[pdkl95]

> UDP is not streamed but message based protocol.

I'm very[1] familiar with the IP family of protocols.

> Open for discussion

If you don't know what your requirements are, you shouldn't be choosing a transport technology. It sounds like you want an library that wraps WebSockets or WebRTC and handles most of the complexity.

> WebUDP could implement it's own [transport] layer over pure UDP

Then you want TCP. The only reason to use UDP is to avoid the complexities of a transport layer. Transport reliability is very hard; this isn't something that is easy to re-implement by yourself in UDP.

More importantly, I take it you don't know what your MTU is? The Maximum Transmission Unit[2] the maximum packet size. On ethernet-based networks, it's probably ~0-100 octets less than ethernet's 1500 octet MTU. You need to keep UDP packets under this limit, or they will fragment. Fragmented IP packets may not arrive at all and even when they do, the OS will wait until all fragments arrive before passing the data up to the app. If you're insane and send HTTP headers in each packet, you've wasted most of your data space. Each packet? Shouldn't we send headers in the first packet only? Except that every packet IS the "first packet" in stateless protocol like UDP. It's the transport features of TCP that create ordered-data semantics.

[1] I used to write firmware for embedded systems. That included writing - from scratch, in Z80 asm - the entire network layer: ethernet (RealTek), ARP, IP, UDP, TCP, SNMP, HTTP, etc.

[2] https://en.wikipedia.org/wiki/Maximum_transmission_unit

[Confiks]

The tone of both of your posts is very demeaning. You completely tear down the proposal, making lots of – possibly correct – assumptions, without showing the slightest of doubt about them or any willingness to engage in a constructive debate.

And while you seemingly have a lot of experience with networking programming, and I have hardly any, I think I can easily correct you on the argument of a small MTU.

Many websites that have a more real-time networking need, currently use Websockets over a TCP channel separate from the HTTP stream. Over this channel many small messages are sent, for example updating the player's coordinates in a game. It is tolerable that some of these message may be delivered out of order or may be lost.

Wouldn't that be good fit for UDP?

Aside from that, you say that "the only reason to use UDP is to avoid the complexities of a transport layer", which I think is exactly right. You then say "transport reliability is very hard", which I can imagine it must be.

But then transport reliability is only one of the possible features of a transport layer. The whole point is that when you have access to UDP as a transport primitive, you can pick and choose which transport layer features you do and don't require on top of that.

[mentat]

There are truths about networking, whether people like them or not. They are not debatable, they are facts, so there's not a need to engage. If someone doesn't want to learn, there's not much to do.

[CyberDildonics]

This person seems to be trying to turn UDP into TCP. This seems to be because they don't understand TCP. Sometimes showing people reality isn't about being 'demeaning'.

[mrmoka]

You probably have not read the document. It's clearly stating - there is no need for reliability and ordered delivery of data. The only requirement from security point of view is congestion control. Please, do read the topic content before making assumptions.

[Matthias247]

>> Minimum header overhead

> Wait, are you thinking about using UDP to transport HTTP?! Do you even know what your MTU is?

> If you're insane and send HTTP headers in each packet, you've wasted most of your data space.

I think header in the requirement just means protocol/PDU header, which is required to deploy any kind of higher level protocol on top of UDP. Just like the UDP header and the IP headers are used at the start of data received in ethernet frames. These headers can be anything depending on the use case, even only a single or even zero bytes. The whole document does not mention that sending HTTP headers on top of UDP (which obviously could cause MTU problems, but nevertheless this kind of mechanism was standardized with CoAP).

[mrmoka]

> I'm very[1] familiar with the IP family of protocols.

Great, you have an expertise to contribute. And with this discussion you already are.

> If you don't know what your requirements are, you shouldn't be choosing a transport technology. It sounds like you want an library that wraps WebSockets or WebRTC and handles most of the complexity. There are "libraries" that wrap over some protocols. They don't make adoption of underlying technology easier, WebRTC in this case.

This effort is to establish clear requirements, not yet to propose exact solution. So this discussion is just a process of establishing those requirements.

High level requirements are clearly stated in the document, and important one is: simplicity. Currently there is no simple solution for low-latency server-client communication.

> > WebUDP could implement it's own [transport] layer over pure UDP > Then you want TCP. The only reason to use UDP is to avoid the complexities of a transport layer. Transport reliability is very hard; this isn't something that is easy to re-implement by yourself in UDP.

Layer on top doesn't have to involve full on replication of TCP techniques or alternatives. Just like WebSockets only adds very little to pure TCP in form of a data framing (header) for messages.

> More importantly, I take it you don't know what your MTU is? The Maximum Transmission Unit[2] the maximum packet size. On ethernet-based networks, it's probably ~0-100 octets less than ethernet's 1500 octet MTU. You need to keep UDP packets under this limit, or they will fragment. Fragmented IP packets may not arrive at all and even when they do, the OS will wait until all fragments arrive before passing the data up to the app. If you're insane and send HTTP headers in each packet, you've wasted most of your data space. Each packet? Shouldn't we send headers in the first packet only? Except that every packet IS the "first packet" in stateless protocol like UDP. It's the transport features of TCP that create ordered-data semantics.

This is really valuable input, and is exactly what is needed to fuel further requirements for an implementation.

You know, you can provide valuable input without trying to "argue" ;)

[cesarb]

All this discussion about UDP and MTU reminded me of an old StackOverflow answer of mine (https://stackoverflow.com/a/276096):

"Alternative answer: be careful to not reinvent the wheel.

TCP is the product of decades of networking experience. There is a reason for every or almost every thing it does. It has several algorithms most people do not think about often (congestion control, retransmission, buffer management, dealing with reordered packets, and so on).

If you start reimplementing all the TCP algorithms, you risk ending up with an (paraphasing Greenspun's Tenth Rule) "ad hoc, informally-specified, bug-ridden, slow implementation of TCP".

If you have not done so yet, it could be a good idea to look at some recent alternatives to TCP/UDP, like SCTP or DCCP. They were designed for niches where neither TCP nor UDP was a good match, precisely to allow people to use an already "debugged" protocol instead of reinventing the wheel for every new application."

[mrmoka]

You are absolutely right. But we need to remember - our motivation is to get a solution without most of TCP mechanisms to suit cases where it is not required. SCTP - is more of an alternative to TCP and implements mechanisms that are not required by our motivation. DCCP - is more close to what we want as it solves security concern: congestion collapse.

And you are right - we do not want reinvent the wheel.

[mentat]

You might want to look at how many of these problems QUIC would solve for you.