Application Protocols · Study deck

Modern HTTP: HTTP/2, HTTP/3, and Selection

Inspect the HTTP/1.1, HTTP/2, and HTTP/3 preserve HTTP application semantics while changing framing, transport, and loss boundaries underneath diagram to see which parts of HTTP stay fixed and where each version places its ordering and loss boundary.

Broker Bex is your guide for this deck.

httpmodern

Broker Bex, the module guide, in a scene from this chapter.

After studying this chapter

Learning objectives

You will be able to:

Explain HTTP/2 Multiplexing: Describe how binary framing, stream multiplexing, and HPACK header compression reduce repeated connection and header work in the chapter's gateway example
Evaluate HTTP/3 vs HTTP/2: Compare QUIC transport benefits against TCP-based HTTP/2 for mobile and cellular IoT deployments, justifying the choice based on network conditions
Select the Appropriate Protocol: Distinguish between HTTP/1.1, HTTP/2, and HTTP/3 based on device RAM constraints, network stability, and firewall policies
Explain how HTTP/2 multiplexing and HPACK reduce IoT gateway overhead

Major section

In 60 Seconds

Telemetry is a time-linked record from a device.

Hypertext Transfer Protocol (HTTP) is a request-and-response method.
Transmission Control Protocol (TCP) is a delivery method that keeps an ordered byte stream.
User Datagram Protocol (UDP) sends separate units without that built-in stream.
Latency is the time data takes to arrive.

Major section

In 60 Seconds (continued)

Constrained Application Protocol (CoAP) is a compact web-style method for small devices.

Message Queuing Telemetry Transport (MQTT) is a lightweight publish-and-subscribe method.
A gateway is a device or service that joins different system parts.
A newer version is not always a better fit.
This makes the trade clear before the team adds more features.

Major section

In 60 Seconds (continued)

Small endpoints may lack memory or library support, while a powered bridge may gain from shared links.

The deeper sections compare the versions and alternatives so each choice has a measured path, clear limit, and fallback.
HTTP/2 and HTTP/3 can make existing HTTP infrastructure useful for gateways and mobile systems.
HTTP/2 multiplexes requests over a reused connection; the chapter's deliberately sequential 50-request example shows a 50× elapsed-time comparison, not a universal speedup.

Major section

Concurrent Data Transfers with HTTP/2 and HTTP/3

That's what HTTP/2 does - it's like a multi-lane highway!".

Meet the Sensor Squad!: Temperature Terry needs to send LOTS of messages to the Cloud Castle, but the old road is SO SLOW!
But the old road only has ONE lane!
Nobody has to wait!".

HTTP/1.1, HTTP/2, and HTTP/3 preserve HTTP application semantics while changing framing, transport, and loss boundaries underneath.

Major section

Concurrent Data Transfers with HTTP/2 and HTTP/3 (continued)

The Problem: Sammy and 49 other sensors all want to send their readings to the Cloud Castle using HTTP/1.1.

"We have to wait in line FOREVER!" complains Sammy. "By the time my message arrives, the temperature has already changed!".
But what about when the road has potholes?".
Max explains HTTP/3: "HTTP/3 uses magic flying cars (QUIC)!

HPACK sends full repeated fields on the first request, populates a shared header table, and then replaces repeated fields with compact index references.

Major section

HTTP/2: Multiplexing and Header Compression

The HTTP/2 side assigns telemetry, configuration, and firmware to separate logical streams whose frames share one secure connection.

That removes application-level queueing between requests, but the final note preserves an important limit: all frames still travel through one ordered TCP byte stream.
The repeated authorization and representation fields below can outweigh a tiny sensor value.
A later request can name indexed fields instead, reducing the example to roughly 15–30 bytes.

HTTP/2 multiplexes independent application streams over one secure transport connection, while HTTP/1.1 often uses several connections or serial exchanges.

Major section

Phoebe's Field Notes: Where the Battery-Life Number Behind the Calculator Comes From

The mathematical gist: A 2000 mAh, 3.7 V battery carries 7.40 Wh by nameplate.

Separately, 2% monthly self-discharge leaves about 1570 mAh after a year.
Under HTTP/3, QUIC keeps those application streams independent, allowing telemetry to progress while the firmware stream waits.
Under HTTP/2, both telemetry and firmware share TCP's ordered byte stream, so the missing bytes hold later data until retransmission repairs the gap.

Major section

Protocol Selection Guide

In the first panel, Bex starts with the endpoint and asks whether its exchange is one-way or two-way.

That final test prevents a paper comparison from becoming a deployment promise, and it sets up the more detailed branch choices in the flowchart below.
The remaining stable, simple path can use HTTP/1.1 with keep-alive.

HTTP Protocol Selection Decision Tree for IoT Applications

Major section

Protocol Selection Guide (continued)

For an HTTP workload, many parallel exchanges favor HTTP/2 multiplexing; a client that changes networks in flight creates a specific case for HTTP/3 connection migration.

Existing HTTP/REST infrastructure must be preserved.
Devices have enough RAM for TLS + HTTP/2 (typically 32 KB+).
Connection reuse is possible (persistent connection to backend).

Deck summary

Key takeaways

Telemetry is a time-linked record from a device.

Constrained Application Protocol (CoAP) is a compact web-style method for small devices.
Small endpoints may lack memory or library support, while a powered bridge may gain from shared links.
That's what HTTP/2 does - it's like a multi-lane highway!".
The Problem: Sammy and 49 other sensors all want to send their readings to the Cloud Castle using HTTP/1.1.

Retrieval practice

Recall check

Broker Bex says: answer from memory, then check your reasoning.

Q1A sensor sends repeated headers over a reused HTTP/2 connection. Why can later requests have smaller headers?

AThey open fresh connections for repeated fields

BThey reference fields in the shared header table

CThey move the repeated headers into TCP

DThey omit the sensor measurement payload

Show answer

Answer: B HPACK establishes table state and later reuses indexed fields.

Q2A gateway loses a firmware packet while sending telemetry on another HTTP/3 stream. What behavior does the chapter predict?

ATelemetry progresses because radio loss is removed

BTelemetry can progress while firmware waits

CTelemetry must wait for the firmware gap

DThe firmware loss ends both application streams

Show answer

Answer: B QUIC keeps the application streams independent when one stream waits for missing data.

Print reference

Answers

Answer key.

B · HPACK establishes table state and later reuses indexed fields.
B · QUIC keeps the application streams independent when one stream waits for missing data.