Minutes for HTTPBIS at interim-2014-httpbis-2
||Minutes for HTTPBIS at interim-2014-httpbis-2
# HTTPbis New York Interim Minutes
- [Thursday, 5 June 2014](#thursday-5-june-2014)
- [[Frame type
- [[Requiring Client Content-Coding
- [[Compress segments rather than
- [[Only restrict HTTP application data and header block fragment
- [[Need way to negotiate "no Huffman" in
- [[allow intervening DATA
- [[Changing the way that altsvc use is
- [[Flushing Alt-Svc
- [[Enabling redirects to other
- [[Intermediaries and
- [[Refine Prior
- [[Race condition in shutdown for
- [[Priority for closed
- [[Enable weight of
- [[Accounting for
- [[Privacy considerations for
- [[BLOCKED should be an
- [[ALTSVC as an
- [Friday, June 6](#friday-june-6)
- [[Make alt-svc an extension to the
- [Deployment, Adoption and Roadmap](#deployment-adoption-and-roadmap) -
[[Prioritisation as an
- [[HTTP URIs over
- [[restrict cipher suite
- [[Service header field to
- [[mandatory to implement cypher
- [[Remove frame-based
- [[Never indexed representation
- [Next Steps and Wrapup](#next-steps-and-wrapup) - [Operational
* Mark Nottingham - Chair
* Barry Leiba (Huawei)
* Hasan Khalil (Google)
* Will Chan (Google)
* Brian Raymor (Microsoft)
* Martin Thomson (Mozilla)
* Sanjay Mishra (Verizon)
* Daniel Stenberg (Mozilla)
* Patrick Mcmanus (Mozilla)
* Stephen Ludin (Akamai)
* Saurabh Kulkarni (Akamai)
* Mike Bishop (Microsoft)
* Tony Hansen (AT&T)
* Ilya Grigorik (Google)
* Peter Lepesky (Viasat)
* Julian Reschke (greenbytes)
* Salvatore Loreto (Ericsson)
* Jeff Pinner (Twitter)
* Gabriel Montenegro (Microsoft)
* Liliana Dinale (Ericsson)
* Emile Stephan (Orange)
* Richard Wheeldon (Cisco)
* Christoph Brunhuber (IAEA)
* Martin Nilsson (Opera)
* Herve Ruellan (Canon)
* William Chow (Mobolize)
* Daniel Sommermann (Facebook)
* Shigeki Ohtsu (IIJ)
* Dan Druta (AT&T)
## Thursday, 5 June 2014
Scribe: Dan Appelquist (DKA)
Blue sheets, scribe selection
Please review the http 2 FAQ (http://http2.github.io/faq/), and suggest updates
### [Frame type extensibility](https://github.com/http2/http2-spec/issues/95)
mnot: First issue, frame type extensibility. As an overview, a number of
people have said "maybe we should rethink extensibility" because it keeps
mnot: we shouldn't open up extensibility willy-nilly.
?: there is extensibility using [...]
mnot: this is about frame type extensibility - whether we want to add a new
Mike: the basic concern is if we want to add a new frame type, using the alpn
string,... what combination of things to support. We want to add a new frame
type and have understandable semantics if you see something you don't
recognize. my proposal  adds a tag, if you overflow the frame type space you
can get an expanded frame, martin's [proposal] says you only get 16 bits... I
think 16 bits is probably plenty
Tony Hansen: difference between utf8 and ucs for unicode... there is an
advantage to having an algorithm stating how to expand it if you need to
Mike: the pieces we have in common - some sort of end-to-end frame that most
... if it's state-changing you have to negotiate it first. The high level idea:
when you want to establish a connection you need to agree with the other party
that you want to do it otherwise only use what the other party can accept.
?: when thinking through - if you have hops that are not http2 then it gets
lost. If you have anything cached then it gets stripped out... put the work in
to put the extension frame in ...
Mike: [for example], blocked is a useful idea for an extension...
Jeff: but it's not end-to-end
Mike: they can't have semantics that you have to have to process the response.
You could throw in a hash of the content...
Jeff: where's your end to end frame layer state?
[some discussion on how this applies to streams]
WIlliam Chan: why are we bringing up extensions again compared to just using
[existing mechanims]? ALPN token
mike: new things keep coming up and I don't think that's gonna stop. As we use
that in the real world we'll keep finding "one more thing" we want to end.
William Chan: one thing that would be interesting: google has mentioned a few
times about other things we'd like to do, if we have extensibility we could do
[xyz]... we've been using existing mechanisms for SPDY experimentation.
Mike: trying to express what combination of extensions you support - you have
to advertise more and more ...
William: [question of whether these new features would require a new extensions
Patrick: the complexity is there whatever mechanism you use.. don't feel that
it makes the protocol more robust. We have a small set of state transitions
within the protocol as it is. And the notion of arbitrary extensions - I'm not
sure we're building anything of same robustness... I like [mike's] draft. I
think we already made the right decision though - let's figure out what we want
http2 to do and then when we want something different do that as 2.1, etc...
we're talking about this because we don't know what we want.
mnot: i'm conscious that people here are willing to put effort in. there are
lots of people who want http2 to be stable for a long period of time. I'm not
sure that adding this kind of extensibility lengthens the life of the protocol.
William: If the extensions are rich enough that you could do e.g. push as an
extension - that would be worth it. But [I can't see that kind of use case...]
Mike: why couldn't push be done?
[discussion on whether push could be implemented with the proposed extension
mike: we also noticed that compressed data introduces a new flag - alt svc
introduces a new frame.
Jeff: in spdy we do it as a header. [we should be considering] things that
cannot be done in the current http extensibility model. For these things that
are a negotiated change to the protocol - it's not transparent.
mnot: in reality to do anything interesting you have to write a new protocol -
so I think we'll end up with http3, http4 -
jeff: once you talk about negotiating extensions you don't have to put it in
mnot: "if we negotiate the setting then this frame type is not available"
Mike: we define that if you don't see a setting mentioned then it defaults to
jeff: where "off" means default behavior under http2.
mnot: the approach means you can negotiate any settings "for this hop".
jeff: the change that would be required - settings have to become "ignore if
you don't understand".
martin: [question of how settings are signaled...]
martin explains how this would work with the existing SETTINGS
jeff: you can either take the delay...
wheeldon: what's the alternative to alpn in the plaintext case?
jeff: upgrade h2 ...
Mike: you can still use setting for negotiation...
jeff: for true non-interpreting intermediaries, e.g. tunnels, they can't
inspect - we've said in the spec that if you see a setting you can't understand
then you fail the connection - [hence that would have to change in the spec]
Martin: I think opening extensibility for frame types and settings would allow
us to do the sorts of things we're talking about but nobody is screaming for an
end-to-end extensibility [mechanism].
William: who is interested in using this? what is the concrete case? would your
rather use alpn?
Jeff: all of our deployment experience has been over TLS so intermediaries
treat it like a tunnel. We don't have experience with true intermediaries.
Thats the only place where I think this might be useful - and we don't have
experience doing that. e.g. intermediary boxes that require a firmware upgrade
to handle new extensions...
mike: honestly that's a reason to get it into the spec. if you define a new
alpn token the intermediary won't speak it, but if we define an extension
mechanism then we can define that intermediaries "pass" extensions.
Patrick: does anyone have a plan for an extension that we're going to build and
test or is this just an escape valve?
Mike: i think there are some pieces of the spec that could be implemented as an
extension - e.g. blocked...
Patrick: we've all expressed interest in winding down. I don't want to
rearrange the whole spec. If we adopt it we need to be confident that it works
and we don't have any candidates.
Jeff: browser to server we need to have implementation experience.
mnot: there are many things in play - you can negotiate the settings and then
all bets are off - then there's the question of a "must ignore" for new frame
types which is a separate question I think.
mike: I'm hearing "no" on the extension frame type.
Martin: i'd be happy without one.
