e current SIP trunk offerings in the market include TLS or SRTP as an option. Hopefully this situation will change. The CUBE can convert between encrypted commu- nications (TLS/SRTP) on one side and nonencrypted (SIP/RTP) on the other side, SO if your business can benefit from (or demands) encryption in the enterprise, you can still connect to a SIP trunk provider. Session Management, Call Traffic Capacity, Bandwidth Control, and QoS Managing simultaneous voice call capacity and IP bandwidth use is essential for provid- ing consistent quality in enterprise communications. Areas regarding session management and CAC to be considered in the design of your network include Trunk provisioning Bandwidth adjustments and consumption Call admission control Chapter 7: Design and Implementation Considerations 125 QoS metrics, such as packet marking, delay, jitter, and echo Voice-quality monitoring Trunk Provisioning The capacity of a SIP trunk is normally defined by the number of simultaneous calls sup- ported and the bandwidth provided for the trunk. An enterprise uses the same Erlang cal- culations traditionally used in a TDM environment to determine the number of simulta- neous calls required on a SIP trunk. Generally service providers offer a tiered service based on capacity. One of the major benefits of a SIP trunk is that as an enterprise's needs expand, the number of simultane- ous calls can be readily expanded without changing the physical interconnection, or even without an increase in provisioned bandwidth, provided excess bandwidth is already available. Bandwidth Adjustments and Consumption Bandwidth consumption for IP call traffic inbound from the PSTN on a TDM gateway is easily predicted and controlled because the codec assignment is done by the gateway (or by the enterprise call agent such as CUCM). The use of a CUBE can ensure that this capability is maintained when an enterprise adds a SIP trunk to its communications infra- structure. CAC policies and features are deployed in the enterprise network based on p