Re: [tram] Benjamin Kaduk's Discuss on draft-ietf-tram-stun-pmtud-10: (with DISCUSS and COMMENT)
Benjamin Kaduk <kaduk@mit.edu> Mon, 19 August 2019 23:50 UTC
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Date: Mon, 19 Aug 2019 18:50:06 -0500
From: Benjamin Kaduk <kaduk@mit.edu>
To: "Felipe Garrido (fegarrid)" <fegarrid@cisco.com>
Cc: "tram-chairs@ietf.org" <tram-chairs@ietf.org>, "draft-ietf-tram-stun-pmtud@ietf.org" <draft-ietf-tram-stun-pmtud@ietf.org>, "iesg@ietf.org" <iesg@ietf.org>, "tasveren@rbbn.com" <tasveren@rbbn.com>, "tram@ietf.org" <tram@ietf.org>
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Subject: Re: [tram] Benjamin Kaduk's Discuss on draft-ietf-tram-stun-pmtud-10: (with DISCUSS and COMMENT)
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Hi Felipe, The new wording is at least enough for me to come up with what seems like a plausible guess for what the identifier (and algorithm thereto) is supposed to be, but I do still feel like I'm guessing. If it's the path identifier used to associate stored (PL)PMTU state across different flows (which is my guess), then maybe "associated to a given path's identifier" would be a further improvement? Thanks, Ben On Mon, Aug 19, 2019 at 02:13:13PM +0000, Felipe Garrido (fegarrid) wrote: > Hi Ben, > > Do you agree with the latest wording changes? A new draft version has been published with them. > > Thanks, > -Felipe > > On 7/8/19, 10:43 AM, "tram on behalf of Felipe Garrido (fegarrid)" <tram-bounces@ietf.org on behalf of fegarrid@cisco.com> wrote: > > Hi Ben, > > Totally agree now that I've re-read it. > > Here's the new proposed wording. > > "The packets that are to be associated to an identifier are selected according to Section 5.2 of [RFC4821]." > > Here's the full text. > > A server supporting this specification will keep the identifiers of > all packets received in a chronologically ordered list. The > packets that are to be associated to an identifier are selected > according to Section 5.2 of [RFC4821]." > > Thanks, > -Felipe > > On 6/27/19, 12:00 AM, "Benjamin Kaduk" <kaduk@mit.edu> wrote: > > Hi Felipe, > > Thanks for following up -- it looks like I filed away the original mail > without responding to it, somehow(!) > The Discuss point's resolution is fine; I just have one more question > (inline). > > -Ben > > On Wed, Jun 26, 2019 at 04:01:58AM +0000, Felipe Garrido (fegarrid) wrote: > > Hi Benjamin, > > > > Just following up on my previous email. Let me know if the below response satisfies your comments. > > > > Thanks, > > -Felipe > > > > From: "Felipe Garrido (fegarrid)" <fegarrid@cisco.com> > > Date: Tuesday, May 21, 2019 at 11:59 AM > > To: "kaduk@mit.edu" <kaduk@mit.edu>, "iesg@ietf.org" <iesg@ietf.org> > > Cc: "draft-ietf-tram-stun-pmtud@ietf.org" <draft-ietf-tram-stun-pmtud@ietf.org>, "tram-chairs@ietf.org" <tram-chairs@ietf.org>, "tasveren@rbbn.com" <tasveren@rbbn.com>, "tram@ietf.org" <tram@ietf.org> > > Subject: Benjamin Kaduk's Discuss on draft-ietf-tram-stun-pmtud-10: (with DISCUSS and COMMENT) > > > > > > Hi Benjamin, > > > > Apologies for the delay in responding, the current authors are having scheduling conflicts and have added me to address the current concerns. Please see my responses inline. > > > > thanks > > -Felipe > > > > > > Benjamin Kaduk has entered the following ballot position for > > draft-ietf-tram-stun-pmtud-10: 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-tram-stun-pmtud/ > > > > > > > > ---------------------------------------------------------------------- > > DISCUSS: > > ---------------------------------------------------------------------- > > > > I was going to report the same thing as Adam, but will just say that I support his Discuss. > > [FG]: I’ll be addressing this Discuss in Adam’s feedback. > > > > I also have one other (also minor and easy to resolve) Discuss point: Section 4.2.6 needs > > to state what the Length field is measuring the length of. > > [FG]: Agree that this is required. Adding the following text to Section 4.2.6. > > “The Length field specifies the length in bytes of the sequence number and application data fields.” > > > > ---------------------------------------------------------------------- > > COMMENT: > > ---------------------------------------------------------------------- > > > > I understand that this document inherently has to be incomplete and "vague", > > since the procedure specified within is only meaningful in the context of a > > STUN usage or other protocol. But in general it seems like there could be > > greater clarity even within the constraints that we must work under. My > > points are probably less interesting than the ones Adam raised already, though. > > The only general observation in this space that I can offer is that some parts of > > the text read as if only the Probe packets are going to be monitored for the > > report (but this is clearly not the case given the document as a whole). > > > > Section 4.2 > > > > The Complete Probing mechanism is implemented by sending one or more > > Probe Indications with a