A Disaggregated Cell Site Gateway or DCSG is a concept developed by the Telecom Infra Project (TIP). It is part of their Open Optical & Packet Transport project group that works on the definition of open technologies, architectures, and interfaces in Optical and IP Networking:
This group works on the definition of open and disaggregated whitebox cell site gateway devices that operators can deploy in their current 2G/3G/4G cell sites, as well as in the upcoming 5G deployments. The team produces technical specifications that define software, hardware and API requirements that represent the needs of mobile network operators and also works with industry partners to develop devices that meet the specifications.Telecom Infra Project
Fundamentally, a DCSG is a router that runs on white box hardware and provides connectivity from a small number of cell sites to the wireless transport network. TIP has defined key features including IEEE 1588 Precision Timing Protocol (PTP), segment routing, hierarchical Quality-of-Service (QoS) on ingress and egress, traditional routing protocols, and Multiprotocol Label Switching (MPLS). TIP has published this as a specification (available to download here).
The DCSG is also expected to facilitate convergence on the network by also supporting broadband and enterprises services. It is a part of TIP overall vision for the transport network which encompasses chassis routers (Disaggregated Open Router) and Disaggregated Optical Systems.
The TIP community consists of both service providers and vendors working together to validate this open and disaggregated approach to 5G transport networks. Their RFIs and extensive testing programs are geared toward creating an ecosystem of hardware and software options that service providers can use.