Damn it's nice reading a simple static site like this. Links open instantly to the next fully laid out page of content. If only the rest of the web could be like this..
Worth nothing, that react application (using React Server Components?)! If you have javascript enabled, it renders as a single page app, fetching each additional page via an API. If you disable JS, it renders it all on the server.
Agreed but where is the actual git repo? I see a text saying this "contents get updated automatically on every commit to this git repository" but where is "this git repository"?
Damn it's nice to log onto Hacker News and see yet another top comment on an interesting article be bike shedding about webshit. And also wrong because if you crack open your react dev tools and have a peak inside the 2MB of javascript you'll see that this site is still everything you despise.
But how will the author know the last 500 websites you visited and where your eyes are looking right now and what you ate last Tuesday? They should put some AnAlYtIcS in.
Well, it seem like is was originally, but isn't now and hasn't been at date of publication.
Edit:
> The initial QUIC protocol was designed by Jim Roskind at Google and was initially implemented in 2012, announced publicly to the world in 2013 when Google's experimentation broadened.
> Back then, QUIC was still claimed to be an acronym for "Quick UDP Internet Connections", but that has been dropped since then.
Here’s a conceptual background about how and why HTTP/3 came to be (recollected from memory):
HTTP/1.0 was built primarily as a textual request-response protocol over the very suitable TCP protocol which guaranteed reliable byte stream semantics. The usual pattern was to use a TCP connection to exchange a request and response pair.
As websites grew more complex, a web page was no longer just one document but a collection of resources stitched together into a main document. Many of these resources came from the same source, so HTTP/1.1 came along with one main optimisation — the ability to reuse a connection for multiple resources using Keep Alive semantics.
This was important because TCP connections and TLS (nee SSL) took many round-trips to get established and transmitting at optimal speed. Latency is one thing that cannot be optimised by adding more hardware because it’s a function of physical distance and network topology.
HTTP/2 came along as a way to improve performance for dynamic applications that were relying more and more on continuous bi-directional data exchange and not just one-and-done resource downloads. Two of its biggest advancements were faster (fewer round-trips) TLS negotiation and the concept of multiple streams over the same TCP connection.
HTTP/2 fixed pretty much everything that could be fixed with HTTP performance and semantics for contemporary connected applications but it was still a protocol that worked over TCP. TCP is really good when you have a generally stable physical network (think wired connections) but it performs really badly with frequent interruptions (think Wi-Fi with handoffs and mobile networks).
Besides the issues with connection reestablishment, there was also the challenge of “head of the line blocking” — since TCP has no awareness of multiplexed HTTP/2 streams, it blocks everything if a packet is dropped, instead of blocking only the stream to which the packet belonged. This renders HTTP/2 multiplexing a lot less effective.
In parallel with HTTP/2, work was also being done to optimise the network connection experience for devices on mobile and wireless networks. The outcome was QUIC — another L4 protocol over UDP (which itself is barebones enough to be nicknamed “the null protocol”). Unlike TCP, UDP just tosses data packets between endpoints without much consideration of their fate or the connection state.
QUIC’s main innovation is to integrate encryption into the transport layer and elevate connection semantics to the application space, and allow for the connection state to live at the endpoints rather than in the transport components. This allows retaining context as devices migrate between access points and cellular towers.
So HTTP/3? Well, one way to think about it is that it is HTTP/2 semantics over QUIC transport. So you get excellent latency characteristics over frequently interrupted networks and you get true stream multiplexing semantics because QUIC doesn’t try to enforce delivery order or any such thing.
Is HTTP/3 the default option going forward? Maybe not until we get the level of support that TCP enjoys at the hardware level. Currently, managing connection state in application software means that over controlled environments (like E-W communications within a data centre), HTTP/3 may not have as good a throughput as HTTP/2.
Thank you for a great overview! I wish HTTP3/QUIC was the "default option" and had much wider adoption.
Unfortunately, software implementations of QUIC suffer from dealing with UDP directly. Every UDP packet involves one syscall, which is relatively expensive in modern times. And accounting for MTU further makes the situation ~64 times worse.
In-kernel implementations and/or io-uring may improve this unfortunate situation, but today in practice it's hard to achieve the same throughput as with plain TCP. I also vaguely remember that QUIC makes load-balancing more challenging for ISPs, since they can not distinguish individual streams as with TCP.
Finally, QUIC arrived a bit too late and it gets blocked in some jurisdictions (e.g. Russia) and corporate environments similarly to ESNI.
> In-kernel implementations and/or io-uring may improve this unfortunate situation, but today in practice it's hard to achieve the same throughput as with plain TCP.
