Category Archives: Network

Internet. Networking.

Firefox, Mozilla, Network, Security

quic wg interim Kista

The IETF QUIC working group had its fifth interim meeting the other day, this time in Kista, Sweden hosted by Ericsson. For me as a Stockholm resident, this was ridiculously convenient. Not entirely coincidentally, this was also the first quic interim I attended in person.

We were 30 something persons gathered in a room without windows, with another dozen or so participants joining from remote. This being a meeting in a series, most people already know each other from before so the atmosphere was relaxed and friendly. Lots of the participants have also been involved in other protocol developments and standards before. Many familiar faces.

Schedule

As QUIC is supposed to be done “soon”, the emphasis is now a lot to close issues, postpone some stuff to “QUICv2” and make sure to get decisions on outstanding question marks.

Kazuho did a quick run-through with some info from the interop days prior to the meeting.

After MT’s initial explanation of where we’re at for the upcoming draft-13, Ian took us a on a deep dive into the Stream 0 Design Team report. This is a pretty radical change of how the wire format of the quic protocol, and how the TLS is being handled.

The existing draft-12 approach…

Is suggested to instead become…

What’s perhaps the most interesting take away here is that the new format doesn’t use TLS records anymore – but simplifies a lot of other things. Not using TLS records but still doing TLS means that a QUIC implementation needs to get data from the TLS layer using APIs that existing TLS libraries don’t typically provide. PicoTLS, Minq, BoringSSL. NSS already have or will soon provide the necessary APIs. Slightly behind, OpenSSL should offer it in a nightly build soon but the impression is that it is still a bit away from an actual OpenSSL release.

EKR continued the theme. He talked about the quic handshake flow and among other things explained how 0-RTT and early data works. Taken from that context, I consider this slide (shown below) fairly funny because it makes it look far from simple to me. But it shows communication in different layers, and how the acks go, etc.

HTTP

Mike then presented the state of HTTP over quic. The frames are no longer that similar to the HTTP/2 versions. Work is done to ensure that the HTTP layer doesn’t need to refer or “grab” stream IDs from the transport layer.

There was a rather lengthy discussion around how to handle “placeholder streams” like the ones Firefox uses over HTTP/2 to create “anchors” on which to make dependencies but are never actually used over the wire. The nature of the quic transport makes those impractical and we talked about what alternatives there are that could still offer similar functionality.

The subject of priorities and dependencies and if the relative complexity of the h2 model should be replaced by something simpler came up (again) but was ultimately pushed aside.

QPACK

Alan presented the state of QPACK, the HTTP header compression algorithm for hq (HTTP over QUIC). It is not wire compatible with HPACK anymore and there have been some recent improvements and clarifications done.

Alan also did a great step-by-step walk-through how QPACK works with adding headers to the dynamic table and how it works with its indices etc. It was very clarifying I thought.

The discussion about the static table for the compression basically ended with us agreeing that we should just agree on a fairly small fixed table without a way to negotiate the table. Mark said he’d try to get some updated header data from some server deployments to get another data set than just the one from WPT (which is from a single browser).

Interop-testing of QPACK implementations can be done by encode  + shuffle + decode a HAR file and compare the results with the source data. Just do it – and talk to Alan!

And the first day was over. A fully packed day.

ECN

Magnus started off with some heavy stuff talking Explicit Congestion Notification in QUIC and it how it is intended to work and some remaining issues.

He also got into the subject of ACK frequency and how the current model isn’t ideal in every situation, causing to work like this image below (from Magnus’ slide set):

Interestingly, it turned out that several of the implementers already basically had implemented Magnus’ proposal of changing the max delay to min(RTT/4, 25 ms) independently of each other!

mvfst deployment

Subodh took us on a journey with some great insights from Facebook’s deployment of mvfast internally, their QUIC implementation. Getting some real-life feedback is useful and with over 100 billion requests/day, it seems they did give this a good run.

Since their usage and stack for this is a bit use case specific I’m not sure how relevant or universal their performance numbers are. They showed roughly the same CPU and memory use, with a 70% RPS rate compared to h2 over TLS 1.2.

He also entertained us with some “fun issues” from bugs and debugging sessions they’ve done and learned from. Awesome.

The story highlights the need for more tooling around QUIC to help developers and deployers.

