urrently using predominantly ATM or Frame Relay, with some IP VPNs here and there. The cost differential between Frame Relay or ATM and MPLS is less than 10%. But if voice and video are added, it can reach 25% and jus- tify the move to both MPLS and IPT. However, many unresolved issues challenge widespread deployment of IPT. For example, the connection to emergency service access systems is problematic. Callers may not know that the IPT phone they are using is not connected to emer- gency services, creating potentially fatal problems. Surveillance is another public safety issue. Data encryption schemes are making it more difficult for law enforce- ment agencies to conduct surveillance because they may not be able to listen to IPT calls in the manner that has become standard in the circuit-switched world. For example, if police officers have to decrypt an IPT call instead of listening in real-time, they may have to wait three weeks after the call took place in order to use it as a basis for arrest. IPT is being deployed today on a trial basis. The main application is currently LAN-to-LAN or cross-enterprise solutions, typically using matched gateways linked Chapter 9 IP Services by private lines. The cost justifications are roughly split between toll bypass or WAN savings and cost reductions in moves, adds, and changes. Justifying the to IPT therefore is largely centered initially around cost justification. Besides benefit of toll bypass, IPT offers a reduction in the cost associated with staff; increased efficiencies due to using the existing IP data networks to also carry voice; less expensive moves, adds, and changes; and applications benefits, such as the ability to combine the Web and computer telephony integration applications and to provide a universal desktop device. Regulatory Issues Surrounding IPT IPT services are not seeing large growth yet, but they are definitely affecting deci- sions about WAN architectures. Ultimately, whether and how quickly we move to IPT is not just a question of technical solut