RE: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"

[Mikkel Fahnøe Jørgensen <[e-mail]>]

I’d suggest adding a priority scheme: for example only send datagrams on
the low latency path, or only on the slow path, or any path if you want to
maximize resources. If you restrict to one path you get sort-of ordering
without a lot of complexity. You might also want to allow fast path to move
to slow path when there is doubt about link quality, but such that only one
path is used at a time. This does not rule out reordering when switching
path, but a single path can also reorder.

In this way you get the desired profile without all the downsides, except
that you get a lower throughput.

Such a scheme does not need agreement on both ends. It doesn’t even need to
be specified in the protocol. It is an API design issue.


Kind Regards,
Mikkel Fahnøe Jørgensen


On 3 December 2020 at 11.14.10, [e-mail] (
[e-mail]) wrote:

Hi Mikkel,



that is the decisive question here. I’m convinced, that almost no
encapsulated service/transport, where the traffic is split over cellular
and Wi-Fi, can cope with the enormous out-of-order delivery due to the
latency differences. That means the multipath experience is probably worse
compared to traditional singe-path usage. Using datagram frames in the 3GPP
scenario does not imply that out-of-order delivery is accepted! That’s why
the LS points explicitly to that. Using in-order delivery from QUIC streams
will introduce re-transmission, right, that’s why it is not in focus of the
LS.



However, I also agree that strict re-ordering is not the solution, since
this causes HoL and it’s open how to deal with lost information. So
probably it’s time for some smart re-ordering mechanisms here?!



Br



Markus



*From:* Mikkel Fahnøe Jørgensen <[e-mail]>
*Sent:* Donnerstag, 3. Dezember 2020 11:01
*To:* [e-mail]; [e-mail]; Amend, Markus <
[e-mail]>; [e-mail]
*Cc:* [e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail]
*Subject:* RE: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"



Are the special ordering concerns beyond single streams?



I don’t think it is useful to reorder datagram frames and streams are by
definition ordered within a stream and not across streams in QUIC v1 and I
don’t see any multipath design that would change that.



If datagram frames were to be ordered, you would loose the ASAP property
you want from those frames, and if cross stream ordering is applied, you
introduce HoL.



Kind Regards,

Mikkel Fahnøe Jørgensen



On 3 December 2020 at 10.33.17, [e-mail] (
[e-mail]) wrote:

Full ACK. 3GPP requests MP-QUIC to be applied between UE and UPF.
Encapsulating the traffic from services on the UE into this MP-QUIC
connection allows communication with the respective remote servers.



Br



Markus



*From:* Waqar Zia <[e-mail]>
*Sent:* Donnerstag, 3. Dezember 2020 09:49
*To:* Jana Iyengar <[e-mail]>; [e-mail]
*Cc:* [e-mail]; [e-mail]; [e-mail];
Apostolis Salkintzis <[e-mail]>; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; Amend, Markus <[e-mail]>;
[e-mail]; [e-mail]; [e-mail]
*Subject:* RE: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"



Hi Jana,



The diagram is the correct depiction as I see: the MP-QUIC connection is
indeed expected to be between the UE and the UPF, not between the UE and a
(3GPP-) external server. Hence the reordering that may happen due to use of
two different access technologies between the UE and UPF needs to be fixed
at the UPF for the uplink and at the UE for the downlink.



Best regards,

Waqar.



*From:* QUIC <[e-mail]> *On Behalf Of *Jana Iyengar
*Sent:* 03 December 2020 05:55
*To:* [e-mail]
*Cc:* [e-mail]; [e-mail]; [e-mail];
Apostolis Salkintzis <[e-mail]>; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]
*Subject:* Re: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"



*CAUTION*: This email originated from outside of the organization.

Speaking only as a user of computer technology, thanks for making this more
palatable as a PDF. A few questions:



- I am a bit confused by the picture, and Spencer or someone else can point
me to something that I haven't read yet -- I thought the QUIC connection
was between the remote server and the UE, not between the UPF and the UE.
Am I missing something?

- Assuming that the QUIC connection is between the UE and the remote
server: Since only endpoints can see the packet numbers, how are the
packets supposed to be re-sequenced at any point in the middle (the UPF)?



