Re: Is "Version Greasing" a new benfit or a new obstacle?

[Mikkel Fahnøe Jørgensen <[e-mail]>]

Any kind of game or low latency control system such as 5G avionics cannot
use TCP as fallback since the buffering would be a non-starter.

I would expect UDP to be more commonly supported both as games with their
own protocols, WebRTC, and QUIC all become more prominent.
Also, it would be helpful to understand where UDP is not supported. For
example, it might be that UDP is blocked on some corporate firewalls
because conferencing is only supported on the internal network, or via VPN.
In these cases QUIC would probably still work perfectly fine for the
intended use cases, assuming the VPN solution does not introduce buffering
in packet tunnelling.

Adding TCP as a fallback isn’t merely tunneling data. It requires a new
QUIC emulation interface and it typically requires a separate host with
separate TLS certificate management. TCP typically runs in kernel where
QUIC runs in userspace and pulling in a userspace TCP stack is also work.
And then of course the latency considerations. So many deployments would
happily sacrifice the 5% of users that are not running UDP as they done
before with users running IE6.


On 15 April 2019 at 13.15.09, Brian Trammell (IETF) ([e-mail])
wrote:



> On 15 Apr 2019, at 11:28, Mikkel Fahnøe Jørgensen <[e-mail]>
wrote:
>
> QUIC is not going to be used only for HTTP/3 and I don’t see how TCP
fallback will work for the general case.
>
> A lot of games, VR applications, streaming services etc. are going to
build semi-proprietary QUIC versions, or at least use QUIC with customised
application protocols where TCP fallback is simply pointless because it
doesn’t support the framing needed and if it were possible, why would adapt
an application layer protocol to work on TCP if you don’t have to - of
course you have to if it gets blocked - hence try to avoid that.

So you see the deployment strategy for these applications to be "zero
availability on non-UDP-accessible networks"? That seems bold to me unless
you're talking about QUIC being used as a replacement for
"application-provided transport layer over UDP", which is certainly a big
part of the market but not all of it.

You could always tunnel UDP over TCP of course, but from a transport layer
perspective (and a transport-visible wire image perspective), that's a TCP
fallback.

> I don’t have any numbers on transparency, but given the reach of voice
call applications, you can probably safely assume that UDP will be
supported through most networks.

When we looked at this, admittedly a few years ago, we saw UDP blocking on
par with the QUIC failure rates reported by Google in 2015 - O(3-6%) of
paths. That's one nine of availability pathwise, which is... not great.

> The problem again is if only some UDP is allowed through traffic
inspection or at least port numbering.
>
> It can be a good thing that a QUIC version is detectable if the
alternative is that anything unknown gets blocked. That is the big unknown.

As I said in my other message this morning, I don't think version
negotiation greasing is useful at this time because there is no reasonable
model of a wire-visible version difference where an on-path device might
want to let through one greased-version and not another greased-version,
because the wire-image profiles and semantic properties of those two
versions are by definition of greasing identical.

At this point, given connection-availability as the metric to optimize for,
it seems like reducing features that might be mistaken for
QUIC-distinguishers in the wire image would be useful, and version greasing
seems like one such feature.

> Will it help to be is opaque as possible, or not? Some of the scenarios I
posted earlier show that no matter what you do, something will get in the
way.

This all comes down to the threat model, and the model of incentives for
on-path devices.

I personally think the correct design target is to put trivial
QUIC-discriminability into the wire image, since there will be a lot of
pressure to distinguish QUIC from not-QUIC traffic regardless of what we
do, and if we don't put grippy bits in the wire image, the distinguishing
functions will grip on to the slippy bits, with difficult to predict
outcomes. I recognize I am in the minority (of people who speak up) on this
issue, though.

