for signaling methods. dancy in connectivity meth- a single SIP trunk with com- ods by offering multiple sig- mon billing. naling channels (for instance, D-channels) for each bearer channel. The natural tendency in SIP was to offer as few sig- naling channels as possible. Feature Trends in Advanced SIP Trunking Features from Service Providers The long-term advanced SIP trunking trends that exist are a specific reaction to the enhanced technology offering in endpoints and applications. These features are also developed based on new and better equipment provided to SPs. One advanced SIP trunk feature dependent on equipment providers is the capability for SIP trunking providers to offer quality monitoring for all calls. This can be accomplished today through the use of either inline or port spanning technologies. However, both of these options have built in weaknesses. Port spanning is the act of duplicating all Ethernet traffic destined for one physical port to a second physical port. This replicates the traffic from SIP trunking devices to a sec- ondary device. This device scores the quality of the calls. The issue with this method is the inherent security threat created by replicating the packets. As such, this method is not expected to be a long-term method of quality scoring offered by the SP. Chapter 2: Trends in IP Telephony 27 The second method for offering call quality scoring is via an inline device that is specifi- cally dedicated to call quality scoring. Such boxes do exist, but an issue with these is that adding this box for call quality scoring can impact the quality of the voice connection and lower the reliability because a failure in the box will disconnect the call, and the box will add some amount of latency to the connection. Because of the inherent weaknesses in these two methods, the best and most widely used method to determine the quality of a call is to have the network itself involved in the measurement of the quality. Specifically, the advanced trend in call quality scoring is to use the n