PADDING attribute over UDP with the DF bit > > set in the IP header followed by a Report Request to the same server. > > A router on the path to the server can reject this Indication with an > > ICMP message or drop it. > > > > nit: I don't think "this" is the right word; perhaps "each" would be > > better. > > > > > > > > [FG]: Agree, updates will be made. > > > > Section 4.2.3 > > > > A server supporting this specification will keep the identifiers of > > all packets received in a chronologically ordered list. The packets > > that are to be associated to a list are selected according to > > Section 5.2 of [RFC4821]. [...] > > > > 4821 doesn't talk about "list"s at all, and in fact the indicated section > > seems to be talking more about where to store a PMTU value after it has > > been determined, rather than what packets to be considering for a report. > > So I'm pretty confused about what this sentence is trying to say. > > > > > > > > [FG]: Agree. Updated wording to make the statement easier to read. > > “The selection process specified in Section 5.2 of [RFC4821] is to be used to determine whether a packet is added with a list.” > > I still don't understand what "the selection process specified in Section > 5.2 of [RFC4821]" is -- can you point me to the text from RFC 4821 > describing the process in question? > > > Section 4.2.4 > > > > nit: I think that all instances of "the Probe Indication" should be > > replaced with "a Probe Indication", in this section. > > > > > > > > [FG]: Agree, updates will be made. > > > > Section 4.2.5 > > > > When using a checksum as a packet identifier, the client calculates > > the checksum for each packet sent over UDP that is not a STUN Probe > > Indication or Request and keeps this checksum in a chronologically > > ordered list. The client also keeps the checksum of the STUN Probe > > Indication or Request sent in that same chronologically ordered list. > > The algorithm used to calculate the checksum is similar to the > > algorithm used for the FINGERPRINT attribute (i.e., the CRC-32 of the > > payload XOR'ed with the 32-bit value 0x5354554e [ITU.V42.2002]). > > > > (editorial) It's pretty confusing to start out with the split between STUN > > and non-STUN messages, only later to clarify that this is because the > > FINGERPRINT is used for STUN messages. So maybe: > > > > When using a checksum as a packet identifier, the client keeps a > > chronologically ordered list of the packets it transmits, along with an > > associated checksum value. For STUN Probe Indication or Request packets, > > the associated checksum value is the FINGERPRINT value from the packet; for > > other packets a checksum value is computed using a similar algorithm to the > > FINGERPRINT calculation. > > > > > > > > [FG]: Agree with changing of the language. It doesn’t change the content and easier to read. > > > > Section 4.2.6 > > > > When using sequence numbers, a small header similar to the TURN > > ChannelData header [...] > > > > Probably want an informative reference for this header. > > > > > > > > [FG]: Agree, updates will be made to reference. > > Section 6.2 > > > > 6.2. PMTUD-SUPPORTED > > > > The PMTUD-SUPPORTED attribute indicates that its sender supports this > > specification. This attribute has no value part and thus the > > attribute length field is 0. > > > > "this specification" is not sufficiently detailed to interoperate, so I > > think this needs to be qualified as more like "supports this mechanism, as > > incorporated into the STUN usage or protocol being used". > > > > > > > > [FG]: Agree, updates will be made. > > > > Section 7 > > > > The contents of the PADDING do not seem to be specified anywhere, so it > > could in theory be used as a side channel to convey other information, > > which has some potential privacy considerations. Nowadays we tend to ask > > for the value of the padding bytes to be deterministic (but validation > > remains optional); I forget if there are STUN-specific considerations that > > would discourage just setting them all to zero. > > > > > > > > [FG]: Agree. Adding language to state contents of PADDING. > > “The padding bits MUST be set to zero on sending and MUST be ignored by the receiver.” > > > > > > > > > > > > > _______________________________________________ > tram mailing list > tram@ietf.org > https://www.ietf.org/mailman/listinfo/tram > >
- [tram] Benjamin Kaduk's Discuss on draft-ietf-tra… Benjamin Kaduk
- [tram] Benjamin Kaduk's Discuss on draft-ietf-tra… Felipe Garrido (fegarrid)
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Felipe Garrido (fegarrid)
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Felipe Garrido (fegarrid)
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Felipe Garrido (fegarrid)
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Felipe Garrido (fegarrid)
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Gonzalo Camarillo
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Gonzalo Salgueiro (gsalguei)
- Re: [tram] Benjamin Kaduk's Discuss on draft-ietf… Gonzalo Camarillo