Video: The QUIC-ematic universe season 2020-2021 preview

QUIC is an encrypted transport protocol with better performance than HTTP and HTTP/2. While young, it’s already seeing some use in the larger internet companies who are learning how best to harness the optimisations. One of the stark differences is that it’s built on top of UDP rather than TCP. This is one of the main ways it increases efficiency. Freed from TCP’s constant acknowledgement of packets, QUIC also ensures reliable delivery but on its own terms which allows it to prioritise speedy delivery over acknowledgement admin. We’ve covered QUIC before, so if it’s new to you, check out this explainer as this talk is an update on what’s happened in 2020 and the plans for 2021 as QUIC aims to be standardised and much more available.

Lucas Pardue from Cloudflare works on the IETF working group devoted to QUIC and spoke at Demuxed 2020. “The IETF are standardisers” he says with QUIC being on its 31st draft with a move to standardise during 2021 what is called ‘IETF QUIC’ to differentiate from a slightly different version of QUIC from Google. IETF quick, Lucas outlines, delivers secure, reliable stream multiplexing.


QUIC actually forms a base layer for other applications like HTTP/3 with HTTP semantics to work on top of. Like most modern standards, QUIC is actually a name for more than one document. There is a transport layer, header compression, TLS handshake description and a document for recovery and loss protection. QUIC itself lives on UDP datagrams which is why one of the new options coming is to turn off some of the reliability which has been built on top of UDP to deliver TCP-like reliability for data which doesn’t really need it. One possibility here is running a QUIC tunnel where one QUIC connection actually has many QUIC streams within it. In this circumstance, you only want any one bit of data being protected by one reliable transmission mechanism. So you’d want to be turning off reliable transmission for your internal QUIC streams as they would be protected by the outer QUIC layer. There is a project called MASQUE which is working on this.

As with anything arriving on the market, it’s important to establish interoperability. We see this with the JT-NM and SRT plugfests. Lucas shows us the QUIC interop tester which automatically tests the latest implementations with each other and shows the results in a matrix plus allows access to logs and packet traces.

Lucas reminds us the QUIC streams are a first-class transport primitive providing reliable delivery. Within a stream, data will be delivered in order, but QUIC doesn’t specify how to schedule multiplexed streams. HTTP3 initially borrowed HTTP/2’s prioritisation scheme but found a better way to prioritise which is currently being discussed and finalised. Lucas has been working on quiche, Cloudflare’s own implementation of QUIC and shows a three-step process to getting quiche up and running.

Web Transport is another offering from QUIC which complements WebSocket which gives web apps better access to QUIC itself. The Chome Origin Trial explains how this is built in Chrome. Lucas talks about a test project he built on top of existing examples which is hosted at

Lucas ends by summarising the coming year: The working group is aiming to deliver documents to an IETF last call ahead of publication. The community will continue to get deployment experience as new users ar already working on enabling the technology and there is still work to be done on other adopted work items as well as considering others. Lucas ends by encouraging viewers to join in with the community,

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Lucas Pardue Lucas Pardue
Senior Software Engineer, Cloudflare
Co-Chair of the QUIC working group, IETF

Video: Providing better video experiences for the next billion users

What’s the best way for a billion people all on mobile networks to have a universally great streaming experience? It’s not trivial, and no service is perfect, but Facebook set out to find out what problems existed and find ways to fix them. This video explains their approach and solutions.

Denise Noyes from Facebook spoke at Demuxed 2020 about their work in India over the year. For Facebook, India is unique for this research as it represents such a large number of people almost universally using Android phones and mobile data. Not only does this allow them to understand the low-bitrate performance of video, but the Android penetration level simplifies comparisons.

The problems that Denise and her colleagues identified were gaps in the bitrate ladders where the ABR ladder either wasn’t well optimised or didn’t go low enough. There were also some ABR logic/decisions that were seen to be causing problems along with server delays from the CDN and internal congestion within the app. The research looked at ‘average bad sessions per user’ rather than the overall number of bad sessions which would be skewed by how many videos people generally watched.

Covid had a bearing on the research as this was being conducted by in-person interviews within India. These teams had to come home but the relevance of the research was acutely highlighted by the networks in other countries which worsened in response to the rising amount of traffic making them closer to the Indian example.

Denise’s team worked with colleagues throughout the company to create improvements across the whole network and delivery stack. On the encoding front, they decreased the lowest encoding level to 100kbps. This doesn’t look amazing, as seen by the metric score, but it’s better than buffering and can be watchable dependent on content. The GOP size was also increased from 2 seconds to 5. Longer GOP sizes are known to deliver improved bitrate, in this case up to 8%, but there is a tradeoff to pay in latency and how frequently you can move up/down the ABR ladder. Facebook found that the tradeoffs were worth the improvement for the viewers.

Denise introduces FB-MOS, Facebook’s objective model of the MOS objective metric. The lower the number, the worse the video looks. Facebook have used the fact that encoding resolution ‘A’ at, say, 400kbps and 200kbps can look better than encoding resolution ‘A’ at 400kbps and using a lower resolution ‘B’ for the 200kbps encode. This has lead to the ABR having 360p at two bitrates and 480p at two bitrates.

That FB-MOS score comes in handy for avoiding the lowest rungs of the ABR ladder. As their MOS score is quite low, the player will only choose it if it really has no choice otherwise, it will prefer to settle on a higher quality version if it isn’t able to go up the ladder. Ironically, they have also implemented logic to limit who gets the highest bandwidth streams since most users would prefer to spend less on data than get that disproportionately low improvement in quality.

