[asterisk-users] Building the Perfect Box

[adebayo omo-dare]

We were also looking at this telecom problem as well. A major complication, with regards to recovery planning, lies in the manner in which Local Loop Unbundling occurs. Even though communication companies may carry different logos, and profess to be independent orgs, they are all/mostly, invariably, in one form or another, dependent on the incumbent. In most, if not all cases, they share the incumbent's exchanges - which usually are individually central to large areas.
   
  If a problem occurs in the Handover Distribution Frame (HDF) - this is where copper pairs are made available to CLECs in an exchange - non-discriminatory multihoming between providers would seem to be the best remedy. However, if the problem - as in the case of a major fire - is in the Main Distribution Frame (MDF) - where all the pre-unbundled wires are held - all providers, bar none, within that exchange will go down.
   
  Strategies such as Dual Parenting (connecting to two processors within the exchange), which is usually offered as a HA option, do little in such extreme cases -and whether you have one or two separate providers, under such circumstances, would matter little.
   
  However, there are other possibilities, such as multihoming with two different technologies - such as connecting to a Cable company, which, indeed, can provide you with an entirely different route - but, though there are ways around what I say next, you may be screwed on the DID issue. Even when the Cable companies Switching Center connects to the PSTN (SS7 ntwk), it does so with with very high availability as its aim- i.e., it is connected to more than one, so if one, say, blows up, switching continues on another route - and the thing you then have to worry about is your building not catching fire, or being flooded in the middle of winter. 
   
  You can also ask providers for information about their networks - with regards to location mapping+coverage. You may be - a big may be - lucky, and be in an area within an area where two or more exchanges deliver services thereby allowing you to connect to two different centers. If both centers are run by the same incumbent, then potential DID issues are easily negated.
   
  Usually you can ask your providers for availability+performance figures (regional/local) -backdated for several years (they should have them on hand)- and mark such figures against your potential losses as tallied against particular frequencies relevant to your org.
   
  If you can do away with not having an SLA, it would usually indicate that your losses in relation to your revenue for the duration of, say, the fault, or, indeed, performance depreciation, are inconsequential. Some may say, in the case of business orgs, it could mean that they are not being assessed, or if they are, they are important enough not to let go. However, requirement usually preceeds the SLA, with the latter being mapped to an assessment of the former.
   
  You should also be very careful of what carriers tell you, as the information you gather is usually only as good as your point of reference. I.e., in many cases, their representative, who may or may not be keyed up, and may, or may not, be very polar with regards to the information she/he is prepared to/can deliver.
   
  This of course is an extremely interesting, as well as being a very wide and complex subject. And I do hope the above in some manner helps.
   
  Bayo

"Jay R. Ashworth" <jra at baylink.com> wrote:
  On Sat, Sep 30, 2006 at 11:14:08AM -0500, Brandon Galbraith wrote:
> On 9/30/06, Tim Panton <[1]tim at mexuar.com> wrote:
> 
> Just to amplify this point. I've tried to claim on an SLA. Our
> internet connection was down for a week due to a fire in
> BT's exchange. My provider refused to do
> anything (despite the premium SLA) on the basis that
> fires weren't covered. I switched providers to a cheaper one
> who didn't pretend to offer uptime :-)
> 
> While an SLA is nice on paper, if your connection is
> business/mission-critical, always always always do redundancy
> yourself. Just having two connections from seperate providers
> is nice, multi-homing with two providers and having automatic
> failover is better (although this mostly applies to larger shops
> where having the phones/internet out per minute costs thousands of
> dollars/euros/etc.).

But see also my earlier comments about the practical impossibility of
guaranteeing physical route diversity for multiple services in the same
format (copper, fiber), even if from different putative carriers.

This is *really* hard to make work; even the carriers themselves will
often *tell* you that you have PRD, and then you'll get backhoe faded
on all circuits anyway.

Cheers,
-- jra
-- 
Jay R. Ashworth jra at baylink.com
Designer Baylink RFC 2100
Ashworth & Associates The Things I Think '87 e24
St Petersburg FL USA http://baylink.pitas.com +1 727 647 1274

"That's women for you; you divorce them, and 10 years later,
they stop having sex with you." -- Jennifer Crusie; _Fast_Women_
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