Robin Eckermann told iTWire that the core of the CVC problem — consumers experiencing slow speeds on the NBN after they switched from their ADSL or cable connections — was the contention ratio at which retail service providers operated the "shared pipes".

There has been a great deal of debate in recent months about the NBN, as more and more people are told their residences can be switched to the network. Nearly every day there are tales in various media outlets about customer complaints.

Eckermann said a level of contention was normal and reasonable, simply because not every customer connection ran at the maximum speed all the time.

But when RSPs did not have sufficient capacity at peak times to support the average bandwidth needs of their customers, then performance would be degraded.

"NBN Co could do users a great service by allowing them to query the current contention ratio at which different RSPs were operating the CVCs that support customers in their area," Eckermann said. 

"For example, if an RSP was supporting (say) 100 customers at 100 Mbps connection speed, 100 at 50 Mbps, 500 at 25 Mbps and 300 at 12 Mbps over a CVC, the total *theoretical* demand that these customers could generate is 31,100 Mbps. 

"If the RSP was buying only (say) 300Mbps CVC capacity to support all these 1000 customers, they would be operating the CVC at a contention ratio of around 104:1 – and at this level, it is predictable that there would be congestion at busy times."

Eckermann said that if other RSPs were operating their CVC capacity at lower contention ratios, customers could make informed choices about the trade-off between the monthly cost of a service, and the likely exposure to congestion during peak times.
"In my view, this would be an effective and comparatively low cost approach to monitoring NBN performance," he said.