Transcript Wireless Internet

Wireless Internet
Introduction
Introduction
 Wireless Internet refers to the extension of the
services offered by the Internet to mobile
users.
 Can access information and data irrespective
of location.
 Wireless Internet not same as wired.
 Protocols like TCP and application protocols
like TELNET, FTP and SMTP used in wired
work poorly in wireless.
Wireless Internet
Major Issues for Wireless Internet
 Address Mobility
 Inefficiency of transport layer protocols
 Inefficiency of application layer protocols
Address Mobility
 Internet protocol (IP) designed for wired
networks for fixed nodes.
 It has hierarchical 32 bit address, mainly
divided into subnet and host id.
 Used to reduce routing table sizes in core
routers, which can use only network id for
routing decisions.
 This may not work for Wireless as mobile
hosts move form one subnet to another.
 Packets addressed to mobile host may be
delivered to old subnet.
Address Mobility
 MobileIP is a solution which uses
address redirection mechanism.
Inefficiency of Transport Layer Protocols
 Transport layer ensures setting up and
maintaining end-to-end connections, end-toend delivery of data packets, flow control
and congestion control.
 TCP used in wired (UDP used in some
applications)
 Wireless medium is inherently unreliable
due to time-varying and environmentdependent characteristics.
Inefficiency of Transport Layer Protocols
 TCP invokes congestion control algorithm to
control congestion.
 If data packet or ACK packet is lost, TCP
assumes congestion and reduces
congestion window by half. Even in case of
link errors or collisions.
 Degraded performance, Low throughput in
wireless.
 Solutions include mobile TCP, snoop TCP,
ITCP etc.
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Inefficiency of Application Layer protocols
HTTP, TELNET, SMTP and markup
languages like HTML optimized for Wired.
Not efficient in wireless, high overhead due to
character encoding, redundant info carried in
HTTP and new TCP connection for every
transaction.
Wireless bandwidth limited and expensive.
Solution is WAP and optimizations over
traditional HTTP.