[Rift] AD review https://datatracker.ietf.org/doc/draft-ietf-rift-rift/ (v-18) (review up to Section 4.3)
James Guichard <james.n.guichard@futurewei.com> Thu, 21 September 2023 11:09 UTC
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From: James Guichard <james.n.guichard@futurewei.com>
To: "draft-ietf-rift-rift@ietf.org" <draft-ietf-rift-rift@ietf.org>
CC: "rift@ietf.org" <rift@ietf.org>, James Guichard <james.n.guichard@futurewei.com>
Thread-Topic: AD review https://datatracker.ietf.org/doc/draft-ietf-rift-rift/ (v-18) (review up to Section 4.3)
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Date: Thu, 21 Sep 2023 11:09:18 +0000
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Subject: [Rift] AD review https://datatracker.ietf.org/doc/draft-ietf-rift-rift/ (v-18) (review up to Section 4.3)
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Dear authors, Please find review comments (up to but not including section 4.3). I have used IDNITs format so that you can see the line numbers for easier review. Section: Introduction: 202 * optional fully automated construction of fat tree topologies based 203 on detection of links without any configuration (Section 4.2.7) 204 while allowing for conventional configuration methods and 205 arbitrary mix of both types of nodes as well, Jim> I do not understand the last part of the above paragraph. Do you mean a mix of ZTP and non-ZTP nodes? Section 4: RIFT: Routing in Fat Trees 767 a protocol optimized for Routing in Fat Trees (RIFT) that in most Jim> No need to expand on RIFT as already did so earlier in the text. 771 unusual combination, it does quite naturally exhibit the desirable 772 properties desired. Jim> Replace 'desirable properties desired' with 'desired properties'. Section 4.1: Overview 808 To account for the "northern" and the "southern" information split 809 the link state database is partitioned accordingly into "north 810 representation" and "south representation" TIEs. In simplest terms Jim> While TIE is in the terminology section it is probably appropriate to expand on it here on the first use. 811 the North TIEs contain a link state topology description of lower 812 levels and and South TIEs carry simply node description of the level Jim> Remove duplicate 'and' in the above sentence. Section 4.1.3: Fallen Leaf Problem 1258 In large fabrics or fabrics built from switches with low radix, the 1259 ToF ends often being partitioned in planes which makes the occurrence Jim> "the ToF ends often being partitioned..." does not parse. I would suggest "the ToF may often become partitioned across planes.." or something like that. Jim> You use both "Top-of-Fabric" and "ToF" terminology. Can you pick one and use that throughout the document? I would suggest ToF as that is defined in section 3.1. 1264 A "Fallen Leaf" is a leaf that can be reached by only a subset, but 1265 not all, of Top-of-Fabric nodes due to missing connectivity. If R is Jim> I would remove "but not all" as by definition a subset means "not all" of the ToF nodes can reach the leaf node. Section 4.1.5: Addressing the Fallen Leaves Problem Jim> General comment: I think the document would be much easier to follow if sections 4.1.2 - 4.1.5 were moved into an appendix with a pointer to that appendix in section 4.1.1 (for those readers interested in multiplane). For those readers not familiar with complex datacenter design it is going to be very confusing to read and in some sense detracts from the specification which is the next section. Section 4.2: Specification 1483 Any attempt to transition from a state towards another on reception 1484 of an event where no action is specified must be considered an Jim> Should 'must' be 'MUST' in the above sentence? it seems that you want to mandate this action so therefore MUST seems more appropriate. 1485 unrecoverable error, i.e. the protocol MUST reset all adjacencies, 1486 discard all the state and may not start again. Jim> What does 'may not start again' actually mean? I assume you do not want to mandate that the router should not restart RIFT but perhaps change 'may not' to 'SHOULD NOT' or even 'RECOMMENDED' not to start again. 1493 The machines can use conceptually "timers" for different situations. Jim> Machines? I assume that you mean FSMs? if so please change the above. Section 4.2.1: Transport 1505 All RIFT packet structures and their contents are defined in the 1506 Thrift [thrift] models in Appendix B. The packet structure itself is Jim> I assume that Appendix B is normative. Please add a note to say so here. Section 4.2.2: Link (Neighbor) Discovery (LIE Exchange) 1541 MUST be sent with an IPv4 Time to Live (TTL) or an IPv6 Hop Limit 1542 (HL) of either 1 or 255 to prevent RIFT information reaching beyond a Jim> 1 or 255? Some guidance here is necessary. RFC5082 for example (GTSM) uses 255 although personally I am not sold on that. The main point are 'options' necessary (if not just pick 1 or 255) and if not, appropriate text should be added, or have something in the security considerations section. 1551 An implementation may listen and send LIEs on IPv4 and/or IPv6 Jim> Should the above 'may' be 'MAY'? 1668 change any of its local addresses or stop IPv4 forwarding, it has to 1669 tear down and rebuild the adjacency. It also has to remove any state Jim> Change 'it has to' to 'MUST' in the above sentences. 1692 (such as LIE is considered a "minimally valid" LIE). Observe that Jim> Change 'as' to 'a' above. Section 4.2.2.1: LIE Finite State Machine 1884 * CLEANUP: The FSM *conceptually* holds a 'current neighbor' 1885 variable that contains information received in the remote node's 1886 LIE that is processed against LIE validation rules. In the event Jim> A pointer to where LIE validation rules are specified would be helpful here. 1892 1. reflecting the neighbor as described in ValidReflection and 1894 2. setting the necessary `not_a_ztp_offer` variable if level was 1895 derived from the last known neighbor on this interface and 1897 3. setting `you_are_flood_repeater` to computed value Jim> I found the above confusing without the text indicating that 'ValidReflection' is part of the FSM whereas 'not_a_ztp_offer' and 'you_are_flood_repeater' are variables of the LIEPacket. Could you make this clear in the text somehow perhaps simply by inserting 'LIEPacket' in front of these variables in the text above? 2357 For Node TIEs to carry more adjacencies than fit into an MTU-sized 2358 packet, the element `neighbors` may contain a different set of 2359 neighbors in each TIE. Those disjoint sets of neighbors MUST be 2360 joined during corresponding computation. Nevertheless, in case 2361 across multiple Node TIEs 2363 1. `capabilities` do not match *or* 2365 2. `flags` values do not match *or* 2367 3. same neighbor repeats in multiple TIEs with different values Jim> I cannot make sense of the above - the text says "in case <blah> do not match etc.." but does not say what is the result of this (?) 2492 adjustement of flooding speeds the encoded packets provide hints to Jim> typo 'adjustement' -> 'adjustment' 2815 TIEs from its remote peer. Such a publisher model can be implemented 2816 in many ways, either in a single thread of execution of in parallel 2817 threads. Jim> The last sentence does not parse please correct. Thanks! Jim
- [Rift] AD review https://datatracker.ietf.org/doc… James Guichard
- Re: [Rift] AD review https://datatracker.ietf.org… Jordan Head
- Re: [Rift] AD review https://datatracker.ietf.org… Tony Przygienda
- Re: [Rift] AD review https://datatracker.ietf.org… James Guichard