Hi, I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. The document defines an extension of Traversal Using Relays around NAT (TURN), a relay protocol for NAT traversal, to allow a TURN client to request TCP allocations, and defines new requests and indications for the TURN server to open and accept TCP connections with the client's peers. After reading the other four-letter protocol specs (TURN, STUN) I have no problems with this document. The new features do not raise any security concerns that are not already addressed in the base TURN documents. Pat Cain