next paragraph, but many of those that are listed here are well known and
require no explanation after their introduction.
The Transmission Control Protocol/Internet Protocol, better known as
TCP/IP, is ultimately responsible for the creation of other TCP-backbone
protocols: HTTP, DHCP, SOAP, Telnet, Rlogin, DNS, FTP, RSH, IMAP, NFS,
SMTP, POP3, NNTP, SNMP, SSH, most chat protocols, and most X Window
FTP, HTTP, and SMTP are three of many widely known standard proto-
cols that are generally supported within an organization and that rely on
TCP as a standard transport mechanism. FTP, HTTP, and SMTP are inter-
active protocols that can trigger events by either programmatic contribution
or encountering a manual user transmission of meaningful information.
We will focus on these protocols in this section because they are the proto-
cols with which most people are familiar.
In the set of circumstances surrounding the HTTP protocol, program-
matic contributions offer a robust way to exchange information between a
client and a server, and Component Services are committed to processing
information in a very efficient manner. For example, the IIS Server does an
excellent job handling HTTP user requests and responses as well as inter-
preting and executing ASP requests. Because of the special relationship of
IIS with MTS and COM+, known as Component Services, server-side
resources can be pooled, including connections to the database and COM+
In effect, the SOAP protocol overcomes the barriers discussed previously
in this chapter regarding earlier attempts at creating custom TCP-based
solutions. Because the SOAP protocol uses XML and the TCP protocol to
bypass firewalls, it masks itself as an HTTP response or request and is eas-
ily passed through virtually all firewalls.
Hence, without TCP/IP, the HTTP protocol could not exist. You might
think of the SOAP protocol as a third-tier protocol and FTP and HTTP as
second-tier protocols, depending on the TCP protocol that provides for
physical transmission. (See Figure 1.1.)
The TCP/IP protocol negotiates handshaking and RPC (Remote Proce-
dure Call) across an intranet and the public Internet. Handshaking is sim-
ply the method by which two programs, through their interfaces,
determine the type of relationship that exists between them. (See Figure
1.2.) RPC is a way for the programs of one computer to actually execute
code on another computer.