That sounds perfect to me :). Also I hope Sally would note this in her draft RFC3448-bis too. Thanks Eddie was considering my suggestions :). Regards Arjuna On 10/4/06, Eddie Kohler <kohler@xxxxxxxxxxx> wrote:
>> - X_inst is always calculated using MSS, as the spec says. >> - t_ipi is calculated using whatever the app is using for the packet >> size variable "s", as the spec says. This might be MSS. > > Do you mean when X_Inst = W_init/R? OK, I was wrong AND misunderstood you. Let me try harder. RFC 4342 has this to say about initial sending rates. Translating this to the packet-based congestion control of CCID 3, the initial CCID 3 sending rate is allowed to be at least two packets per RTT, and at most four packets per RTT, depending on the packet size. The initial rate is only allowed to be three or four packets per RTT when, in terms of segment size, that translates to at most 4380 bytes per RTT. The formula you gave, min(4*MSS, max(2*MSS, 4380))/R, is not actually recommended by RFC 4342. That equation comes from a discussion of what RFC 3390 contains; RFC 3390 is about TCP. The normative text above, which actually defines what CCID3 senders should do, follows that formula, but does not imply the formula, as you point out. One implementation choice would be to set, as you recommend, W_init to min(4*s, max(2*s, 4380)). Here's how to alter the paragraph above to clarify this point. Therefore, in contrast to [RFC3448], the initial CCID 3 sending rate is allowed to be at least two packets per RTT, and at most four packets per RTT, depending on the packet size. The initial rate is only allowed to be three or four packets per RTT when, in terms of segment size, that translates to at most 4380 bytes per RTT. This might be implemented, for example, by setting the initial sending rate to min(4*s, max(2*s, 4380 bytes)), where "s" as usual is the packet size in bytes. Will send an errata in once all this has settled down, clearly more specificity would help here... Eddie
-- Dr.Arjuna Sathiaseelan Electronics Research Group University of Aberdeen Aberdeen AB24 3UE Web: www.erg.abdn.ac.uk/users/arjuna Phone : +44-1224-272780 Fax : +44-1224-272497