Jeff: what we have experience with is "drop what you don't understand."
mnot: negotiate changes in settings but ignore what you don't understand.
jeff: what that means is that you can rfc an extensibility model - an extension
extension to http2. you can have an rfc that is the extensibility mechanism.
[expands on this]
Mnot: only concern is the scenario - where everyone goes off and creates
extensions and there are collisions then it could get messy. If you are going
to start creating extensions then you need to coordinate.
[roberto comment on "what is http2" - please paste someone]
roberto_peon: Thx: 'hint'-style extensions should not need negotiation before
use (else they're not usable for an RT minimum), they should be ignored if not
understood, though a mechanism to say 'stop' should be there (which could be
the negotiation). roberto_peon: Extensions that change protocol semantics, of
course, must need the negotiation.
martin: frame types - I don't think we can change the size of these [8 bit] -
my proposal includes an IANA registry with a small experimental space. I am
updating the pull request.
mnot: in principle we agree that we want a limited extensibility mechanism
along these lines.
Martin: before we say that it's the mood in the room.. i want to make sure that
it's true - accepting extensibility is adding complexity. We want to make sure
we're getting a good bang for the buck.
mnot: we're not saying "this is how we're going to proceed" - it's small
changes to the document, not requing implementation changes...
jeff: does that mean we take out alt svc, ...
mnot: no, because we want to get this thing done.
jeff: if these things are not removable with this extension model...
patrick: I push pack a bit - it's a significant operational change. the way
that it could be used.. I'm suspicious that we're not buying enough for that
complexity. I like the current model.
mike: on that basis, we could say even informative extensions need to be
william: lots of these types of extensions we don't want to [wait for?]
mike: ... case were the client wants to send an informative frame on the first
mnot: i hesitate to bring it up but one factor that brings to mind - what is
the future going to look like. if people think it's likely we'll be working on
http3 then we could just say http2 doesn't have extensibility... we don't
need to have that conversation right now, but if we're going to have a new
version of the protocol in the not-to-distant future then maybe we don't need
the extensibility mechanism right now.
william: is there a value to having these extensension mechanism...
Stephen: the only argument I've heard agains the ALPN is the namespace issue...
Jeff: and the "firmware" [middlebox] issue.
mnot: that's if you believe we have a well layered...
[some discussion on streams]
mnot: what should we do now, jeff?
Jeff: i think if we think it's valuable to reconsider extensions in the spec
then we should consider doing it, writing it in such a way that it's
hop-by-hop, and not opening up that you can receive any frame type that you
mnot: more aligned with what mike proposed.
Martin: how does varying an identifier change...?
jeff: putting everything inside a frame ties it to a steam state.
martin: no matter where you put the identifier...
mike: I think if we're focusing on the hop-by-hop case, stream0 seems a logical
place... part of the goal is to "leave the door open" - the question is how
tightly to shut the door on extensions.
jeff: hardware [e.g. load balancers] are going to need to do this - if I can
interpret it at stream0 then I'm writing the proxy in software and the idea of
why extensibility is useful (in my mind) goes away. if we think: "http2 is
going to be widely deployed - there will be middle boxes" ...
mnot: more concerning case is middle boxes that are out of control of either
sender or receiver. We're flapping wildly back and forth... we've gone back and
forth on this. maybe we made the right decision in zurick [to not do an
extensibility mechanism]. we can't do this and stick to our timelines.
martin: (conversely) we've got people coming to us and saying "you did it
wrong." this is an answer to them.
jeff: it could be saying "here's your extensibility mechanism". Lots of mailing
list traffic on whether we did it wrong.
Barry Leiba: http1 succeeded because it was simple.
mnot: this is going to blow out the schedule.
DKA: concern whether an extensibility mechanism will appease the people
criticizing the process here. and the schedule is important.
Martin: we have people pushing hard on this and Id like to say "fine -
understand your concerns - write an extension."
? what is the guidance of whether something should be which kind of extensions
mnot: the answer has been to use ALPN.
mnot: pushing back - if we get through our issues list today and tomorrow then
we can go to working group last call. if we do extensibility then we will blow
the schedule out.
Johnny G: is there value to saying how you can use ALPN tokens...
mike: it's combinatorial explosion ...
mnot: I'm more interest in getting good itnerop of one ALPN token right now.
jeff: when you talk about
Daniel S: couldn't the extension model be a proving ground for next generation
mike: I think there could come a time where "these 5 extensions are widely
deployed - http2.1 means http2 + these extensions]
Barry L: I like the idea that you can prototype extensions with alpn tokens.
As AD when you do the write up you need a good paragraph on this discussion...
mnot: where do we sit? I hear people saying "use ALPN tokens" and "we need more
extensibility." Options are : leave it as alpn tokens [post-zurich] or we need
to have a serious conversation about extensibility. Not something we can do in
the next couple days.
mike: for me, we've had the zurich discussion and the whole time after that
we've heard "maybe we didn't make the right decision."
mnot: the reality is we have to ship it.
Roberto: so... what I would love to see would be that h2 allows ignorable frame
types that can't change protocol semantics and any extensions that does more
than that be ... [h2e for example]. that gives us both worlds.
mnot: we would define h2e?
[now or later?]
Roberto: yes and later.
mnot: if I understand it - it would be that the only change would be to ignore
frame types that you don't understand.
Mike: should we make it frame types and settings?
jeff: i would say no because we have implementation experience in the former
but not the latter.
Daniel S: ignoring frames seems
Patrick: but then these are the scenarios - the other end has a bug - this adds
significant complexity. any time there's a mismatch...
mnot: take a moment - how important do people think this is in relation to
time. Are we willing to blow out the schedule to get extensibility right?
martin: the answer is obviously no because getting extensibility right is
martin: there's a whole rfc on this topic...
?: I like the approach of having the lenient h2 ...
martin: that's what roberto is saying...
jeff: h2e would be defined as h2 + extensions...
mnot: but roberto's approach wouldn't make patrick happy...
?: I would propose a stricter one - h2 and h2e where you could send unknown
settings and frames...
DKA: You don't know if the extensibility mechanism you've defined is the right
patrick: the only extensions I'm aware of web sockets should have gone into
the protocol itself... and other extensions have not materialized.
patrick: the world is not beating down the door for extensions to web sockets.
gabriel: my observation - we were presumptuous in zurich about not needed
extensibility. we could realize we were too presumptuous. this proposal for
laying the ground work - from the pov of schedule - we could make the decision
that if one more frame is to be defined then we say "no." ship http base, and
jeff: I think everything that has come up is something we don't want anyway.
Martin: I think we made about 20 different extensions - purely between the
client and the proxy - since we have the client and the server - perfectly good
to just do it but we'd prefer middle boxes to work with it...
jeff: we have a pseudo metadata model - for control channels - that's all
within the framing layer. anything like that - parental control - doesn't fit
in the extension model anyway. We're talking about non-semantic signaling.
jeff: for frame layer extensibility whether it's metadata in headers ... we're
defining the multiplexing and connection coalescing capabilities of the client.
Saying that your
martin: i changed my mind - i agree with mark. if we continue to discuss in
this fashion then we're not getting anywhere.
mnot: my position is informed by my experience of [how long it takes] to
martin: let's leave as is / or take a proposal
martin: i've put in a pull request.
mike: i support.
mnot: one implicit proposal : the status quo; martin's proposal;
roberto: proposal allow unknown frametypes on h2. semantic extensions on h2-e,
? : only difference I would suggest is "an endpoint may send a settings of 'i
know there is a extension type of this id, please don't send it to me."
Mike: that was in my first draft but I pulled it out.
[discussion of whether you need this]
? : wI will say that google's servers would be more inclined to [support what
the spec says]
mnot: let's assume that some of this strict mode would be part of martin's
? : you would send a settings strictmode=true
martin: and once you get an ack you would be fully entitled to send protocol
william: what to clients do -
mike: semantics of strict mode would be : don't send me any frame that I
haven't asked for.
mnot: this smells like a committee compromise.
mnot: so we have status quo; martin's proposal; any other proposals?
mnot: what people prefer of those two proposals? And what people can't live
with either of those two proposals?
jeff: [anecode] when we did spdy we had to add a settings identifier that was
not in the spec... spdy at the time had nothing about settings you don't
understand. after more implementation experiences [we realized] we needed a
mnot: that's good input - we need to see wether we need a [didin't hear]
mike: we intentionally do ignore unknown frame types - so at least 2
implementions have done this.
patrick: you're not dropping unknown frames...
