In 1999, the Wireless Application Protocol (WAP) was introduced. It gained an extreme amount of interest and hype the following years. We know what happened. It failed completely after a few years only.
WAP is a set of protocols focused on the delivery of media to mobile phones. Essentially it is a whole new stack of protocols besides the already established HTTP/(TLS/)TCP/IP stack for content transfer and HTML to express the content. The protocols were motivated with the need for protocols more suited to less capable devices. It was believed that HTML+HTTP was too heavy for mobile phones.
And it was, sort of. Mobiles had bad Internet connectivity and small monochrome screens with a low resolution. However, as you know, this changed rather quickly. Now our mobile phones have megabits of bandwidth to the Internet and a high-resolution color displays and very capable multi-core processors. It did not take long until it was realized that: yes, a mobile can handle the ordinary Internet protocols for content distribution: HTTP+HTML and email and so on.
Is the IoT world in a WAP-phase today?
It is suggested today that the ordinary TCP/IP stack cannot be used for IoT devices because of the limitations they have in processing power, connectivity, energy consumption. Instead, special IoT protocols are suggested. In particular, CoAP/UDP is often suggested.
I don't know, but perhaps we are in a temporary phase (5-10 years) where some 8-bit IoT devices cannot speak the same language as the rest of the Internet. But will that situation last? The vast majority of the protocols that we associate with "Internet" uses TCP/IP. And nowadays and mostly TLS/TCP/IP is used to encrypt the Internet communication. This TLS/TCP/IP stack is used for the World Wide Web (HTTP), for SSH to control computers remotely, for REST to present cloud APIs, for email (IMAP, SMTP) and just about everything else on the Internet. Even Netflix uses TLS/TCP/IP to stream vast amounts of video data to its customers.
So, if we want our physical IoT devices to interact directly with the existing Internet, they should speak the same language. They should speak TLS/TCP/IP. Reusing only IP with, for example, CoAP/UDP/IP is typical for IoT devices today. However, I believe it may be only a matter of time before IoT devices also speak TLS/TCP/IP and thus can interact directly with existing Internet services without translation and with end-to-end security.
Notably, the IoT services: AWS IoT Core and Google IoT Core mandate the TLS/TCP/IP stack. So, to use those services end-to-end, a device must speak that stack. I wonder about Amazon's and Google's choice of not supporting CoAP/UDP/IP, for example. Instead of supporting such protocols for their cloud services, they advocate using a local bridge that translates, for example, CoAP/UDP/IP traffic to TLS/TCP/IP.
We will see. In 2030, we know the answer. No one knows. In the Internet world, the experts are often wrong. Me included. However, I think we should consider whether we can reuse the existing, well-established "big-Internet" protocols also for our smallest devices. Yes, there is some overhead, but it might be worth it. When we send IoT communication on the public Internet, we do have the same need for security. At least. Also, there are efforts to make the existing TLS/TCP/IP stack more efficient. Those efforts include TLS 1.3, TCP Fast Open, efficient TLS implementations, and 6LowPAN. Perhaps we should focus our energy on that instead of building up a separate, incompatible stack of protocols for IoT devices just like we did for mobile phones with WAP.