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Increased penetration of broadband Internet is driving
the adoption of voice over Internet Protocol (VoIP) both for consumer
and business markets, and VoIP is now on its way to becoming the main
mode of multimedia communications in the coming years. High quality
multimedia communications along with rich presence, universal mobility
and availability, and low cost are some of the benefits VoIP brings to
end-users. For operators, it promises new revenues from new and
converged services, service bundling, increased customer loyalty, and
lower capital and operation expenses (capex/opex) by building and
running a single IP-based network for all communications services.
Ironically, the main driving force behind VoIP adoption
also poses one of the biggest challenges - VoIP calls do not work well
in many broadband situations. In short, the problem is as follows:
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More than 90% of PCs or end-devices access the
broadband service using private IP addresses. These private IP
addresses get mapped into real Internet addresses using a mechanism
called Network Address Translation (NAT), which is implemented in
all broadband access devices (also called broadband routers) and
sometimes again in the service provider network.
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Most users have one or more packet-filtering
firewalls to protect them from hacker attacks or malicious users.
Firewall features are implemented in most broadband routers these
days and also in operating systems such as Windows XP and Vista.
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Most VoIP solutions in the market do not work well
through NATs and firewalls – callers may sometimes fail to connect
to each other or the quality and performance may be unacceptable.
In this white-paper we investigate the root-causes and
challenges for the NAT/firewall traversal problem for VoIP, summarize
recent work and progress made by standards-bodies and the industry on
NAT traversal, and finally, present a comprehensive solution to this
problem comprising a client-side SDK and a scalable carrier-grade
server.
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