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. This document defines a simple enhancement to RFC 2198 to support RTP sessions with forward-shifted redundant encodings, i.e., redundant data sent before the corresponding primary data. Forward-shifted redundancy can be used to conceal losses of a large number of consecutive media frames (e.g., consecutive loss of seconds or even tens of seconds of media). The security considerations section is not written in gramatically correct English. While this reader was able to decipher the meaning, I hope that someone with more editorial capabilities can massage the text into actual correct English sentences. Beyond the editorial issues, the document does address the single issue I see, which is the potential denial of service attack where the sender sends bogus forward-shifted data, potentially claiming large buffers in the receiver. Once the security considerations section is cleaned up it will more clearly state that "outrageous values" should be ignored. -derek -- Derek Atkins 617-623-3745 derek at ihtfp.com www.ihtfp.com Computer and Internet Security Consultant