TDMoIP product (known as IPmux-4) to provide bundled services including TDM private lines, TDM leased lines and a variety of IP and Ethernet services. In 2001, the IETF set up the PWE3 working group, which was chartered to develop an architecture for edge-to-edge pseudowires, and to produce specifications for various services, including TDM. Other standardization forums, including the ITU and the MPLS - Frame Relay Alliance, are also active in producing standards and implementation agreements for pseudowires. Handling TDM structure Although TDM can be used to carry arbitrary bit streams at the rates defined in G.702, there are standardized methods of carrying bit streams in larger units each containing the same number of bits, called frames. TDM framing locks the frame rate to the sampling frequency of voice traffic, so that there are always 8000 frames per second; a T1 frame consists of 193 bits and an E1 frame of 256 bits. Unlike unframed TDM for which all bits are available for payload, framed TDM requires dedicating of some number of bits per frame for synchronization and perhaps various other functions (e.g. 1 bit per T1 frame, 8 bits per E1 frame). Framed TDM is often used to multiplex multiple voice channels each consisting of 8000 8-bit samples per second in a sequence of timeslots recurring in each frame. When this is done we have "channelized TDM" and additional structure must be introduced. In order to efficiently transport slowly varying channel associated signalling bits, second order structures known as multiframes or superframes are defined. For example, for E1 trunks the CAS signaling bits are updated once per multiframe of 16 frames (every 2 milliseconds) while for T1 ESF trunks the superframe is 24 frames (3 milliseconds). Other types of second order structures are also in common use. In GSM cellular networks, the Abis channel that connects the Base Transceiver Station (BTS) and Base Station Controller (BSC) is an E1 link with several framing alternatives, all of which have a basic superframe duration of 20 milliseconds. The term "structured TDM" is used to refer to TDM with any level of structure, including 'framed TDM' and 'channelized TDM'. TDMoIP transport is denoted "structured-agnostic" when the TDM is unframed, or when it is framed or even channelized, but the framing and channelization structure are completely disregarded by the transport mechanisms. In such cases all structural overhead must be transparently transported along with the