End-to-end analysis

End-to-end analysis

The WAP user does not need to be aware of the WAP gateway between itself and the WWW server.
From the users point of view he or she has a direct connection from the wireless mobile device to the
WWW server. In this section I will discuss the end-to-end behaviour experienced by a user of a
mobile client when browsing web pages from a Web server via a WAP gateway.
While the user surfs the Internet and encounter problems, such as missing information or bad data
rate, the user, in an end-to-end discussion, only complain at the WWW server though he is not aware
of the gateway. Without the gateway, as an interpreter, between the two endpoints there should not be
possible to communicate at all because they do not understand the same language. The WWW server
understands HTML while the WAP client talks WML. So how is the conversion done?

8.1 Language conversions

Today there are only a few gateways that are able to do the conversion and there are a few problems.
The fact that HTML is a kind of non-standard language, due the fact that third part developers
(Netscape and Microsoft) has implemented tags that only is supported in their own
software/webbrowsers (Netscape and Explorer respectively), is a big problem in the conversion part.
The HTML language is a much bigger language than WML and not all tags in HTML have a meaning
in WML. How should we for example handle frames?
Different wireless devices have different kinds of terminals and different interactive possibilities. By
sending information about the client possibilities with the URL request the gateway can convert the
HTML page to a WML page that suites the specific client. This will lead to more complexity in the
WAP gateway and every client will not be supported by every gateway.
Another problem is the fact that a HTML page is designed for desktop computers (or other devices
with a relatively big screen) and assumes a greater bandwidth than 9.6kbps. This means that a HTML
page may consist of long texts and different kinds of image types. These pages are almost impossible
to display on a small display without loosing significant information and/or the structure that you can
experience on a big screen.
For the moment the only image type that WML support is WBMP (Wireless Bitmap) in a
monochromatic manner. Image types in a HTML page such as GIF or JPG is very hard (read
impossible) to display in a cell phone display with an accurate and desired result.

8.2 Security issues

If we have a secure transmission between the two endpoints, does this mean that we have a secure
transmission the whole way? In the WAP gateway the packet has to be unpacked and here we may
have a security leak. It is obvious that security issues have to be taken care of in the gateway to ensure
a secure transmission in the end-to-end system.