[dropping known frames vs. known frames vs. unknown frames]
[the inevitable hum-vote]
recorded : no hums for "can't live with status quo" or "can't live with
recorded : more hums in favor of martin's proposal than "status quo."
recorded : many "can't live with" Roberto's proposal.
mnot: what do people think about that
[discussion of a change to martin's proposal and whether it's worth pursuing]
mnot: it's a settings you send that say "I don't want extensions"
mnot: I worry about the complexity it adds.
jeff: I don't think it's going to be complex... lots of things will get dropped.
[more discussion on this point]
william: [in favor of strict mode]
mnot: if we specify the strict mode which implementers will turn it on by
[Yes from 3 implementers...]
mnot: does strict mode apply only to frame types or also to settings?
[consensus only frame types]
roberto: there are a couple of variations that are interesting - browsers can
switch into strict mode after on RT. Whole idea is to try new stuff. So 99% of
time you can be in strict mode.
[some further debtate]
mnot: if we don't put strict mode in will you [object]
patrick: I think solving complexity with complexity is the wrong engineering
path. from a committee point of view I think it's the wrong design decision...
I think the status quo is the right thing. I think if we have extensibility we
will have an extensibility committee which is not in the long term interest of
the protocol. That way lies madness. I think the history of the extensibility
mechanism of higher layer protocols hasn't been successful. [In this context] i
think it's a useful attribute, but if everything's going to have it on then why
martin: strict mode could be an interesting extension.
william: only way this will work is from the beginning we have some extensions.
if it's not in use from the beginning then people won't implement it.
patrick: you want people to prove it out... you're gonna have interop problems.
we will not have made the protocol stronger.
mnot: my experience has been that when you have extensibility it becomes a
vehicle for vendors to exert power over interop. doesn't foster interop and
jeff: what extensions are available in tcp? how many of these are used?
mnot: but the implementer community is different?
[discussion on tcp extensions and how useful these have been]
william: if we have extensions we get some early ones in and unless we have big
implementers that are randomizing extensions then that's the only way we can
keep it clean...
jeff: that goes back to taking some things like blocked out of the spec and
turning them into extensions...
william: we can take some frames and move them out to extensions but unless we
do the randomized extensions - let's say chrome - and then we have a name
collision in the future ...
mnot: personally I agree with [patrick] on staying with status quo.
jeff: in http2 because of the interop problems we've seen we should be strict
front he start.
mnot: you stated you only want to implement across TLS -
jeff: my concern is with load balancers, firmware, etc...
mnot: but martin's proposal would satisfy this...
mnot: does anyone think we need the negotiation mechanism for strict mode?
martin: I don't think we want it.
mnot: an alternative would be : you sent too many extensions.
jeff: it makes it so that later specs can still be compliant to h2.
mnot: anybody still want to stand up for doing strict mode.
mnot: let's re-do the hums.
[slightly more hums for "can't live with martin's proposal" and slightly more
humming for "status quo". Still no hums for can't live with status quo.]
[discussion of whether people who prefer extension mechanism really can still
live with status quo]
martin: who is going to have significant pain...?
mnot: we do have a mechanism now, the alpn token...
patrick: we can implement [the extension mechanism] but I still think it's the
wrong decision and I think it's going to [blow] the schedule.
martin: that's why I suggested the coin toss?
mnot: it's more important to make a decision.
[a coin toss]
[The coin toss results in martin's proposal]
mnot: we're going to follow martin's proposal with a few tweaks, without strict
mode. Anything else to talk about with extensibility?
Jeff: what about alt svc - ?
mnot: this is my concern - that people will use extensibility to [take things
out] that they don't agree with.
martin: i think it's worth bringing up because there wasn't strong consenus on
adopting these [alt svc, blocked, per-frame compression].. we now have the
escape hatch [extensions].
mnot: per-frame compression is optional.
mike: in my draft in an appendix I define a compressed data frame.
mnot: a lot of people didn't want it because they didn't want to use it.
mnot: there are a wide variety of use cases...
jeff: padding... could be put into the extension framework... the
[discussion now on given that we will have martin's proposed extension
mechanism, what if anything needs to be brought front he core spec to become an
martin: feedback that I've had is that what we have is unfortunately necessary.
mnot: moving on, incorporating martin's proposal without strict mode. and that
will close that issue.
mnot: if showstoppers come along we can introduce new settings or error codes
william: we will have defacto standards emerge...
patrick: we already have that and it's not good...
mnot: records resolution on github issue.
mnot: let's talk about websockets. Suggest we close this issue since it could
be done with extensibility.- a new ALPN token.
Brian: where does that leave n-segment?
mnot: web sockets was one use case but not only one...
mnot: we have an editorial issue - we need more explanation...
mnot [ closes issue]
### [Requiring Client Content-Coding
mnot: implicit gzip content-encoding makes it difficult to be a semantically
interoperable HTTP/1.X<=>HTTP/2 gateway...
mnot: implicit gzip may work well for the common browsing case, but is
difficult for other cases like PUT
martin: elephant in room - intermediation. often there aren't intermediaries if
you are using TLS
mnot: virus scanners are the big concern
mike bishop: wininet has issues being a HTTP/1.X<=>HTTP/2 intermediary
from an application perspective. e.g. content-length
mnot: etags are the bigger concern
mnot: people who want implicit gzip are the same people who want TLS
roberto: http2=>http/1.x say use a accept-encoding: http2-encoding
martin.nilsson: does it get bad if we don't have implicit a-e?
jeff: yes, relying on clients supporting gzip is good
jeff also had an alternate proposal that I missed that would remove this as a
patrick is arguing in favor of status quo, talking about browsers wanting this
for performance reasons. talking about intermediaries.
mnot points out that there's a tradeoff between performance and better interop
patrick points out that the existing deployment experience hasn't revealed this
to be an issue.
julian: what problem does this solve?
lots of discussion about the existing problems with accept-encoding: gzip
getting stripped by intermediaries on the web
jeff: we already have the reverse problem with clients advertising gzip support
but not actually supporting it
discussions about what the httpbis spec says about how to enable/disable gzip
will: (1) compression is very important for big webperf (2) this is a great
hammer to get this webperf improvement for a large majority of the web
lots of people object to using *this* hammer, and question the tradeoff between
webperf and interop
lots of discussion about the nature of these client side intermediaries,
whether they're big virus scanner vendors, or there are a lot of less savory
lots of discussion about UA-detection type of work on the server-side to
compress responses regardless of what the client says
jeff raises the possibility of using the power of big implementations to kill
connections where gzip is not supported in order to prevent intermediaries from
mucking with this
mnot is writing up the consensus decision to remove implicit gzip from the spec.
will doublechecks that we have consensus on the solution, are content-providers
going to actually do this?
roberto: we need a new error code or new http semantics to force downgrade to
will keeps arguing about making sure we don't resolve the issue too soon
without having a reasonable option to preserve the performance improvement
end resolution was to remove implicit gzip and google folks are supposed to put
up a proposal for coming up with a ratchet / hard fail solution to move first
to lock in support for compression, so any intermediary that tries to break it
afterward will cause a hard fail.