Load balancers

Martin talked about load balancers and servers, and how they could or should communicate to work correctly with routing and connection IDs.

The room didn’t seem overly thrilled about this work and mostly offered other ways to achieve the same results.

Implicit Open

During the last session for the day and the entire meeting, was mt going through a few things that still needed discussion or closure. On stateless reset and the rather big bike shed issue: implicit open. The later being the question if opening a stream with ID N + 1 implicitly also opens the stream with ID N. I believe we ended with a slight preference to the implicit approach and this will be taken to the list for a consensus call.

Frame type extensibility

How should the QUIC protocol allow extensibility? The oldest still open issue in the project can be solved or satisfied in numerous different ways and the discussion waved back and forth for a while, debating various approaches merits and downsides until the group more or less agreed on a fairly simple and straight forward approach where the extensions will announce support for a feature which then may or may involve one or more new frame types (to be in a registry).

We proceeded to discuss other issues all until “closing time”, which was set to be 16:00 today. This was just two days of pushing forward but still it felt quite intense and my personal impression is that there were a lot of good progress made here that took the protocol a good step forward.

The facilities were lovely and Ericsson was a great host for us. The Thursday afternoon cakes were great! Thank you!

Coming up

There’s an IETF meeting in Montreal in July and there’s a planned next QUIC interim probably in New York in September.

cURL and libcurl, Network, Open Source

curl, http2 and quic on the Changelog

Three years ago I talked on a changelog episode about curl just having turned 17 years old and what it has meant for me etc.

Fast forward three years, 146 changelog episodes later and now curl has turned 20 years and I was again invited and joined the lovely hosts of the changelog podcast, Adam and Jerod.

Changelog episode 299

We talked curl of course but we also spent time talking about where HTTP/2 is and how QUIC is coming around and a little about why and how its UDP nature makes things a little different. If you’re into either curl or web transport, I hope you’ll find it interesting.

Network

Now at 1000 mbit

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A little over six years since I got the fiber connection installed to my house. Back then, on a direct question to my provider, they could only offer 100/100 mbit/sec so that’s what I went with. Using my Telia Öppen Fiber and Tyfon (subsequently bought by Bahnhof) as internet provider.

In the spring of 2017 I bumped the speed to 250/100 mbit/sec to see if I would notice and actually take advantage of the extra speed. Lo and behold, I actually feel and experience the difference – frequently. When I upgrade my Linux machines or download larger images over the Internet, I frequently do that at higher speeds than 10MB/sec now and thus my higher speed saves me time and offers improved convenience.

However, “Öppen Fiber” is a relatively expensive provider for little gain for me. The “openness” that allows me to switch between providers isn’t really something that gives much benefit once you’ve picked a provider you like, it’s then mostly a way for a middle man to get an extra cut. 250mbit/sec from Bahnhof cost me 459 SEK/month (55 USD) there.

Switching to Bahnhof to handle both the fiber and the Internet connection is a much better deal for me, price wise. I get an upgraded connection to a 1000/1000 mbit/sec for a lower monthly fee. I’ll now end up paying 399/month (48 USD)  (299 SEK/month the first 24 months). So slightly cheaper for much more speed!

My household typically consists of the following devices that are used for accessing the web regularly:

  • 4 smart phones
  • 1 iPad
  • 4 laptops
  • 3 desktop computers
  • 1 TV computer

Our family of 4 consumes around 120GB average weeks. Out of this, Youtube is the single biggest hogger with almost 30% of our total bandwidth. I suppose this says something about the habits of my kids…

Out of these 13 most frequently used devices in our local network only 5 are RJ45-connected, the rest are WiFi.

Switch-over

I was told the switch-over day was May 15th, and at 08:28 in the morning my existing connection went away. I took that as the start signal. I had already gotten a box from Bahnhof with the new media converter to use.

I went downstairs and started off my taking a photo of the existing installation…

So I unscrewed that old big thing from the wall and now my installation instead looks like

You can also see the Ethernet cable already jacked in.

Once connected, I got a link at once and then I spent another few minutes to try to “register” with my user name and password until I figured out that my router has 1.1.1.1 hardcoded as DNS server and once I cleared that, the login-thing worked as it should and I could tell Bahnhof that I’m a legitimate user and woof, my mosh session magically reconnected again etc.

