Speaking on Deep Background, the Press Secretary whispered:
(Anybody here *NOT* seen cases where the 2 fibers leave the building on opposite
sides, go down different streets - and rejoin 2 miles down the way because
there's only one convenient bridge/tunnel/etc over the river, or similar?)
A friend works for Uncle Sam, and he is required to audit the
routes used on certain high-availability systems, to insure the
diversity we pay for. (It's in the contracts with the carriers..)
He describes it as a long drawn-out exercise in futility. A
non-trivial employee has to spend eons on the task. It's a recursive
onion peeling, or a data version of Tom Lehrer's "I Got It From
Agnes"...
And once done... the errors found, the diversity restored, and the
report signed off; it's soon worthless...because the carriers
soon shuffle things around Yet Again.
And I agree re: the building entrance issue and later choke points.
Anyone recall the time several years ago that most of the Valley was
isolated? One route was across the ?Bay? Bridge; it was down for
planned maintenance when backhoe fade struck around San Jose.
How many paths is enough?
And I agree re: the building entrance issue and later choke points.
Anyone recall the time several years ago that most of the Valley was
isolated? One route was across the ?Bay? Bridge; it was down for
planned maintenance when backhoe fade struck around San Jose.
How many paths is enough?
In my opinion, the following rule of thumb is reasonable.
1 path is enough for a site/enterprise that shuts
down its services evenings and weekends.
2 paths is enough for a site/enterprise that provides
a 24 hour, 7 day per week service.
3 paths is enough for a population center with under
a million inhabitants.
5 paths is enough for a population center with over
a million inhabitants.
And a very few population centers such as New York,
London, Tokyo, and Cheyenne Mountain should probably
have more than 5 paths.
--Michael Dillon
Michael.Dillon@radianz.com writes:
In my opinion, the following rule of thumb is reasonable.
1 path is enough for a site/enterprise that shuts
down its services evenings and weekends.
2 paths is enough for a site/enterprise that provides
a 24 hour, 7 day per week service.
3 paths is enough for a population center with under
a million inhabitants.
5 paths is enough for a population center with over
a million inhabitants.
And a very few population centers such as New York,
London, Tokyo, and Cheyenne Mountain should probably
have more than 5 paths.
Given that anything larger than a single enterprise has no central
coordinating body, how is it useful to say how many paths is "enough"
for a city of any size? Service providers will build as many paths as
make commercial sense, whatever that may be, and if customers have
opinions and are willing to back it up with money, they should express
those opinions to their providers.
So here's the 64GB/s question:
If carriers are being paid to ensure physical separation between
circuits for the life of the circuit, why is it that they haven't
implemented change management systems (and I don't solely mean the
software) to ensure they they *can* (not even that they will) manage to
ensure such separation?
A simple "don't move this circuit without investigation" flag that
would drill-up to higher level flows would seem to be enough -- though
certainly I am not familiar with the internals of the CMSen at such
scale carriers.
Cheers,
-- jra
So here's the 64GB/s question:
If carriers are being paid to ensure physical separation between
circuits for the life of the circuit, why is it that they haven't
implemented change management systems (and I don't solely mean the
software) to ensure they they *can* (not even that they will) manage to
ensure such separation?
Simple math. The cost of the occasional SLA credit and/or circuit
regrooming when the customer discovers a non-diverse path where one
was specified is obviously much less than the cost of tracking,
maintaining ( and surely providing ) path diversity.
Surely large providers have spent a lot more time and money
developing processes and software that allow them to groom circuits
into the least number of physical paths possible. Or at least I
would, if I were paying for the facilities.
matto
--matt@snark.net------------------------------------------<darwin><
The only thing necessary for the triumph
of evil is for good men to do nothing. - Edmund Burke