### [Compress segments rather than
mnot/martin restated Roberto's comments that we don't want to compress by
segments because it has higher state requirements
topic: issue 480 headers and flow control
Roberto is reassessing the problem, basically that headers are unbounded (not
flow controlled), which is problematic for implementations.
mnot: is a solution to just add a new error code "you're sending too many
roberto: yes, this is a solution, but there are many other solutions
mnot: what's your pref?
roberto: have a limit on the total number of headers you're allowed to have
outstanding at any point
will: are you saying you want flow control for headers?
roberto: no...it'd be nice to separate out a SYN frame
will: so you want to rollback to SPDY? :P
roberto: when you are flow controlling that updates compression state, it can
lead to deadlock.
roberto mentioned some solution and got booed
roberto: you know how a non-malicious client triggers this in practice? imagine
an rpc protocol.
rwheeldo: more examples...e.g. stock ticker updater
will: imagining the client bug reports and creation of de facto standards
because of implementation specific thresholds for sending out such a header
jeff and roberto discuss the possibility for deadlock when you have flow
controlled headers. jeff points out an example of a 32KB cookie when the flow
control window is 16KB, except that you can't fragment headers like we can do
with DATA frames.
roberto discusses his idea of creation of a new METADATA frame that is flow
controlled and doesn't change connection state.
johnny/jeff/roberto discuss further. you have to crack open the METADATA and
make sure the hpack opcodes don't update state, or else you do not apply the
opcode and you send an error for that stream.
mike.bishop: isn't this just a DATA frame?
roberto: yes, except it's a different opcode
roberto: we have to fix this
will: why? we've lived with it for this long.
roberto: that's because no one has tried to abuse this yet.
mnot: i'm not sure we're convinced that it's important to fix
will: what other vendors feel like this is important
roberto: i know f5 cares about this
stephen: we just terminate the connection
roberto: we have more non-web clients
mnot: would a new frame type that carries headers that are not compressed help?
roberto: that's even more than what i proposed, but yes, that would be fine
jeff: because you can segment that
mnot: and thus it won't update state
stephen: isn't the way this works that best practices emerge, and if you go out
those bounds, then your performance just sucks?
mnot: but then roberto's claim is that some people will really want to do these
stephen: the way this works is someone debugs this use case, identifies the
performance issue is because you're sending 7000 headers, and you work around
will: but maybe we should just accommodate this use case rather than have them
have to work around this, like we do domain sharding to work around http/1.x.
we are fixing those workarounds in http2.
more discussions, then around having a solution that traverses proxies
rwheeldo: clients that send a high volume of headers...i think that decent
compression will take care of most of the pain of that. stupidly large headers
fall into 3 camps: (1) huge stupid cookies and that's out of scope of this WG,
(2) stupid large custom headers, (3) user-agents
mike.bishop: also kerberos tickets
jeff: i see encoding viewport state in protobufs and send them across as headers
hasan: i'm fine with these people having broken shit
roberto: i'll point out hasan that if you say that in the context of the gfe at
google, that will cause you problems, since we see this problem, especially
with number and size of cookies
hasan: we've been able to crack down on these people abusing cookies
roberto: tell that to the next acquisition that wants to go behind a gfe
martin: we do allow arbitrary header blocks...do we still want to allow those
based on this discussion?
mnot: pull request 482 "Advice on dealing with large header blocks"
roberto: i wouldn't mind a bigger change here to be honest. i wouldn't mind if
hpack only worked on the initial headers frame.
jeff: one way to handle this is to say that streams are created with the colon
headers only, although i know this won't work for all intermediaries like gfe
which may rely on other attributes for routing, and then subsequently headers
get sent later.
martin: i considered this but this is a little tricky because it's not clear
what headers are necessary for routing.
mike.bishop: this would really mess with the reference set
jeff: we could have different hpack frames, one for initial headers, one for
brian: i have a question about this pull request.
roberto: there is a way that we can make hpack streamable.
jeff: if we start going down this route...
will cuts him off: maybe we should revisit whether or not we want to go down
jeff: is flow control of headers a big enough issue that we're willing to
absorb a non-trivial rewrite
roberto: well, it depends on what you mean by a large rewrite
will: it seems like we're talking about a theoretically valid use case that we
have no data or implementation experience about.
jeff: i could see how this could become a potentially valid use case
mnot: sounds like there's not much interest in this
roberto: so, error code?
jeff: we should keep track of the things we want to revisit for in http/3, and
this is the only one that i see that could drive a big architectural change.
### [Only restrict HTTP application data and header block fragment
mnot: jeff, can we short circuit this? can we close?
jeff: i'd like to discuss this edge case to see if we can get rid of this,
especially if we have padding bit flags.
jeff would prefer to remove the padding flags and use a separate padding frame
jeff: the entire reason we use padding flags is so that padding is flow
jeff: i don't see any clients sending this
will: that's because a user agent doesn't have knowledge to send it. it's
primarily application specific, therefore server=>client. at least until the
web platform exposes a way for web apps to control request padding.
### [Need way to negotiate "no Huffman" in
mnot: this was filed by michael sweet
martin: there are issues with huffman: (1) complicated to implement (2) vague
concerns around maybe having security concerns that are enabled by huffman
martin: i don't really buy this concerns. and if we screwed up, then we rev the
jeff: if you want to play with the big boys, find yourself a huffman library.
close with prejudice. i think there will be plenty of huffman libraries.
mike.bishop: we've had some discussions around whether or not we'd like to be
able to turn huffman off. i think we have mild preference for being able to,
but we won't fight hard. on a link where we're not bandwidth constrained, but
rather CPU constrained, it'd be nice to disable huffman to save on CPU.
martin: at that point, huffman isn't your biggest concern.
###[allow intervening DATA
mike.bishop: the problem here is you have to hold onto the uncompressed data
while getting the interleaving frames
roberto: the reason we disallowed interleaving frames was in order to easily
reason about error cases and buffering requirements.
martin: simplifies because you can treat a header block like a single frame
johnny: why is this a perf issue?
martin: HoL blocking
###[Changing the way that altsvc use is
mnot explains to willchan what/why: it's an analog to sni and other routing info
lots of discussion about the various motivations around this: loop detection,
load feedback, etc
will pushes back in order to figure out if this is really necessary, playing
stephen starts explaining how loop detection happens
stephen: this doesn't happen a ton, maybe a 1% case that we load balance you to
somewhere else, and then another that we load balance you back.
Talking about Service header field
long discussion about looping, need for the header field
Gabriel: Can we use a hop counter?
Martin: Hops aren't tightly bound.
Martin N: Confirming that servers aren't expected to have differing behavior
based on which service.
Mark: No, not a use case.
Johnny: This is the host header for Alt-Svc
Mark taking action to dig up explanation of problem case and send to list.
Better description of use cases for Service header will help us decide how to
Don't have support to change mechanism header field to frame, just discussing
how to define header field.
resolution: mnot to write up better motivations, willchan leaning towards being
Martin: Does the Service header need to be a MUST? Possible privacy concerns
Mark: No objection to clients who might do this for privacy reasons, but
theres a performance trade-off. SHOULD, but with explanation why this is
### [Flushing Alt-Svc Cache](https://github.com/http2/http2-spec/issues/444)
Mark: Goes beyond suspicious entries, make this a recommendation for full
Mike Bishop: Make sure this stays as SHOULD; issue text sounds like moving to
### [Enabling redirects to other
Patrick: Frame on stream zero can already do this
Mark: Right, so why is the header different? Make it the same.
Johnny: If header supports everything the frame does, why do we need the frame?
Mark: Kind of nice to have from layer perspective, but not strongly opposed to
getting rid of the frame.
Patrick: Lets you do things as soon as a connection starts without waiting for
Mark: Yes, that's the killer feature.
Johnny: Is it a concern that this can be done over an unauthenticated
connection to begin with?
Mark: Frame doesn't require it either, just an implementation choice right now.
Will reraised Service header stuff. These are more bits to fingerprint. Should
this header be controlled by author content?
mnot/stephen: maybe a bit is good enough for loop detection
###[Intermediaries and Alt-Svc](https://github.com/http2/http2-spec/issues/462)
Martin: Proxies will anyway.
Mark: True, but at least we've documented that they shouldn't.
Richard: Is there even value in using this if youre proxied?
Mark: Yes. Upgrade to TLS. Note that Alt-Svc shouldn't be used to configure
Will: Proxy could append Alt-Svc to EVERY RESPONSE to get coalesced
connections and better perf for users.
