Re: [dccp] dccp spec review (Rescorla)

[Eddie Kohler <kohler@icir.org>]

Hi Eric, thanks for your comments! They are greatly appreciated, and quite
helpful. Here's a response.


> 2.0 General Comments
> --------------------
> The basic congestion control design appears to be sound. However,
> I'm not an expert in congestion control, so I could easily have
> missed something important here. However, there are some 
> protocol engineering aspects not related to the functioning
> of the congestion control mechanisms that I'm not so
> thrilled with. I don't think the protocol is fundamentally
> flawed, but I would prefer to see it undergo substantial 
> modification before advancement.

We don't really see this from the rest of your comments. It seems like the
main modification you would like to make is described in Section 2.1
(response below). Is there something else?


> 2.1 Need for Multiple Congestion Control Regimes
> ------------------------------------------------
> DCCP provides two congestion control regimes: CCID-2 and CCID-3.
> Do we really need both of them? 

We think so, but we should expand upon the discussion of this in one of the
DCCP documents.

> Naively, it seems to me that there will be two classes of traffic: (1)
> more or less real-time traffic that happens to be over UDP, such as NFS
> and to some extent RealAudio (2) Real-time traffic such as VoIP.

I'm not sure how things like multiplayer game traffic would fit in to this
classification. Furthermore, more or less real-time video traffic would be
another class of traffic that could use DCCP. 

DCCP doesn't yet have a CCID that would be a great fit for VoIP. One
possibility for this would be TFRC-PS (TFRC-PacketSize), but first it has
to be designed and entered into the IETF process.