production numbers are changed from TDM PSTN access to SIP trunk. Evaluate Future New Services Video and services, like high-fidelity wideband codecs for rich-media collaboration appli- cations such as Cisco Telepresence, currently are not available on general commercial SIP trunk offerings. At some point, though, they will be and you should put some thought into how and when such services, when available, would make sense to your network. This can influence some of the choices you make now regarding: Selecting SPs Reviewing your network for bandwidth, QoS, and CAC Selecting the equipment to terminate a SIP trunk into your network Designing the network architecture (for example, centralized or distributed trunking as discussed in Chapter 6) 248 SIP Trunking Assess Security Implications A SIP trunk is physically an IP feed coming into your network. For most mid-sized and larger enterprises, this is most likely delivered over an Ethernet medium. It often means that the physical connection into the network might not fall within the purview of the voice group as a PRI would, but instead is managed by the traditional data group. If you do not have these organizational challenges, count yourself lucky and move on. If you do, be sure to involve all affected groups as soon as possible SO that they feel as if they have ownership of the planning and execution of the deployment. Another potential wrinkle, due to the IP connectivity of a SIP trunk, is making sure that your security group is involved in ensuring the connection is adequately secured. This can mean choices regarding deploying new firewalls or reusing existing ones, and the placement of border elements inside the demilitarized zone (DMZ) of your data center (either in front of, or behind, the firewall). Be sure to work through the physical network design of the SIP trunk terminations with your security group long before you get to the installation of the trunk. Evaluating a SIP Trunk Offering Following are three major goals of the second step, evaluating a SIP t