Mark: Not willing to spend time on this -- if it raises discussion, will just
rip the whole statement out instead.
### [Refine Prior Knowledge](https://github.com/http2/http2-spec/issues/418)
Emile: Tied to discovery; browser could find prior knowledge via DNS.
Patrick: Interested, but not willing to block on it.
Mark: Interest from the DNS community on using DNS with HTTP/2; probably a BOF
on HTTP/2. In the interest of this community to engage and help level set in
Toronto, but not wanting to block the working group on this.
Richard: Does prior knowledge mean you can make a TLS connection without ALPN
if you already know?
Mark: No, not the intention.
Martin: Spec doesn't actually read that way; will fix.
### [Race condition in shutdown for
Daniel: If upstream connection closes while a request is in flight, the
connection will fail. Need a way to enable this to drain; DRAINING frame,
double GOAWAY, etc. No strong feelings which approach is best.
JPinner: Weve already implemented this, BTW.
Roberto: Adding to spec raises the odds that a client will do the right thing
on a subsequent GOAWAY.
General agreement in room that double GOAWAY is acceptable.
Gabriel: Is there mandatory language here?
Martin: No, one SHOULD. Just a requirement to handle the case.
### [Priority for closed
Martin: Implicit feature that reprioritizing high-in-tree node changes the
priority of everything underneath it. One way to do this is use the original
request as a placeholder for everything on a given tab/set. This is only
possible if a PRIORITY frame can be sent on a closed stream. Currently, only
on open or when possibly racing with a RST_STREAM. Text changes this to allow
PRIORITY frames at any time once the stream has been opened. Lots of changed
lines from reflow, but the change is simple.
Not trying to add new feature, just clarifying what was intended and omitted
from the commit.
Mike B.: Means retaining state for all streams as long as there are dependent
Martin: Servers can always prune, but should try to keep things that are near
the root if possible.
Roberto: Should be a max of two RTTs anyway.
Martin: Not wanting to offer too much advice here; implementers will discover
what works and what doesn't.
### [Enable weight of 0](https://github.com/http2/http2-spec/issues/436)
Herve: Weight of zero enables pausing; useful in several scenarios such as
Mike: If the goal is just to pause, why not use flow control?
JPinner: Don't need an RTT to restart; restarts as soon as other data has been
Tony: Why not just use 1 vs. 256, which is what is already specified there?
Herve: Many low-priority streams add up to a considerable share of the
Gabriel: Seems like were working around a case that flow control ought to
handle better; is there a shortcoming there?
Herve: Can be solved using flow control, yes, but lose the RTT.
Roberto: Would be equivalent if WINDOW_UPDATEs could be negative; have to wait
until it drains, which may be more than an RTT.
Mike, Martin, Jeff: Not really pausing. Really background.
Martin: Equivalent to "dependent on everything"
Jeff: Priorities were designed to be proxyable; proxies that pass a weight of
zero will probably stall any client that requests it.
Richard: If there are other ways to do this and you don't actually want it,
there are better ways.
Jeff: The right way to do this is make it dependent on the more important
Roberto: This is requiring a special case; not feeling comfortable.
Mark: Not hearing much support; talked about this a number of times, probably
not going to make it.
### [Accounting for Proxies](https://github.com/http2/http2-spec/issues/413)
Mark: Have we accounted for this in all our various updates?
Martin: Yes, we've added the text.
### [State Diagram](https://github.com/http2/http2-spec/issues/484)
Richard: Like a tube diagram, better to have something that can be followed
than something that's geographically accurate.
Gabriel: Weve encountered this before and chosen to take the diagram out.
Maybe we should do that if its causing issues.
Martin: In RFCs, figures are always illustrative, never normative.
Mark: Only Greg seems to be bothered? Does anyone share his concern, modulo
some corrections to the current diagram?
Jeff: Consider HEADERS+CONTINUATIONS a single frame for state-transition
Roberto: Current diagram is comprehensible.
Tony: add note about substates?
Jeff: Nothing to do with frames, just stream lifecycles. The substates have
to do with partially-received frames. PING doesn't show up either, because it
doesn't change the state of streams.
### [Privacy considerations for
Mark: Creating dynamic hostnames gives an unbounded amount of entropy for
tracking. Unless the client doesn't send the Service header.
Martin N.: Until IPv6, with a unique IP address as well as unique hostnames.
Mark: Need something about Alt-Svc -- adding this for now.
### [BLOCKED should be an
Jeff: BLOCKED would have been an extension had extensions been available, now
they are, so it should be.
Hasan: As long as there are still enough plans to implement, no objection.
Richard: Helps shorten the HTTP/2 spec, enables better flexibility.
Hasan: Not planning on revving in the future, but makes a good proof of
concept for extensions.
Patrick: Extensions will be less reliable, may want to keep if you care about
it getting through intermediaries.
Roberto: Lets take the path of least resistance -- which one is that?
Hasan, Patrick: Cant change freely anyway once its defined and implemented
Mark: If people are balanced, creating extra documents does have extra
Mike: Can put multiple extensions in one document; could scale.
Hasan: Good for proving out the extension model.
Martin N.: Also helps reduce the size of the spec.
BLOCKED is an extension. Mike to share source of current I-D with Hasan who
will submit BLOCKED as a new draft.
### [ALTSVC as an extension](https://github.com/http2/http2-spec/issues/499)
Roberto: If BLOCKED is an extension, ALTSVC should be too.
Patrick: Don't want to be in the situation where we cant use it because no one
Will et al.: Its already optional, we have all the vendors here, and it will
be basically the same.
Mark: Either way, Alt-Svc stands or falls on its own, and people who don't
implement need to be convinced by experience.
Jeff: And it unblocks the core spec.
Hasan: And it looks better to the people who are complaining about the
protocol being too complex -- marketing is important.
Daniel: Alt-Svc seems pretty core, not clear why you say its able to stand
Jeff: We have a widely deployed protocol with all these features that works
okay without Alt-Svc -- it helps, but its not required.
Hasan: Theres a dichotomy here: a spec-compliant client can ignore Alt-Svc,
but its core to the spec. We need to resolve that, and it will influence the
Mark: When its already optional and only about how the content is split into
different documents, its an editorial reason. Lets leave this to the editor.
Jeff: If its core to the protocol, why isn't Alt-Svc part of the core document
Julian: Theres a normative reference, so we cant move forward until Alt-Svc is
Decision: Leave to Martin. Martin wants more feedback before making a
decision. Martin has text, but no pull request yet.
## Friday, June 6
Mnot: Have left: security issues, other issue during meeting, next steps
### [Make alt-svc an extension to the
(continued from Thursday)
mnot's position is that whether it's an extension or not doesn't affect
adoption. Other folks had stronger objections
Patrick: This extension is a real mistake on many levels I chased a SPDY bug
where I got two replies for the same stream. This is an example of wishy-washy
error handling. It would need to be defined in the most broad term.
Patrick's objection is to extensions in general
Mnot: The decision yesterday was to allow extensibility
Roberto: I would feel more comfortable if we said what the frames we're going
to send it so we can start rejecting them as soon as possible.
Hasan: That's a discussion about the extension, not alt-svc
Roberto: People are uncomfortable with people handling this as an extension
when we're not sure
Patrick: I don't like extensions and don't like the idea of moving things out
into extension when we have experience from other protocols of this hurting
Mnot: What do we think the role of extensibility is. What is the purpose down
Jeff: The purpose of extensibility is to provide hints which are not part of
the core protocol. For example, blocked is a hint for performance
Patrick: Blocked may be a hint ...
Jeff: If you need in in the protocol to function properly then you can't ignore
mnot: Patrick is saying that extensibility is giving him increasing discomfort
Has anyone had a strengthening of feeling overnight?
What we've been talking about with these extensions aren't really extensions.
