30 Chapter 2
For example, an operator may choose to deploy a media gateway controller (MGC) for call
and session control, but it has many choices for the session control protocol.
Even if an operator selects SIP, there is little defined in the way of implementation
for SIP today to support security. Certainly if we investigate the breaches that have
been committed today in VoIP networks, we will find that these breaches were a direct
result of implementation weaknesses.
Quality of Service (QoS) and bandwidth management are a couple of key areas that
have required work in the past as well. Operators have adopted numerous methodologies
for dealing with these issues and have begun transitioning their core network to IP.
Before an operator can take advantage of IP services, it must first convert the backbone
network to packet-based. Look at how the GSM network has evolved. Wireless provides
a good model for this discussion because of the planned and methodical approach
taken by GSM operators to evolve the networks to support packet-based services.
GSM operators first added an overlay network to their existing infrastructure for
data traffic. The base station controllers (BSCs) moved packet data traffic away from
the mobile switching centers (MSCs) to this packet data network (the General Packet
Radio Service, or GPRS).
The GPRS network then provided IP facilities into the Internet and other IP-based
networks.
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