access point with an Ethernet switch and an Ethernet router. The integrated switch connects the integrated access point and the integrated Ethernet router internally, and allows for external wired Ethernet LAN devices to be connected as well as a (usually)
single WAN device such as a cable modem or DSL modem. A wireless router advantageously allows all three devices (mainly the access point and router) to be configured through one central configuration utility, usually through an integrated web server. However one disadvantage is that one may not decouple
the access point so that it may be used elsewhere.
‪#‎to_be_continue‬

Protocols

#‎Protocols‬
A protocol (TCP/IP IPX/SPX, APPLE TALK) is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. Sending and receiving systems need to use the same protocol unless a gateway service sits between networks and translates from one to the other.

Most protocols specify one or more of the following properties:
*Detection of the underlying physical connection (wired or wireless), or the existence of the other endpoint or node
*Handshaking
*Negotiation of various connection characteristics
*How to start and end a message
*How to format a message
*What to do with corrupted or improperly formatted messages (error correction)
*How to detect unexpected loss of the connection, and what to do next
*Termination of the session or connectio

‪#‎NetBIOS‬
NetBIOS is an acronym for Network Basic Input/Output System. The NetBIOS API allows applications on separate computers to communicate over a local area network. NetBIOS must be enabled for Windows File and Print Sharing to work.

NetBIOS provides three distinct services:
*Name service for name registration and resolution
*Session service for connection-oriented communication
*Datagram distribution service for connectionless communication.

Name service In order to start Sessions or distribute Datagrams, an application must register its NetBIOS name using the Name service. NetBIOS names are 16 bytes in length.
Session service Session mode lets two computers establish a connection for a “conversation,” allows larger messages to be handled, and provides error detection and recovery. In NBT, the session service runs on TCP port 139.

Datagram distribution service Datagram mode is “connectionless”. Since each message is sent independently, they must be smaller; the application becomes responsible for error detection and recovery. In NBT, the datagram service runs on UDP port 138.
IPX/SPX (NWLINK)

Internetwork Packet Exchange (IPX) is the OSI-model Network layer protocol in the IPX/SPX protocol stack. The IPX/SPX protocol stack is supported by Novell’s NetWare network operating system. Because of Netware’s popularity through the late 1980s into the mid 1990s, IPX became a popular internetworking protocol. Novell derived IPX from Xerox Network Services’ IDP protocol. IPX usage is in general decline as the boom of the Internet has made TCP/IP nearly universal.

Computers and networks can run multiple network protocols, so almost all IPX sites will be running TCP/IP as well to allow for Internet connectivity. It is also now possible to run Novell products without IPX, as they have supported both IPX and TCP/IP since NetWare reached version 5.
Sequenced Packet Exchange (SPX) is a transport layer protocol (layer 4 of the OSI Model) used in Novell Netware networks. The SPX layer sits on top of the IPX layer (layer 3 – the network layer) and provides connection-oriented services between two nodes on the network. SPX is used primarily by client/ server applications.

NWLink is a IPX/SPX-compatible protocol developed by Microsoft and used in its Windows NT product line.NWLink is Microsoft’s version of Novell’s IPX/SPX Protocol. The Microsoft version of NWLink includes the same level of functionality as the Novell Protocol. NWLink includes a tool for resolving NetBIOS names.NWLink packages data to be compatible with client/server services on NetWare Networks. However, NWLink does not provide access to NetWare File and Print Services. To access the File and Print Services the Client Service for NetWare needs to be installed.

AppleTalk
AppleTalk is a suite of protocols developed by Apple Computer for computer networking. It was included in the original Macintosh (1984) and is now used less by Apple in favour of TCP/IP networking.

AppleTalk contains two protocols aimed at making the system completely self- configuring. The AppleTalk address resolution protocol (AARP) allowed AppleTalk hosts to automatically generate their own network addresses, and the Name Binding Protocol (NBP) was essentially a dynamic DNS system which mapped network addresses to user-readable names.

For interoperability Microsoft maintains the file services for Macintosh and the print services for Macintosh

TCP/IP
The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet and most commercial networks run. It is sometimes called the TCP/IP protocol suite, after the two most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were also the first two defined.The Internet protocol suite like many protocol suites can be viewed as a set of layers, each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted.The OSI model describes a fixed, seven layer stack for networking protocols.

