Subject: [core] Roman Danyliw's No Objection on draft-ietf-core-hop-limit-06: (with COMMENT)

From: Roman Danyliw via Datatracker <[email-masked]>
Date: Tue, 15 Oct 2019 05:14:15 -0700

Roman Danyliw has entered the following ballot position for
draft-ietf-core-hop-limit-06: No Objection

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COMMENT:
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** Section 1.0, What is an “involved application agent”?

** Section 1.1 Per “CoAP proxies that do not have specific knowledge that proxy
loops are avoided in some way …”, how would a proxy know that?

** Section 7.  Perhaps also add that a malicious proxy can induce more subtle
failures than just straight packet drops by manipulating the Hop Limit value.

** Editorial Nits:

-- Section 1.1.  Editorial. s/ The Hop-Limit option has originally been
designed for a/The Hop-Limit option was originally designed for a/

-- Section 3.  Recommend being clearer on what it means for “Hop-Limit
detection gets broken” when proxies on boundaries re-write the hop limit value.
 Perhaps something on the order of: s/ This modification should be done with
caution in case proxy-forwarded traffic repeatedly crosses the administrative
domain boundary in a loop and so Hop-Limit detection gets broken ./ This
modification should be done with caution in case proxy-forwarded traffic
repeatedly crosses the administrative domain boundary in a loop rendering
negating the efficacy of loop detection through the Hop-Limit field.

-- Section 4.  Per “Only one information per proxy should appear in the
diagnostic payload”, what is “one information” (it seems like a few words are
missing here)?

-- Section 4.  Per “Doing so allows to limit the size of the TBA1 …”, this
sentence doesn’t parse for me.

---

From: <[email-masked]>
Date: Tue, 15 Oct 2019 14:06:27 +0000

Hi Roman, 

Thank you for the review. 

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : Roman Danyliw via Datatracker [mailto:[email-masked]]
> Envoyé : mardi 15 octobre 2019 14:14
> À : The IESG
> Cc : [email-masked]; Jaime Jimenez; core-
> [email-masked]; [email-masked]; [email-masked]
> Objet : Roman Danyliw's No Objection on draft-ietf-core-hop-limit-06: (with
> COMMENT)
> 

[Med] Agents (client, server, proxy) that are involved in an application-specific communication. 

> loops are avoided in some way …”, how would a proxy know that?

[Med] Fair point. FYI, this point was raised recently in the WG (https://mailarchive.ietf.org/arch/msg/core/X_4k3i6SMAur5nve-V3N-mkKjKQ), the change we are currently considering is: 

"New CoAP implementations MUST ..." 

> failures than just straight packet drops by manipulating the Hop Limit

[Med] I'm hesitating to add this as this is a variation of the MiTM threat vector (already mentioned in Section 11.2 of RFC7252). 

> designed for a/The Hop-Limit option was originally designed for a/

[Med] OK. Thanks. 

> negating the efficacy of loop detection through the Hop-Limit field.

[Med] Sure. Will consider rewording. 

> diagnostic payload”, what is “one information” (it seems like a few words

[Med] This is in reference to the information mentioned in the previous para/sentence:  

   To ease debugging and troubleshooting, the CoAP proxy which detects a
   loop includes its information in the diagnostic payload under the
                 ^^^^^^^^^^^^^^^^
   conditions detailed in Section 5.5.2 of [RFC7252].  That information
   MUST NOT include any space character.  The information inserted by a
   CoAP proxy can be, for example, a proxy name (e.g., p11.example.net),
   proxy alias (e.g., myproxyalias), or IP address (e.g., 2001:db8::1).

   Each intermediate proxy involved in relaying a TBA1 (Hop Limit
   Reached) error message prepends its own information in the diagnostic
                                   ^^^^^^^^^^^^^^^^^^^^ 
   payload with a space character used as separator.  Only one 
   information per proxy should appear in the diagnostic payload.

> sentence doesn’t parse for me.

[Med] Can change to: "This approach allows to ....". Better?