Re: [tsvwg] WGLC Announcement for draft-ietf-tsvwg-sctp-sack-immediately-02: 19th March 2013

[Yoshifumi Nishida <[e-mail]>]

Hello Randy,

What I meant was "in ideal equilibrium state", I mean a situation something
like where SCTP is in CA, cwnd is relatively large, self-clocking works
perfectly.
In this situation, while cwnd -1 packets are outstanding, you'll get one
ACK for 1 MSS from the receiver, then you'll send 1 packet. If I-bit is
enabled, I-bit will be set in the packet since it fills cwnd.
Then, you'll get one ACK for 1MSS due to I-bit and sender sends 1 packet
with I-bit and so on...
But, as I wrote before, I don't think this won't be a problem, I just would
like to clarify there might be a situation where I-bit is set in many
packets. Please point out if I miss something..

Thanks,
--
Yoshifumi


On Fri, Apr 19, 2013 at 5:20 AM, Randy Stewart <[e-mail]> wrote:

> Nishida-san:
>
> Sorry for the later reply.. just catching up on my email. ;-)
>
> in-line
>
>
> On Apr 2, 2013, at 2:09 PM, Yoshifumi Nishida wrote:
>
> > Hi Michael,
> >
> > On Tue, Apr 2, 2013 at 12:27 AM, Michael Tuexen
> > <[e-mail]> wrote:
> >> On Apr 2, 2013, at 8:29 AM, Yoshifumi Nishida wrote:
> >
> >>> 2: Because this rule will be checked on every packet transmission, I
> >>> would like to know if the draft suggests to set I-bit everytime we
> >>> have a chance or there might be a case where we shouldn't.
> >> The sender could do it to switch off delayed SACK. However, this
> >> might not be useful. Therefore, as stated, the sender should set it,
> >> when he is waiting for an SACK.
> >
> > OK. I just wanted to mention that in ideal equilibrium state, we might
> > need to set I-bit every packet since you'll get an ACK for 1 MSS,
> > which opens 1 MSS in cwnd.
> > But, as far as I can think this won't be a problem as the receiver has
> > a freedom to ignore it if it's necessary. (e.g. too much overhead)
>
>
> I am a little confused here on the above. If I get an ACK for
> 1 MSS, I then increment my cwnd (say by 1 MSS in Slow start) and
> also decrease my flight size by the amount acked, 1 MSS, which then
> allows me to send 2 MSS.
>
> In CA if I can only send 1 MSS, then I am a situation where 1 RTT
> is being sent per RTT. Which means my PBA will have increased one whole
> cwnd and I again should be able to advance my cwnd by 1 whole segment… so
> again 2 segments are ready to send… assuming I have them to send.
>
> Where I don't have 2 full segments I could see the i-bit but I guess I
> am missing the scenario in my mind where this would happen.. could be just
> me this AM ;-)
>
> R
>
> >
> > BTW, we might want to set I-bit when we find there's no more packet to
> > send in buffer after sending a packet, even though
> > SCTP_SACK_IMMEDIATELY is not used.
> > Do you have any comment on this?
> >
> > Thanks,
> > --
> > Yoshifumi
> >
>
> -----
> Randall Stewart
> [e-mail]
>
>
>
>
>