You will see many similarities between these
protocols and SIP, including many of the procedures defined for mail delivery and Web
browsing. However, there is also a caveat to using these protocols.
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58 Chapter 3
Internet protocols are not well known for robust security. The Internet community
leaves security to the end devices that access the network. This leads the service providers
providing Internet access to ignore breaches and other security holes in their
networks. It likewise means that the consumers must take things into their own hands
to ensure they are not violated through a lack of security on their computers and access
devices.
This model does not work for a traditional telecommunications service provider. With
revenues tied directly to access and usage of the network, as well as many services,
operators cannot afford security breaches stealing these very same assets. For this
reason telecommunication networks build very robust security procedures to prevent
fraudulent access and denial of service attacks.
The requirements for interoperability and security are therefore much higher in
these networks than they are in conventional Internet networks. This is the reason
the 3GPP set out to define a version of SIP that would support the authentication and
authorization procedures needed for wireless networks. The many extensions that have
been defined by 3GPP were added for exactly this reason, as well as charging of services
within an IMS.
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