The scale of streaming video on the Internet.
bicknell at ufp.org
Thu Dec 2 14:21:51 CST 2010
Hidden in the Comcast and Level 3 press release war are some
facinating details about the scale of streaming video.
Comcast suggest that "demanded 27 to 30 new interconnection ports".
I have to make a few assumptions, all of which I think are quite
reasonable, but I want to lay them out:
- "ports" means 10 Gigabit ports. 1GE's seems too small, 100GE's seems
too large. I suppose there is a small chance they were thinking OC-48
(2.5Gbps) ports, but those seem to be falling out of favor for cost.
- They were provisioning for double the anticipated traffic. That is,
if there was 10G of traffic total they would ask for 20G of ports.
This both provides room for growth, and the fact that you can't
perfectly balance traffic over that many ports.
- That substantially all of that new traffic was for Netflix, or more
accurately "streaming video" from their CDN.
Thus in round numbers they were asking for 300Gbps of additional
capacity across the US, to move around 150Gbps of actual traffic.
But how many video streams is 150Gbps? Google found me this article:
It suggests that low-def is 2000Kbps, and high def is 3200Kbps. If
we do the math, that suggests the 150Gbps could support 75,000 low
def streams, or 46,875 high def streams. Let me round to 50,000 users,
for some mix of streams.
Comcast has around ~15 million high speed Internet subscribers (based on
year old data, I'm sure it is higher), which means at peak usage around
0.3% of all Comcast high speed users would be watching.
That's an interesting number, but let's run back the other way.
Consider what happens if folks cut the cord, and watch Internet
only TV. I went and found some TV ratings:
Sunday Night Football at the top last week, with 7.1% of US homes
watching. That's over 23 times as many folks watching as the 0.3% in
our previous math! Ok, 23 times 150Gbps.
Yowzer. That's a lot of data. 345 10GE ports for a SINGLE TV show.
But that's 7.1% of homes, so scale up to 100% of homes and you get
48Tb/sec, that's right 4830 simultaneous 10GE's if all of Comcast's
existing high speed subs dropped cable and watched the same shows over
I think we all know that streaming video is large. Putting the real
numbers to it shows the real engineering challenges on both sides,
generating and sinking the content, and why comapnies are fighting so
much over it.
Leo Bicknell - bicknell at ufp.org - CCIE 3440
PGP keys at http://www.ufp.org/~bicknell/
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