Re: [tram] Mirja Kühlewind's Discuss on draft-ietf-tram-turnbis-27: (with DISCUSS and COMMENT)

"Konda, Tirumaleswar Reddy" <TirumaleswarReddy_Konda@McAfee.com> Sat, 27 July 2019 15:14 UTC

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From: "Konda, Tirumaleswar Reddy" <TirumaleswarReddy_Konda@McAfee.com>
To: Mirja Kuehlewind <ietf@kuehlewind.net>
CC: The IESG <iesg@ietf.org>, "tram-chairs@ietf.org" <tram-chairs@ietf.org>, "draft-ietf-tram-turnbis@ietf.org" <draft-ietf-tram-turnbis@ietf.org>, "tram@ietf.org" <tram@ietf.org>, "brandon.williams@akamai.com" <brandon.williams@akamai.com>
Thread-Topic: [tram] Mirja Kühlewind's Discuss on draft-ietf-tram-turnbis-27: (with DISCUSS and COMMENT)
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Date: Sat, 27 Jul 2019 15:12:58 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tram/jY9ZSLm1l9u_CBS0aC48ChwPCu8>
Subject: Re: [tram] Mirja Kühlewind's Discuss on draft-ietf-tram-turnbis-27: (with DISCUSS and COMMENT)
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Hi Mirja,

Please see inline

> -----Original Message-----
> From: Mirja Kuehlewind <ietf@kuehlewind.net>
> Sent: Saturday, July 27, 2019 12:37 PM
> To: Konda, Tirumaleswar Reddy <TirumaleswarReddy_Konda@McAfee.com>
> Cc: The IESG <iesg@ietf.org>; tram-chairs@ietf.org; draft-ietf-tram-
> turnbis@ietf.org; tram@ietf.org; brandon.williams@akamai.com
> Subject: Re: [tram] Mirja Kühlewind's Discuss on draft-ietf-tram-turnbis-27:
> (with DISCUSS and COMMENT)
> 
> This email originated from outside of the organization. Do not click links or
> open attachments unless you recognize the sender and know the content is
> safe.
> 
> Hi Tiru,
> 
> Thanks for your quick reply and update and sorry for my delay! I’ve just
> cleared my discuss but see two quick comments in line below.
> 
> > On 15. Jul 2019, at 02:31, Konda, Tirumaleswar Reddy
> <TirumaleswarReddy_Konda@McAfee.com> wrote:
> >
> > Hi Mirja,
> >
> > Thanks for the review. Please see inline
> >
> >> -----Original Message-----
> >> From: tram <tram-bounces@ietf.org> On Behalf Of Mirja Kühlewind via
> >> Datatracker
> >> Sent: Wednesday, July 10, 2019 9:25 PM
> >> To: The IESG <iesg@ietf.org>
> >> Cc: tram-chairs@ietf.org; draft-ietf-tram-turnbis@ietf.org;
> >> tram@ietf.org; brandon.williams@akamai.com
> >> Subject: [tram] Mirja Kühlewind's Discuss on
> >> draft-ietf-tram-turnbis-27: (with DISCUSS and COMMENT)
> >>
> >> This email originated from outside of the organization. Do not click
> >> links or open attachments unless you recognize the sender and know
> >> the content is safe.
> >>
> >> Mirja Kühlewind has entered the following ballot position for
> >> draft-ietf-tram-turnbis-27: 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-turnbis/
> >>
> >>
> >>
> >> ---------------------------------------------------------------------
> >> -
> >> DISCUSS:
> >> ---------------------------------------------------------------------
> >> -
> >>
> >> One quick discussion which probably is only an oversight and
> >> therefore should be easy got fix:
> >>
> >> I'm bit confused about the requirement on using authentication. This
> >> draft says in section 5 (as RFC5766 does):
> >>
> >> "The server MUST demand that all requests  from the client be
> >> authenticated using this mechanism, or that a  equally strong or
