nanog mailing list archives
Re: Capacity planning , transit vs last mile
From: Blake Hudson <blake () ispn net>
Date: Fri, 1 Apr 2016 09:32:04 -0500
Jean-Francois Mezei wrote on 4/1/2016 1:38 AM:
While the formula provided by Baldur may very well be accurate, it allows projections on several data points (advertised speed, average per customer speed, customer counts, customers online @ peak) which may or may not turn out to be accurate or could be fudged to create misleading estimates. I think a simpler projection, taking harder numbers into account may be easier to implement as a requirement and less likely to be gained by someone. I think it would be sufficient to simply specify a minimum Mbps bound per customer (aka a committed information rate) for a network build. As you and others have stated, typical current use is currently ~1-2Mbps per household/customer. If we forecast growth to be 30% per year, a 10 year build might anticipate using a last mile technology capable of providing ~13Mbps CIR [using the compound interest formula where A = 1Mbps * (1 + 0.3)^10years ] in 10 years time. This projection uses growth, which has historical precedent, and current usage, which you indicate is already being measured and reported. Something that is less static would be the technology improvements. An operator might be able to assume gpon now and 10G-pon in a few years (or DOCSIS 3.0 -> 3.1), to meet future requirements.My question has to do with how does one determine that theshold where you start to get more chaotic patterns and need more capacity per customer than if you had over 1000 customers ? My goal is to suggest some standard to prevent gross underprovisioning by ISPs who win subsidies to deploy in a region. From what I am reading, the old standard (contention ratio of 50:1 for residential service) is no longer valid as a single metric especially for smaller deployments with higher speeds.
Regarding your question about how such a formula might scale, especially on the small end. I think it's a valid concern. This could be measured in today's rural HFC networks or wireless network where it may be common to have fewer than 50 customers sharing a 40Mbps-100Mbps access media. I think you'll find that at this small a scale, the 1-2Mbps per customer number probably still holds true. You obviously won't be able to sell 1000Mbps service (or even 100Mbps) to these customers, given the access media limitations. This could be addressed elsewhere in your requirements. For example, if it were required that operators "...offer services capable of delivering 100Mbps service to each end user with a CIR derived from table A", the operator would be forced to provide a 100Mbps+ pipe even if it were only serving 10 customers on that pipe that see ~ 20Mbps aggregate peak period usage today. That 80Mbps of overhead is not wasted, it's intentionally there for your users' future needs and to provide burst capacity. A smart operator would probably avoid such cases and attempt to aggregate users in ways that minimize expense and make the most of the access technology.
--Blake
Current thread:
- Re: Capacity planning , transit vs last mile Baldur Norddahl (Apr 01)
- <Possible follow-ups>
- Re: Capacity planning , transit vs last mile Mike Hammett (Apr 01)
- Re: Capacity planning , transit vs last mile Blake Hudson (Apr 01)
- Re: Capacity planning , transit vs last mile takashi tome (Apr 03)