  Since its earliest days, the Worldwide LHC Computational Grid (WLCG) has
relied on GridFTP to transfer data between sites. The announcement that Globus
is dropping support of its open source Globus Toolkit (GT), which forms the
basis for several FTP client and servers, has created an opportunity to
reevaluate the use of FTP. HTTP-TPC, an extension to HTTP compatible with
WebDAV, has arisen as a strong contender for an alternative approach.
  In this paper, we describe the HTTP-TPC protocol itself, along with the
current status of its support in different implementations, and the
interoperability testing done within the WLCG DOMA working group's TPC
activity. This protocol also provides the first real use-case for token-based
authorisation for this community. We will demonstrate the benefits of such
authorisation by showing how it allows HTTP-TPC to support new technologies
(such as OAuth, OpenID Connect, Macaroons and SciTokens) without changing the
protocol. We will also discuss the next steps for HTTP-TPC and the plans to use
the protocol for WLCG transfers.