All in all, I was offline for shorter than 30 minutes.

Speeds and round-trips

These days a short round-trip is all the rage and is often more important than high bandwidth when browsing the web. I’m apparently pretty close to the Stockholm hub for many major services and I was a bit curious how my new operator would compare.

To my amazement, it’s notably faster. google.com went from 2.3ms to 1.3ms ping time, 1.1.1.1 is at 1.3ms, facebook.com is 1.0ms away.  My own server is 1.2ms away and amusingly even if I’m this close to the main server hosting the curl web site, the fastly CDN still outperforms it so curl.haxx.se is an average 1.0ms from me.

So, the ping times were notably reduced. The bandwidth is truly at gigabit speeds in both directions according to bredbandskollen.se, which is probably the most suitable speed check site in Sweden.

A rather smooth change so far. Let’s hope it stays this way.

cURL and libcurl, Network, Open Source, Security

Play TLS 1.3 with curl

The IESG recently approved the TLS 1.3 draft-28 for proposed standard and we can expect the real RFC for this protocol version to appear soon (within a few months probably).

TLS 1.3 has been in development for quite some time by now, and a lot of TLS libraries already support it to some extent. At varying draft levels.

curl and libcurl has supported an explicit option to select TLS 1.3 since curl 7.52.0 (December 2016) and assuming you build curl to use a TLS library with support, you’ve been able to use TLS 1.3 with curl since at least then. The support has gradually been expanded to cover more and more libraries since then.

Today, curl and libcurl support speaking TLS 1.3 if you build it to use one of these fine TLS libraries of a recent enough version:

  • OpenSSL
  • BoringSSL
  • libressl
  • NSS
  • WolfSSL
  • Secure Transport (on iOS 11 or later, and macOS 10.13 or later)

GnuTLS seems to be well on their way too. TLS 1.3 support exists in the GnuTLS master branch on gitlab.

curl’s TLS 1.3-support makes it possible to select TLS 1.3 as preferred minimum version.

cURL and libcurl, Firefox, Network, Security

Inspect curl’s TLS traffic

Since a long time back, the venerable network analyzer tool Wireshark (screenshot above) has provided a way to decrypt and inspect TLS traffic when sent and received by Firefox and Chrome.

You do this by making the browser tell Wireshark the SSL secrets:

  1. set the environment variable named SSLKEYLOGFILE to a file name of your choice before you start the browser
  2. Setting the same file name path in the Master-secret field in Wireshark. Go to Preferences->Protocols->SSL and edit the path as shown in the screenshot below.

Having done this simple operation, you can now inspect your browser’s HTTPS traffic in Wireshark. Just super handy and awesome.

Just remember that if you record TLS traffic and want to save it for analyzing later, you need to also save the file with the secrets so that you can decrypt that traffic capture at a later time as well.

curl

Adding curl to the mix. curl can be built using a dozen different TLS libraries and not just a single one as the browsers do. It complicates matters a bit.

In the NSS library for example, which is the TLS library curl is typically built with on Redhat and Centos, handles the SSLKEYLOGFILE magic all by itself so by extension you have been able to do this trick with curl for a long time – as long as you use curl built with NSS. A pretty good argument to use that build really.

Since curl version 7.57.0 the SSLKEYLOGFILE feature can also be enabled when built with GnuTLS, BoringSSL or OpenSSL. In the latter two libs, the feature is powered by new APIs in those libraries and in GnuTLS the library’s own logic similar to how NSS does it. Since OpenSSL is the by far most popular TLS backend for curl, this feature is now brought to users more widely.

In curl 7.58.0 (due to ship on Janurary 24, 2018), this feature is built by default also for curl with OpenSSL and in 7.57.0 you need to define ENABLE_SSLKEYLOGFILE to enable it for OpenSSL and BoringSSL.

And what’s even cooler? This feature is at the same time also brought to every single application out there that is built against this or later versions of libcurl. In one single blow. now suddenly a whole world opens to make it easier for you to debug, diagnose and analyze your applications’ TLS traffic when powered by libcurl!

