Open Radar

 
Summary: iCloud Backup easily saturates a DSL Internet connection and causes other clients on the network to experience extremely slow browsing; makes VoIP calls impossible

Steps to Reproduce: 1. On the iPhone, associate with a WiFi network that has a modest Internet connection (DSL, slower cable connection) and other clients (a MacBook, another iPhone, etc.)
2. Sign in to iCloud with an Apple ID and enable iCloud Backups (from the Settings app.)
3. Allow the phone to sleep while connected to a power source and within range of the Wifi network.
4. After some time, backupd will trigger an iCloud backup. It will begin to upload data.
5. Browse the Internet from one of the other devices on the network. Although plenty of downlink is available, DNS queries and HTTP requests are delayed by 2-3 seconds by the large upload being transmitted by backupd.

Expected Results: backupd should throttle its upload in order to minimize impact to other network users.

Actual Results: backupd does not throttle at all or enough and does impact the network.

Regression: Only in iOS 5.0 and up.

Notes: Here is the device log when a backup begins:

Jan  5 14:56:21 unknown backupd[1809] <Warning>: INFO: Scheduling next backup at 1/5/12 2:56:51 PM
Jan  5 14:56:51 unknown backupd[1809] <Warning>: INFO: Backup starting
Jan  5 14:56:51 unknown backupd[1809] <Warning>: INFO: DeviceID="[snipped]", DeviceName="Pulsar", ProductType="iPhone3,3", BuildVersion="9A405"
Jan  5 14:56:52 unknown profiled[1812] <Notice>: (Note ) profiled: Service starting...
Jan  5 14:56:53 unknown wifid[25] <Error>: WiFi:[347486213.545121]: Client itunesstored is background application
Jan  5 14:56:55 unknown backupd[1809] <Warning>: INFO: Refreshed cache in 1.773 s
Jan  5 14:56:55 unknown backupd[1809] <Warning>: INFO: Snapshot 56 is uncommitted
Jan  5 14:57:01 unknown backupd[1809] <Warning>: INFO: Scanned in 5.489 s
Jan  5 14:57:01 unknown backupd[1809] <Warning>: INFO: Found 26 deleted files in 0.079 s
Jan  5 14:57:01 unknown backupd[1809] <Warning>: INFO: Updated snapshot 56 (added 61 files of size 35.0 MB)
Jan  5 14:57:01 unknown backupd[1809] <Warning>: INFO: Created backup and snapshot in 0.771 s
Jan  5 14:57:01 unknown backupd[1809] <Warning>: INFO: Adding 61 files of size 35.0 MB

If 35.0MB is an unreasonable backup slug, there may be another bug.