Middleware

Middleware
Wireless network middleware is an intermediate software component generally located on the
wired network between the wireless appliance and the application or data residing on the wired
network (refer to Figure 6.19). The overall goal of middleware is to increase performance of
applications running across a wireless network. To accomplish this, middleware attempts to
counter wireless network impairments, such as limited bandwidth and disruptions in network
connections.
The following are common features found in middleware products that go beyond the basic
functionality of connecting appliances to applications and databases located on the wired network:
• Optimization techniques—Many middleware products include data compression at the
transport layer to help minimize the number of bits sent over the wireless link. Vendors
use a variety of compression algorithms to perform the compression, including V.42bis,
Hoffman encoding, run-length encoding, and proprietary compression techniques. Some
implementations of middleware use header compression, in which mechanisms replace
traditional packet headers with a much shorter bit sequence before transmission.
• Intelligent restarts—With wireless networks, a transmission may be cut at midstream
due to interference or operation in fringe areas. An intelligent restart is a recovery
mechanism that detects when a transmission has been cut. When the connection is reestablished,
the middleware resumes transmission from the break point instead of at the
beginning of the transmission.
• Data bundling—Some middleware is capable of combining (bundling) smaller data
packets into a single large packet for transmission over the wireless network. This is
especially beneficial in helping lower transmission service costs of wireless WANs.
Because most wireless data services charge users by the packet, data bundling results in
a lower aggregate cost.
• Embedded acknowledgements—Rather than send acknowledgements as separate small
packets, middleware products tend to embed acknowledgements in the header of larger
information-carrying packets, to reduce the number of packets traversing wireless network.
Many network protocols (including Novell’s IPX) require stations to send
acknowledgements to each other to continue data flows.
• Store-and-forward messaging—Middleware performs message queuing to ensure message
delivery to users who might become disconnected from the network for a period of
time. When the station comes back online, the middleware sends the stored messages to
the station.
• Screen scraping and reshaping—The development environment of some middleware
products enables the developer to use visual tools to “scrape” and “reshape” portions of
existing application screens to more effectively fit within the smaller display of data collectors.
• Support for Mobile IP—Some middleware products offer home-agent and foreignagent
functions to support the use of Mobile IP protocols.
• Operational support mechanisms—Some middleware products offer utilities and tools
to monitor the performance of wireless appliances, enabling MIS personnel to better
troubleshoot problems.
The following are attributes of middleware connectivity:
• Highly efficient operation over wireless networks—Middleware reduces the load on
the wireless network through the use of optimization techniques such as data compression
and screen scraping.
• No programming required on the appliance or host/server—Most middleware products
offer a development environment that shields the developer from understanding
appliance and host-based development environments.
• Support for migration from terminal/host to client/server systems—Many companies
are migrating from terminal/host (that is, mainframes) to client/server systems.
Middleware is a cost-effective solution for supporting these migrations, enabling connections
to both terminal-based systems and client/server databases simultaneously.
• Support of multiple-vendor appliances—Middleware products interface with a wide
variety of appliances.
• Long-term cost savings—Because of easier support of operational wireless applications,
middleware provides considerable long-term cost savings.
• Higher initial costs for implementations with smaller numbers of appliances—The
cost for middleware is $5,000 to $10,000 per site, making it relatively expensive for
implementing wireless systems that have fewer than 10 appliances. Be sure, though, to
consider all the advantages of middleware before finalizing a business case.