Re: [Dots] Improve controllability and predictability of keepalives
<mohamed.boucadair@orange.com> Thu, 14 November 2019 10:17 UTC
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From: mohamed.boucadair@orange.com
To: Carsten Bormann <cabo@tzi.org>
CC: "dots@ietf.org" <dots@ietf.org>
Thread-Topic: Improve controllability and predictability of keepalives
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Date: Thu, 14 Nov 2019 10:17:19 +0000
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Subject: Re: [Dots] Improve controllability and predictability of keepalives
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Hi Carsten, all, As promised, we updated the draft to take into account your inputs. The candidate version is available at (see section 4.7 in particular): https://github.com/boucadair/draft-ietf-dots-signal-channel/blob/master/draft-ietf-dots-signal-channel-39.txt The main changes are: * Use PUT to send heartbeat requests * Use 2.04 instead of 2.03 * DOTS agents can negotiate a probing-rate * Provide some guideline for setting the probing-rate. Do you have any further comment on the new heartbeat mechanism? Thank you. Cheers, Med > -----Message d'origine----- > De : Dots [mailto:dots-bounces@ietf.org] De la part de > mohamed.boucadair@orange.com > Envoyé : mardi 12 novembre 2019 17:24 > À : Carsten Bormann > Cc : dots@ietf.org > Objet : Re: [Dots] Improve controllability and predictability of keepalives > > Re-, > > Please see inline. > > Cheers, > Med > > > -----Message d'origine----- > > De : Carsten Bormann [mailto:cabo@tzi.org] > > Envoyé : mardi 12 novembre 2019 14:12 > > À : BOUCADAIR Mohamed TGI/OLN > > Cc : dots@ietf.org > > Objet : Re: Improve controllability and predictability of keepalives > > > > Hi Med, > > > > what the text below doesn’t say is what kind of information you want to > > derive from the heartbeats. > > [Med] How to interpret HBs by endpoints is discussed in Section 4.7. > > The way they currently (draft -39) are > > defined, the client uses a GET (*). GET is not supposed to influence > > application state, so the server will not learn anything from that > > heartbeat. Is the intention that only the client needs to react to > > heartbeat failures? > > [Med] No, the server needs to react to heartbeat failures. The cases that > are discussed in the spec are as follows: > > * If the DOTS server receives traffic from the peer DOTS client but > maximum 'missing-hb- > allowed' threshold is reached, the DOTS server MUST NOT consider the > DOTS signal channel session disconnected. The DOTS server MUST keep > on using the current DOTS signal channel session so that the DOTS > client can send mitigation requests over the current DOTS signal > channel session. In this case, the DOTS server can identify the DOTS > client is under attack and the inbound link to the DOTS client > (domain) is saturated. > > * If the DOTS server does not > receive a mitigation request from the DOTS client, it implies the > DOTS client has not detected the attack or, if an attack mitigation > is in progress, it implies the applied DDoS mitigation actions are > not yet effective to handle the DDoS attack volume > > * If the DOTS server does not receive any traffic from the peer DOTS > client during the time span required to exhaust the maximum 'missing- > hb-allowed' threshold, the DOTS server concludes the session is > disconnected. The DOTS server can then trigger pre-configured > mitigation requests for this DOTS client (if any). > > > > > RFC 7252 defines PROBING_RATE as 1 B/s. If you get a response within the > > heartbeat interval to the non-confirmable requests, that is not relevant. > > If you don’t, your heartbeat interval "MUST be chosen in > > such a way that an endpoint does not exceed an average data rate of > > PROBING_RATE in sending to another endpoint that does not respond. > > If your interval is intended to be 15 s, that would mean your requests > must > > be ≤ 15 B, or you need to define PROBING_RATE differently for your > > application. > > It seems right now you are not trying to be particularly frugal with the > > heartbeat message, which is probably OK since most of your networks will > be > > Ethernet and that will expand the frame size to 64 B anyway. But that > > means that you need to define PROBING_RATE to be ~ 5 B/s if you don’t > want > > to be slowed down in probing. > > [Med] Good point. Will update accordingly. > > > > > Grüße, Carsten > > > > (*) And expects a 2.03, which would mean