ANSI SCTE 136-2-2019 pdf download.Cable Modem TDM Emulation Interface Standard
5.1 Background
Throughout the evolution of communication networks the T1 and E1 service that is delivered to the customer has remained relatively consistent (in large part due to the strict ITU and ANSI standards), however the method of delivering the T1 or E1 service has changed to increase efficiencies and leverage new technologies. Both SONET and ATM historically have been adapted to transport T1 and E1 services; now MPLS and IP networks are also being used. Various standards bodies and vendors have created methods for circuit emulation of T1 and E1 services across IP networks, leveraging the successful ATM circuit emulation technology developed in the 90s. This standard leverages the work done in the ITU and IETF to define circuit emulation of T1 and E1 over a DOCSIS network. This standard describes the architecture and components of a network that delivers emulated T1 or E1 or NxDS0 services over DOCSIS. It defines the T1, E1, or NxDS0 service delivered to the end customer, the requirements of a BSoD-TE compliant cable modem (TE-CM), and the requirements of a BSoD-TE compliant CMTS (TE-CMTS), the requirements of the TDM Emulation Adaptor (TEA), and Pseudo Wires (PW) that cross the packet network connecting two TEAs.
5.4 Architecture
A BSoD-TE service can be deployed in several architectures. In any architecture the BSoD-TE service has two end points that each contain a TEA or eTEA (TEA peers). Each device presents a TDM interface to the customer or network and a Pseudo Wire connecting the TEA peers logically across the IP network. Three general architectures exist based on the existing market for T1 and E1 services. In all three architectures one end of the BSoD-TE service originates in a TE-CM containing an eTEA. The three architectures differ based on where the other end of the service is terminated and thus where the other TEA/eTEA exists. There are a variety of existing T1/E1 services including wireless backhaul, private line, PBX extension, PBX PSTN access, etc. Comprehensive T1/E1 service may include a combination of these three architectures and may include partnering with other operators for part of the implementation.
5.4.1 TE-CM to TE-CMTS w/TEA
In this architecture the BSoD-TE service originates in a TE-CM (containing an eTEA) and terminates at the TE- CMTS which contains a TEA. Figure 5–5 shows this architecture with the Pseudo Wire flow shown as the dotted line. This is not the termination of the T1 or E1 circuit, just the two ends of the BSoD-TE circuit emulation. The T1 or E1 service will continue from the CMTS into the traditional TDM network. This architecture places delay and QoS requirements on the DOCSIS network, but minimizes the impairments that the IP network may place on the BSoD-TE service. This architecture however requires TDM transport facilities at the hub/headend locations where the CMTS is located which may not be feasible or cost effective for some operators that prefer or require the BSoD-TE service to have a more centralized termination.
5.4.2 TE-CM to Centralized TEA
In this architecture the BSoD-TE service originates in a TE-CM and terminates in a centralized router or other unspecified device that contains a TEA. The TEA may exist in a router, gateway, switch or other device which is out-of-scope for this standard with the exception of the TEA functionality. Figure 5–6 shows this architecture with the Pseudo Wire flow shown as the dotted line. This is not the termination of the T1 or E1 circuit, just the two ends of the BSoD-TE circuit emulation. The T1 or E1 service will continue from the CMTS to its termination within traditional TDM network. This architecture places delay, synchronization and QoS requirements on the TE-CMTS, which in this case does not contain a TEA. This architecture places delay and QoS requirements on the DOCSIS and core managed IP network. While this architecture requires a slightly more complex provisioning of the network, it centralizes the termination of the BSoD-TE circuit emulation in the core. This means there are fewer BSoD-TE devices to manage and that the TE-CMTS does not have an integrated TEA. This simplifies the TE-CMTS and reduces or eliminates modifications to existing installed CMTSs. This architecture eliminates the need for TDM transport facilities at each hub/headend since the Pseudo Wires will pass through the TE-CMTS (as IP packets) and be routed over the existing IP transport to the core.ANSI SCTE 136-2-2019 pdf download
