Re: [CCAMP] Benjamin Kaduk's Discuss on draft-ietf-ccamp-rsvp-te-bandwidth-availability-14: (with DISCUSS and COMMENT)
Benjamin Kaduk <kaduk@mit.edu> Thu, 11 April 2019 18:56 UTC
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Date: Thu, 11 Apr 2019 13:55:48 -0500
From: Benjamin Kaduk <kaduk@mit.edu>
To: "Yemin (Amy)" <amy.yemin@huawei.com>
Cc: The IESG <iesg@ietf.org>, "ccamp@ietf.org" <ccamp@ietf.org>, "ccamp-chairs@ietf.org" <ccamp-chairs@ietf.org>, Daniele Ceccarelli <daniele.ceccarelli@ericsson.com>, "draft-ietf-ccamp-rsvp-te-bandwidth-availability@ietf.org" <draft-ietf-ccamp-rsvp-te-bandwidth-availability@ietf.org>
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Subject: Re: [CCAMP] Benjamin Kaduk's Discuss on draft-ietf-ccamp-rsvp-te-bandwidth-availability-14: (with DISCUSS and COMMENT)
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On Wed, Apr 10, 2019 at 10:40:06PM +0000, Yemin (Amy) wrote: > Hi Benjamin, > > Thanks for the comments. Please see reply inline below. > Thanks. > > BR, > Amy > ________________________________________ > 发件人: Benjamin Kaduk via Datatracker [noreply@ietf.org] > 发送时间: 2019年4月10日 1:37 > 收件人: The IESG > 抄送: draft-ietf-ccamp-rsvp-te-bandwidth-availability@ietf.org; Daniele Ceccarelli; ccamp-chairs@ietf.org; daniele.ceccarelli@ericsson.com; ccamp@ietf.org > 主题: Benjamin Kaduk's Discuss on draft-ietf-ccamp-rsvp-te-bandwidth-availability-14: (with DISCUSS and COMMENT) > > Benjamin Kaduk has entered the following ballot position for > draft-ietf-ccamp-rsvp-te-bandwidth-availability-14: Discuss > > When responding, please keep the subject line intact and reply to all > email addresses included in the To and CC lines. (Feel free to cut this > introductory paragraph, however.) > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > for more information about IESG DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-ccamp-rsvp-te-bandwidth-availability/ > > > > ---------------------------------------------------------------------- > DISCUSS: > ---------------------------------------------------------------------- > > As the genart review notes, when Section 3.2 says: > > When a node does not support the Availability TLV, the node SHOULD > generate a PathErr message with the error code "Extended Class-Type > Error" and the error value "Class-Type mismatch" (see [RFC2205]). > > is attempting to place a normative requirement on implementations that > do not implement this specification, which cannot possibly work. > The appropriate thing to do here is to say something like "as described > in Section Y of [RFC XXXX], a node that does not support the > Availability TLV will [behave in this fashion]", with no normative > language. (Also, the RFC 2205 reference is not very helpful to me; as > far as I can tell it is just providing information about how to encode a > PathErr but does not tell me anything about the specific error code and > value indicated.) > > [Amy] > Serveral comments were received about the normative requirement here. > How about the following text: > When a node does not support the Availability TLV, the node should send a PathErr > message with Error Code "Unknown Attributes TLV[RFC 5420]". That's an improvement. Might I suggest: When a node does not support the Availability TLV, the node should send a PathErr message with Error Code "Unknown Attributes TLV", as specified in [RFC 5420]. > Thanks for point it out, the "error code "Extended Class-Type Error" and the error value "Class-Type mismatch" (see [RFC2205])", the text is referenced from RFC6003. > After double check, they are not defined in the RFC2205, neither in some other RFC. > Unknown Attributes TLV from RFC 5420 should be better here. > > I'll also hold a placeholder discuss point to wait for the [IEEE754] > reference for the floating-point format. (I think that format is not a > great fit for this application, for many of the reasons that Magnus > notes, but RFC 8330 has kind of forced us into keeping it.) > > [Amy] Yes, it's better to use the floating-point format in order to align with RFC8330. > IEEE754 will be added as a reference. Agreed. (I saw all the discussion going on elsewhere and was confident the right thing was going to happen, so this part was just to procedurally do the right thing as well.) > ---------------------------------------------------------------------- > COMMENT: > ---------------------------------------------------------------------- > > Section 1 > > If the bandwidth availability requirement is not specified in the > signaling message, the bandwidth will be reserved as the highest > bandwidth availability. [...] > > Is this the behavior mandated by RFC 3209/etc., or a new description in > this document? > [Amy] Good point. How about change the text to: > the bandwidth may be reserved as I think I actually prefer the original version. Maybe "will likely be reserved", if that is accurate? > Section 3.1 > > Type (2 octets): 0x04 > > I think this should really have been "0x04 (suggested; TBD by IANA)". > The current text (both here and in Section 5.1) is very close to > codepoint squatting. I have entered DISCUSS positions on documents in > the past for codepoint squatting, but relucantly decline to do so here, > since the IANA considerations do state that the indicated value is only > a suggestion, and the registration procedure of Standards Action > strongly limits the potential for a conflicting registration to be > processing in parallel. > [Amy] will change as suggested. > > When the Availability TLV is included, it MUST be present along > with the Ethernet Bandwidth Profile TLV. If the bandwidth > requirements in the multiple Ethernet Bandwidth Profile TLVs have > > nit: this is the first time we talk about "the multiple" TLVs; should we > give it a less-subtle introduction, like "If there are multiple > bandwidth requirements present (in multiple Ethernet Bandwidth Profile > TLVs) and they have different [...]"