that the server confirms the > ETag > > given in the request. But there is no ETag in that request, and I really > > don’t see why a 2.05 with an empty payload wouldn’t also work. But maybe > > you want to move to POST anyway (so there can be application semantics, > > like taking note of the heartbeat, on the server), and 2.04 would fit > that > > very well (see RFC 7252 Section 5.8.2). > > [Med] Will consider the use of POST instead of GET. > > > > > > On Nov 12, 2019, at 10:18, <mohamed.boucadair@orange.com> > > <mohamed.boucadair@orange.com> wrote: > > > > > > Hi Carsten, > > > > > > You indicated the following in an offline message (I’m adding dots > > mailing list as you were OK; see below): > > > > > > > I would have expected using requests sent in non-confirmable > messages, > > > > requiring more work on the application side (interpreting losses) but > > also > > > > delivering a more regular, predictable, less noisy signal. > > > > A little bit of specification text is then needed to ensure that > those > > > > requests/responses meet the requirements of RFC 8085 and the related > > > > specifications in RFC 7252, and that both sides are in a good > position > > to > > > > interpret the signal they get. > > > … > > > > If not, I would like to discuss the issue on the DOTS mailing list, > and > > see > > > > whether a small set of changes to the keepalive mechanisms employed > can > > > > improve its controllability and predictability. > > > > > > Assuming that non-confirmable application HBs are used, which changes > do > > you think are needed to enhance the DOTS mechanism to meet 8085/7252 > > requirements? > > > > > > As a reminder we do have the following for setting the hb parameters: > > > > > > ====== > > > Note: heartbeat-interval should be tweaked to also assist DOTS > > > messages for NAT traversal (SIG-011 of [RFC8612]). According to > > > [RFC8085], keepalive messages must not be sent more frequently > > > than once every 15 seconds and should use longer intervals when > > > possible. Furthermore, [RFC4787] recommends NATs to use a state > > > timeout of 2 minutes or longer, but experience shows that sending > > > packets every 15 to 30 seconds is necessary to prevent the > > > majority of middleboxes from losing state for UDP flows. From > > > that standpoint, the RECOMMENDED minimum heartbeat-interval is 15 > > > seconds and the RECOMMENDED maximum heartbeat-interval is 240 > > > seconds. The recommended value of 30 seconds is selected to > > > anticipate the expiry of NAT state. > > > > > > A heartbeat-interval of 30 seconds may be considered as too > chatty > > > in some deployments. For such deployments, DOTS agents may > > > negotiate longer heartbeat-interval values to prevent any network > > > overload with too frequent keepalives. > > > > > > Different heartbeat intervals can be defined for 'mitigating- > > > config' and 'idle-config' to reduce being too chatty during idle > > > times. If there is an on-path translator between the DOTS client > > > (standalone or part of a DOTS gateway) and the DOTS server, the > > > 'mitigating-config' heartbeat-interval has to be smaller than the > > > translator session timeout. It is recommended that the 'idle- > > > config' heartbeat-interval is also smaller than the translator > > > session timeout to prevent translator traversal issues, or > > > disabled entirely. Means to discover the lifetime assigned by a > > > translator are out of scope. > > > ======= > > > > > > Thank you. > > > > > > Cheers, > > > Med > > _______________________________________________ > Dots mailing list > Dots@ietf.org > https://www.ietf.org/mailman/listinfo/dots
- [Dots] Improve controllability and predictability… mohamed.boucadair
- Re: [Dots] Improve controllability and predictabi… Carsten Bormann
- Re: [Dots] Improve controllability and predictabi… mohamed.boucadair
- Re: [Dots] Improve controllability and predictabi… mohamed.boucadair
- Re: [Dots] Improve controllability and predictabi… Carsten Bormann
- Re: [Dots] Improve controllability and predictabi… Carsten Bormann
- Re: [Dots] Improve controllability and predictabi… mohamed.boucadair
- Re: [Dots] Improve controllability and predictabi… Carsten Bormann
- Re: [Dots] Improve controllability and predictabi… mohamed.boucadair
- Re: [Dots] Improve controllability and predictabi… Carsten Bormann
- Re: [Dots] Improve controllability and predictabi… mohamed.boucadair
- Re: [Dots] Improve controllability and predictabi… Valery Smyslov