Re: Adding ECN to Transport and Recovery
Kazuho Oku <kazuhooku@gmail.com> Fri, 08 June 2018 22:17 UTC
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References: <26584f2a-230b-c55e-db16-d32225c8ee4d@ericsson.com> <5a82e9ef-971f-6510-866c-9886e73796a9@ericsson.com> <20180608150833.GB13418@ubuntu-dmitri> <CAKcm_gM_OHgWcJ+ktAg9BCQx1rtHc9GFg2bZG40-NcO2MoVG9w@mail.gmail.com>
From: Kazuho Oku <kazuhooku@gmail.com>
Date: Sat, 09 Jun 2018 01:17:14 +0300
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Subject: Re: Adding ECN to Transport and Recovery
To: Ian Swett <ianswett=40google.com@dmarc.ietf.org>
Cc: Magnus Westerlund <magnus.westerlund@ericsson.com>, IETF QUIC WG <quic@ietf.org>
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2018-06-08 19:40 GMT+03:00 Ian Swett <ianswett=40google.com@dmarc.ietf.org>: > As Dmitri said, the num blocks is currently a varint, it's not a single byte > like it was in GQUIC, so stealing a bit from it is a bit awkward and would > not change the limit on the number of ack blocks from 256 to 128, and > instead it would decrease it from 2^62 to 2^61. > > Can you make the least significant bit of the ACK frame type indicate > whether the ECN section is present, such as by using the 0x0d and 0x0e code > points? This is basically equivalent to defining two types, admittedly, but > by making the least significant bit the indicator, one could write up the > text as a single frame if people prefer that. +1 to using different frame types. We do not want to introduce complexity for conserving the frame types. That was the conclusion of the extension discussion, wasn't it? I would prefer having different frame types, unless we find a very clean way of encoding ACK and ACK_ECN using a single frame type. Stealing bits from a varint encoding is a haphazard approach that comes with a complexity. Personally, I doubt if we will ever run out of frames types, considering how we have done so far with TLS ContentType and HTTP/2 frame type. And if we do run out, we have the luxury of renumbering unlike TCP or TLS, because QUIC encrypts the frame types. > > On Fri, Jun 8, 2018 at 11:08 AM Dmitri Tikhonov > <dtikhonov@litespeedtech.com> wrote: >> >> On Fri, Jun 08, 2018 at 04:51:36PM +0200, Magnus Westerlund wrote: >> > My understanding of the views at the interim was that eliminating the >> > additional ACK_ECN frame was desired. >> >> That is my understanding as well. >> >> > I will next update the pull request to use an updated ACK frame with a >> > signaling bit for the present or absence of the ECN counters. The plan >> > is to steal a bit in the ACK Block count and make that into a fixed >> > 7-bit field rather than a variable length encoding. Limiting an ACK >> > Frame to 128 ACK blocks. >> >> Even though I don't have strong feelings about this, I wonder if there >> is another way. The ACK frame (Section 7.15 of >> [draft-ietf-quic-transport-12]) is all varints. Changing a field to a >> fixed encoding would go against the "flavor of the frame," if one may >> say so. Perhaps we could keep the varint encoding and interpret the >> decoded value as an ORed block count with the ECN bit (the low bit)? >> >> Introducing an artifial limit to where there was none is a separate >> discussion. Perhaps 128 blocks is really enough for all practical >> purposes. And yet: at some point the block limit was removed as we >> went from gQUIC to IETF QUIC... >> >> - Dmitri. >> > -- Kazuho Oku
- Re: Adding ECN to Transport and Recovery Magnus Westerlund
- RE: Adding ECN to Transport and Recovery Lubashev, Igor
- Re: Adding ECN to Transport and Recovery Ian Swett
- Re: Adding ECN to Transport and Recovery Eggert, Lars
- RE: Adding ECN to Transport and Recovery Lubashev, Igor
- Re: Adding ECN to Transport and Recovery Magnus Westerlund
- Re: Adding ECN to Transport and Recovery Dmitri Tikhonov
- Re: Adding ECN to Transport and Recovery Magnus Westerlund
- Re: Adding ECN to Transport and Recovery Ian Swett
- Re: Adding ECN to Transport and Recovery Kazuho Oku
- Re: Adding ECN to Transport and Recovery Brian Trammell (IETF)
- Re: Adding ECN to Transport and Recovery Christian Huitema
- Re: Adding ECN to Transport and Recovery Christian Huitema
- Re: Adding ECN to Transport and Recovery Ian Swett
- Re: Adding ECN to Transport and Recovery Jana Iyengar
- RE: Adding ECN to Transport and Recovery Lubashev, Igor
- Re: Adding ECN to Transport and Recovery Magnus Westerlund
- Adding ECN to Transport and Recovery Magnus Westerlund