Thanks!

- jana



On Tue, Dec 1, 2020 at 11:14 AM <[e-mail]> wrote:

Including Apostolis into the loop.



*De :* [e-mail] [mailto:[e-mail]]
*Envoyé :* mardi 1 décembre 2020 12:07
*À :* [e-mail]; MORAND Lionel TGI/OLN <[e-mail]>
*Cc :* [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]; [e-mail];
[e-mail]; [e-mail]
*Objet :* RE: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"



Thanks for raising this topic. With
https://tools.ietf.org/html/draft-amend-iccrg-multipath-reordering-01 we
consider exactly that and try to provide input to develop/discuss different
re-ordering strategies. My personal belief is, that without any re-ordering
implementation in the UPF or UE the end-to-end delivery will be worse.



*From:* QUIC <[e-mail]> *On Behalf Of *Kazuho Oku
*Sent:* Dienstag, 1. Dezember 2020 11:29
*To:* [e-mail]
*Cc:* Magnus Westerlund <[e-mail]>; Liaison Statement
Management Tool <[e-mail]>; [e-mail];
[e-mail]; [e-mail]; Lucas Pardue <
[e-mail]>; Marten Seemann <[e-mail]>; Lars
Eggert <[e-mail]>; QUIC Discussion List <[e-mail]>; Martin Duke
<[e-mail]>
*Subject:* Re: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"



Lionel, thank you for converting the statement to PDF.



Reading the document, I have one question.



"The simultaneous transmission of a data flow across two accesses should
not result in out-of-order delivery"

I wonder what this sentence means. Is it suggesting that UPF (and possibly
UE) would buffer packets that arrive on the faster path until the packets
that were sent on the slower path reach that node? To give an example,
let's say that UE has sent three packets: packet 1 sent using WiFi, packet
2 using LTE, packet 3 using WiFi. UPF receives packets in the order of 1,
3, 2. Is UPF expected to postpone the forwarding of packet 3 until it
receives packet 2?

I raise the question, because during the interim, some have pointed out
that such buffering has negative effects on loss recovery, and that we
should devote our efforts to designing an end-to-end multi-path design,
rather than having an intermediary that aggregates paths (in this case UPF).





2020年12月1日(火) 18:43 <[e-mail]>:

Hi,



Here is a pdf version.



Regards,



Lionel



*De :* Marten Seemann [mailto:[e-mail]]
*Envoyé :* mardi 1 décembre 2020 05:17
*À :* Liaison Statement Management Tool <[e-mail]>
*Cc :* Lucas Pardue <[e-mail]>; Lars Eggert <
[e-mail]>; Magnus Westerlund <[e-mail]>;
MORAND Lionel TGI/OLN <[e-mail]>;
[e-mail]; [e-mail]; [e-mail]; QUIC
Discussion List <[e-mail]>; Martin Duke <[e-mail]>
*Objet :* Re: New Liaison Statement, "LS on ATSSS Phase 2 conclusions"



Would it be possible to publish this document in a format that can be
opened by everyone without using proprietary software?



Thank you,

Marten



On Mon, Nov 30, 2020 at 10:40 PM Liaison Statement Management Tool <
[e-mail]> wrote:

Title: LS on ATSSS Phase 2 conclusions
Submission Date: 2020-11-30
URL of the IETF Web page: https://datatracker.ietf.org/liaison/1710/

From: Susanna Kooistra <[e-mail]>
To: Lars Eggert <[e-mail]>,Lucas Pardue <[e-mail]>
Cc: QUIC Discussion List <[e-mail]>,Martin Duke <
[e-mail]>,Magnus Westerlund
<[e-mail]>,Lucas
Pardue <[e-mail]>,Lars Eggert <[e-mail]>,
[e-mail],[e-mail]
Response Contacts: [e-mail],[e-mail]
Technical Contacts:
Purpose: For information

Body:
Attachments:

    S2-2009400_8852r02

https://www.ietf.org/lib/dt/documents/LIAISON/liaison-2020-11-30-3gpp-tsgsa-sa2-quic-ls-on-atsss-phase-2-conclusions-attachment-1.doc



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