Pipeline Publishing, Volume 3, Issue 11
This Month's Issue:
The Long Arm of Telecommunications Law
download article in pdf format
last page next page
Carrier Grade: The Myth and the Reality of Five Nines
back to cover

article page | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |

report on the quality of the early frame relay network. A big requirement was to measure the availability of the network and produce one monthly number for availability. He was a data guy and trained as a scientist and engineer. So he set out to “measure” availability – directly measure availability. His team developed automated methods of pinging every network port and of correlating down and up link alarms; by merging these two methods (direct measured ping non-

The Voice NOC had seemingly qualified away rigor in order to meet the mandated goal of five-nines.


removal from service of terminating CPE routers at the customer presence. He then explained the difference between precise and accurate. He tried to explain that normalization (or adjustments) was not empirically possible and the measure should be just one of many indications of customer usage after uptake. Further, he showed that


responses and interpolated differences in time between down link alert and uplink alert), an automated measure of network up time was generated. This was sent up the management chain every month. After a few months, down from the management chain came the request to generate this KPI weekly, next month it became a demand for daily data. Finally the newly appointed General Manager of the division paid a personal visit to Wedge. The GM needed to find out why the network was “so bad”. The automated network availability figures were much lower than five-nines. Five-nines availability was the corporate standard and the accounting people were “going to shut down the network if the quality did not immediately improve.” In the face of this terrible report card, the VP of Engineering was blaming the VP of Operations (“You cannot run a network or fix anything on time”) who was tossing the responsibility right back (“You provided us inferior equipment”). Furthermore the Voice Network division, using a different set of calculations, said their network met five-nines and this is what all the customers expect. “Your inferior data network is dragging us down.”

Wedge spent a day presenting the methodology for measuring and computing availability. He stood firm that the measure was absolutely precise, but not necessarily accurate since they could not control the


the number was steadily getting better as more units were deployed and more customers placed commercial applications on their VPNs (and so kept their routers running). It was here that Wedge learned that this approach to calculating availability, that the data guys had developed from ground zero (read through IETF group brainstorming sessions), was not the normal telecom approach.

It seems that in order to meet the GOAL of five-nines, which had somehow become transferred from an individual network element requirement to an overall network requirement, the voice telecom NOC had successively kept ruling outages out of the computation of “availability.” Voice people reported availability out of their trouble ticket system. There was no direct measurement of the network. Availability was computed from the time a ticket was opened until it was closed. Than came the exclusions: only customer opened tickets counted – proactive restorations did not count (if the tree fell and no one noticed before it was propped up, it did not fall), then the beginning of the outage start time was from the time the ticket was opened (a somewhat long time from when the problem physically occurred), and lastly, any time the ticket was transferred to the customer (“on the customer’s clock”)


article page | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |

last page back to top of page next page

© 2006, All information contained herein is the sole property of Pipeline Publishing, LLC. Pipeline Publishing LLC reserves all rights and privileges regarding
the use of this information. Any unauthorized use, such as copying, modifying, or reprinting, will be prosecuted under the fullest extent under the governing law.