Page 256 - Using MIS

224 Chapter 6 The Cloud

html with JavaScript that correctly
requests services and processes responses

Browser
Commerce server Database server
service requests service requests
& responses & responses
Browser DBMS DB

Load Balancer Web Server DB Load Balancer
Browser Commerce DBMS DB
Commerce
Server
Commerce
Server
Commerce
Server
Commerce
Web Server
Server
Commerce
Server
Web Server
Server
Web Server
Browser Web Server DBMS DB
Web Server
1, 3, 100, 1000, etc. 1, 3, 50
Web Servers Database Servers
…
Figure 6-13
SOA Principles Applied to Browser
Three-Tier Architecture
In addition, on the back end, SOA services are defined between the Web server and the
database server. Accordingly, the database server need do nothing as the number and location
of Web servers is adjusted. And that’s a two-way street. Nothing in the Web servers need be
changed if the number and location of database servers is adjusted. However, load balancing for
database servers is considerably more complicated.
Do not infer from this discussion that SOA services and the cloud are only used for three-
tier processing. Such services and the cloud are used for multitudes of applications across the
Internet. This three-tier application is just an example.
From this discussion, you can understand how cloud elasticity is possible. However, for
many organizations to use the cloud and to be able to mix and match Web services, they need to
agree on standard ways of formatting and processing service requests and data. That leads us to
cloud standards and protocols. Again, we discuss these at a very high level.

Protocols Supporting Web Services

A protocol is a set of rules and data structures for organizing communication. Because the
cloud’s Web services use the Internet, the protocols that run the Internet also support cloud
processing. We will start with them.

TCP/IP Protocol Architecture

The basic plumbing of the Internet is governed by protocols that are defined according to
an arrangement called the TCP/IP protocol architecture. This architecture has five lay-
ers; one or more protocols are defined at each layer. Data communications and software
vendors write computer programs that implement the rules of a particular protocol. (For
protocols at the bottom layer, the physical layer, they build hardware devices that imple-
ment the protocol.)

Internet Protocols: http, https, smtp, and ftp

The only Internet protocols that you as a business professional are likely to encounter are those
at the top, or the application layer of the TCP/IP architecture, shown in Figure 6-14. Hypertext
Transfer Protocol (http) is the protocol used between browsers and Web servers. When
you use a browser such as Internet Explorer, Safari, or Chrome, you are using a program that