In playback, Denise explains that they have reduced the impact of occasional anomalies on the bandwidth estimation and adjusted prefetching to prefetch the first chunk of all videos it would like to prefetch before getting the next chunk. This has reduced the chance that someone is able to choose a video which hasn’t yet been buffered and hence have to wait for it to start.

Lastly Denise covers the work done at the network layer seeing a move from HTTP/2 to QUIC. We see how the removal of head-of-line blocking has helped and that, not only has this the move to QUIC seen an overall improvement in performance but as congestion increased, QUIC traffic has shown a disproportionate improvement.

Denise concludes highlighting that this work across the network stack with wide collaboration has not only delivered the desired results but is a vital approach for any company looking to make marked improvements in customer experience.

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Denise Noyes Denise Noyes
Software Developer,

Video: HTTP over QUIC is the next generation

There’s a lot to like about HTTP/3 from encryption as standard, faster set-up time, better compression and promises better throughput by removing head-of-line blocking. A new protocol making its way through the IETF and based on QUIC, this could have a real impact on anyone involved in streaming.

wolfSSL’s Daniel Stenberg and cURL maintainer, talks to us about HTTP/3 but starts at the beginning with HTTP 1 and 1/1. He outlines some of the issues we had in 1997 such as head-of-line blocking and ephemeral TCP connections. Zooming forward to 2005, HTTP/2 comes on the scene with a single HTTP connection, thus removing the significant overhead of ephemeral TCP connections. HTTP/2 went with a ‘streamed’ connection and could have multiple such streams but one thing that wasn’t solved was head-of-line blocking.

Before moving beyond HTTP/2, Daniel describes the problems that have set in due to ‘ossification’, that is to say, that the routers that time forgot which are still on very old, and often buggy TCP implementations. Innovating is very difficult if replacing the TCP within even a subset of boxes would mean I wasn’t able to send my website globally.

Addressing this ‘ossification’ issue, QUIC has stepped in. Developed on UDP instead of TCP QUIC solves a number of problems. First off, moving from TCP to UDP allows the protocol to live in userspace making it easier to update. Working on UDP instead of TCP means that the protocol regains control of the retransmissions allowing for something more efficient than TCP’s strict acknowledgement rules.

So QUIC becomes the transport layer of HTTP/3. Freeing ourselves from TCP, Daniel explains, allows us to remove the TCP head-of-line blocking problem. HTTP/3 on QUIC brings with it faster handshakes and a connection ID. This connection ID allows you to change IP addresses and still maintain your connection which is a significant improvement on what has gone before. Daniel continues by explaining more benefits of QUICK and HTTP/3 such as its encryption and the ability to have multiple streams.

Daniel finishes up outlining eight challenges for HTTP/3. These include the fact that up to 7% of QUICK attempts fail, dealing with ‘fall back’ algorithms, UDP having seen historically low usage and are less optimised as well as the downsides of userland protocol stacks being that it’s harder to get a standard.

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Download the presentation

Daniel Stenberg Daniel Stenberg
curl master, wolfSSL
main author,

Video: There and back again: reinventing UDP streaming with QUIC

QUIC is an encrypted transport protocol for increased performance compared to HTTP but will this help video streaming platforms? Often conflated with HTTP/3, QUIC is a UDP-based way evolution of HTTP/2 which, in turn, was a shake-up of the standard HTTP/1.1 delivery method of websites. HTTP/3 uses the same well-known security handshake from TLS 1.3 that is well adopted now in websites around the world to provide encryption by default. Importantly, it creates a connection between the two endpoints into which data streams are multiplexed. This prevents the need to constantly be negotiating new connections as found in HTTP/1.x so helping with speed and efficiency. These are known as QUIC streams.

QUIC streams provide reliable delivery, explains Lucas Pardue from Cloudflare, meaning it will recover packets when they are lost. Moreover, says Lucas, this is done in an extensible way with the standard specifying a basic model, but this is extensible. Indeed, the benefit of basing this technology on UDP is that changes can be done, programmatically, in user-space in lieu of the kernel changes that are typically needed for improved TCP handling on which HTTP/1.1, for example, is based.

QUIC hailed from a project of the same name created by Google which has been taken in by the IETF and, in the open community, honed and rounded into the QUIC we are hearing about today which is notably different from the original but maintaining the improvements proved in the first release. HTTP/3 is the syntax which is a development on from HTTP/2 which uses the QUIC transport protocol underneath or as Lucas would say, “HTTP/3 is the HTTP application mapping to the QUIC transport layer.” Lucas is heavily involved within the IETF effort to standardise HTTP/3 and QUIC so he continues in this talk to explain how QUIC streams are managed, identified and used.

It’s clear that QUIC and HTTP/3 are being carefully created to be tools for future, unforeseen applications with clear knowledge that they have wide applicability. For that reason, we are already seeing projects to add datagrams and RTP into the mix, to add multiparty or multicast. In many ways mimicking what we already have in our local networks. Putting them on QUIC can enable them to work on the internet and open up new ways of delivering streamed video.

The talk finishes with a nod to the fact that SRT and RIST also deliver many of the things QUIC delivers and Lucas leaves open the question of which will prosper in which segments of the broadcast market.

The Broadcast Knowledge has well over 500 talks/videos on many topics so to delve further into anything discussed above, just type into the search bar on the right. Or, for those who like URLs, just add your search query to the end of this URL

Lucas has already written in detail about his work and what HTTP 3 is on his Cloudflare blog post.

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Lucas Pardue Lucas Pardue
Senior Software Engineer,