This is an OPS-DIR review of Distributed Denial of Service (DDoS) Open Threat Signaling Requirements (draft-ietf-dots-requirements) This document lists requirements for a protocol to used between providers of DDOS mitigation services and users of such services, as such there can be no direct operational issues with the document. I also did not find any indirect operational issues. I think the document would benefit from the addition of a section before the requirements section that specifically describes the setup assumed by the document. The descriptions before there hint at a presumed setup but a new section that clearly states the setup would be helpful. (the setup appears to be one where all network traffic to and from a protected entity flows through a DDoS mitigation service provider. The provider includes one or more DOTS servers. The protected entity includes one or more DOTS clients that communicate with the DOTS servers) Requirement SIG-005 addresses channel redirection – maybe there needs to be a way that clients can move to a new server on their own if they lose hearbeat from the server they were using – that might include a way for a server to provide a list of alternative servers to the clients