 the current DLCs to next-generation DLCs, called NGDLCs. Chapter 8 - Next-Generation OSS NGDLCs basically integrate the function of DSLAMs with that of a DLC. On the line-side, it will have a DSL interface to the end-user, in addition to the analog voice interfaces, and on the trunk side it will have a packet interface, typically ATM, to the fiber that runs to the CO. The NGDLC will house a splitter to separate voice and data streams, a PCM module to digitize voice, a SAR module to process large voice data packets into cells and an ATM module that will combine the data and voice ATM streams (virtual channels) for transport over to the CO. NGDLCs will support voice and data services from the same box and also drive down loop length, and thus enhance the value of DSL by increasing the number of subscribers that can be served. Remote Terminal Side CO-Side Analog Analog Digital Voice Voice Voice and Data Voice Encoding, Fiber Segmentation and Uplink Packet Splitter Reassembly Terminal Network GR-303 Class 5 NGDLC Switch Figure 35. An Example of a Next-Generation DLC As the name implies, Session Initiation Protocol (SIP) is about initiation of interactive communications sessions involving multimedia elements such as voice, video, chat, gaming and virtual reality among users. It is a signaling The Ultimate Guide to Building and Delivering OSS/BSS protocol, standardized by IETF, designed for use within an IP-based network. The distributed nature of SIP along with its simplicity and flexibility have made it attractive for service providers to use for delivering advanced services. In addition to initiation, SIP also handles termination and modification of the session. SIP doesn't actually describe what the session is; this is described within the content carried by a SIP message. As part of session initiation, SIP dynamically locates the called user(s). For initiation, a user agent sends an INVITE request, addressed to the called party using a special URL format. Once the user is located, SIP delivers a description of th