Cryptographic Protocols - Codes: The Guide to Secrecy from Ancient to Modern Times - page 219

so. For instance, in 1996 the Internet Engineering Task Force (IETF), 5.3
the agencythat develops protocol standards for the Internet, formed a
committee, the Transport Layer Security (TLS) working group. Their
mandate was to to develop a standard for Secure Sockets Layer (SSL) a
protocol that originated at Netscape in 1994, and which we will describe in
detail in this section. In January1999, the TLS working group published
the TLS protocol. However, TLS is essentiallya version of SSL, so we
will not describe it here, but rather wait to get the full description of SSL,
which is not, in itself, a single protocol, but rather two layers of protocols
using TCP to provide a secure connection with WWW browsers .
This is an appropriate juncture to explain the Internet terminologythat
we will be using. For instance, WWW is the acronym for the World
Wide Web , which is the information network using HTTP and HTML on
Internet host computers. HTTP is the acronym for HyperText Transfer
Protocol , which is the protocol used to transfer files from an Internet server
onto a browser in order to view that page on the Internet. HTTP is a
one-waysstem in the sense that the contents of a page from the server
are downloaded to the computer's browser for viewing, but files cannot
be transferred to the computer's memory. HTML is the acronym for
HyperText Markup Language , which is the text format for WWW pages.
Browser is a short form for WWW browser, which is a software application
used to locate and displayWWW pages. The two most popular browsers
are Netscape Navigator and Microsoft Internet Explorer . Both of these
are graphical browsers, meaning theycan displaygraphics as well as text.
Plug-ins are usuallyrequired for presentation of multimedia information.
To summarize, and expand the role of this layer, essentially the transport
layer decides how to utilize the network layer to render a virtual error-
free connection between hosts. Thus, it both initiates and terminates
connections between hosts.
5. Session Layer : This layer uses the transport layer to establish a connection
between hosts for certain processes. It essentiallyhandles the securityside
and the creation of the session itself.
6. Presentation Layer : This layer executes such functions as text com-
pression and format conversions. This is the mechanism for ironing out
differences between two hosts. If there are incompatible processes in the
next layer up, the presentation layer allows the process to communicate
via the session layer.
7. Application Layer : The top layer essentially handles the user's needs. For
instance, it deals with such issues as allowing a user to access a remote
5.3 The IETF is indirectly overseen by the Internet Society , a nonprofit organization that acts
as a conscience and guide for the Internet. The Internet Society supports the Internet Archi-
tecture Board (IAB), which oversees the technical development of the Internet. In particular,
IAB supervises IETF. See http://ietf.org/ .