[Note: AT&T weathered the storm just fine. There were no reports of outages or delays on launch day.]
AT&T will test its mobile network's resilience on 25-Sep-09 when it rolls out an upgrade with support for MMS (Multimedia Messaging Service) for iPhone users in the United States. MMS allows including audio, video, pictures alongside text messages. The iPhone OS has supported MMS since version 3.0's release in June 2009, and many international carriers already offer the service.
Some press reports cite internal sources who believe the increased network load could be 40 percent above normal usage as people try the service for the first time. Recent reports continue to show that AT&T is facing a strain on its network, delaying Visual Voicemail messages and dropping calls. Elinor Mills wrote about calling problems at some length at CNET recently.
The big news about MMS is that it's entirely boring. If you've ever sent email with a photo embedded, MMS isn't much more exciting than that. Sure, it works across carriers (where a phone and carrier support it), and it's easier to send an MMS than an email message because of better software integration. (Although that's debatable on the iPhone, where email is easy to send.)
But MMS is a huge win for carriers in terms of profit margins, which are very high, while still consuming extremely low bandwidth relative to other behavior. A 1 MB email message containing several photos would cost nothing to send on an iPhone, whereas a 100 KB MMS message would require either a $5 to $20 per-month plan or $0.30 to send without a plan. You can see which the carriers would prefer.