[asterisk-users] Who are XO and L3?

[Alex Balashov]

On Thu, 31 May 2007, Zeeshan Zakaria wrote:

> Almost all DID providers refer to XO and L3. Are they the only sources 
> for DIDs in USA and everybody has to go to them? Could someone explain 
> how exactly it works?

   They are very large CLECs (and IP transit providers) that have a vast 
market and LATA footprint, large amounts of number inventory, and lots of
end-office trunking -- particularly in Level3's case.  They also run
large media gateway / signaling gateway farms to provide VoIP<->PSTN
termination and origination.

   They are certainly not the only places you can go to for PSTN 
interconnection and numbers, and their pricing is certainly not the best. 
However, because of their large footprint they do provide considerable
economies of scale, especially for people looking to do nationwide 
service.

   Another issue to consider is that few smaller providers are able to 
provide symmetrical origination and termination.  Just because you can 
pick up calls somewhere doesn't mean you can originate them into that same 
LATA or that you even have tandem trunks there.  It all depends on the 
particular carrier, their interconnection agreements and their tariffs. 
I know of quite a few places that will hand off PSTN calls to you as VoIP 
from a DID of almost any locality, but you'll have to go to someone else 
to originate.  The reverse probably happens too but is less common.

--
Alex Balashov
Evariste Systems
Web    : http://www.evaristesys.com/
Tel    : +1-678-954-0670
Direct : +1-678-954-0671