DataFox is an easy to use, cross platform & customizable extension to Firefox, which you can use to monitor your DataOne Broadband & MTNL TriBand bandwidth usage. It is not a standalone program and will only work when installed as an extension to Firefox. 

DataFox is non-intrusive and does not monitor your network activity, it just obtains the information from the BSNL / MTNL websites. The collected info is displayed in your Firefox status bar area and additional info is displayed in a tooltip. The latest version is DataFox 1.4 which works with BSNL's new bbservice.bsnl.in portal.

Note: These only work if you fill in the Bandwidth limit field you see on the General preference page. 

Let us assume you have 6000MiB of transfer for the month, and you're in the month of June (which has 30 days). DataFox will calculate that you have 6000/30 = 200MiB of transfer available per day (let's call this TPD); assuming that you're using your bandwidth at a regular rate. 

This means, on the 1st of the month, you're allowed 1*TPD = 200MiB, on the 5th of the month, your usage could go upto 5*TPD = 1000MiB and you'd still be within limits. 

So, 

Surplus Transfer = Allowed Transfer - Chargeable Transfer (Chargeable Transfer is the actual bandwidth that is recorded by your ISP and deducted from your bandwidth cap - this is the figure you usually keep track of). 

Now, if your Surplus Transfer is negative, DataFox puts your usage in the Overlimit category and the Overlimit colors will be used for the text and the progress bar (see the Progress preference page). 

If your Surplus Transfer is positive, your usage is OK and a different set of colors is used. 

It is important to note that the Surplus transfer is not the difference between your monthly limit and the amount used till date. It is the difference between the allowed usage on that date as calculated by DataFox and your actual usage. The following illustration should help you to understand how these figures are calculated. 

Bandwidth cap: 6000MiB, Nr. of Days in month: 30, therefore TPD = 200MiB. 

Chargeable Transfer as recorded by your ISP = 850MiB. 

Allowed Transfer as calculated by DataFox = 5 * TPD = 1000MiB. 

Surplus Transfer = Allowed - Chargeable = 1000 - 850 = 150MiB. 

Surplus Transfer is positive, usage is OK. 

Chargeable Transfer as recorded by your ISP = 3300MiB. 

Allowed Transfer as calculated by DataFox = 15 * TPD = 3000MiB. 

Surplus Transfer = Allowed - Chargeable = 3000 - 3300 = -300MiB. 

Surplus Transfer is negative, usage is Overlimit. 

Chargeable Transfer as recorded by your ISP = 6500MiB. 

Allowed Transfer as calculated by DataFox = 29 * TPD = 5800MiB. 

Surplus Transfer = Allowed - Chargeable = 5800 - 6500 = -700MiB. (Note how the surplus is -700 and not -500 as you still have a day to go before the month ends) 

Surplus Transfer is negative, usage is Overlimit. 

DataFox is also capable of calculating the allowed usage on an hourly basis instead of on a daily basis (see radio buttons on Progress preference page). 

Here DataFox calculates a TPH figure as 6000 MiB / (30 * 24) hours = 8.3MiB per hour. 

At 2pm on the 5th of the month, 4 * 24 + 14 = 110 hours have passed. Your allowed usage at this time is: 110 * 8.33 = 916.3MiB. The remaining calculations are the same. I programmed this in before the daily mode and then I realized this was probably too accurate to be useful, so I made the daily mode the default. 

DataFox provides a few variables allowing users to customize the text displayed as a tooltip and on the statusbar (see General preference page). Beyond simple substitution of variables for their values, after the substitution, DataFox attempts to "eval" the resulting string as if it were a snippet of Javascript. If this results in a Javascript String object, DataFox will use that string instead. 

Consider the following tooltip string where cX is 3000: 

Chargeable transfer: {cX} MB 

After substitution: 

Chargeable transfer: 3000 MB 

The above is not valid Javascript and will therefore be displayed as is. 

If we change the string to the following (assume the date is the 13th): 

var d = (new Date()).getDate(); 

'Chargeable transfer per day: ' + {cX}/d + ' MB' 

After substitution: 

var d = (new Date()).getDate(); 

'Chargeable transfer per day: ' + 3000/13 + ' MB' 

The above is a valid Javascript snippet and the result displayed will be: 

Chargeable transfer per day: 230.7693 MB 

Here's an advanced example which prints your daily average transfer and your download/upload ratio, please note the single quote characters, they are essential: 

var d = (new Date()).getDate(); 

'Up: {tS}MB Down: {tR}MB\n' + 

'Chargeable transfer: {cX}MB ({uP}%)\n' + 

'Surplus transfer: {sX}MB\n' + 

'Hours: {tH} Period: {YM}\n' + 

'Last updated: {tT}\n' + 

'Daily average: ' + Math.round(1000 * {tX}/d) / 1000 + '\n' + 

'Download/Upload: ' + Math.round(1000 * {tR}/{tS}) / 1000; 

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