What we're doing is moving the protocol's non-verifiable behavior into
mnot: Our charter is to improve end-user experienced latency for the common
mnot: We're talking for a moment about extensibility and our approach to it
jeff: from environments with high-latency (mobile.twitter.com) we see large
latency reductions without the new prioritization scheme ... compression gets
you a lot because you can serve requests without large rtts
will: In the app case, the business logic is largely downloaded already
jeff: packet drops are where you get the large latency requests - crowded, long
mnot: The argument for prioritization is to move hueristics out of the browser
jeff: If you had to pick between prioritization and multiplexing and you chose
prioritization you'd realise you needed multiplexing
mnot: we're getting off track... Regarding extensibility I'm hearing more
discomfort from Patrick but no-one else.
roberto: Uncomfortable about putting certain parts of the spec into extensions:
mnot: This remains an editorial decision for Martin to handle. If we disagree.
Let's take all the extension ones and flip them to editorial ... OK. let's go
through them quickly
jeff: I have a number of implementors saying we're going to take the DAG
priorities and drop them on the floor. We're had months of interop and no
browsers are sending them.
mnot: Shipping twelve has happend but I'm not seeing much interop - complex
uses of hpack, etc.
Brian R: and push
### Deployment, Adoption and Roadmap
[ we diverted to a meta-discussion ]
mnot: We have a protocol and it's still being used experimentally. SPDY is
still out there and gaining traction. I'm worried it's getting entrenched.
People are unwilling to deploy this in production but are willing to deploy
SPDY/3.1. We'll be deploying something we don't have significant performance
experience. I'm happy with this only if we ship it real soon.
martin: there are a number of things we're doing here which are highly
speculative. to get experience, we either need to deploy a draft widely (which
is unlikely) or say "we're done"
roberto: I'm perfectly happy to kill old versions of SPDY, why don't we relabel
this spdy/5 and ship it
will: this would still be a branding issue. it wouldn't be seen as http2. If we
do release something for wide deployment having it called http/2 would be a
roberto: we've given people spec and said they're not going to change
mnot: we could make the next draft is a longer-lived one for experience only
hasan: with bug fixes only
mnot: if we ship it as h2, then it's the final protocol
jeff: it's slightly different with spdy because it's already been in live with
market pressure driving it more than a spec
will: one thing that can really hurt us is if hpack doesn't work well on the
server. if that's a performance issue, they'll pick spdy over http2
roberto: there's no reasonable implementation in which hpack will be slower
jeff: you're assuming reasonable implementations
roberto: i've run tests, written code...
jeff: where are they?
mnot: we need to figure out how to set this up so it encourages deployment
[ a bunch of discussion about people's different hpack implementations ]
jeff: we need fast, interoperable compression libs
roberto: I agree but that's not what's causing us to lack experience. It just
takes time to get changing drafts out there. The changes made between SPDY
release were smaller. My personal preference is ship the darn thing call it
"h2-near-final" or something
mike.bishop: how long are chrome's reviews.
will: our stable channel releases every size weeks. beta every four, dev every
week. to go from code to release is twelve weeks or longer
hasan: there is a canary which is the equivalent of firefox's nightly
mike.bishop: how long is it going to take to get it out to a wide enough
mnot: every month that we don't ship and spdy gains support it becomes harder
to argue that we have something better. i want browsers to eol spdy ... as long
as we're comfortable knowing that there are some things that aren't complete
then we should look at shipping quickly
patrick:I haven't seen anything that's going to give me more confidence
martin: extensions is the biggest change
jeff: there are still issues that we need to address
johnny: we want strong interop for the major pieces. we want to start rolling
it our by the end of the quarter including how we use the new priority scheme
on user's machines
jeff: we had good interop on the last release. most of the changes were around
hpack. since then we've added padding, changed, priority, ... It's in
production but it's a thing we don't know about. When we did spdy we turned it
on and off for six months before it was stable. If we ship it, it'll be months
of debugging and interop.
Roberto: interop is going to happen whether we ship it as draft or whatever
jeff: It hasn't based on previous draft
stephen: stamp it and ship it. we will learn a lot over the next couple of years
jeff: let's pull out stuff we can do as extension and get to something we can
mnot: patrick has said he's willing to push the button and ship. chome will
ship in canary. are other implementors willing to ship it as it is now?
jeff: as it is, many of the features won't be implemented. e.g. priority is a
hasan: yes, absolutely I can put it on some machine and see it perform. i can't
put it everywhere unless i can prove it won't bring down google
mnot: are we comfortable putting this out as h2 when we might not outperform
hasan / martin: no
mnot: we need an exit criteria
martin: I'd like a generous last call
jeff: if we go with something that's more complex ... people won't go with it
roberto: we need four-six months to see adoption but we don't need four-six
months from today because there haven't been big changes in -12; can do 4-6
months from previous implementation draft.
mnot: we're competing with spdy. third parties who are not participating in
this are shipping spdy
jeff: safari is shipping with spdy and it won't be updateable so we'll need to
rob trace: microsoft will be able to pull out spdy
mnot: there are also server implementations, nginx, jetty, ...
???: the question is whether their customer will update to non-SPDY versions
will: we're committed to the standards process and will EOL spdy.
hasan: the power is still in the browsers. os upgrades for safari are good
patrick: my advice to customer is to wait for http/2 because we'll yank spdy
but they're starting not to believe me
jeff: we won't be pulling support for spdy
hasan: that's different because some of your clients aren't negotiating spdy
jeff: so are some of yours
hasan: we'll be turning off npn as well
Roberto: If we don't make big changes we should see some big deployments in a
couple of months
mnot: I've heard statements from big implementers making commitments about
turning off spdy which makes me a little bit more comfortable. jeff is
unwilling to annoy customers but this commitment is important to get other
folks moving. we can turn our attention to : how do we ship the best protocol
in a reasonable about of time. that's the context for the rest of our discussion
brian: moving stuff out to extensions sounds good
### [Prioritisation as an
mnot: no discussion w.r.t. blocked, some discomfort with alt-svc, unclear with
jeff: some people say they won't implement prioritization
johnny: my biggest concern is if we make prioritzation as an extension, would
that mean we have not prioritization in http/2. .. I think we need one true
roberto: doing anything as an extension implies optionality
martin: we have something we've debated for 2 1/2 year. we debated because we
knew the simple scheme wasn't sufficient. we've had other proposals which
jeff: I want to see a spec out and minted within a reasonable amount of time.
???: are you saying to move to an extension and leave it?
jeff: no, if we have much better experience we can pull it back in.
Daniel Sommermann: how do we mux it through a proxy?
roberto: anything we have isn't proxyable. that isn't the world we're heading
into, especially with plain text impls as well.
martin: i'm uncomfortable with putting things to the side and optionality
jeff: you cannot verify that proxies are maintaining prioritization
roberto: the difference between priority and data is that things will proceed
without it but they may be slower. This scheme allows priorities to survive
proxies. a lot of the things this achieves aren't visible to the client,
they're just better for overall health of the system.
jeff: I'm looking to hear servers actually committing to implement it (not just
Stephen: akamai will do. i'm not convinced by roberto's argument but it makes
me curious enough to implement it to get experience. It's in fall before it'll
mnot: who prefers making this an extension?
jeff: I want interop
roberto: removing priorities as an extension? why? it needs to be implemented
mnot: I'm hearing from jeff that he want's to fall back to a simpler scheme
??? : if you make it an extension, someone can come back with another proposal
martin: If these are the discussions they lead to, I'm against extensions now.
let's mark it as at risk and acknowledge that it's less tested
mnot: then it will fail last call potentially
jeff: my concern with this is gc because you're holding onto state after things
are gone. If this fails, we can drop back to the spdy implementation which
isn't proxiable but has been subject to real experience. chrome has said
they'll turn it on
jeff: a fallback plan scheme is that dependency must be zero. weight is
priority which makes it a flat scheme
hasan: this is what gfe does now
jeff: am I the only idiot intending on making a tree with this?
hasan: if it's in the graph, gfe and chrome will make use of it
jeff: we can mark the implementation of trees as at risk
Mike: for that matter you can get away without changing the spec and making
this a best practice
jeff: but you can rip out the tree stuff from the spec
mnot: are people happy with this resolution: mark it at risk
ten minute break
### [Forbit/Permit Coalescing](https://github.com/http2/http2-spec/issues/490)
mnot: ekr, the interpretation of 6066 and whether this forbids coalescing? this
potentially gives us performance gains but other problems
ekr: I agree, rfc 6066 discourages this. the notion makes people queasy, sni or
mnot: imagine we're in a situation where the cert is valid for all host being
used. is there a security reason for the constraint?
ekr: this is 11 year old text. having mutually suspicious people over the same
tls connection has caused problems.
mnot: this is assuming that the boundary is at a per-origin level which is not
always true. the web origin model is there but in other parts the decision is
made per-resource, on cookies, CORS, ...
ekr: i think of CORS as extending the origin model rather than ignoring it
mnot: it sounds if we keep it we'd need a big section in the security
mike: if you make a request for a different host than in the sni you will get a
400 in iis - it's a should in the rfc, but IIS enforces it.
