[VoiceOps] Geographic redundancy

Mark R Lindsey lindsey at e-c-group.com
Thu Aug 13 15:58:40 EDT 2009

On Aug 13, 2009, at 3:41 PM, Paul Timmins wrote:
> Mark R Lindsey wrote:
>> On Aug 13, 2009, at 12:46 PM, Kenny Sallee wrote:
>>> * redundancy for CLEC
>> In the case of a site fault, the remaining site would detect the  
>> fault and assume full control. It's critically important in these  
>> designs that the two call control servers have connectivity that's  
>> the most reliable part;...
> It sounds like for the entire effort and cost of this, there's still  
> a SPOF, not to mention it requires you always augment at 45% or  
> lower so if you lose one server, you don't block.

Good point; I was imprecise. You must certainly have redundant paths  
between your two SS7-attached call control servers. And there are voip  
platforms that support this fully.

This "dual brain" fault occurs when BOTH of your redundant links  
between your SS7-attached call control servers are dead.

You are also correct that you you engineer so that any one component  
in a fault-tolerance pair can support all of the load. But that's a  
familiar refrain in systems design: we do that with SS7 link members  
(neither link may exceed 50% utilization) and with our RAID-1 arrays  
(two disks, filled to 50% the cumulative capacity).

Mark R Lindsey lindsey at e-c-group.com http://e-c-group.com/~lindsey  

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