Page 170 - E-Bussiness and E-Commerce Management Strategy, Implementation, and Practice

M03_CHAF9601_04_SE_C03.QXD:D01_CHAF7409_04_SE_C01.QXD 16/4/09 11:09 Page 137

Chapter 3 E-business infrastructure 137

‘Internet’ refers to the global information system that – (i) is logically linked together by a
globally unique address space based on the Internet Protocol (IP) or its subsequent exten-
sions/follow-ons; (ii) is able to support communications using the Transmission Control
Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or
other IP-compatible protocols; and (iii) provides, uses or makes accessible, either publicly
or privately, high level services layered on the communications and related infrastructure
described herein.

TCP/IP

TCP/IP TCP/IP development was led by Robert Kahn and Vince Cerf in the late 1960s and early
The Transmission Control 1970s and, according to Leiner et al. (2000), four rules controlled Kahn’s early work on this
Protocol is a transport-
layer protocol that protocol. These four rules highlight the operation of the TCP/IP protocol:
moves data between
applications. The Internet 1 Distinct networks would be able to communicate seamlessly with other networks.
Protocol is a network- 2 Communications would be on a best-effort basis, that is, if a data packet did not reach the
layer protocol that moves
data between host final destination, it would be retransmitted from the source until successful receipt.
computers. 3 Black boxes would be used to connect the networks; these are now known as‘gateways’ and
‘routers’ and are produced by companies such as Cisco and 3Com. In order to keep them
simple there would be no information retained by the ‘gateways’.
4 There would be no global control of transmissions – these would be governed by the
requester and sender of information.
It can be seen that simplicity, speed and independence from control were at the heart of the
development of the TCP/IP standards.
The data transmissions standards of the Internet such as TCP/IP are part of a larger set of
standards known as the Open Systems Interconnection (OSI) model. This defines a layered
model that enables servers to communicate with other servers and clients. When imple-
mented in software, the combined layers are referred to as a ‘protocol stack’. The seven layers
of the OSI model are:
Application. The program such as a web browser that creates and receives messages.
Presentation. These protocols are usually part of the operating system.
Session. This includes data-transfer protocols such as SMTP, HTTP and FTP.
Transport. This layer ensures the integrity of data transmitted. Examples include the
Internet TCP and Novell SPX.
Network. Defines protocols for opening and maintaining links between servers. The best

known are the Internet protocol IP and Novell IPX.
Data link. Defines the rules for sending and receiving information.
Physical. Low-level description of physical transmission methods.
The postal service is a good analogy for the transmission of data around the Internet using
the TCP/IP protocol. Before we send mail, we always need to add a destination address. Like-
wise, the IP acts as an addressed envelope that is used to address a message to the
appropriate IP address of the receiver (Figure 3.13).
The Internet is a packet-switched network that uses TCP/IP as its protocol. This means
that, as messages or packets of data are sent, there is no part of the network that is dedicated
to them. This is like the fact that when your letters and parcels are sent by post they are mixed
with letters and parcels from other people. The alternative type of network is the circuit-
switched network such as phone systems where the line is dedicated to the user for the
duration of the call. Taking the analogy further, the transmission media of the Internet such
as telephone lines, satellite links and optical cables are the equivalent of the vans, trains and
planes that are used to carry post. Transmission media for the Internet include analogue
media such as phone lines and faster, digital media such as Integrated Service Digital Network
technology (ISDN) and more recently the Asynchronous Digital Subscriber Line (ADSL).