> >> stronger mechanism for client authentication is  used."
> >>
> >> However, RFC 8155 which is even now cited in this draft, updates
> >> RFC5766 and relaxes this requirement. Later in the section 7.2. this draft
> says:
> >>
> >> "The server SHOULD require that the request be authenticated."
> >>
> >> I assume the requirement in section 5 is an oversight?
> >
> > Yes, removed the requirement in Section 5.
> >
> >>
> >> I also recommend to only specify this requirement normatively in one
> place.
> >
> > Done, updated step 1 in Section 5 to address the comment from Ben as
> follows:
> >
> >  1.   The TURN server provided by the local or access network MAY
> >       allow unauthenticated request in order to accept Allocation
> >       requests from new and/or guest users in the network who do not
> >       necessarily possess long term credentials for STUN
> >       authentication and its security implications are discussed in
> >       [RFC8155].  Otherwise, the server MUST require that the request
> >       be authenticated.  If the request is authenticated, the
> >       authentication MUST be done either using the long-term
> >       credential mechanism of [I-D.ietf-tram-stunbis] or the STUN
> >       Extension for Third-Party Authorization [RFC7635] unless the
> >       client and server agree to use another mechanism through some
> >       procedure outside the scope of this document.
> >
> >>
> >>
> >> ---------------------------------------------------------------------
> >> -
> >> COMMENT:
> >> ---------------------------------------------------------------------
> >> -
> >>
> >> Some other technical comments/questions:
> >>
> >> 1) Sec 3.7:
> >> "or use UDP fragmentation [I-D.ietf-tsvwg-udp-options]."
> >> I believe the possibility to use UDP fragmentation was brought up by
> >> the TSV-ART review (Thanks Joe!). However, I would like to mention
> >> that this can only be used if supported by both endpoints and that
> >> should probably also be remarked here. The next sentence in the draft
> >> indicated this by saying "until UDP fragmentation support is
> >> available", however, this actually seem to be editorially a bit
> >> misplaced there and could explain more. See also this text in
> >> draft-ietf-tsvwg-udp-options:
> >>
> >> "FRAG needs to be used with extreme care because it will present
> >> incorrect datagram boundaries to a legacy receiver, unless encoded
> >> as LITE data (see Section 5.8)."
> >>
> >> Also note that draft-ietf-tsvwg-udp-options is still under
> >> development and we don't have much deployment experience with it yet.
> >
> > Yes, Joe suggest the above change. I have added the following line:
> > Note that the UDP fragmentation option needs to be supported by both
> endpoints, and at the time of writing of this document, UDP fragmentation
> support is under discussion and is not deployed.
> >
> >>
> >> And further, in the same section. There is also
> >> draft-ietf-tsvwg-datagram- plpmtud on "Packetization Layer Path MTU
> >> Discovery for Datagram Transports". Please also be aware that there
> >> is an extensive TSV-ART for draft-ietf-tram-stun-pmtud. Both might
> >> impact the final content of this section.
> >
> > The draft does not refer to draft-ietf-tsvwg-datagram- plpmtud.
> 
> Yes, but I though you maybe should cite it as well :-)