Like the description above for browsers, you

  1. set the environment variable SSLKEYLOGFILE to a file name to store the secrets in
  2. tell Wireshark to use that same file to find the TLS secrets (Preferences->Protocols->SSL), as the screenshot showed above
  3. run the libcurl-using application (such as curl) and Wireshark will be able to inspect TLS-based protocols just fine!

trace options

Of course, as a light weight alternative: you may opt to use the –trace or –trace-ascii options with the curl tool and be fully satisfied with that. Using those command line options, curl will log everything sent and received in the protocol layer without the TLS applied. With HTTPS you’ll see all the HTTP traffic for example.

Credits

Most of the curl work to enable this feature was done by Peter Wu and Ray Satiro.

cURL and libcurl, Network, Security

Say hi to curl 7.56.0

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Another curl version has been released into the world. curl 7.56.0 is available for download from the usual place. Here are some news I think are worthy to mention this time…

An FTP security issue

A mistake in the code that parses responses to the PWD command could make curl read beyond the end of a buffer, Max Dymond figured it out, and we’ve released a security advisory about it. Our 69th security vulnerability counted from the beginning and the 8th reported in 2017.

Multiple SSL backends

Since basically forever you’ve been able to build curl with a selected SSL backend to make it get a different feature set or behave slightly different – or use a different license or get a different footprint. curl supports eleven different TLS libraries!

Starting now, libcurl can be built to support more than one SSL backend! You specify all the SSL backends at build-time and then you can tell libcurl at run-time exactly which of the backends it should use.

The selection can only happen once per invocation so there’s no switching back and forth among them, but still. It also of course requires that you actually build curl with more than one TLS library, which you do by telling configure all the libs to use.

The first user of this feature that I’m aware of is git for windows that can select between using the schannel and OpenSSL backends.

curl_global_sslset() is the new libcurl call to do this with.

This feature was brought by Johannes Schindelin.

New MIME API

The currently provided API for creating multipart formposts, curl_formadd, has always been considered a bit quirky and complicated to work with. Its extensive use of varargs is to blame for a significant part of that.

Now, we finally introduce a replacement API to accomplish basically the same features but also with a few additional ones, using a new API that is supposed to be easier to use and easier to wrap for bindings etc.

Introducing the mime API: curl_mime_init, curl_mime_addpart, curl_mime_name and more. See the postit2.c and multi-post.c examples for some easy to grasp examples.

This work was done by Patrick Monnerat.

SSH compression

The SSH protocol allows clients and servers to negotiate to use of compression when communicating, and now curl can too. curl has the new –compressed-ssh option and libcurl has a new setopt called CURLOPT_SSH_COMPRESSION using the familiar style.

Feature worked on by Viktor Szakats.

SSLKEYLOGFILE

Peter Wu and Jay Satiro have worked on this feature that allows curl to store SSL session secrets in a file if this environment variable is set. This is normally the way you tell Chrome and Firefox to do this, and is extremely helpful when you want to wireshark and analyze a TLS stream.

This is still disabled by default due to its early days. Enable it by defining ENABLE_SSLKEYLOGFILE when building libcurl and set environment variable SSLKEYLOGFILE to a pathname that will receive the keys.

Numbers

This, the 169th curl release, contains 89 bug fixes done during the 51 days since the previous release.

47 contributors helped making this release, out of whom 18 are new.

254 commits were done since the previous release, by 26 authors.

The top-5 commit authors this release are:

  1. Daniel Stenberg (116)
  2. Johannes Schindelin (37)
  3. Patrick Monnerat (28)
  4. Jay Satiro (12)
  5. Dan Fandrich (10)

Thanks a lot everyone!

(picture from pixabay)

cURL and libcurl, Network, Web

“OPTIONS *” with curl

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(Note: this blog post as been updated as the command line option changed after first publication, based on comments to this very post!)

curl is arguably a “Swiss army knife” of HTTP fiddling. It is one of the available tools in the toolbox with a large set of available switches and options to allow us to tweak and modify our HTTP requests to really test, debug and torture our HTTP servers and services.

That’s the way we like it.

In curl 7.55.0 it will take yet another step into this territory when we finally introduce a way for users to send “OPTION *” and similar requests to servers. It has been requested occasionally by users over the years but now the waiting is over. (brought by this commit)

“OPTIONS *” is special and peculiar just because it is one of the few specified requests you can do to a HTTP server where the path part doesn’t start with a slash. Thus you cannot really end up with this based on a URL and as you know curl is pretty much all about URLs.

