Nobody really does calculations for “average” speed on PON for business. The typically methodology is to add customers to PON as long as capacity allows, and at some deflection point look into either a) splitting PON into a smaller serving group, or b) migrating larger bandwidth consumers to higher speed PON. To put it into perspective, it is very common to have different PON branches with very different number of customers, ranging from 2-3 to 16-20 or more, all depending on the customer density in the given area. Residential builds are more predictable in that number of homes passed can be to some extent predicted and accounted for in capacity design. Business services do not have really this luxury.
I do not agree with the statement: “more cost effective to be able to add additional capacity beyond that of the first 25G by being able to allocate ONUs to additional instances of 25G” – this might work for future residential access, but it makes very little sense for business services, where capacity growth is much faster than in residential, primarily because of types of provided services, as well as SLA profiles. In fact, if we were locked down to 25G in the future, it would bring the need for a new standard sooner, which defeats I believe one of the requirements for scalable architecture up to 100G.
Regards
Marek Hajduczenia, PhD, CCNA CSCO12874393
Network Architect, Principal Engineer
Bright House Networks
From: Francois Menard [mailto:fmenard@xxxxxxxxxxx]
Sent: Monday, March 07, 2016 2:36 PM
To: STDS-802-3-NGEPON@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_NGEPON] 25G ONU Options to increase Network Capacity
Marek said:
Re. 1) – the statements on flagship speeds apply really only to residential deployments. In terms of business services, there are no flagship speeds, and we deploy any data rates that make economic sense on the given platform.
I agree that ‘Flagship & Billboard’ speeds are ‘residential’ concepts, wherein non-guaranteed & temporary peak speed have a perceived value.
I understand that business services are dimensioned according to an SLA based on ‘Sustained Average Throughput’ on the PON.
When 32 customers share a single 100 Gbps pipe, the average throughput per customer is 100 Gbps / 32 = 3.1 Gbps.
For some reason there is an underlying assumption that we need to build 4x25G system, that looks and feels like NG-PON2.
By being able to effect channel bonding at the PCS layer, the MAC rate can be greater than that of a single Ethernet lane. So it may be easier to argue that the 4x25G is more of a 4x25 Gbp PCS Lane system than a 4x25G MAC rate system. The idea is that when there is a need to burst at a faster rate than 25G, two PCS lanes of 25G can be bonded into a 50G MAC rate and four PCS lanes of 25G can be bonded into a 100G MAC rate. I understand that the are that in this case, should these lanes need to make use of λ0 for instance, than no 25G ONU at λ0 are allowed to burst when a 100G ONU is monopolizing all PCS lanes while transmitting.
It would seem to be much more cost effective to be able to add additional capacity beyond that of the first 25G by being able to allocate ONUs to additional instances of 25G, rather than make it mandatory to make use of 50G & 100G ONUs.
I am concerned with the limitations that would stem from NG-EPON having only a single channel of 25G and requiring that any expansion of capacity beyond 25G necessarily be done through the addition of 50G ONUs with a 2.5X relative cost or 100G ONUs with a 5.5X relative cost.
This would mean that any expansion beyond 25G would be occurring at greater cost than which could be afforded by the transition of Tunable ONUs from their current 3.5X relative cost to a plausible 1.5X relative cost between now and such time as 100G EPON becomes deployed by operators.
-=Francois=-