Why is my iPad connecting to S3 and using lots of bandwidth? [closed]

Question

I noticed my connection has been extremely slow lately at some random times. I figured someone in my house was torrenting, so I booted up tcpdump on the router. What I found out is that it appears that I am the culprit.

My iPad is uploading at about 80 kB/s (which is my maximum upload speed) and completely saturating the network:

09:23:51.414956 IP s3-external-1.amazonaws.com.https > My-iPad.53293: . ack 19082635 win 61472
09:23:51.421163 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19124395:19125835(1440) ack 5762 win 16384
09:23:51.421498 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19125835:19127275(1440) ack 5762 win 16384
09:23:51.449702 IP s3-external-1.amazonaws.com.https > My-iPad.53293: . ack 19085515 win 61472
09:23:51.453923 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19127275:19128715(1440) ack 5762 win 16384
09:23:51.454259 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19128715:19130155(1440) ack 5762 win 16384
09:23:51.484554 IP s3-external-1.amazonaws.com.https > My-iPad.53293: . ack 19088395 win 61472
09:23:51.487558 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19130155:19131595(1440) ack 5762 win 16384
09:23:51.488039 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19131595:19133035(1440) ack 5762 win 16384
09:23:51.521405 IP s3-external-1.amazonaws.com.https > My-iPad.53293: . ack 19091275 win 61472
09:23:51.525480 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19133035:19134475(1440) ack 5762 win 16384
09:23:51.525816 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19134475:19135915(1440) ack 5762 win 16384
09:23:51.558379 IP s3-external-1.amazonaws.com.https > My-iPad.53293: . ack 19094155 win 61472
09:23:51.561336 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19135915:19137355(1440) ack 5762 win 16384
09:23:51.561816 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19137355:19138795(1440) ack 5762 win 16384
09:23:51.593105 IP s3-external-1.amazonaws.com.https > My-iPad.53293: . ack 19097035 win 61472
09:23:51.596258 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19138795:19140235(1440) ack 5762 win 16384
09:23:51.596737 IP My-iPad.53293 > s3-external-1.amazonaws.com.https: . 19140235:19141675(1440) ack 5762 win 16384

I unplugged the iPad, and it stopped uploading. When I plugged it in again, it started again.

My guess is it's uploading something to Apple (who must be using S3), but I can't find any information about that on Apple's site or elsewhere online.

What's it doing, and how can I either stop it or throttle its bandwidth to a more reasonable limit (anything over 60 kB/s completely saturates my network).

Answer 1

This is caused by backups to iCloud, Apple's cloud storage service. While I can't find any official information from Apple, some sites are reporting that Apple is using both Azure and S3 to store iCloud data.

I've not found any way to limit the bandwidth through the device itself; limiting the throughput on the router seems to be the only way to throttle it¹. It can be turned off completely in the iCloud settings.

Backups are only done while connected to USB power (for power-saving reasons), which is why unplugging it stopped the backup.

^{1. Theoretically it should be possible to throttle only to a certain host (S3) but I went ahead and just throttled the iPad's bandwidth to all hosts}