The OPTIONS method was introduced in HTTP 1.1 already back in RFC 2068, published in January 1997 (even before curl was born) and with curl you’ve always been able to send an OPTIONS request with the -X option, you just were never able to send that single asterisk instead of a path.

In curl 7.55.0 and later versions, you can remove the initial slash from the path part that ends up in the request by using –request-target. So to send an OPTION * to example.com for http and https URLs, you could do it like:

$ curl --request-target "*" -X OPTIONS http://example.com
$ curl --request-target "*" -X OPTIONS https://example.com/

In classical curl-style this also opens up the opportunity for you to issue completely illegal or otherwise nonsensical paths to your server to see what it does on them, to send totally weird options to OPTIONS and similar games:

$ curl --request-target "*never*" -X OPTIONS http://example.com

$ curl --request-target "allpasswords" http://example.com

Enjoy!

cURL and libcurl, Network

curling over HTTP proxy

Starting in curl 7.55.0 (this commit), curl will no longer try to ask HTTP proxies to perform non-HTTP transfers with GET, except for FTP. For all other protocols, curl now assumes you want to tunnel through the HTTP proxy when you use such a proxy and protocol combination.

Protocols and proxies

curl supports 23 different protocols right now, if we count the S-versions (the TLS based alternatives) as separate protocols.

curl also currently supports seven different proxy types that can be set independently of the protocol.

One type of proxy that curl supports is a so called “HTTP proxy”. The official HTTP standard includes a defined way how to speak to such a proxy and ask it to perform the request on the behalf of the client. curl supports using that over either HTTP/1.1 or HTTP/1.0, where you’d typically only use the latter version if you the first really doesn’t work with your ancient proxy.

HTTP proxy

All that is fine and good. But HTTP proxies were really only defined to handle HTTP, and to some extent HTTPS. When doing plain HTTP transfers over a proxy, the client will send its request to the proxy like this:

GET http://curl.haxx.se/ HTTP/1.1
Host: curl.haxx.se
Accept: */*
User-Agent: curl/7.55.0

… but for HTTPS, which should provide end to end encryption, a client needs to ask the proxy to instead tunnel through the proxy so that it can do TLS all the way, without any middle man, to the server:

CONNECT curl.haxx.se:443 HTTP/1.1
Host: curl.haxx.se:443
User-Agent: curl/7.55.0

When successful, the proxy responds with a “200” which means that the proxy has established a TCP connection to the remote server the client asked it to connect to, and the client can then proceed and do the TLS handshake with that server. When the TLS handshake is completed, a regular GET request is then sent over that established and secure TLS “tunnel” to the server. A GET request that then looks like one that is sent without proxy:

GET / HTTP/1.1
Host: curl.haxx.se
User-Agent: curl/7.55.0
Accept: */*

FTP over HTTP proxy

Things get more complicated when trying to perform transfers over the HTTP proxy using schemes that aren’t HTTP. As already described above, HTTP proxies are basically designed only for doing HTTP over them, but as they have this concept of tunneling through to the remote server it doesn’t have to be limited to just HTTP.

Also, historically, for decades people have deployed HTTP proxies that recognize FTP URLs, and transparently handle them for the client so the client can almost believe it is HTTP while the proxy has to speak FTP to the remote server in the other end and convert it back to HTTP to the client. On such proxies (Squid and Apache both support this mode for example), this sort of request is possible:

GET ftp://ftp.funet.fi/ HTTP/1.1
Host: ftp.funet.fi
User-Agent: curl/7.55.0
Accept: */*

curl knows this and if you ask curl for FTP over an HTTP proxy, it will assume you have one of these proxies. It should be noted that this method of course limits what you can do FTP-wise and for example FTP upload is usually not working and if you ask curl to do FTP upload over and HTTP proxy it will do that with a HTTP PUT.

HTTP proxy tunnel

curl features an option (–proxytunnel) that lets the user forcible tell the client to not assume that the proxy speaks this protocol and instead use the CONNECT method with establishing a tunnel through the proxy to the remote server.

