Pseudo Content Delivery Protocol (CDP) for Protecting Multiple Source Flows in the Forward Error Correction (FEC) Framework
draft-ietf-fecframe-pseudo-cdp-05

Same question as Wes':
"I didn't find a very clear description of why doing this is a good thing,
rather than just keeping separate repair flows.  For instance, is it intended
to have a savings in packet count, does it impact latency, does it minimize
encoder/decoder state to be kept, etc?"

I have no problem with the publication of this document, but do have some non-blocking comments/questions...

1. I support Wes' comments on this draft.

2. The abstract refers to a "full-pledged" protocol, I assume this should be a "full-fledged" protocol.

3. The last sentence of the abstract seems odd.  Do you really mean for this approach to "design a protocol"?  I would think that it would make more sense to say form/develop/implement a CDP.

4. I am curious if there is a well-accepted definition of what a CDP provides.  How can a reader determine if this approach really provides the necessary functions needed for a CDP?  Are there aspects of CDPs that this approach does not provide?

5. Section 3 states that both the source and destination need to know the Flow ID and that the Flow ID is generated from header fields such as IP addresses and transport-layer port numbers.  Are there implications for this approach introduced by NATs and other types of middleboxes?

6. The Security Considerations section references the Security Considerations in RFC 6363, which is good.  Would any of the security issues in RFC 6364 also apply?

  The authors agreed to make some changes based on the comments provided
  in the Gen-ART Review by Miguel Garcia on 27-Sep-2012, but they have
  not appeared yet.

1) no action required - I have to admit that when I first read this draft I thought it odd that it's called a pseudo CDP, but I now get that this draft is supposed to be like a cookbook for how to put everything together to get a CDP.

2) a: r/full-pledged/full-fledged

3) s1: (let's assume it does ;) r/aims at providing/provides

4) s2: Probably nit picking here a bit, but are you also importing the 2119 language at the end of s2 in RFC 6363?  If not maybe:

   This document uses all the definitions and abbreviations from Section
   2 of [RFC6363] minus the 2119-requirements language.

or something like that.

5) Where's the bit about how the security protocol gets picked!?  I guess I'm just saying an even better non-trivial scenario would have included security.

I didn't find a very clear description of why doing this is a good thing, rather than just keeping separate repair flows.  For instance, is it intended to have a savings in packet count, does it impact latency, does it minimize encoder/decoder state to be kept, etc?

It was not clear to me whether the rates of the N source flows come into play or need to be aligned in some way (i.e. if they don't have fixed rates, have odd harmoics, or could have phase issues in how they present bits into the encoder).  For instance, if some flows stall and others don't, does the encoder need to idle fill in order to have enough input to produce the repair blocks? If there are some assumptions on this, it really should be made clear, as it could impact the effectiveness or latency of the FEC.