[Anima-signaling] draft-ietf-anima-grasp-08: DULL comments discovery be performed over TCP?)
Toerless Eckert <tte+ietf@cs.fau.de> Thu, 03 November 2016 22:11 UTC
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Date: Thu, 03 Nov 2016 23:10:54 +0100
From: Toerless Eckert <tte+ietf@cs.fau.de>
To: brian.e.carpenter@gmail.com, draft-ietf-anima-grasp@ietf.org, anima-signaling@ietf.org
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References: <20161031221855.GA1970@faui40p.informatik.uni-erlangen.de> <18011.1478097279@obiwan.sandelman.ca>
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Subject: [Anima-signaling] draft-ietf-anima-grasp-08: DULL comments discovery be performed over TCP?)
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Brian: Suggestions for 3.5.2 1. I think SONN is not necessary best described as "limited security", but "constrained functionality". Therefore i would suggest to use "Constrained functionality Instances" as the title. imited Security such as DULL is also well in scope of "Constrained functionality". 2. The initial text for DULL says: "2) During initialisation, before a node has joined the applicable trust infrastructure, [I-D.ietf-anima-bootstrapping-keyinfra], it is impossible to secure messages." This was i think suggested by the anima-bootstrap team before it decided that it wants mDNS. At that time i thought we would also use one objective for both BRSKY and ACP, therefore ACP was never mentioned in this text. Which now hits us. I would suggest changing the text so that: a) it will allow ACP discovery to use DULL GRASP. b) it will allow any other services with similar requirements to use DULLG GRAP c) the text can continue stay unchanged whether or not BRSKY will use DULL GRASP. Suggested text: 2) Services may need to perform neighbor discovery without being able to use pre-existing security associations. This includes discovery of candidate ACP neighbors [I-D.ietf-anima-autonomic-control-plane], discovery of bootstrap proxies [I-D.ietf-anima-bootstrapping-keyinfra] or for (example) services in networks only using GRASP without being fully autonomic (eg: no ACP). [unmodified:] Such usage MUST be limited to link-local operations and MUST be confined to a separate insecure instance of GRASP with its own copy of all GRASP data structures. This instance is nicknamed DULL - Discovery Unsolicited Link Local. ... [modify:] A responder MUST silently discard any message referring to a GRASP Objective that is not directly part of the bootstrap creation process. [to:] A responder MUST silently discard and ignore any message referring to a GRASP Objective that is not directly part of the service(e) that require this insecure discovery. Also, to optimize / minimize signaling, i'd love to see change: A responder MAY send a Discovery Response message A responder SHOULD NOT send a Discovery Response message FInally: i have some decades of pain optimizing this type of fast & lightweight discovery - IGMP/MLD/PIM, so i have a lot of opinions on the details. Let me summarize them below, and you decide if/which of these might be useful to add (with rewording as you like) to the GRASP spec: - "Announcements" in the following means LL-multicast of 1 or more packets needed to cover all the necessary insecure LL objectives that need to be announced. IMHO those "Announcements" are best all Flood-Synchroniation messages (Discovery messages would require another round of exchanges). - Announcements are send periodic. Good default is 30 seconds. Periodic announcements really only needed when connections are established that do not affect link-state on the neighbors (eg: inside a LAN, between switches etc..). - On link-up, announcments are sent repeated N-times to allow fast discovery in the presence of loss probability. N=2 is a good default. The periodic timer is then reset. - On reception of Announcements from a previously unknown neighbor, we also send N-time repeated Announcements and reset our periodic timer. - Announcements should allow for a "Generation-ID" feature for each objective that indicates that the objective was restarted without memory of prior state. This means that any followup action for that objective (eg: building a connection to the objetive, BRSKY, ACP,..) need to be restarted. Upon change of Generation-ID, we also send N-time repeated Announcements and reset periodic timer. - To deal with link-up-flaps and other issues, there should be an exponential backup sending triggered announcements since the lasst triggered announcements (1,2,3,8,16). - Platforms often indicate link-up before packets can actually be send. Trigered announcements do need to send accordingly delayed to avoid these platform issues. Cheers Toerless
- [Anima-signaling] draft-ietf-anima-grasp-08: DULL… Toerless Eckert
- Re: [Anima-signaling] draft-ietf-anima-grasp-08: … Brian E Carpenter
- Re: [Anima-signaling] draft-ietf-anima-grasp-08: … Brian E Carpenter