It should of course be noted that very few deployed HTTP proxies in the wild allow clients to CONNECT to whatever port they like. HTTP proxies tend to only allow connecting to port 443 as that is the official HTTPS port, and if you ask for another port it will respond back with a 4xx response code refusing to comply.

Not HTTP not FTP over HTTP proxy

So HTTP, HTTPS and FTP are sent over the HTTP proxy fine. That leaves us with nineteen more protocols. What happens with them when you ask curl to perform them over a HTTP proxy?

Now we have finally reached the change that has just been merged in curl and changes what curl does.

Before 7.55.0

curl would send all protocols as a regular GET to the proxy if asked to use a HTTP proxy without seeing the explicit proxy-tunnel option. This came from how FTP was done and grew from there without many people questioning it. Of course it wouldn’t ever work, but also very few people would actually attempt it because of that.

From 7.55.0

All protocols that aren’t HTTP, HTTPS or FTP will enable the tunnel-through mode automatically when a HTTP proxy is used. No more sending funny GET requests to proxies when they won’t work anyway. Also, it will prevent users from accidentally leak credentials to proxies that were intended for the server, which previously could happen if you omitted the tunnel option with a few authentication setups.

HTTP/2 proxy

Sorry, curl doesn’t support that yet. Patches welcome!

Mozilla, Network, Web

HTTP Workshop s03e02

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(Season three, episode two)

Previously, on the HTTP Workshop. Yesterday ended with a much appreciated group dinner and now we’re back energized and eager to continue blabbing about HTTP frames, headers and similar things.

Martin from Mozilla talked on “connection management is hard“. Parts of the discussion was around the HTTP/2 connection coalescing that I’ve blogged about before. The ORIGIN frame is a draft for a suggested way for servers to more clearly announce which origins it can answer for on that connection which should reduce the frequency of 421 needs. The ORIGIN frame overrides DNS and will allow coalescing even for origins that don’t otherwise resolve to the same IP addresses. The Alt-Svc header, a suggested CERTIFICATE frame and how does a HTTP/2 server know for which origins it can do PUSH for?

A lot of positive words were expressed about the ORIGIN frame. Wildcard support?

Willy from HA-proxy talked about his Memory and CPU efficient HPACK decoding algorithm. Personally, I think the award for the best slides of the day goes to Willy’s hand-drawn notes.

Lucas from BBC talked about usage data for iplayer and how much data and number of requests they serve and how their largest share of users are “non-browsers”. Lucas mentioned their work on writing a libcurl adaption to make gstreamer use it instead of libsoup. Lucas talk triggered a lengthy discussion on what needs there are and how (if at all) you can divide clients into browsers and non-browser.

Wenbo from Google spoke about Websockets and showed usage data from Chrome. The median websockets connection time is 20 seconds and 10% something are shorter than 0.5 seconds. At the 97% percentile they live over an hour. The connection success rates for Websockets are depressingly low when done in the clear while the situation is better when done over HTTPS. For some reason the success rate on Mac seems to be extra low, and Firefox telemetry seems to agree. Websockets over HTTP/2 (or not) is an old hot topic that brought us back to reiterate issues we’ve debated a lot before. This time we also got a lovely and long side track into web push and how that works.

Roy talked about Waka, a HTTP replacement protocol idea and concept that Roy’s been carrying around for a long time (he started this in 2001) and to which he is now coming back to do actual work on. A big part of the discussion was focused around the wakli compression ideas, what the idea is and how it could be done and evaluated. Also, Roy is not a fan of content negotiation and wants it done differently so he’s addressing that in Waka.

Vlad talked about his suggestion for how to do cross-stream compression in HTTP/2 to significantly enhance compression ratio when, for example, switching to many small resources over h2 compared to a single huge resource over h1. The security aspect of this feature is what catches most of people’s attention and the following discussion. How can we make sure this doesn’t leak sensitive information? What protocol mechanisms exist or can we invent to help out making this work in a way that is safer (by default)?

Trailers. This is again a favorite topic that we’ve discussed before that is resurfaced. There are people around the table who’d like to see support trailers and we discussed the same topic in the HTTP Workshop in 2016 as well. The corresponding issue on trailers filed in the fetch github repo shows a lot of the concerns.

Julian brought up the subject of “7230bis” – when and how do we start the work. What do we want from such a revision? Fixing the bugs seems like the primary focus. “10 years is too long until update”.