Mike: if we do permit coalescing, we need a way for the server to reject it.
mnot: we have alt-svc the arguments in favour: it's good for performance, it
makes transitioning from sharding easier. we need security consideration and we
need a mechanism for the server to say no
rsw: i'm concerned about information leaking due to identity reuse on tcp / tls
mnot: are we happy to leave this in?
mnot: we leave coalescing in, we have a new security section especially for
different authorities on the same connection and a way for servers to say no.
if we write this in the next can you get back to us by toronto, ekr?
ekr: yes, I believe so. If tls had a way to bootstrap new contexts, would this
Mike: we're not really in favour of coalescing on http. we think tls giving us
different contexts would help
mnot: I'm relucant to make the security decision in the spec because there are
cases where it's safe
Gabriel: the default should be don't
jeff: what if the cname is the same?
martin: text currently says host and port
mike bishop: should be host, port and sni name
mnot: there's a number of ways to determine this. is it ok to leave this to
mike bishop: is it worth having a way for the server to say upfront that
coalescing shouldn't be used? server settings or whatever.
will: in practice it's not going to make much difference; browsers will cache
after being rejected once
mnot: is it worth speccing that the connection is origin-specific as setting?
will / patrick: yes
jeffs: how's a host supposed to send this when it hasn't seen the host?
Mike: based on the sni
?? it's just saying it doesn't support coalescing at all
mnot: do we want this or not?
patrick: now i'm in favour of an extension
jeff: PLEASE write that down!
jeff: I have a question regarding extensions, should we have a 32-bit space for
martin: alt-svc has a status code which says "you made this request to the
mnot: don't use this connection to talk to this server
mike: we could use that status
mnot: are we ok with this resolution? needs some colaboration with tls wg
### [HTTP URIs over TLS](https://github.com/http2/http2-spec/issues/315)
mnot: next issue, http uris over tls. we talked about it a while ago and
punted. now we have some implementation experience. we need to specify how
http2 adresses pervasive monitoring. if we show http over tls this would
demonstrate something. we should adopt a document or spin up another to specify
how to do this separate from and non-blocking for http2. I'm sure people will
want it to be implemented for everything but we won't get consensus.
??? could this work for http/1? if so how?
mnot: you'd send back an alt-svc, the client wouldn't check the cert but use
mnot: we have a private draft. do we want to adopt it? another option is "no,
we want to do something else to address pervaisve monitoring" or "no, we don't
want to address it" and deal with the consequences.
???if our story on pervasive monitoring is to get https everywher, how do we
get from 30% to 100%?
mnot: our remit is that we have to have considered it and have a position
Mike: we encourage tls adoption by improving performance / behavior
Dan Appelquist: it's better to sit in the group than be implemented elsewhere
[reference STRINT workshop report:
https://www.w3.org/2014/strint/draft-iab-strint-report.html] [The STRINT report
was largely supportive of "opportunistic encryption" as a mitigation strategy
for pervasive monitoring.]
mnot: it's in scope for the wg. any good reason to not adopt this doc?
jeff: an argument is that the wg puts a bigger stamp of oe being the way to
deal with pm
martin n : if we do oe, proxies will start doing opportunistic decryption /
mnot: we have to have eenough evidence that we've discussed this and considered
jeff: I'm happy to take an item to sort this out after http/2 ships
mnot: what's mozilla's position if this doesn't get adopted?
patrick: doesn't really change much; still plan to experiment
dan applegate: so it's better to have the implementations tracked via this group
mnot: there's some concern i'm hearing about schedule. I'm mostly concerned
that when I get to iesg review that we've done enough
Barry: the job of a shepherd write up is to give a summary of the conversation.
i can't commit to what an ad may or may not say. the requirement is to have it
considered and no-one can say it wasn't. .. opportunistic security is the
current term. if you have a good idea of where you want to go, it can be a
proposed standard rather than experimental
jeff: we have no idea how easy this will be to downgrade or how effective it
Richard: one thing that was discussed was sending http over tls and another was
that you could ignore the cert check
lots of folks: that's what we're talking about
jeff: nothing stops clients ignore cert checks
S. Ludin: akamai will continue working with mozilla
mnot: what do people think about wg experimental?
Barry: are there objections? I hope if you take it forward it will solve a
mnot: doc will be adopted. people should have a look, raise issues, ...
martin: the feedback from the security area group was "hmm"
### [TLS Renegotiation](https://github.com/http2/http2-spec/issues/363)
martin: tls had an interim meeting 2/3 weeks ago. there was pretty strong
feeling that renegotiation would not be part of tls 1.3 http appears to be the
only protocol to use client auth mid-session. there is talk about how to do
re-keying. there's good reasons not to do renegotiation : there are assumptions
made which are invalidated but may not be updated in the application. it's led
to a long series of vulnerabilities, applications making bad choices. they are
interested in pursuing things on a longer timescale. complicating a security
protocol is something we need to be cautious off. despite the layering concerns
(http needs to make assertions about tls) they're inclined for us to solve it.
client auth is a less-used part of the protocol and people may be willing to
make compromises on, for example, performance. what we're looking for is a
transitional story that will get to something good without tls improvements.
I've written a draft which mozilla may implement. this is a new auth challenge.
you send a 401 response with a challenge that says you need a client cert and
the client is expected to go away and re-auth on a new connection.tls 1.3
includes features in which large parts of the handshake are encrypted so we
should be ok when we hand over the cert.
mnot: if i have a server i need to cope with the idea that most browsers won't
martin: if you're running http/1.1 over tls you can use the mechanism you use
today .. tls is hop-by-hop
mnot: in our doc we say "don't renegotiate"
martin: you should do this before sending the preface. the question is if we
have a good story for people who do want to do client cert and
renegotiation.... i've updated the draft i wrote that includes hints in the
handshake so the client can select the right certificate
mnot: what's the transitional story?
Mike: this is a good use-case for how can we push something to 1.1 ?
mnot: has anyone opened an issue for force-downgrade? ... #496 ... not
authoritive just means not this connection
Mike: 505 is almost right, not quite; "refuses to serve this request over the
major version that is used"
martin: what else is needed?