Comparisons between the OSI model and TCP/IP can give further insight into the significance of the components of the IP suite, but can also cause confusion, as TCP/IP consists of only 4 layers.
The four layers in the DoD model, from bottom to top, are:

*The Network Access Layer is responsible for delivering data over the particular hardware media in use. Different protocols are selected from this layer, depending on the type of physical network.
*The Internet Layer is responsible for delivering data across a series of different physical networks that interconnect a source and destination machine. Routing protocols are most closely associated with this layer, as is the IP Protocol, the Internet’s fundamental protocol.
*The Host-to-Host Layer handles connection rendezvous, flow control, retransmission of lost data, and other generic data flow management. The mutually exclusive TCP and UDP protocols are this layer’s most important members.
*The Process Layer contains protocols that implement user-level functions, such as mail delivery, file transfer and remote login.
Network Services

DNS (Domain Naming System)
The Domain Name System (DNS) stores and associates many types of information with domain names, but most importantly, it translates domain names (computer hostnames) to IP addresses. It also lists mail exchange servers accepting e-mail for each domain. In providing a worldwide keyword- based redirection service, DNS is an essential component of contemporary Internet use.
The DNS pre-eminently makes it possible to attach easy-to-remember domain names (such as “es-net.co.uk”) to hard-to-remember IP addresses (such as 270.146.131.206). People take advantage of this when they recite URLs and e-mail addresses.

WINS (Windows Internet Naming Service)
Windows Internet Naming Service (WINS) is Microsoft’s implementation of NetBIOS Name Server (NBNS) on Windows, a name server and service for NetBIOS computer names. Effectively, it is to NetBIOS names what DNS is to domain names – a central mapping of host names to network addresses. However, the mappings have always been dynamically updated (e.g. at workstation boot) so that when a client needs to contact another computer on the network it can get its up-to-date DHCP allocated address. Networks normally have more than one WINS server and each WINS server should be in push pull replication; the favoured replication model is the hub and spoke, thus the WINS design is not central but distributed. Each WINS server holds a full copy of every other related WINS system’s records.

There is no hierarchy in WINS (unlike DNS), but like DNS its database can be queried for the address to contact rather than broadcasting a request for which address to contact. The system therefore reduces broadcast traffic on the network, however replication traffic can add to WAN / LAN traffic.

DHCP (Dynamic Host Configuration Protocol)
The Dynamic Host Configuration Protocol (DHCP) automates the assignment of IP addresses, subnet masks, default routers, and other IP parameters. The assignment usually occurs when the DHCP configured machine boots up or regains connectivity to the network. The DHCP client sends out a query requesting a response from a DHCP server on the locally attached network. The DHCP server then replies to the client with its assigned IP address, subnet mask, DNS server and default gateway information.The assignment of the IP address usually expires after a predetermined period of time, at which point the DHCP client and server renegotiate a new IP address from the server’s predefined pool of addresses. Configuring firewall rules to accommodate access from machines who receive their IP addresses via DHCP is therefore more difficult because the remote IP address will vary from time to time.

Administrators must usually allow access to the entire remote DHCP subnet for a particular TCP/UDP port. Most home routers and firewalls are configured in the factory to be DHCP servers for a home network. ISPs (Internet Service Providers) generally use DHCP to assign clients individual IP addresses.DHCP is a broadcast-based protocol. As with other types of broadcast traffic, it does not
cross a router.

APIPA (Automatic Private IP Addressing)
If computers are unable to pick an address up from a DHCP server they use Automatic Private IP Addressing (APIPA). This means the computer will assign itself a random address between 169.254.0.1 – 169.254.254.254/16, allowing it to communicate with other clients who are also using

APIPA.
Automatic Private IP Addressing (APIPA), this allows unknowledgeable users to connect computers, networked printers, and other items together and expectthem to work. Without Zeroconf or something similar, a knowledgeable user must either set up special servers, like DHCP and DNS, or set up each computer by hand.
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#‎Networks‬
A Local Area Network (LAN) is a computer network covering a small local area, like a home, office, or small group of buildings such as a home, office, or college. Current LANs are most likely to be based on switched Ethernet or Wi-Fi technology running at 10, 100 or 1,000 Mbit/s.The defining characteristics of LANs in contrast to WANs (wide area networks) are: their much higher data rates; smaller geographic range; and that they do not require leased telecommunication lines.

A Personal Area Network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. The reach of a PAN is typically a few metres and may use Bluetooth, wireless or USB for connection.

A Wide Area Network (WAN) is a computer network covering a wide geographical area, involving a vast array of computers. This is different from personal area networks (PANs), metropolitan area networks (MANs) or local area networks (LANs) that are usually limited to a room, building or campus. The most well-known example of a WAN is the Internet. WANs are used to connect local area networks (LANs) together, so that users and computers in one location can communicate with users and computers in other locations.