The 100 Gbit/s problem in your network

William McCall william.mccall at gmail.com
Tue Feb 12 17:52:50 UTC 2013


On Mon, Feb 11, 2013 at 10:05 PM, Tim Durack <tdurack at gmail.com> wrote:

>
> Multicast is dead. Feel free to disagree. :-)
>
> Tim:>
>


I really wish I could agree! It would have saved me some time dealing with
it.

There is the argument of alternative bit rates, compression, etc., but HD
streams are assumed[1] at 15 Mbps.

At 100Gbps, I can do max 6826 streams of HD streaming. Multicast
deployments laugh at this pathetically low number of viewers.

At an upstream aggregation point, I can easily serve ~128K subs (7 slots, 8
ports per slot, 3 ports per $ACCESS, 8K[3] users per $ACCESS, 1 slot for
upstream). I now assume 2.5 STBs per sub[2]. This results in, more or less,
320,000 STBs.

To me, the math says its not dead and we'll need a couple of orders of
magnitude (to accommodate the core) in speed improvements to get the same
delivery unicast.

[1] http://www.cablelabs.com/specifications/OC-SP-CEP3.0-I04-121210.pdf Lists
15Mbps as safe harbor value for HD
[2] http://www.aceee.org/files/proceedings/2012/data/papers/0193-000294.pdf Has
some stat (good or bad) wrt STBs/household
[3] uBR10K (my $ACCESS comparison) specs out for max 64K CPE. One of my
guys indicates to me that the actual number might be closer to 15-25K CPE
on a given node. Please make adjustments as necessary.

(required note: employer is Cisco. Views are my own.)

-- 
William McCall



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