Uncharted Territory

September 4, 2012

Skype Video Call Bandwidth Usage

Filed under: Internet, Skype, Technology, Telecomms — Tim Joslin @ 3:57 pm

For once my title avoids any of my usual no doubt misguided attempts at wit or humorous alliteration. For this is a serious business. I mentioned a couple of days ago my confusion at having to deal with one particular supplier, Thames Water, as a result of having to move home. My preferred mode of behaviour is to set up Direct Debits with these guys and forget about them, apart from filing away bills in case there’s some kind of a problem – which is why I prefer paper bills sent to me in the post rather than online ones to which the supplier controls access. But let’s not digress too much as that would defeat the object of the title chosen for this post.

My Thames Water induced confusion has been as nothing compared to the ordeal of having to switch internet provider. I’ll save the long story for another post, but against my better judgement – nay, naively, or perhaps through mis-selling – I’ve chosen a usage-limited package, the heavily advertised BT Total Broadband Option 1. I thought 10GB per month would be plenty since the household very rarely downloads anything at all, and downloads were all BT happened to mention:

And 10GB/month would be plenty if it weren’t for that pesky Scooby-Doo, sorry, Skype.

For it rather seems Skype video calling uses as much bandwidth as it can get its hands on, at least up to around 1GB/hour – which is quite a bit when you’ve only got 10GB to use a month.

Now, I’m not such an idiot that I didn’t think of this before signing on the dotted line with BT. I assumed Skype would use about a 10th of what it is using. My logic was essentially that Skype is nowhere near movie quality and BT suggest on their website that you could download 15 movies a month with your 10GB allowance (seems a bit optimistic – more on that another time) and random sampling of BBC iPlayer content suggests a 60 minute programme takes up 640GB.

And indeed when I tested Skype video calling over a relatively slow work WiFi connection to the BT ethernet-connected desktop PC at home it did seem to use only 30kBps bandwidth (big B for byte, not little b for bit!) in total for both upload and download, which does indeed equate to around 100MB/hour or 0.1GB/hour.

But then I tested Skype at home from the desktop PC to a laptop operating over WiFi. And – besides shattering all the windows with feedback (best turn the radio off before you try this yourself!) – I did indeed manage to consume bandwidth at a prodigious rate, equating to the 1GB/hour I’ve already mentioned. Though the beauty of this experiment was that the usage seemingly didn’t count towards my 10GB monthly allowance – Skype is peer-to-peer, so I guess the video calls never left the flat!

How did I determine my bandwidth usage?

I’m presuming the answer to this question will be the most useful part of this blog entry – at least for those, like me, using Windows 7 Home Premium (and possibly those with other recent Windows releases) – so I’ll go into some detail and provide some pretty pictures.

In fact there are at least 3 simple ways of determining the same information (besides BT’s oh so useful daily updated Broadband Usage “Monitor”). I used them all and the results were consistent.

1. Skype’s Call Technical Information

Skype maintain a set of answers to FAQs, such as FA10415, Can I see how much bandwidth a video call is using? which I first came across in the answer to a query about a household exceeding a 250GB a month usage limit(!). The procedure FA10415 is slightly confusing in two respects.

First, FA10415 starts off by detailing how to switch on the feature to display technical information during calls, before noting that this has been unnecessary since Skype 5.2. As I’m on it would seem there have been a lot of updates since version 5.2. So, unless you have an old version of Skype, the first part of FA10415 is redundant. You can check your Skype version by using the drop-down menu to select Help, About Skype. You can keep up to date via Tools, Options, Advanced, Automatic Updates, presuming you have Administrator access.

Second, the menu item Call Technical Info only exists during calls! – it would be more consistent for it to be greyed out when not available.

So, to determine their video or voice-only call bandwidth usage most Skype users will simply be able to call up the Call drop-down menu:

Selecting Call Technical Info should result in something like this (personal information redacted for reasons of paranoia):

The figures we’re interested in are at the bottom of the Basic section, i.e. in this case upload at 56kBps and download 146kBps (B for byte in this case, b for bit being more usual). This represents a lot of bandwidth, and in fact both PCs I used settled down to just under 150kBps for both upload and download after I took the above snapshot.

A total of 300kBps represents bandwidth usage of 300*3600kBph (hour), i.e. 3*360MBph – call it a round 1GBph!

2. Connection Status information

You can verify what Skype is telling you, and determine bandwidth usage over a period of time by viewing your network Connection Status Information. If you’re using an ethernet cable to access the internet you need to right-click on the network icon (two terminals at the right side of your taskbar – sorry no pic handy) and then select Open Network and Sharing Centre. You can also call up the Network and Sharing Centre from the Control Panel. From the Network and Sharing Centre you just need to click on View Status for your network to call up the required data. You might then see something like this:

If you’re using WiFi you can access the Network Connection Status directly (i.e. without visiting the Network and Sharing Centre) by clicking on the network icon (the 5 bar signal strength indicator at the right side of the task bar) then right-clicking the relevant network (the one that’s Connected!) and selecting Status.

3. Task Manager information

Finally, if you want a snapshot of second-by-second network bandwidth usage, you can use the Task Manager. Holding CTRL and ALT while pressing DELETE calls up a menu. Selecting the last entry, Start Task Manager fires up a window allowing you to view what’s going on in your system in real time. Tab Networking is the one we want. Calling it up then initiating a Skype call might result in something like this:

The grid of subdivisions of axis units are not the ones I would have chosen – each box seems to represent 6 seconds (10 per minute) and dividing 5% into three, with one label is odd, to say the least – but it’s clear enough what’s going on.

In this example you can see that Skype (nothing else of significance was using the network at the time) managed to use around 2.5 to 3% of the 54Mbps bandwidth available. Note that we’re now working in b for bits, rather than B for bytes. Irritating, isn’t it? Anyway, 2.75% of 54Mbps is 1.5Mbps, WLEE (within the limits of experimental error) as they told me to write in O-level science. Dividing by 8 to get bytes from bits results in 200kBps, WLEE. This is not so different to the 56kBps upload + 146kBps download speeds in the snapshot of the same call I took a few minutes later using Skype’s Call Technical Info (see section 1, above).


It seems all three methods of determining real-time bandwidth usage by Skype on a Windows 7 machine yield consistent results, compatible with the getting on for 1GB per hour of bandwidth usage during Skype video calls deduced from BT’s daily bandwidth usage summaries. Task Manager provides only one figure for upload and download (though maybe more information could be gleaned were one to break the hacker’s code and actually RTFM, read the manual), but otherwise the choice of which method to use depends merely on convenience, or whether one prefers to deal in bits or bytes!

Issues arising may (meaning I don’t always keep my promises!) be dealt with in subsequent posts. These are unlikely to include how to reduce Skype’s network bandwidth usage, since investigation suggests that such a capability does not exist for users (perhaps they’d consider introducing it) – though please feel free to make a comment disabusing me of this notion. I do have plenty to say, though, on BT’s marketing of their 10GB BT Total Broadband Option 1, so watch this space!


1 Comment »

  1. Duh. It’s almost a year later, but someone had to say it: OF COURSE A CALL INSIDE YOUR LOCAL NETWORK DOESN’T COUNT TOWARDS YOUR BANDWIDTH QUOTA. It never leaves the network, and Skype fires up it’s data rate to the maximum allowed (a lot on a LAN).

    Comment by Bilbo — April 17, 2013 @ 7:26 am

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