[Asterisk-Users] Connecting 20+ asterisk servers together

[Greg Boehnlein]

On Mon, 9 May 2005, David Choo wrote:

> Actually, this is whats facing me right now. I think Dundi will resolve the
> problem, but I've never really placed it to the test. Anyone tested Dundi?
> 
> Best Regards,

I run it in production on CVS-Stable and it works without a problem.

Our usage of it is to have multiple gateway servers that can dynamically 
respond to outages without human intervention. I.E. a customer's dial-plan 
will be setup to return multiple routes and it will try them in order of 
preference. If one fails, the next available route will be tried and so 
on.

Here is a snippet of some information from one of the working drafts that 
N2Net is putting together on using Dundi as the core of a Fault-Tolerant 
network. It is incomplete, and has some stuff that is a bit wrong, but it 
is a starting point. Much of the really intelligent sounding stuff is 
ripped right from the Dundi RFC...


"The two gateways will be reponsible for publishing weighted Dundi 
routes to their PSTN (PRI) and VoIP Termination carriers. They will 
also be responsible for recieving inbound PSTN and VoIP traffic and 
routing the calls back to the customer.

DUNDi is designed to facilitate the sharing of resources that can be 
used to terminate phone numbers by using a peer to peer system, 
requiring no centralized controlling authority, no single point of 
failure, and no enforced heirarchy. In this way, systems sharing a 
dialplan across an enterprise or across the globe can be assembled in 
an ad-hoc manor, while retaining confidence in the accuracy of the 
routes that are supplied and the security of both the queries and the 
answers within the trust group.

Route Weights
-------------
A Weight is a value indicating the relative cost or indirection of a 
particular published number. A lower weight represents a route which 
is more direct to the intended location. The lowest weight value is 0. 
The generally accepted route weights for the Dundi Peering network are 
0,100 and 400. The HAC will publish route weights of 0-99 to internal, 
private peers, and 100-400 for external Dundi-E.164 and Dundi-Test 
networks.

This will allow routes to be prioritized, such that PSTN will always 
be used where possible but VoIP routes will be available if PSTN 
access is not. This will also allow the HAC to preferentially route 
International traffic using a Least Cost Routing method, preferring 
VoIP routes, or a particular PRI span if neccessary.

A weight of 0-24 indicates a PSTN route to a dedicated carrier.
A weight of 25-49 indicates a failover PSTN route to a carrier.
A weight of 50-74 indicates a Primary VoIP route.
A weight of 75-99 indicates a Seconddary VoIP route.
A weight of 100+ indicates a least-preferred route to a private or 
public Dundi connected network, such as Dundi-E.164, Dundi-Test or 
FWD-out."

For what it's worth..