Why Are You Speeding Up My Wi-Fi Calling, Apple? (It Might Make Things Worse)

It's summer in Los Angeles, which can only mean one thing: Sequels!

As movie fans indulge in a third 'Avengers', a fifth 'Jurassic Park', and what feels like a seven hundreth 'Star Wars', this here blog is providing a sequel to a probably-long-forgotten Sniff Wi-Fi post called 'Why Are You Slowing Down My Wi-Fi, Apple?'

Turn down the lights, pop some popcorn, and enjoy the twists and turns of this harrowing look into Wi-Fi Calling on iPhones.

Several months ago, this blog highlighted the Wi-Fi behavior of the iPhone X using OmniPeek.  Truth be told, that post was a little bit like the latest 'Spider-Man' sequel: attention-grabbing title, some interesting content, but ultimately nothing consequential.  And just as movie fans knew that Michael Keaton's flying bird character wasn't going to beat the lead superhero,  a lot of Wi-Fi folks already knew that Apple iOS devices use Protection (called a "TXOP" in the blog post; Devin Akin corrected me, pointing out "TXOP" can refer to non-RTS/CTS communication) when transmitting Wi-Fi traffic.

At this point, some Wi-Fi folks might be feeling like movie fans who missed the last 'Jurassic Park' movie, and are wondering why Chris Pratt's character cares about Blue the Raptor: "What is Protection," they might ask.

Protection occurs when an AP or client device reserves the Wi-Fi channel for a window of time before transmitting data.  Just as Universal Studios has reserved April 10, 2020 as the release date for the next 'The Fast & the Furious' sequel, Wi-Fi devices (both clients and APs) reserve windows of time via Request-to-Send/Clear-to-Send (RTS/CTS).  Both RTS and CTS frames carry a large Duration value in their headers, thus causing all nearby Wi-Fi devices on the channel (even devices on neighboring Wi-Fi networks) to stay quiet, and avoid causing a Vin Diesel/Jason Statham style collision.  The downside of RTS/CTS (and the reason for the 'Why Are You Slowing Down...' part of the title of the prequel to this post), is that RTS and CTS frames use channel time without carrying data, much like The Rock uses screen time without being a true member of the Fast & Furious family.

But alas, things are not always what they seem.  And just as Split was a surprising entry to the 'Unbreakable' universe, the way Wi-Fi Calling is done has created a twist in the world of RTS/CTS Protection.

Behold, a recent capture of an iPhone doing Wi-Fi Calling:

Whoops.  Apologies.  That's a screenshot from the toilet scene of 'Dumb & Dumber', a movie that could have done without its sequels.

Here is the Wi-Fi Calling capture:

The Wi-Fi traffic pattern above is just as noticeable as Luc Besson's pattern of casting women he wants to hook up with in 'Transporter' sequels: Data -> Ack -> Data -> Ack.  Nary a RTS or CTS to be found.

As with the sequel to 'Terms of Endearment' (can any Sniff Wi-Fi readers even name that sub-classic?) the audience of this blog post may be asking "what's the point?"

The point is that Apple is pulling a 'Crank: High Voltage' with iPhones' Wi-Fi Calling: making it faster, but with a higher likelihood of collisions.

Removing Protection from Wi-Fi Calling doesn't make a whole lot of sense if the goal is to have collision-free calls, but then again it didn't make a whole lot of sense to set the sequel to 'Speed' on a boat.  Perhaps Apple's rationale is that the Voice category of 802.11e quality of service (QoS) is good enough to avoid collisions, similarly to how the producers of 'Speed 2: Cruise Control' felt that Jason Patric was a good enough facsimile of Keanu Reeves. 

Whatever Apple's rationale, the moral of the iPhone story is that Protection has been disabled for Wi-Fi Calling, just as the moral of 'John Wick: Chapter 2' was that John Wick will kill people using a variety of firearms, even for reasons beyond avenging a canine.


If you like my blog, you can support it by shopping through my Amazon link, becoming a Patron on Patreon, or by donating bitcoin to 1CcEkG8DJD6VWUr27GwtGzPWRQDFt3qgye

Thank you.

Twitter: @Ben_SniffWiFi

ben at sniffwifi dot com


  1. I finally found a great article here. I will stay here again. I just added your blog to my bookmarking sites. Thank you. Quality postings are essential to get visitors to visit the website, that's what this website offers.
    Business Analytics Course

  2. I am a new user of this site, so here I saw several articles and posts published on this site, I am more interested in some of them, will provide more information on these topics in future articles.

    Cloud Computing Course in Bangalore


  3. It's like you've got the point right, but forgot to include your readers. Maybe you should think about it from different angles.

    Best IoT Training Institute in Bangalore

  4. I'm always looking online for articles that can help me. I think you also made some good comments on the functions. Keep up the good work!

    [url=https://360digitmg.com/india/data-science-course-in-erode]Data Science Course in Erode[/url]

  5. Very informative message! There is so much information here that can help any business start a successful social media campaign!

    Data Analytics Course in Bangalore

  6. Very informative message! There is so much information here that can help any business start a successful social media campaign!

    Data Analytics Course in Gorakhpur

  7. Very best as well as Most affordable Jabodetabek Individual Training, our own staff members plus educators appear to your home, fixed your personal analyze program and can opt for almost any area connected with review ... go to https://bimbel-calistung.netlify.app/les-privat-calistung-jakarta-utara.html for more details

  8. Perhaps you will find a cheaper fee compared to the table above, make sure again around the qualifications of the teacher / Kindergarten teacher recommended to your account ... for detail https://ipa-exed.blogspot.com/2022/04/les-privat-ipa-di-pancoran-terdekat.html


Post a Comment

Popular posts from this blog

Five Facts About 6 GHz Wi-Fi

Chips, Glorious Wi-Fi 6E Chips!

Go To Sleep, Go To Sleep, Go To Sleep Little iPhone