Re: [ippm] R: WGLC for draft-ietf-ippm-explicit-flow-measurements

"Lubashev, Igor" <> Tue, 26 July 2022 19:41 UTC

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From: "Lubashev, Igor" <>
To: Cociglio Mauro <>, "Marcus Ihlar" <>
CC: Tommy Pauly <>, IETF IPPM WG <>
Thread-Topic: [ippm] R: WGLC for draft-ietf-ippm-explicit-flow-measurements
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Date: Tue, 26 Jul 2022 19:41:01 +0000
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Subject: Re: [ippm] R: WGLC for draft-ietf-ippm-explicit-flow-measurements
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It is a very interesting question why spin bit has not received a wider adoption, and whether it is related to its perceived privacy properties.  It is also possible that there is just not enough interest from the industry.  The spin bit was designed by researchers for research purposes.  Loss bits have a significant engagement from the industry.

  *   Igor

From: Cociglio Mauro <>
Sent: Tuesday, July 26, 2022 6:21 AM

Hi Marcus,
thanks for your interesting suggestions that allow me to explain better Explicit Measurement draft background.
The important thing for us is to recover visibility on performance even using the new QUIC protocol. Explicit measures, if present in all implementations, could achieve this important result. In this way, the legitimate interests of those who develop the applications would not collide with those of the service providers.
The motivation for the inclusion of the Hidden Delay bit in the draft derives from the poor adoption of the spin bit on the net.
The idea is only to provide one more option if the measurement of the end-to-end RTT was a brake to the Spin bit (or Delay bit) adoption.
Starting from this draft, our intention would be to formulate a proposal to the QUIC WG, and maybe even the Hidden Delay bit could be useful in that context, it's hard to know in advance.
Thanks again.


Da: ippm <<>> Per conto di Marcus Ihlar
Inviato: lunedì 25 luglio 2022 23:03
A: Tommy Pauly <<>>; IETF IPPM WG <<>>
Oggetto: [EXT] Re: [ippm] WGLC for draft-ietf-ippm-explicit-flow-measurements

Replying here as an individual without the chair hat on.
I think this is good work and describes different useful mechanisms and how they can be combined.

However, I have some problems with the section describing the “Hidden Delay Bit”.
First of all, the motivation for including it is not that strong in my opinion. When the QUIC wg was working on the spin-bit there was a thorough analysis of potential privacy implications. In particular it was shown that using the RTT for geo-location is very difficult and leads to imprecise results. If there has been more recent work in this space that suggest otherwise I think it’s important that this is clearly mentioned in the draft.

The second issue I have with the hidden delay bit is that it actually doesn’t solve the hypothetical problem of RTT-based geo-location. It is fairly straight forward to measure initial RTT by observing handshake packets see (<*name-measuring-initial-rtt__;Iw!!GjvTz_vk!Q2_0tdUpNityV8-getpja839nWOUqt_Yo3zArfJAkASl70BfKb0HtDWcDua4NMKtRiwabhHmk_NCG6HoJEjrN33GlV6ACQ$> for instance). An observer that can collect enough initial RTT samples will have enough information to attempt geo-location. Also, with that minimum RTT knowledge it is trivial for an observer to determine the offset used by the client.

So in summary, I think it’s a useful document that has potential to guide future transport protocol work, but I think the hidden delay bit should be removed from the document before moving it forward unless more solid motivation for it can be provided.


From: ippm <<>> On Behalf Of Tommy Pauly
Sent: Wednesday, 6 July 2022 12:04
Subject: [ippm] WGLC for draft-ietf-ippm-explicit-flow-measurements

Hello IPPM,

This email starts a Working Group Last Call for draft-ietf-ippm-explicit-flow-measurements. This informational document describes various techniques for using exposed bits in protocols to participate in measurement, intended as input for protocols that would like to adopt such techniques.<;!!GjvTz_vk!Q2_0tdUpNityV8-getpja839nWOUqt_Yo3zArfJAkASl70BfKb0HtDWcDua4NMKtRiwabhHmk_NCG6HoJEjrN30Tx8BjgQ$><;!!GjvTz_vk!Q2_0tdUpNityV8-getpja839nWOUqt_Yo3zArfJAkASl70BfKb0HtDWcDua4NMKtRiwabhHmk_NCG6HoJEjrN30ZgMN3vQ$>

We’ll run this WGLC up until the IETF week, and we can discuss any feedback as necessary at the IETF 114 meeting.

Please review the document and reply to this email with your comments, and if you think this document should proceed, by Monday, July 25.

Tommy & Marcus


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