Kazuho talked about “HTTP/2 attack mitigation” and how to handle clients doing many parallel slow POST requests to a CDN and them having an origin server behind that runs a new separate process for each upload.

And with this, the day and the workshop 2017 was over. Thanks to Facebook for hosting us. Thanks to the members of the program committee for driving this event nicely! I had a great time. The topics, the discussions and the people – awesome!

Mozilla, Network, Web

HTTP Workshop – London edition. First day.

The HTTP workshop series is back for a third time this northern hemisphere summer. The selected location for the 2017 version is London and this time we’re down to a two-day event (we seem to remove a day every year)…

Nothing in this blog entry is a quote to be attributed to a specific individual but they are my interpretations and paraphrasing of things said or presented. Any mistakes or errors are all mine.

At 9:30 this clear Monday morning, 35 persons sat down around a huge table in a room in the Facebook offices. Most of us are the same familiar faces that have already participated in one or two HTTP workshops, but we also have a set of people this year who haven’t attended before. Getting fresh blood into these discussions is certainly valuable. Most major players are represented, including Mozilla, Google, Facebook, Apple, Cloudflare, Fastly, Akamai, HA-proxy, Squid, Varnish, BBC, Adobe and curl!

Mark (independent, co-chair of the HTTP working group as well as the QUIC working group) kicked it all off with a presentation on quic and where it is right now in terms of standardization and progress. The upcoming draft-04 is becoming the first implementation draft even though the goal for interop is set basically at handshake and some very basic data interaction. The quic transport protocol is still in a huge flux and things have not settled enough for it to be interoperable right now to a very high level.

Jana from Google presented on quic deployment over time and how it right now uses about 7% of internet traffic. The Android Youtube app’s switch to QUIC last year showed a huge bump in usage numbers. Quic is a lot about reducing latency and numbers show that users really do get a reduction. By that nature, it improves the situation best for those who currently have the worst connections.

It doesn’t solve first world problems, this solves third world connection issues.

The currently observed 2x CPU usage increase for QUIC connections as compared to h2+TLS is mostly blamed on the Linux kernel which apparently is not at all up for this job as good is should be. Things have clearly been more optimized for TCP over the years, leaving room for improvement in the UDP areas going forward. “Making kernel bypassing an interesting choice”.

Alan from Facebook talked header compression for quic and presented data, graphs and numbers on how HPACK(-for-quic), QPACK and QCRAM compare when used for quic in different networking conditions and scenarios. Those are the three current header compression alternatives that are open for quic and Alan first explained the basics behind them and then how they compare when run in his simulator. The current HPACK version (adopted to quic) seems to be out of the question for head-of-line-blocking reasons, the QCRAM suggestion seems to run well but have two main flaws as it requires an awkward layering violation and an annoying possible reframing requirement on resends. Clearly some more experiments can be done, possible with a hybrid where some QCRAM ideas are brought into QPACK. Alan hopes to get his simulator open sourced in the coming months which then will allow more people to experiment and reproduce his numbers.

Hooman from Fastly on problems and challenges with HTTP/2 server push, the 103 early hints HTTP response and cache digests. This took the discussions on push into the weeds and into the dark protocol corners we’ve been in before and all sorts of ideas and suggestions were brought up. Some of them have been discussed before without having been resolved yet and some ideas were new, at least to me. The general consensus seems to be that push is fairly complicated and there are a lot of corner cases and murky areas that haven’t been clearly documented, but it is a feature that is now being used and for the CDN use case it can help with a lot more than “just an RTT”. But is perhaps the 103 response good enough for most of the cases?

The discussion on server push and how well it fares is something the QUIC working group is interested in, since the question was asked already this morning if a first version of quic could be considered to be made without push support. The jury is still out on that I think.

ekr from Mozilla spoke about TLS 1.3, 0-RTT, how the TLS 1.3 handshake looks like and how applications and servers can take advantage of the new 0-RTT and “0.5-RTT” features. TLS 1.3 is already passed the WGLC and there are now “only” a few issues pending to get solved. Taking advantage of 0RTT in an HTTP world opens up interesting questions and issues as HTTP request resends and retries are becoming increasingly prevalent.

Next: day two.