Page 97 - Electronic Commerce

Chapter 2

The worldwide growth in the number of mobile devices and the Internet of Things has
consumed existing IPv4 addresses much faster than anyone had predicted and current
72 estimates are that new IPv4 addresses will no longer be available as soon as 2015.
Although many companies have been slow to adopt the new protocol for their computer
networks, mobile networks run more efficiently on IPv6, which has given telecom
companies and NSPs an incentive to invest in IPv6-compatible hardware. This build-out of
IPv6 in mobile networks is expected to push its adoption in more settings.
The major advantage of IPv6 is that it uses a 128-bit number for addresses instead of
the 32-bit number used in IPv4. The number of available addresses in IPv6 (2 128 )is34
followed by 37 zeros—billions of times larger than the address space of IPv4. The new IP
also changes the format of the packet itself. Improvements in networking technologies
over the past 20 years have made many of the fields in the IPv4 packet unnecessary. IPv6
eliminates those fields and adds fields for security and other optional information.
IPv6 has a shorthand notation system for expressing addresses, similar to the IPv4
dotted decimal notation system. However, because the IPv6 address space is much larger,
its notation system is more complex. The IPv6 notation uses eight groups of 16 bits
(8 × 16 = 128). Each group is expressed as four hexadecimal digits and the groups are
separated by colons; thus, the notation system is called colon hexadecimal or colon hex.
A hexadecimal (base 16) numbering system uses 16 characters (0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
a, b, c, d, e, and f). An example of an IPv6 address expressed in this notation is:
CD18:0000:0000:AF23:0000:FF9E:61B2:884D. To save space, the zeros can be omitted,
which reduces this address to: CD18:::AF23::FF9E:61B2:884D.

Electronic Mail Protocols
Electronic mail,or e-mail, that is sent across the Internet must also be formatted
according to a common set of rules. Most organizations use a client/server structure to
handle e-mail. The organization has a computer called an e-mail server that is devoted to
handling e-mail. Software that runs on the e-mail server stores and forwards e-mail
messages. People in the organization might use a variety of programs, called e-mail client
software, to read and send e-mail. These programs include Microsoft Outlook, Mozilla
Thunderbird, and many others. The e-mail client software communicates with the e-mail
server software on the e-mail server computer to send and receive e-mail messages.
Many people also use e-mail on their computers at home. In most cases, the e-mail
servers that handle their messages are operated by the companies that provide their
connections to the Internet. An increasing number of people use e-mail services that are
offered by Web sites such as Yahoo! Mail, or Google’s Gmail. In these cases, the e-mail
servers and the e-mail clients are operated by the owners of the Web sites. The individual
users only see the e-mail client software (and not the e-mail server software) in their Web
browsers when they log on to the Web mail service.
With so many different e-mail client and server software choices, standardization and
rules are very important. If e-mail messages did not follow standard rules, an e-mail
message created by a person using one e-mail client program could not be read by a
person using a different e-mail client program. As you have already learned in this
chapter, rules for computer data transmission are called protocols.

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