Operating Systems for WAP
WAP
is a communications protocol and an application environment. It can be
built on any operating system including PalmOS®, EPOC, Windows CE,
FLEXOS, OS/9, and JavaOS. WAP provides service interoperability even
between different device families. WAP uses existing Internet
standards, and the WAP architecture (illustrated in Figure 22.1) was designed to enable standard off-the-shelf Internet servers to provide services to wireless devices.
In addition to wireless devices, WAP uses many Internet
additions when communicating standards such as XML, UDP, and IP. WAP
wireless protocols are based on Internet standards such as HTTP and
Transport Layer Security (TLS), but have been optimized for the unique
constraints of the wireless environment. Internet standards such as
HTML, HTTP, TLS, and TCP are inefficient over mobile networks, requiring
large amounts of mainly text-based data to be sent. Standard HTML Web
content generally cannot be displayed in an effective way on the small
screens of pocket-sized mobile telephones and pagers, and navigation
around and between screens is not easy in one-handed mode. HTTP and TCP
are not optimized for the intermittent coverage, long latencies, and
limited bandwidth associated with wireless networks. HTTP sends its
headers and commands in an inefficient text format instead of
compressed binary. Wireless services using these protocols are often
slow, costly, and difficult to use. The TLS security standard requires
many messages to be exchanged between client and server which, with
wireless transmission latencies, results in a very slow response for
the user. WAP has been optimized to solve all these problems, utilizing
binary transmission for greater compression of data, and is optimized
for long latency and low-to-medium bandwidth. WAP sessions cope with
intermittent coverage and can operate over a wide variety of wireless
transports using IP where it is possible and other optimized protocols
where IP is impossible. The WML used for WAP content makes optimum use
of small screens; allows easy, one-handed navigation without a full
keyboard; and has built-in scalability from two-line text displays
through to the full graphic screens on smart telephones and
communicators. [6] Figure 22.2 illustrates the relationship between WAP and the Web.
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