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Q3 How Does the Cloud Work? 225

WSDL/SOAP Web Service Protocols
http, https,
Application layer smtp, ftp
protocols
Internet Protocols
(TCP/IP Protocol
Internet ‘plumbing’ 4 more layers Architecture)
protocols of protocols
Figure 6-14
Protocols that Support Web
Services

implements the http protocol. At the other end, at the New Zealand hotel, for example, there
is a server that also processes http. Even though your browser and the server at the hotel have
never “met” before, they can communicate with one another because they both follow the rules
of http. Similarly, in Figure 6-13, the browsers send and receive service requests to and from the
commerce server using http.
As you will learn in Chapter 10, there is a secure version of http called https. Whenever you
see https in your browser’s address bar, you have a secure transmission and you can safely send
sensitive data like credit card numbers. When you are on the Internet, if you do not see https,
then you should assume that all of your communication is open and could be published on
the front page of your campus newspaper tomorrow morning. Hence, when you are using http,
email, text messaging, chat, videoconferencing, or anything other than https, know that what-
ever you are typing or saying could be known by anyone else.
Two additional TCP/IP application-layer protocols are common. smtp, or Simple Mail
Transfer Protocol, is used for email transmissions (along with other protocols). ftp, or
File Transfer Protocol, is used to move files over the Internet. Google Grid and Microsoft
OneDrive use ftp behind the scenes to transmit files to and from their cloud servers to your
computer.

WSDL, SOAP, XML, and JSON

To wrap up the discussion, we will briefly consider four standards that are used extensively for
Web services and the cloud. Those standards and their purpose are as follows:

WSDL (Web Services A standard for describing the services, inputs and outputs, and
Description other data supported by a Web service. Documents coded ac-
Language) cording to this standard are machine readable and can be used
by developer tools for creating programs to access the service.
SOAP A protocol for requesting Web services and for sending respons-
(no longer an acronym) es to Web service requests.
XML A markup language used for transmitting documents. Contains
(eXtensible Markup Language) much metadata that can be used to validate the format and com-
pleteness of the document, but includes considerable overhead
(see Figure 6-15a).

JSON A markup language used for transmitting documents. Contains
(JavaScript Object Notation) little metadata and is preferred for transmitting volumes of data
between servers and browsers. While the notation is the format
of JavaScript objects, JSON documents can be processed by any
language (see Figure 6-15b).