rting Billing and call accounting QoS marking Topology hiding (security) These demarcation features are critical to the maintenance, security, and management of your network. An SBC, such as the CUBE, can be placed at the edge of your network to Chapter 7: Design and Implementation Considerations 109 terminate the SIP trunk entry point and fulfill the needed demarcation role in an all-IP network connection. For smaller businesses CUCM Express might be deployed, which includes SIP trunk capability and border element demarcation features. All the areas of demarcation are discussed in the remainder of this section, except topology hiding, which is further discussed in the "Security Consideration" section in this chapter. Service Provider UNI Compliance SIP trunk service providers offer an explicit UNI specification of what message types, formats, and fields are valid on their service offering. For the enterprise to comply with this UNI, it is often easier to place a border element at the edge of the network to normalize all the variants from different enterprise applications and endpoints than to try to configure each individual application or endpoint to comply with the UNI. It is especially true if the enterprise connects to multiple different SIP trunk providers, per- haps for least-cost routing or for redundancy purposes. For the service provider, it is often easier to drop off a validated border element CPE device to ensure that the enterprise or small business network complies with its UNI- rather than certify each possible vendor and release combination of the possible applications and endpoints, the enterprise or small business might want to connect to their service. Different deployment scenarios result from this need for network demarcation. Often enterprises want to manage their own border element SO that they can control the config- uration of this device and adjust it for new applications, application upgrades, or call flows. Alternatively, the service provider might provide a border element as a CPE de