[TylerE]

Essentially, no.

HTTP/1.1 contains tons of optional features. Practially no two implementations support the same set.

HTTP/2 is all 100% mandatory. Any compliant HTTP/2 implementation will support an EXACT set of known features.

[peterfirefly]

Won't that create the same problems as XML and XHTML where full compliance is/was mandatory -- and the reality turned out to be different?

[entropy_]

Probably not, most, if not all, non-compliant XML/XHTML is either written by hand or by very bad generation tools. In the case of HTML/2 it's a protocol that needs to be implemented by browsers and web servers and there are only so many of those. In the case of XML/XHTML any person throwing up a website or sending a document does the generation with a different set of tools(or by hand)

[jimktrains2]

I've seen tons of computer-generated terrible xml. It's in use in so many custom API's I can't even describe to you. Poor escaping, nesting, &c.

[byuu]

> HTTP/2 is all 100% mandatory

That's a nice idea in theory, but what makes you think anyone is going to adhere to that?

Developers have always, and will always, do whatever they want when they implement your standards.

It was bad enough that when I worked on a binary delta patching format, I made sure there were absolutely zero possible undefined values, because I knew someone might try and use them to add new functionality in.

For something as complex as HTTP, I can guarantee you people will ignore parts of the spec they don't care about. And you can yell at them and say it's not a valid/legal HTTP/2 implementation, but they won't care. They'll keep on doing what they're doing.

[TylerE]

It's still a much better situation than HTTP/1.1. At least an HTTP/2 compliant implementation has an exact definition, that it either is, or isn't. An HTTP/1.1 implementation has a vast number of corner cases and optional bits.

Sure, if you're out-of-spec, all bets are off. It's just that with hTTP/1.1 even 100% in-spec implementations are a pretty wide target zone.

[bhouston]

> HTTP/2 is all 100% mandatory. Any compliant HTTP/2 implementation will support an EXACT set of known features.

But over the next couple of years, won't people come up with new ideas and add them as optional extensions? How is that handled?

I suspect some of these optional extensions will be really useful in special cases such as support for LZMA/LZHAM compression in addition to just gzip.

[TylerE]

There is support for extensions, but they're, well, extensions. The only thing the protocol specifies is that a compliant implementation must pass-through unchanged any block it doesn't understand.

Compare with HTTP/1.1 where for instance the entire content negotiation mechanism is optional and clients need to be able to deal with it not being available.

[josteink]

> There is support for extensions, but they're, well, extensions.

So down the line, it will be pretty much exactly like HTTP 1.0 and 1.1 then.

Good to hear someone thought this thoroughly through before creating a mega-complex protocol unimplementable by most industry-grade engineers, which will also need to be debugged and maintained for all internet-eternity.

[spacecowboy_lon]

Well in that case Apache Ngix Microsoft and the IETF need to keep control of the satndard any one that tries to add the http/2 equivelent of <blink> gets taken out and shot.

I have seen this before with OSI when MCI decided that part of the x.400 standard was optional. And not to mention ICL who thought that starting counting from 0 was a good idea when that standard said MUST START from 1 (and you wonder why the UK doesnt have a mainframe maker any more)