This would depend on how the server application is written, no? Using io-uring and similar should minimise context-switches from userspace to kernel space.
> I also vaguely remember that QUIC makes load-balancing more challenging for ISPs, since they can not distinguish individual streams as with TCP.
Not just for ISPs; IIRC (and I may be recalling incorrectly) reverse proxies can't currently distinguish either, so you can't easily put an application behind Nginx and use it as a load-balancer.
The server application itself has to be the proxy if you want to scale out. OTOH, if your proxy for UDP is able to inspect the packet and determine the corresponding instance to send a UDP packet too, it's going to be much fewer resources required on the reverse proxy/load balancer, as they don't have to maintain open connections at all.
It will also allow some things more easily; a machine that is getting overloaded can hand-off (in userspace) existing streams to a freshly created instance of the server on a different machine, because the "stream" is simply related UDP packets. TCP is much harder to hand-off, and even if you can, it requires either networking changes or kernel functions to hand-off.
Glad you found it helpful! Most of it is distilled from High Performance Browser Networking (https://hpbn.co/). It’s a very well organised, easy to follow book. Highly recommended!
Unfortunately, it’s not updated to include QUIC and HTTP/3 so I had to piece together the info from various sources.
That's basically what QUIC is? It is a UDP based protocol over which HTTP can be run.
How else would you consider "just" switching HTTP to UDP? There are minimum required features such as 1. congestion control 2. multiplexed streams 3. encryption and probably a few others that I forgot about.
QUIC is actually a level 4 protocol, on the same level as UDP and TCP, it could work on IP directly, making it QUIC/IP.
They chose to keep the UDP layer because of its minimal overhead over raw IP and for better adoption and anti-ossification reasons, but conceptually, forget about UDP, QUIC is a TCP replacement that happens to be built on top of UDP.
Now for the answers:
- Why not HTTP over UDP? UDP is an unreliable protocol unsuitable for HTTP. HTTP by itself cannot deal with packet loss, among other things.
- Why not keep HTTP/2? HTTP/2 is designed to work with TCP and work around some of its limitations, it could probably work over QUIC too, but you would lose most of the advantages of QUIC
- Why not got back to HTTP/1? I could turn out to be a better choice than HTTP/2, but it is not a drop-in replacement either, and you would lose all the intersting features introduced since HTTP/2
> As the packet loss rate increases, HTTP/2 performs less and less well. At 2% packet loss (which is a terrible network quality, mind you), tests have proven that HTTP/1 users are usually better off - because they typically have up to six TCP connections to distribute lost packets over. This means for every lost packet the other connections can still continue.
Makes sense. One idea would be if the browser could detect packet loss (e.g. netstat -s and look for TCP retransmissions, and equivalent on other OSes) and open more sockets if there is.
Email is mostly dead - we use Gmail (or Microsoft 365) now. It is to email what Slack is to IRC. With only one or two vendors, the need for widely interoperable protocols is gone - they only need to interoperate between a few large service providers, and that can be done by private agreement.
You realize those ESPs use and support the industry standard open protocols under the hood, right? Slack is 100% proprietary and does not use industry standard protocols for interchange or federation. These are not even remotely comparable. Slack would need to use industry standard and open protocols (i.e. XMPP) to allow federation with products like Teams and Discord for the situations to be comparable.
Readit News
I can't find a link to the source anywhere.
(using a search engine is faster than asking for a link on HN)
There are a also ton of outbound requests for JS on first load.
[0]: view-source:https://http3-explained.haxx.se/
I need fancy javascript crap like I need a hole in my head.
Looks unmaintained, though.
Edit:
> The initial QUIC protocol was designed by Jim Roskind at Google and was initially implemented in 2012, announced publicly to the world in 2013 when Google's experimentation broadened.
> Back then, QUIC was still claimed to be an acronym for "Quick UDP Internet Connections", but that has been dropped since then.
from https://http3-explained.haxx.se/en/proc
HTTP/1.0 was built primarily as a textual request-response protocol over the very suitable TCP protocol which guaranteed reliable byte stream semantics. The usual pattern was to use a TCP connection to exchange a request and response pair.
As websites grew more complex, a web page was no longer just one document but a collection of resources stitched together into a main document. Many of these resources came from the same source, so HTTP/1.1 came along with one main optimisation — the ability to reuse a connection for multiple resources using Keep Alive semantics.
This was important because TCP connections and TLS (nee SSL) took many round-trips to get established and transmitting at optimal speed. Latency is one thing that cannot be optimised by adding more hardware because it’s a function of physical distance and network topology.