Cheers,

Brian

> On 15 April 2019 at 11.20.25, Brian Trammell ([e-mail]) wrote:
>
>> hi Mikkel,
>>
>> perhaps a bit late to this party, I'm not sure I understand the process
you envision by which the TCP fallback will go away.
>>
>> Once it's in, it'll get used in a high enough proportion of cases that
the availability risk of turning it off, balanced against the fact that it
already works (as it's pretty much mandatory for deploying in today's
95%-UDP-transparent Internet), will go away very slowly indeed.
>>
>> Cheers,
>>
>> Brian
>>
>> > On 11 Apr 2019, at 10:20, Mikkel Fahnøe Jørgensen <[e-mail]>
wrote:
>> >
>> > In a not so distant future, a fallback to TCP would not be a viable
alternative for a number of services. Think WebRTC.
>> > If QUIC and other encrypted protocols become dominant, just blocking
everything would literally block everything.
>> > Of course, http(s) as we know it, it will continue to live on, but
many mobile apps would not.
>> >
>> >
>> > On 11 April 2019 at 10.03.14, Mirja Kuehlewind (
[e-mail]) wrote:
>> >
>> >> Hi Mikkel,
>> >>
>> >> I guess it is much more likely that any of those actors would just
block QUIC all together (as there is actually a fallback to TCP).
>> >>
>> >> Mirja
>> >>
>> >>
>> >>
>> >> On 10.04.19, 21:57, "QUIC on behalf of Mikkel Fahnøe Jørgensen" <
[e-mail] on behalf of [e-mail]> wrote:
>> >>
>> >>
>> >> Let’s say China makes a deal with Google to allow their search engine
(a not entirely unreasonably proposition).
>> >> The Great Firewall of China (GFC) is reconfigured to accept traffic
from a specific IP range for QUIC protocol v1.
>> >>
>> >>
>> >>
>> >> Google later upgrades to v2. GFC is updated. Later, out of ignorance,
some other department within said company decides that its browsers should
all use forced version aliases as a rule. GFC breaks. (Assuming Googles
servers are not located within the demilitarised
>> >> zone and users use Chrome).
>> >>
>> >>
>> >> Alternative 1: Google up front decides to deploy forced version
aliasing. China rejects the deal because they do not want to support random
traffic through GFC.
>> >>
>> >>
>> >> Alternative 2: Google up front decides to deploy forced version
aliasing, and China does not reject the deal, out of ignorance. Later some
department in China GFC oversight realises the deal and forces Google to
remove forced version aliasing, or shut down
>> >> its service.
>> >>
>> >>
>> >> Alternative 3: Google up front decides to deploy forced version
aliasing and China says, of course, we trust everything from Googles IP
range.
>> >>
>> >>
>> >> Alternative 4: Google realises that forced version aliasing does not
work in the general case, and makes a special case for users within a
certain geographical area.
>> >>
>> >>
>> >> Disclaimer: I’m not affiliated with Google and this might not at all
be how things would work, but it does highlight some of the challenges.
>> >>
>> >>
>> >> Of course, to be fair, China is not the only government entity that
might have a vested interest. Let's take a fictional example of US a real
estate investor with heavy ties to the eastern european block who somehow
finds himself elected as president needing
>> >> to find leverage on trade negotiations without effectively hurting
personal finances. It turns out that blocking certain digital services from
said eastern european block is the perfect tool in the trade negotiations..
Advisers point out that those services
>> >> run heavily encrypted on the dark web with perpetual circulation of
IP ranges so, ignoring any legal concerns, it would not be practically
possible. Eventually someone figures out that these services all usually
are at the forefront of technology and currently
>> >> use QUIC v3.2 and no-one else has deployed that version yet, so it
would suffice to ask NSA to tap into the backbone and disrupt specific
packets. Of course, this ends up taking down the Bavarian local government
election process in Germany where they are
>> >> the first to use a new digital election system. Not that the is an
issue, since trade negotiations are also running hot in that area, so that
is just an accidental bonus.
>> >>
>> >>
>> >> Or an endless number of other developments over the next few decades
if the past few years is anything to go by.
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> On 10 April 2019 at 20.13.59, Gorry (erg) ([e-mail])
wrote:
>> >>
>> >> Thanks Mikkel, I do understand that various actors intentionally drop
- but are you saying these actors would specifically choose to block a new
version of QUIC ... I do not understand that assertion.
>> >>
>> >>
>> >> Gorry
>> >>
>> >> On 10 Apr 2019, at 18:25, Mikkel Fahnøe Jørgensen <[e-mail]>
wrote:
>> >>
>> >>
>> >>
>> >> China blocks as a rule.
>> >> Russia is running an experiment to block the rest of the internet.
