Blowing past Comcast's bandwidth cap

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In all the heady excitement of backing up all my computers over the Internet after writing my comprehensive review of online backup services for Macworld, I forgot one tiny but massively important fact: some Internet service providers limit the amount of data you can transfer every month. Including mine.

So here’s the story: I went ape-wild in uploading and downloading files both at work and at home. At home, I was particularly interested in duplicating a 300 GB set of photos, movies, and other documents that my wife and I have stored on a networked server. I’ve created clones and archives and taken them off site, as well as uploaded specific images to Flickr. But I was feeling quite out of date.

In the aftermath of comparing all of those backup services, I chose to use CrashPlan ( ), and set up local, peer-to-peer, and CrashPlan Central backups. I set up my work and office machines to use local high-capacity drives to store both their own backups as well as a mirror of their counterparts’, and pointed to CrashPlan Central for cloud storage.

My setup was a pretty clever backup strategy. But as a broadband move, it was huge mistake.

You see, my provider at home is Comcast, and the company has a now well-documented 250 GB per month bandwidth cap for combined upstream and downstream traffic. According to the reasonable person I spoke to at Comcast’s security and policy department, I had used more than 600 GB in August; one more month of overage and I’d have my service canceled and not be eligible for service for another 12 months.

I don’t dispute that I used a massive amount of bandwidth in August. It was just so easy to do, I didn’t really consider what was happening until it was too late. At my house, which has Comcast’s “up to 15Mbps downstream” service, I can actually transfer files downstream at approximately 25Mbps. But by my calculations, this means that I could probably blow through Comcast’s bandwidth cap in a single day if I worked at it. (The upstream rate is far slower, but I have topped 10 Mbps in that direction, too.)

The biggest problem with Comcast’s bandwidth cap is not the cap itself, but the fact that Comcast doesn’t provide any tools or alerts for customers to make sure they stay on the right side of the line. (The Comcast representative I spoke to suggested I install software on every computer and add the totals together myself.)

Compare this with the tools attached to my Chase credit-card account. I can have Chase alert me when payments post, when transactions exceeding a certain size have been posted, and when a billing date approaches. Of course, if I miss paying on time, then it’s my own damned fault.

If Comcast had paired its cap policy with alerts and online reporting, I would have noticed the pace of my bandwidth-hogging backups, throttled them, and gradually spaced them out. Instead, I got a final warning and am now one step away from no longer being a Comcast customer.

The Comcast representative I spoke with said that the company is definitely looking closely at providing a bandwidth-monitoring tool. Perhaps the first step Comcast could take is providing it to people on the inside: the person I talked to at Comcast couldn’t actually tell me how much bandwidth I’d already used in September. For all I know, I’m already over the cap and am a two-time offender with a red-flagged account.

This is an issue that could hit many of you, as well, if you take the advice I wrote in my article. None of the online-backup services I reviewed provides any overall bandwidth usage monitoring or tools, although most provide some kind of throttle to prevent overwhelming a network or a broadband connection. (All the packages tell you how much you’ve backed up, but those aren’t cumulative totals.)

My top pick in the article, CrashPlan, does offer a couple of ways around the problem I ran myself into, and I should have considered both of them. First, for peer-to-peer backups, you can copy a local backup, take it physically to the other location, and point CrashPlan at the folder. Then only changes to the original backup have to be transferred over the network.

Second, CrashPlan Central offers a mail-in seeding option for up to 1 TB of files. True, this costs either $125 (ground) or $145 (2-day) with prepaid shipping. But you can include backups from multiple machines, and it might have been worth the cost.

The moral of this story? I won’t know the outcome until October, but I should have been more alert to overages, and Comcast needs to step up to the plate in providing monitoring tools and alerts. I freely admit that it was my own massive file transfers that got me into this situation. I only wish Comcast provided tools to warn me that I was about to break its rules, so I could change my behavior before receiving a call from Comcast security.

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