Re: [Dots] Tsvart last call review of draft-ietf-dots-signal-channel-31

[Yoshifumi Nishida <[e-mail]>]

Hi Tiru,

On Tue, Apr 9, 2019 at 1:26 AM Konda, Tirumaleswar Reddy <
[e-mail]> wrote:

> Please see inline [TR3]
>
>
>
> *From:* Dots <[e-mail]> *On Behalf Of * Yoshifumi Nishida
> *Sent:* Tuesday, April 9, 2019 12:26 PM
> *To:* Konda, Tirumaleswar Reddy <[e-mail]>
> *Cc:* [e-mail]; Yoshifumi Nishida <[e-mail]>;
> [e-mail]; [e-mail];
> [e-mail]; [e-mail]; Yoshifumi Nishida <
> [e-mail]>
> *Subject:* Re: [Dots] Tsvart last call review of
> draft-ietf-dots-signal-channel-31
>
>
>
> *CAUTION*: External email. Do not click links or open attachments unless
> you recognize the sender and know the content is safe.
> ------------------------------
>
> Hi Tiru,
>
>
>
> I put my comments in lines.
>
>
>
> On Mon, Apr 8, 2019 at 1:40 AM Konda, Tirumaleswar Reddy <
> [e-mail]> wrote:
>
> Hi Yoshi,
>
>
>
> Please see inline [TR2]
>
>
>
> *From:* Yoshifumi Nishida <[e-mail]>
> *Sent:* Monday, April 8, 2019 12:24 PM
> *To:* Konda, Tirumaleswar Reddy <[e-mail]>
> *Cc:* Yoshifumi Nishida <[e-mail]>;
> [e-mail] <[e-mail]>;
> [e-mail]; [e-mail]; [e-mail];
> [e-mail] <tsv-art@ietf..org>; Yoshifumi Nishida <
> [e-mail]>
> *Subject:* Re: [Dots] Tsvart last call review of
> draft-ietf-dots-signal-channel-31
>
>
>
> *CAUTION*: External email. Do not click links or open attachments unless
> you recognize the sender and know the content is safe.
> ------------------------------
>
> Hi Tiru,
>
>
>
> On Thu, Apr 4, 2019 at 10:46 PM Konda, Tirumaleswar Reddy <
> [e-mail]> wrote:
>
> Hmm. let's say the results of the happy eyeballs was TCP over IPv4 (just
> like the figure 4) and the client cache the info.
>
> After certain period of time, the client will do happy eyeball again
> because other better connections might be available . But, in this case,
> how the cached info will be used?
>
>
>
> [TR] The cache expires after a specific time period. If the cache has not
> expired, the client uses the information from the cache. If cache has
> expired, the client performs happy eyeball again.
>
>
>
> It seems that an implementation that doesn't cache the info at all and
> does happy eyeballs at every 10 hours won't be allowed in this draft.
>
>
>
> [TR] No, but if the subsequent attempt is within few seconds after the
> first attempt of happy eyeball, it would trash the network. The endpoint
> may have to re-establish the (D)TLS session within few seconds for several
> reasons (e.g. TLS session got terminated, DOTS server rebooted NAT rebooted
> etc.).
>
>
>
> Thanks for the explanation. The logic makes sense to me.
>
> I think it would be good to articulate this a bit more in the draft.
>
> For example, the figure 4 example explains the probing period, but doesn't
> mention about the cache period.
>
>
>
> [TR2]
>
> Sure, we can update the text as follows:
>
>
>
> Note that the DOTS client after successfully establishing a connection
> MUST cache information regarding the outcome of each
>
> connection attempt and the cached information should be flushed when its
> age exceeds a system-defined maximum on the order of few minutes (e.g. 2
> minutes).
>
> If the DOTS client has to re-establish the connection with the DOTS server
> within few seconds after the Happy Eyeballs mechanism is complete,
>
>   caching avoids trashing the network in the presence of DDoS attack
> traffic.
>
>
>
> Thanks for the updates. But, one thing.. The text suggests cache period
> would be the order of few minutes.
>
> But, this value seems to be much smaller compared to "probing SHOULD NOT
> be done more than every 24 hours".
>
>
>
> [TR3] The probing is for a scenario where the client is using TLS (over
> TCP) for the signal channel and probes to check if DTLS (over UDP) becomes
> available. If the probing finds DTLS over UDP is available, the client
> disconnects the TLS over TCP and re-connects to the server using DTLS over
> UDP transport.
>

Thanks for explanation.
OK. so, probing and cache is irrelevant. I have thought about if this is
confusing or not for a bit. But, I think it's ok after I re-read the text.
I don't have any more comments.
Thanks,
--
Yoshi