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Computer
C O M M U N I C A T I O N S
T he rapid evolution and expan-
sion of wireless-enabled envi-
ronments have increased the
need for sophisticated service
discovery protocols (SDPs).
Typically, service discovery involves a
client, service provider, and lookup or
directory server. Service registration
and lookup, or matching, are impor-
tant components of most common
SDPs including Jini, the service loca-
tion protocol (SLP), Salutation, UPnP
(universal plug and play), and UDDI
(universal description, discovery, and
integration).
To discover a service, a client uses one
of these protocols to issue a query to a
central server or an individual service
provider. The service description in the
query may contain a specific name and
set of one or more attributes. The server
or provider attempts to match the
query’s pattern with the pattern of a ser-
vice its database contains, then it returns
the appropriate response to the client.
These SDPs assume the existence of
• continuous and robust network
connectivity,
• support from network protocols
such as IP,
• support from transport protocols
such as TCP (transmission-control
protocol) and UDP (user data-
gram protocol), and
• network layer mechanisms such as
multicasting.
However, some or all of these require-
ments may not be met in wireless net-
works, especially those formed in an
ad hoc manner. For example, tempo-
rary disconnections occur frequently in
such networks, and the negative
impact on TCP performance in turn
decreases SDP performance.
Bluetooth (http://www.bluetooth.
com) short-range wireless technology
operates in the globally available 2.4-
GHz ISM (industrial, scientific, and
medical) frequency band and provides
data rates of up to 432 Kbps (symmet-
ric) and 721 Kbps (unsymmetric). The
Bluetooth protocol stack currently
includes specifications that define the
SDP, RFCOMM (for cable replace-
ment), the logical link control and
adaptation protocol (L2CAP), a host
controller interface (HCI), the link
manager protocol (LMP), the base-
band protoc