Wednesday, 31 July 2013

NBN: Predicting access rate from Download volume

The Sandvine exponential traffic distribution (1% uses 10%, 50% use 6.4%) suggests that for a mean of 30GB, the top 1% download 300Gb/month. That's around 90% utilisation of 1Mbps. "Theoretically", achievable on all NBN plans.

For modelling, how to tie customer download volume to access rate. Normally in bulk statistical analyses, don't care about per-group access rates, but with NBNCo's tiered access pricing, it matters...

My thesis is that time to complete tasks is critical determinant in access rate selection.

For high-volume users, 30-300GB/mth, I posit there are 3 classes of users [not based on research]:

  • WFH: work from home, exchanging files with server.
    • mostly daytime, 5-days per week
      •  20 days/month
    • equal volume per work-day
    • roughly equal download:upload split
      •  60%::40%
  • HVB: High-volume home user, browsing, images & videos.
    • mostly evenings, not every day
      • 10-20 days/month
    • volume variable
    • dominated by download
      • 80%::20%
  • SRV: Scheduled loads. (backups, video/image upload/sync)
    • overnight (02:00-05:00) 7-days,
      • 30 days/mth
    • Mostly upload
      • 5% :: 95%
I'll use 300GB/month in calculations for 100/40Mbps, or 10MB/sec down, 4MB/sec up.
30GB/month is 10% of the time of 300GB

Download time for 4GB = 400 seconds
Upload time for 1GB = 250 seconds.

WFH

Daily 300GB ÷ 20 days = 15GB/day (over 8-10 hours)

Ratio: 60% :: 40% = 9GB download, 6GB upload

300GB Time = 900 seconds + 1500 seconds = 2400 seconds = 40 minutes in 8 hours (8.3% wait-time)
30GB Time = 240 seconds


HVB

Daily 300GB  ÷ 15 days = 20GB/day (over 6-8 hours)

Ratio: 80% : 20% = 16GB download, 4GB upload

Time = 1600 seconds + 1000 seconds = 2600 seconds = 45 mins in 6 hours (12% wait-time)
30GB Time = 260 seconds


SRV

Daily 300GB  ÷ 30 days = 10GB/day (over 3-4 hours)

Ratio: 5% :: 95% = 0.5GB download, 9.5GB upload

Time = 50 seconds + 2375 seconds = 2424 seconds = 40-45 minutes in 3 hours (22.5% wait-time)
30GB Time = 240 seconds


Summary:

The 3 case studies, surprisingly, have similar link use times: 2400-2600 seconds/day active.

What this doesn't inform is the threshold value - is it 240 seconds (unlikely) or 800-1,000 seconds or higher?

Perhaps the perceived download time of large files, file 4GB for a DVD is a reliable indicator.
download 4GB 
100 Mpbs = 400 seconds
50 Mbps = 800 seconds
25 Mbps = 1600 seconds
12Mbps = 3200 seconds

Upload 1GB
40 Mbps = 250 seconds
20 Mbps = 500 seconds
10 Mbps = 1,000 seconds
5 Mbps = 2,000 seconds
1 Mbps = 10,000 seconds


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