HTTP/2 came along as a way to improve performance for dynamic applications that were relying more and more on continuous bi-directional data exchange and not just one-and-done resource downloads. Two of its biggest advancements were faster (fewer round-trips) TLS negotiation and the concept of multiple streams over the same TCP connection.
HTTP/2 fixed pretty much everything that could be fixed with HTTP performance and semantics for contemporary connected applications but it was still a protocol that worked over TCP. TCP is really good when you have a generally stable physical network (think wired connections) but it performs really badly with frequent interruptions (think Wi-Fi with handoffs and mobile networks).
Besides the issues with connection reestablishment, there was also the challenge of “head of the line blocking” — since TCP has no awareness of multiplexed HTTP/2 streams, it blocks everything if a packet is dropped, instead of blocking only the stream to which the packet belonged. This renders HTTP/2 multiplexing a lot less effective.
In parallel with HTTP/2, work was also being done to optimise the network connection experience for devices on mobile and wireless networks. The outcome was QUIC — another L4 protocol over UDP (which itself is barebones enough to be nicknamed “the null protocol”). Unlike TCP, UDP just tosses data packets between endpoints without much consideration of their fate or the connection state.
QUIC’s main innovation is to integrate encryption into the transport layer and elevate connection semantics to the application space, and allow for the connection state to live at the endpoints rather than in the transport components. This allows retaining context as devices migrate between access points and cellular towers.
So HTTP/3? Well, one way to think about it is that it is HTTP/2 semantics over QUIC transport. So you get excellent latency characteristics over frequently interrupted networks and you get true stream multiplexing semantics because QUIC doesn’t try to enforce delivery order or any such thing.
Is HTTP/3 the default option going forward? Maybe not until we get the level of support that TCP enjoys at the hardware level. Currently, managing connection state in application software means that over controlled environments (like E-W communications within a data centre), HTTP/3 may not have as good a throughput as HTTP/2.
Unfortunately, software implementations of QUIC suffer from dealing with UDP directly. Every UDP packet involves one syscall, which is relatively expensive in modern times. And accounting for MTU further makes the situation ~64 times worse.
In-kernel implementations and/or io-uring may improve this unfortunate situation, but today in practice it's hard to achieve the same throughput as with plain TCP. I also vaguely remember that QUIC makes load-balancing more challenging for ISPs, since they can not distinguish individual streams as with TCP.
Finally, QUIC arrived a bit too late and it gets blocked in some jurisdictions (e.g. Russia) and corporate environments similarly to ESNI.
EDIT: I found https://news.ycombinator.com/item?id=45387462 which is a way better discussion than what I wrote.
This would depend on how the server application is written, no? Using io-uring and similar should minimise context-switches from userspace to kernel space.
> I also vaguely remember that QUIC makes load-balancing more challenging for ISPs, since they can not distinguish individual streams as with TCP.
Not just for ISPs; IIRC (and I may be recalling incorrectly) reverse proxies can't currently distinguish either, so you can't easily put an application behind Nginx and use it as a load-balancer.
The server application itself has to be the proxy if you want to scale out. OTOH, if your proxy for UDP is able to inspect the packet and determine the corresponding instance to send a UDP packet too, it's going to be much fewer resources required on the reverse proxy/load balancer, as they don't have to maintain open connections at all.
It will also allow some things more easily; a machine that is getting overloaded can hand-off (in userspace) existing streams to a freshly created instance of the server on a different machine, because the "stream" is simply related UDP packets. TCP is much harder to hand-off, and even if you can, it requires either networking changes or kernel functions to hand-off.
Unfortunately, it’s not updated to include QUIC and HTTP/3 so I had to piece together the info from various sources.
How else would you consider "just" switching HTTP to UDP? There are minimum required features such as 1. congestion control 2. multiplexed streams 3. encryption and probably a few others that I forgot about.
They chose to keep the UDP layer because of its minimal overhead over raw IP and for better adoption and anti-ossification reasons, but conceptually, forget about UDP, QUIC is a TCP replacement that happens to be built on top of UDP.
Now for the answers:
- Why not HTTP over UDP? UDP is an unreliable protocol unsuitable for HTTP. HTTP by itself cannot deal with packet loss, among other things.
- Why not keep HTTP/2? HTTP/2 is designed to work with TCP and work around some of its limitations, it could probably work over QUIC too, but you would lose most of the advantages of QUIC
- Why not got back to HTTP/1? I could turn out to be a better choice than HTTP/2, but it is not a drop-in replacement either, and you would lose all the intersting features introduced since HTTP/2
Why doesn't HTTP/2 use more than one socket?
Deleted Comment
https://http3-explained.haxx.se/~gitbook/pdf?limit=100
[1]: https://en.wikipedia.org/wiki/JSON_Meta_Application_Protocol