Mike: the server should "generate a representation" of what's acceptable; not
martin: how about header with an enumeration of acceptable versions? alpn
mnot: mike, martin and I to go away and come back with a proposal. would people
be ok with considering this?
jeff: Can it be 4XX? I can't send a 5. I don't think this is unique to my site.
we break the spec and return 405 for methods we don't understand because 5s
affect the failure statistics
mnot: in principle this sounds good (updates issue) ... back to issue 363.
knowing we'll eventually have something better do we have a resolution?
martin: I don't think there's any good solution in this space.
gabriel: Is negotiation a must not or should not?
mnot: must not?
martin: if it's not must not, some servers will do it, clients will need to
support it, ...
mnot: in which case, don't we need to protocol error?
martin: once you have a deployment of http/2 with renegotiation you'll have
inertia against updating the tls stack. we want them on 1.3. We don't want
folks to have incentives to stay on older tls
ekr: we want people doing the best thing and all doing the same thing
mnot: resolution. marking editor ready. 496 isn't and this is blocking
### [restrict cipher suite
martin: we got some wishy-washy advice on rc4. the trend is that tls 1.3 will
remove all modes other than the aead ones. those are in good shape which cannot
be said for the rest. rc4 is on its way out and we have the opportunity to
update the advice to aead only
Mike: what's the right forum for this? to discuss in the spec or point to
something from the tls wg? this is a good idea but not http specific
martin: the problem is reference to something that is blocking
ekr: I think is a good idea. http wg should make a statement about this. if i
was in uta i wouldn't say things which create a compatibility problem. i don't
think there's anything you're going to come up with won't match consensus.
mnot: should we take 494, the pull request?
Stephen: I hugely want this change to happen but it feels wrong that we're
doing it because it's the wrong layer but I won't fight it.
Mike: the other thing that makes me hesitant is lifetimes. tls cipher aging has
???: does this take new ciphers coming down the pipe? cha-cha, etc.
ekr: tls wg has no plan to publish best practices - that's uta
mnot: I'm not hearing concerns on procedural stuff. I don't think uta's
presence stops us from doing this.
martin: we need this text or something like it. It seems logical that if people
are using new software they should use new cipher suites
mnot: do we want the text as a white or black list?
martin: it'll have the same effect.
mnot: will all ciphers be aead till the end of time?
martin: the text should say if an acceptable cipher cannot be selected, then
http2 should not be done
ekr: the text is more or less fine
mnot: that was the last security issue.
### [Service header field to
Stephen Ludin: just a binary flag that this came from a redirect would be fine,
no need for entire Service header. this is good from privacy point of view
mnot: if 1.1 send as a header otherwise...
will: no, just be consistent
mnot: Service = 1 indicating an alt svc is being accessed; allow for
extensibility in the field. and change name to Alt-Svc-Used. Since it is 1 bit,
change to MUST as it is not as much a privacy concern.
Richard: we punted onproxy considerations yesterday, why add something for
browsers to add while not specifying what intermediaries do with it
Richard: no guarantee, not reliable
mnot: sure, it is a header which can be stripped. sure we have to separate
generation of it from consumption of it.
stephen: hope is browsers will have an incentive for perf gains
mnot: editor ready
### [simplify padding](https://github.com/http2/http2-spec/issues/505)
Jeff summarizing the issue. remove padding from header-frames and reduce
padding length to 1 byte. Padding at purely framing layer does not play well
with proxies at which point it may cause blocking and multiplexing/pri trouble.
and HPACK has security mechanism itself already. the draft recently
added.CONTINUATION. and remove PAD_HIGH only using PAD_LOW thus removing a
conditional case even if it is framing change. still allow padding on data but
flow controlled, tied to a stream so easier to proxy
mnot: still not defining a padding frame type, so easier to trip firewall rules
jeff: plenty of other dos so nothing new here
roberto: so only 1 pad bit? any larger padding use a pad frame
martin: or split the data frames
jeff: could have padding -only data frames
roberto: could be more complicated
jeff: already need to know the limit for frames large enough. and this removes
some conditional error checking.and no padding onheaders push promise and
roberto: not sure how I feel about that
hasan; agree that padding on headers while hpack has some mechanism seemed
weird to me. what is min pad on hpack?
jeff: 2 bytes now, used to be 1 byte
roberto: actually no ability to pad on hpack unless we change the spec a little
jeff: well you can insesrt dummy pad headers. but having lots of padding raises
the aforementioned issues with no flow control and multiplexing
roberto with a padding frame a bit could indicate flow controlled or not, etc
mnot: sounds like removing pad_high has some support. the other part of the
proposal requires more security review
jeff: the rest can be done inhpack, or use 0x80 which currently is not used to
roberto: conflation of layers, do not like it, but I am happy with padding
frame with a bit for flow control
jeff: agree that no need in continuation frames?
roberto: agree, also more cpu now due to more state changes.
mnot summarizing: remove pad_high, yes. as for continuation frames, seems ok.
pad_low might continue in push_promise and headers.
hasan: prefer pad frame. so add this to the conclusion
martin: not liking this issue any more
some discussion about padding usage nowadays...
Stephen: not even on our radar
martin: remove pad_high, no padding frame,
roberto: need to ask for security review as there may be timing attacks
hasan: sharing info from security guys. have seen between 0 and 255 bytes of
padding per response both http 1.1 and 2
jeff: implies pad_low is enough
hasan: yes, so agree on removing pad_high. padding remains in data, headers and
Saurabh: would prefer to leave it in continuation to reduce code churn
jeff: padding for headers is not proxyable
mnot: once you are muxing all bets are off
mike: intermediary must make its own decision
mnot: so they may pass through for header-bearing frames but should maintain
padding in data frames.
hasan: google sec guys are happy with the decision including no padding in
### [mandatory to implement cypher
martin: tls 1.3 will have an MTI cypher suite in Toronto or so
mnot: could we punt on this until the TLS guys know more?
martin: Andrei tells me that schannel might have trouble with a couple of items
mnot: wait till toronto
### [Remove frame-based
Jeff: not compatible as this puts a sync flush context
Mike: this was an approx. to transfer encoding but at the framing layer
Jeff: it tries to be so, but fails. but it could be an extension frame that is
Christian: issue is that there is no way to partially compress a response
mnot: nobody is going to implement this, so why do it? and now with
extensibility one could negotiate an extension to satisfy your use case.
actually, your point is an http general issue, not specific to http/2
mnot: no implementor interest, sec issues with proxying, potentially addressed
via extension, and long term with semantic changes in HTTP. for now remove this.
### [Never indexed representation
roberto: not "sensitive" vs "not sensitive" but about the provenance. but this
is not useful, too hard.
mnot: strong pushback, closed
### Next Steps and Wrapup
Mnot: how long to another rev?
martin: 1 week
mnot: hpack guys also please look over your doc to polish
mnot: and mark this as implementation draft, maybe more...
mnot: mark an impl draft as something really serious. e.g., -13 marked as
"h2-rc" and go to WG LC, mint it after some interop during 6 months and be
done. LC could be parallel to this.
hasan: like it.
Richard: implications are?
mnot: wire protocol would not change
patrick: then why not use the "h2" token?
mnot: we only get one change of using that token, so make sure we have some
interop before claiming it.
mnot: how long will it take to take -13/lc into wide deployment?
johnny for chrome: to show up in dev? about end of Q3, but not really stable dev
patrick: early October for stable
rob for MS: end of summer Q3. IIS: the challenge is getting real services, not
just test servers
daniel on Curl: shipping already
pinner on twitter: will not have on client until RFC, server: end of july
hasan: on GFE real world data by end of Q2
Stephen Ludin on Akamai: end of Q3
Hasan: mod_spdy for apache is off to apache, but are happy to help apache
foundation, but they have to own it. our guy who wrote mod_spdy is only 1/4 on
mnot: encourage wg members to allow and help with code and info
mnot: in 1 week I can make a decision about meeting or not in Toronto
mnot: see estimate of mid to late Q3 for both client and server. so real data
only till late oct or early November. so declare WG LC now on -13, sep 1 WG LC
ends, start IETF LC OCT1 telechat on Dec 4, resolve discusses in Jan, so RFC by
feb or so.
lots of discussion of how data will be collected, how soon, how shareable, what
parts of the spec
### Operational Advice
mnot: See draft-nottingham-http2-ops; we need to capture this, RFC is only one
will: wrote the spdy best practices wiki, seems like the good type of document,
martin: github pages are a good place
mnot: need contribution terms to be able to submit to ietf if need be
eventually. will seed the wiki.
will: just copy and paste from my doc
mnot: perhaps not meeting in Toronto, perhaps not meeting in Honolulu... but
there are proxy and other discussions which might cause meetings to happen,