Chapter 6

The Cloud

You hear the term all the time, "Its in the cloud", but what does that really mean?  We are going to take a look at the cloud and its parts to ensure we have a general understanding of what it is and how it does what it does.  First lets use the generally accepted definition and then break that down a little.  The cloud is the elastic leasing of pooled computer resources over the internet.  There are a couple of key words that really make the cloud what it is.  First off it is elastic, this means that its capacity can vary literally one second to the next.  We will talk a little bit about the resources that are used to do this but gist is that the the computing power that is being used can be varied based on the need or demand for it.  The next part is that the resources are pooled.  What this means is that different applications or even different organizations can use the same physical resources at different times based on their need then.  This is performed through virtualization which we discussed depth earlier.  What you need to remember is that virtualization is "creating" a system through software that doesn't actually physically exist from the rest of the system.  The final key part is that this is done over the internet.  This is painfully straight forward in its meaning.  When these things occur in conjunction you have all the ingredients you need for cloud computing.  Okay but why is the cloud a thing?  Where did it come from all of the sudden?  Well there are three factors that have enabled cloud computing to be developed and implemented as a viable business model and tool.  First of as we discussed integrated circuits reduce in cost exponentially, this has led to systems where processors, data communication and storage are so cheap it is viable to great much larger systems than we have seen in the pass.  This is especially true when economies of scale are at play such as we see in large data centers.  Another factor is the advancement of virtualization software.  Modern virtualization software has allowed data centers to turn from massive simple storage caches to computing powerhouses that can easily reallocate resources to different processes or applications on a whim.  This a created a whole new industry often referred to as software driven data centers or SDDCs.   Finally the advent of universal standards in computer technology, specifically in the realm of data communication has allowed hosting companies to provide the flexible resources in a meaningful way that can be utilized across almost all sectors of industry.  This has made cloud computing the alternative to in house hosting which is how most of these applications were implemented in the past.  Cloud computing is more flexible as we have said but it also allows for easier budgeting as there are no surprises in cost when scaling occurs and the initial capital requirement is very small when compared to establishing an in house system.  Firms also do not have to worry about equipment becoming obsolete and needing to replace it as the hosting firm takes on that responsibility as well as the cost of maintaining the system.  We can see the economies of scale coming into play here again.  

Tech Makes The Cloud

Lets look at the components that make up the cloud starting with the most basic terms.  First is the network which is simply a collection of computers that communicate with each other.  This can be done over transmission lines or wirelessly.  All networks fit into four types.  First there is the personal area network or PAN, this is a network of personal connected devices that center around one person.  Your cell phone, Bluetooth headset and laptop can all be a part of your own PAN.  Next you have LANs or local area networks.  These are networks of computers that are connected at a single physical site.  Think of the computers at the library, they are all part of the same LAN.  Next there are wide area networks or WANs.  The are computers that are connected between two or more physical sites.  Consider a firm that has several locations across the country.  If these sites systems are all connected via in house networking the create a WAN.  Finally you have THE Internet or individual Internets which are simply networks of networks.  Anytime one separate network talks to another you have created an internet. The way in which these networks can so easily communicate with each other is enabled through standardized protocols or sets of rules and data structures for organizing communication.  The Institute for Electrical and Electronic Engineers creates committees that create and publish these protocols and standards that allow for universal communication.  Another factor is enabling networks to "call" each other using "phone numbers" or IP addresses.  IPv4 is the most common format, it looks something like xxx.xxx.xxx.xxx where x is a digit between 0 and 9.  Every system has a IP address including your phone and laptop.  This allows for devices to be identified individually.  This gets more complicated when talking about how a host router communicates with a server using IP address as things can be changed to make traffic more efficient then.  When you look at host websites how ever you never have to punch in a phone number, so how does that work.  Well most IP address are assigned to a domain name and when used in conjunction with the appropriate protocol, i.e. https, your traffic is routed to the correct location through a domain name server or DNS.  DNS communicate with internet service provider servers or ISPs.  All of this in combination leads to the three tier architecture that make up clouds.  The first tier is the user tier which consists of computers, phones and other devices that use browsers to request and process web page data.  Next is the server tier.  This consists of computers that run web servers and process web applications.  Web servers are servers that run programs that manage internet traffic by sending, receiving and processing request for web page data.