Re: [ippm] Robert Wilton's Discuss on draft-ietf-ippm-ioam-direct-export-09: (with DISCUSS and COMMENT)
Tal Mizrahi <tal.mizrahi.phd@gmail.com> Thu, 18 August 2022 12:59 UTC
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From: Tal Mizrahi <tal.mizrahi.phd@gmail.com>
Date: Thu, 18 Aug 2022 15:59:38 +0300
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To: Robert Wilton <rwilton@cisco.com>
Cc: The IESG <iesg@ietf.org>, draft-ietf-ippm-ioam-direct-export@ietf.org, ippm-chairs@ietf.org, ippm@ietf.org, tpauly@apple.com
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Subject: Re: [ippm] Robert Wilton's Discuss on draft-ietf-ippm-ioam-direct-export-09: (with DISCUSS and COMMENT)
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Dear Robert, Many thanks for the comments. We have uploaded an updated version that hopefully addresses the DISCUSS comments. https://datatracker.ietf.org/doc/draft-ietf-ippm-ioam-direct-export/ Please see my responses below, marked [TM]. Please let us know if there are further comments. Cheers, Tal. On Thu, Jun 30, 2022 at 1:37 PM Robert Wilton via Datatracker <noreply@ietf.org> wrote: > > Robert Wilton has entered the following ballot position for > draft-ietf-ippm-ioam-direct-export-09: 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/about/groups/iesg/statements/handling-ballot-positions/ > for more information about how to handle DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-ippm-ioam-direct-export/ > > > > ---------------------------------------------------------------------- > DISCUSS: > ---------------------------------------------------------------------- > > Hi, > > I had a couple of minor discuss comments to clarify a couple of points that > seemed unclear: > > 1) Definition of Sequence Number: > > Sequence Number An optional 32-bit sequence number starting from 0 > and increasing by 1 for each following monitored > packet from the same flow at the encapsulating node. > The Sequence Number, when combined with the Flow ID, > provides a convenient approach to correlate the > exported data from the same user packet. > > Please can you clarify. Is this every packet in the flow (presumably not)? > Does monitored packet means just those with the DEX option? Could it include > other packets [TM] The text was updated - only packets with the DEX option are counted. > > 2. Optional field ordering. > Optional fields The optional fields, if present, reside after the > Reserved field. The order of the optional fields is > according to the respective bits that are enabled in > the Extension-Flags field. Each optional field is 4 > octets long. > > Please can clarify that the order is from most significant bit to least > significant bit of the option field. > [TM] Fixed. > 3. Allocation is based on the "RFC > Required" procedure, as defined in [RFC8126]. > > Given the number of extensions is so limited, is RFC required (e.g. allows ISE) > really a strict enough allocation policy? [TM] Agree. Changed to "IETF Review" > > Regards, > Rob > > > ---------------------------------------------------------------------- > COMMENT: > ---------------------------------------------------------------------- > > Here are my non-blocking comments: > > 1. > This draft has evolved from combining some of the concepts of PBT-I > from [I-D.song-ippm-postcard-based-telemetry] with immediate > exporting from [I-D.ietf-ippm-ioam-flags]. > > I'm not sure that this paragraph is really helpful now, and could probably be > deleted - you could use the datatracker to indicate the document history and > which previous drafts this document replaces. > > 2. > N >> M > > I'm assuming that by ">>", this means much greater than? It would be better > use words here, or at least define what this means (e.g., as opposed to a > bit-shift). > > 3. > An IOAM node > MAY maintain a counter or a set of counters that count the events in > which the IOAM node receives a packet with the DEX Option-Type and > does not collect and/or export data due to the rate limits. > > Given that this is a MAY, I wasn't sure that this really specifies anything, I > guess that it is just offering a suggestion. > > 4. > Exported packets SHOULD NOT be exported over a path or a tunnel that > is subject to IOAM direct exporting. Furthermore, IOAM encapsulating > nodes that can identify a packet as an IOAM exported packet MUST NOT > push a DEX Option-Type into such a packet. This requirement is > intended to prevent nested exporting and/or exporting loops. > > It was unclear to me how that that SHOULD NOT can really be enforced, if the > exported packets are allowed to leave the limited domain. Perhaps the "SHOULD > NOT" should be limited to the domain where IOAM is operating? > > 5. > transit or decapsulating IOAM node that receives an unknown IOAM- > Option-Type ignores it (as defined in [RFC9197]), and specifically > nodes that do not support the DEX Option-Type ignore it. Note that > as per [RFC9197] a decapsulating node removes the IOAM encapsulation > and all its IOAM-Option-Types, and specifically in the case where one > of these options is a (possibly unknown) DEX Option-Type. The > ability to skip over a (possibly unknown) DEX Option-Type in the > parsing or in the decapsulation procedure is dependent on the > specific encapsulation, which is outside the scope of this document. > For example, when IOAM is encapsulated in IPv6 > > I found the sentence from "Note that ..." to be somewhat unclear. > > 6. Option-Type Format > > Would it be more helpful to explicitly specify what the length is. I.e., X > bytes + 4 * number of set bits in the Extension-Flags? > > 7. Extension-Flags > > More a question for my own knowledge: I presume that the length calculation > (i.e., checking for the count of set bits) can be performed efficiently? I.e., > if calculating the length is important on any fast path. > > 8. subject to birthday problem conflicts, while centralized > > Would it be helpful to spell out what is meant by "birthday problem conflicts", > or perhaps include an informative reference to the wiki page? > > Nits: > N>100 => N > 100 > > >
- [ippm] Robert Wilton's Discuss on draft-ietf-ippm… Robert Wilton via Datatracker
- Re: [ippm] Robert Wilton's Discuss on draft-ietf-… Tal Mizrahi