[asterisk-dev] NFAS Implementation Spanning Multiple Servers

Matthew Fredrickson creslin at digium.com
Thu Feb 2 16:41:56 MST 2006

On Feb 2, 2006, at 5:04 PM, Steve Totaro wrote:
> Recently I asked a question on the list about NFAS being able to span
> across multiple servers.  Kevin F said that this was something in the
> works and should show up very soon.

I think that maybe something he said that's out of context.  This topic 
has come up in discussion, and I've thought a lot about how to 
implement it, but I have no immediate plans to write such a solution.  
It would take a significant amount of time (which equal money by the 
way :-) ), testing, and especially planning for such a thing to come 
into existence.

> I have a real need for this.  I have a T3 going into an Adtran MX2800
> and then into seven asterisk boxes with quad T1 cards.  The way things
> are now, I need seven D channels to go PRI.
> Problem:  Our carrier charges $100/mo per D channel.

That's understandable.  That's how they pay for their hardware too :-)

> Solutions:
> 1.  Lose PRI alltogether and get straight T3
> 2.  Pay the money (there has to be a better way $8,000 is too much)
> 3.  Buy a high end Adtran that can break the T3 D channel into one D
> channel per T1 port which would pay itself off in about three years if
> my estimates are correct.
> 4.  Get Kevin motivated enough (or anybody else for that matter) to get
> NFAS to be able to span multiple servers.  This could be in exchange 
> for
> a $$$ bounty, case study, testimonial or whatever.

There are a lot of technical issues that need to be addressed for 
something of this nature to work.  If we were just talking about 
terminating incoming calls from the PRI on the boxes, I can see a very 
clear way to do this.  However, remotely registered phones and having 
incoming and outgoing calls to successfully make it through this 
"cloud" is going to be more challenging (adds a lot more to what you 
have to be able to support in this solution).  There would probably be 
some sort of control box that would terminate the D-channel, then we'd 
have groups of bearer channel termination boxes.  There would have to 
be a protocol for telling the b-channel box what b-channel to expect a 
call on, or make a call on, and also to accept an RTP stream from an 
endpoint (whilst keeping the signaling running through the d-channel 

As you can see, this is going to be a LOT of work :-)  although I do 
see it as a necessary feature in the future.

> We will be willing to GPL our source in exchange for the NFAS feature 
> as
> a barter, pay for it, or whatever.  Make some suggestions please 
> people.
> Maybe I am missing somehting.

It's going to be expensive :-)

Matthew Fredrickson

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