Sure, updated text as follows:
The Packetized Path  MTU Discovery algorithm defined in [RFC4821] is one such algorithm and a set of algorithms are defined in [I-D.ietf-tsvwg-datagram-plpmtud].

> 
> >
> >>
> >> 2) sec 11.5:
> >> "When the server receives an ICMP packet, the server verifies that
> >> the  type is either 3 or 11 for an ICMPv4 [RFC0792] packet or either
> >> 1, 2,  or 3 for an ICMPv6 [RFC4443] packet."
> >> Restricting to a set of known types, doesn't seem to support future
> >> extensibility very well...
> >
> > Good point, added the following lines:
> > New ICMP types or codes can be defined in future specifications. If the
> server receives an ICMP error packet, and the new type or code field can
> help the client to make use of the ICMP error notification and generate
> feedback to the application layer, the server sends the Data indication with
> an ICMP attribute conveying the new ICMP type or code.
> >
> >>
> >> 3) sec 12.5:
> >> "Over TCP and TLS-over-TCP, the ChannelData message MUST be padded
> to
> >> a multiple of four bytes in order to ensure the alignment of
> >> subsequent messages."
> >> Not exactly sure why this is useful...? Is this to align with STUN
> >> and therefore make processing somehow easier? Is that really needed.
> >> And exception should be easy to implement and should save some bytes
> >> which is the as I understood it the whole purpose of channels, no?
> >
> > This behavior is not new, it is defined and deployed in TURN
> > https://tools.ietf.org/html/rfc5766#section-11.5
> >
> >>
> >> 4) 12.6:
> >> "Note that if
> >>  the Length field in the ChannelData message is 0, then there will be
> >> no data in the UDP datagram, but the UDP datagram is still formed and
> >> sent."
> >> Can you maybe add some more text and explain why this is useful?
> >
> > Sure, added reference to Section 4.1 in
> > https://tools.ietf.org/html/rfc6263
> >
> >>
> >> 5) sec 15:
> >> RFC6824 will soon be obsoleted by draft-ietf-mptcp-rfc6824bis and
> >> please s/TCP multi-path/Multipath TCP/.
> >
> > Thanks, updated.
> >
> >>
> >> 6) Just a thought looking at section 14 and 16: It could have been
> >> nice to provide an ECN feedback field from the server to the client
> >> in case a ECN marked packet is received from the peer... however, I
> >> guess that future work at this point in the process...
> >>
> >> 7) sec 18.13: Maybe I missed this because I reviewed this doc over 3
> >> days, but is only the ICMP Attribute send to the client or is the
> >> actual ICMP packets or as much as possible of that packet includes as well?
> >
> > Yes, only the ICMP attribute is sent to the client.
> 
> Here also, I can imagine that sending as much of the ICMP packet as possible
> could be useful as well. Was that considered?

Yes, the decision was not send the ICMP packet (Please see https://mailarchive.ietf.org/arch/msg/tram/dk5PzVhBzzCUSAftYVoSpYQl0o4) 

Cheers,
-Tiru


> 
> Mirja
> 
> 
> >
> >>
> >> 8) sec 23:
> >> "Response: TURN will no longer be needed once there are no longer any
> >> NATs.  Unfortunately, as of the date of publication of this document,
> >> it no longer seems very likely that NATs will go away any time soon.
> >>  However, the need for TURN will also decrease as the number of NATs
> >> with the mapping property of Endpoint-Independent Mapping [RFC4787]
> >> increases."
> >> Yes... so you don't think that IPv6 will be any help here?
> >
> > Yes, IPv6 will not help in some scenarios, updated Introduction to list them.
> >
> >  In many enterprise networks, direct UDP transmissions are not
> > permitted between clients on the internal networks and external IP
> > addresses.  To permit media sessions in such a situation to use UDP
> > and to avoid forcing the media sessions through TCP, Enterprise
> > Firewall can be configured to allow UDP traffic relayed through an
> > Enterprise relay server.  This scenario is required to be supported
> > by the WebRTC requirements (Section 2.3.5.1 in [RFC7478]).  In
> > addition, in a SIP or WebRTC call, if the user wants IP location
> > privacy from the peer then the client can select a relay server
> > offering IP location privacy and only convey the relayed candidates
> > to the peer for ICE connectivity checks (see Section 4.2.4 in
> > [I-D.ietf-rtcweb-security]).
> >
> >>
> >> Editorial comments:
> >>
> >> 1) Sec 6:
> >> "The relayed transport address MUST be unique across all
> >> allocations, so it can be used to uniquely identify the allocation.
> >>
> >>  Both the relayed transport address and the 5-tuple MUST be unique
> >> across all allocations, so either one can be used to uniquely
> >> identify the allocation, [...]"
> >> These two sentences seem quite redundant. The first one was added in
> >> this draft. The second one was already there in RFC5766.
> >
> > Thanks, removed the second sentence.
> >
> >>
> >> 2) sec 7.1:
> >> "Since this specification only
> >>  allows UDP between the server and the peers, it is RECOMMENDED that
> >> [...]"
> >> Wordings ("only allows") seems weird to me given use of other
> >> proposals is at least to some extend discussed.
> >
> > The specification does not allow any other protocol other than UDP
> between the server and peers (As you know, UDP is the preferred transport
> for media streams).
> >
> >>
> >> Nits:
> >> sec 7.1.: s/the client pick a currently unused transport address/the
> >> client picks a currently unused transport address/
> >
> > Fixed.
> >
> > Cheers,
> > -Tiru
> >>
> >>
> >> _______________________________________________
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> >> tram@ietf.org
> >> https://www.ietf.org/mailman/listinfo/tram