>> >> USA blocks net neutrality.
>> >> EU blocks cookies.
>> >> GB blocks itself.
>> >>
>> >>
>> >> So blocking is not limited to what an operator considers best for
business.
>> >>
>> >>
>> >>
>> >> On 10 April 2019 at 18.59.15, Border, John ([e-mail])
wrote:
>> >>
>> >>
>> >> I understand why people want to come down on the side of preventing
ossification. But, things have changed. There are a lot of more negative
consequences now when people unnecessarily block things. I think operators
would put a lot of pressure on vendors to
>> >> not do it now and to fix it if they did "by accident". Of course, I
am only one operator. It would be nice to hear from others...
>> >>
>> >>
>> >>
>> >> John
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: QUIC <[e-mail]> On Behalf Of Roberto Peon
>> >> Sent: Wednesday, April 10, 2019 12:52 PM
>> >> To: G Fairhurst <[e-mail]>;
>> >> [e-mail]
>> >> Subject: Re: Is "Version Greasing" a new benfit or a new obstacle?
>> >>
>> >> WARNING: The sender of this email could not be validated and may not
match the person in the "From" field.
>> >>
>> >> CAUTION: 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.
>> >>
>> >>
>> >> You're kinda between a rock-and-a-hard-place either way:
>> >>
>> >> - We've seen how much fun ossification is in TCP and HTTP. If the
thing is observable, it will be ossified seems to be the lesson. A lot of
the reason why QUIC was started in the first place was because of the
inability to improve TCP due to this ossification.
>> >> - OTOH, there is the fear of unknown/unobservable which might cause
operators to block things, whether predictably or not.
>> >>
>> >> My opinion is that it is better to start with preventing
ossification, and then if that results in too large a percentage of
operators blocking things, to re-evaluate.
>> >>
>> >> My guesses:
>> >> IP+port tuples and traffic patterns are still observable (for better
and worse), which implies operators will still have significant tools for
managing traffic. I believe that these are acted on/matched (ML or not)
regardless of any other data presented. In
>> >> other words, I have a doubt that stating the version in an observable
way will prevent the use of such tools.
>> >>
>> >> Most problems I've seen associated with implementations rather than
protocol versions (though when the latter happens it is pretty severe).. If
you believe this assertion, then acting on protocol version is less
interesting than attempting to act based on implementation
>> >> fingerprints.
>> >> -=R
>> >>
>> >>
>> >> On 4/10/19, 1:48 AM, "QUIC on behalf of G Fairhurst" <
[e-mail] on behalf of
>> >> [e-mail]> wrote:
>> >>
>> >> Obscuring the version of a protocol seems like a major design design
>> >> decision for wider use cases. So, I'm trying to understand the
>> >> motivation for version greasing.
>> >>
>> >> (1) I know there were instances where some early versions of QUIC
were
>> >> blocked due to an uninitentional matching of the header. Is there
>> >> evidence of intentional attempts to block updates to protocols?
>> >>
>> >> (2) Thinking about operating a network that cares about user support
and
>> >> protection from unwanted traffic, I would expect that there would be
>> >> cases where traffic pattern anomolies are found and the appropriate
>> >> thing would be to try to determine if a new protocol had been
deployed
>> >> and monitor it, if not, then the next most obvious thing could be to
>> >> block all unexpected traffic, that seems like a decision to hide the
>> >> version could increase ossification for new versions in these cases..
>> >>
>> >> (3) Similarly, if a threat is known to impact only a specific (older)
>> >> version, it would seem to motivate a drop of that traffic that seeks
to
>> >> use that version, while still permitting other traffic. Forcing
version
>> >> detection to use pattern matching/ML will lead to less predictable
>> >> outcomes, or blocking based on address, etc.
>> >>
>> >> (4) This obfusticates the most basic piece of reporting information
used
>> >> for support. It hides the extent of deployment of the current
protocol
>> >> version and prevlance of old implementations.
>> >>
>> >> (5) On the support, if a problem only emerges when a particular
version
>> >> is used with a particular address, then this helps pinpoint the
issues.
>> >> Matching client versions to servers is much more of an issue if the
user
>> >> community uses a wide range of servers (less so, I expect for major
>> >> providers: google, facebook, etc, etc), but significant when there is
a
>> >> use of a diverse set of external sites and sites with their own load
>> >> balancers, etc and a need to manage interactions with L2 services.
>> >>
>> >> I am intersted in knowing if this is likely to benefit or be a new
obstacle?
>> >>
>> >> Gorry