Throttling and Prioritization Explained

Throttling

Throttling occurs when data transfer is capped at a specific speed. Often, caps apply to all data usage. For example, as of April 2019:

• Mint Mobile subscribers who’ve used up their allotted high-speed data have speeds throttled to a maximum of 128kbps.¹

• Visible generally caps data speeds at 5 megabits per second (Mbps).²

In my experience, carriers are usually transparent about (a) the existence of throttling on data speeds and (b) the speeds that subscribers will be capped at.

Carriers may also throttle specific applications or types of traffic. Targeted throttling often affects video streaming. For example, streaming video is limited to 480p quality on Verizon’s prepaid plans.³

Prioritization

Prioritization can affect the quality of service that subscribers receive when networks are congested. Rather than treating all users of a congested network equally, network operators generally prioritize some users’ activities over other users’ activities. Unlike throttling, prioritization is not going to affect an individual’s wireless experience when a network is not congested.

As a general rule, subscribers on more expensive, postpaid plans are likely to be prioritized over other subscribers. However, that general rule leaves out a lot of nuances. Sometimes prioritization differences may exist within a single class of customers. Postpaid customers that use excessive amounts of data on unlimited plans may have their network access deprioritized. Here are a few examples of prioritization policies affecting those that subscribe to Verizon’s postpaid unlimited plans:⁴

• GoUnlimited: “In times of congestion, your data may be temporarily slower than other traffic.”
• BeyondUnlimited: “After 22 GB/line, in times of congestion, your data may be temporarily slower than other traffic.”
• AboveUnlimited: “After 75 GB/line, in times of congestion, your data may be temporarily slower than other traffic.”

In the weeds

Carriers aren’t usually upfront about the details of their prioritization procedures.⁵ I’ve seen a number of people express the view that networks regularly use several prioritization tiers. According to this view, network operators assign prioritization levels based on how profitable different types of subscribers are: postpaid subscribers are the highest priority, followed by prepaid subscribers, with subscribers to mobile virtual network operators (carriers that use networks owned by other companies) receiving the lowest priority.⁶ I don’t think this view is quite right. I explain my best guesses about each major network’s prioritization polices in the following articles:

• AT&T’s network
• T-Mobile’s network
• Sprint’s network
• Verizon’s network

1. “When your data is reduced, it will be reduced to 128 kpbs.”
   From a Mint Mobile support response on the Mint Mobile community forum (archived here).
2. “We’re built for life on the go, so instead of giving you extra speed you don’t need (and making you pay for it), you get unlimited data at speeds up to 5 Mbps.”
   From Visible’s FAQ as of 4/24/2019 (archived here).
3. “DVD-quality streaming (up to 480p) on smartphones.”
   From Verizon’s prepaid page on 5/27/2019.
4. These examples come from Verizon’s unlimited plans web page as of 4/26/2019.
5. In my experience, carriers often mention that deprioritization is a possibility, but they rarely share enough details for consumers to really assess how significant an effect deprioritization is liable to have on their experience. As of April 2019, I’ve never seen a third-party company try to make a rigorous, empirical assessment of differences in prioritization between services.
6. This is a view I’ve seen expressed multiple times in Reddit’s NoContract community.