? > [Amy] will change as suggested. > > different Availability requirements, multiple Availability TLVs > SHOULD be carried. In such a case, the Availability TLV has a one > > It's surprising to see this as a "SHOULD" (not "MUST")... > [Amy] will change to "MUST". > > to one correspondence with the Ethernet Bandwidth Profile TLV by > having the same value of Index field. If all the bandwidth > requirements in the Ethernet Bandwidth Profile have the same > Availability requirement, one Availability TLV SHOULD be carried. > In this case, the Index field is set to 0. > > ... and this extra complication seems like it might be premature > optimization. A strict one-to-one matching requirement is easy to > implement and easy to verify; the logic needed for this is more > complicated and prone to error. > [Amy] I think just one additional step. > First to judge if the index is 0, if yes, then apply the only availability value to all the bandwidth request; > if not, apply the availability values to each the bandwidth request. > A strict one-to-one matching surely is also possible. I don't have strong opinion here. I don't have a strong opinion, either; this is just a non-blocking comment. > Section 3.2 > > When two LSPs request bandwidth with the same availability > requirement, contention MUST be resolved by comparing the node IDs, > with the LSP with the higher node ID being assigned the reservation. > This is consistent with general contention resolution mechanism > provided in section 3.2 of [RFC3473]. > > It seems to me that Section 4.2 of RFC 3471 may be a better reference > than Section 3.2 of RFC 3473, since the latter does not actually say > anything about the higher node ID winning. > [Amy] Thanks, will use RFC 3471 instead. > > Section 3.2 > > When a node receives Availability TLVs which mixed of zero index and > non-zero index, the message MAY be ignored and SHOULD NOT be > propagated. [...] > > How would such a message be processed if the MAY is ignored (i.e., the > message is processed)? Perhaps this is better as a MUST? > [Amy] If strict one-to-one matching is applying, the error process should become simpler. > I see the point now. > > MAY be ignored and SHOULD NOT be propagated. When a node receives > several <bandwidth, availability> pairs, but there're are extra > > nit: s/there're are/there are/ > [Amy] will fix the nits. > > bandwidth-TLVs without matching index Availability-TLV, the extra > bandwidth-TLVs MAY be ignored and SHOULD NOT be propagated. > > This is perhaps an interesting recommendation to make, since it means > that implementations that support this document will ignore the > bandwidth-TLVs but implementations that do not support this document > will process them, leading to different behavior in terms of how many > reservations are actually made. (And the "SHOULD NOT be propagated" > makes things highly path-dependent and possibly exciting to debug.) > [Amy] How about change both to MUST/MUST NOT? That seems helpful, to me. (The first comment is mostly just an observation, and I don't see any easy changes that would improve things.) > Section 4 > > Thank you for removing the "does not introduce any new security > considerations" text as requested by the secdir reviewer, and adding the > "closed network" discussion. > > That said, I expected to see some discussion about how the mechanisms > defined in this document impose consistency requirements between > Bandwidth TLVs and the newly defined Availability TLVs that can increase > the risk of reservation requests being rejected. > > There could also be some text about the edge cases where behavior will > differ, for a given request, when some/all of the nodes on the path > do/don't support this extension. > [Amy] If some/all of the nodes on the path do/don't support this extension, > it's still possible to set up the LSP as long as there's enough bandwidth along > the path. It's just that the availability level of the reserved bandwidth is > unknown along the path(or in some part of the path), which makes the > mechnism less useful. That's probably still worth saying explicitly. Thanks, Ben > Section 5.1 > > I'm not sure why we need to mention the registration procedure for the > registry -- we're not creating the registry, just allocating a > codepoint from it. IANA will check/follow the required procedure, but > the reader of this document doesn't need to care. > [Amy] Just follow the usual format in IANA section. > > Section 7 > > Thank you for this example, which really helps to clarify that the total > bandwidth is allocated into *non-overlapping* segments with different > max-availability metrics. (That is, that even though there is 400 Mbps > capacity in clear weather, we don't report 400 Mbps at 99.99% > availability, since we need to use some of that capacity for the higher > availability levels.) I a little bit wonder if this could be reiterated > in prose earlier in the document, but don't have any concrete > suggestions for how to do so. > [Amy]This is additional information to help understanding the availability better. > So it's as appendix. > >
- [CCAMP] Benjamin Kaduk's Discuss on draft-ietf-cc… Benjamin Kaduk via Datatracker
- Re: [CCAMP] Benjamin Kaduk's Discuss on draft-iet… Yemin (Amy)
- Re: [CCAMP] Benjamin Kaduk's Discuss on draft-iet… Benjamin Kaduk