Communications of the ACM

Unfortunately, for consumer broadband connections, uplink speeds tend to be much lower than downlink speeds: Comcast’s standard high-speed Internet package, for example, offers 6Mbps for download but only 384Kbps for upload (1/16th of download throughput). 11

This limitation is not as acute today as it was nearly a decade ago when upload speeds in the U.S. hovered around .5Mbps. Figure 1 shows the current upload and download as taken from Speedtest.net (http://www.speedtest. net/reports/). These data points show that global “last-mile” throughput rates are nearly 30 times their 2008 counterparts. Is this enough? Would a peer with an upload rate at the lower quartile of these metrics (~4Mbps) suffice? This question has been thoroughly explored in regard to actual webpage load time.

When Mike Belshe, of Google
SPDY fame, looked at the relationship
between end-client bandwidth and
page-load time, he discovered that
“bandwidth doesn’t matter (much).” 3
Once the client’s available bandwidth
reached 5Mbps, the impact on the end
user’s page load is negligible. Figure
2 shows page-load time as a function
of client bandwidth, assuming a fixed
RTT (round-trip time) of 60ms.

Availability. The next major hurdle for the distributed Internet is peer availability. Namely, are there enough peers, and are they online and available for enough time to provide value? In the past 10 years the edge device count has certainly increased, but has it increased enough? Looking at “Internet Trends 2017,” 14 compiled by Mary Meeker of the venture capital firm KPCB, you can see how much the “available peer” count has increased over the past ten years from mobile alone (see Figure 3).

Today, approximately 49% of the
world’s population is connected10—
around 3. 7 billion people, many with
multiple devices—so that’s a big
pool of edge devices. Peter Levine of
the venture capital firm Andressen
Horowitz has taken us out a few years
further and predicted we will shortly
be going beyond billions and heading
toward trillions of devices. 12

You can get a sense of scale by looking at an Edgemesh network for a single e-commerce customer’s website with a global client base.

It’s probably safe to say there are enough devices online, but does the average user stay online long enough to be available? What is “long enough” for a peer to be useful?

A sensible place to start might be to want peers to be online long enough for any peer to reach any other peer anywhere on the globe. Given that, we can set some bounds.

The circumference of the Earth is approximately 40,000km. The rule of thumb is that light takes 4. 9 microseconds to move 1km through fiber optics. That would mean data could circumnavigate the globe in about 1/5th of a second (196 milliseconds). Oh, if wishing only made it so, but as Stanford Unversity’s Stuart Cheshire points out in “It’s the Latency, Stupid,” 6 the Internet operates at least a factor of two slower than this. This 2x slowdown would mean it would take approximately 400 milliseconds to get around the globe. Unfortunately, I have spent some time in telecom— specifically in latency-optimized businesses13 —and I think this time needs to be doubled again to account for global transit routing; thus, the data can go around the world in some 800 milliseconds. If users are online and available for sub-800 millisecond in-

Figure 1. Bandwidth rates (upload/download, broadband/mobile).

Terrestrial Yo Y% Mobile Yo Y%

Region
Download
(Mbps)

Upload
(Mbps) Download Upload
Download
(Mbps)

Upload (Mbps) Download Upload

UnitedStates 54. 97 18. 88 42% 51% 19. 61 7. 94 794% 28% UnitedKingdom 40. 12 40. 12 18% 23% 24. 19 10.03 38% 31% Singapore 190.9 178.69 18% 20% 45. 61 17. 93 16% 13% HongKong 153.53 146.69 13% 0% 18. 9 8. 78 5% 1% Brazil 16. 53 6.08 8% 11% 11. 31 4. 27 37% 35%