Re: [asterisk-users] network config

[David Gibbons]

snip
A client has two offices in the Virgin Islands that MUST maintain data
connectivity, and there are no available leased line options to run
a P2P link between them.
snip
Is there line of sight? I've been wanting to do a long-shot wifi link and my 
company would give it a shot if you want :).

snip
Do you lose an in progress call when the tunnel switches from one link to
the other?
/snip
Any 'fail-over' router with links from separate providers that don't route the 
same subnets (cable/dsl) will have to change its default route when it 
'fails-over'. As such, the VPN tunnel will be disconnected and reconnected. I'm 
sure you could make it brief, but yes, calls will likely be completely dropped.

snip
And finally - is there a device that will manage the tunnel such that a
high water mark of latency will also cause the tunnel to switch to the
other link, rather than actual packet loss?
/snip
See above. Fail-over routers have to wait some criteria are met in order to 
fail over (ping latency, ping loss, etc). This means that the connection you're 
using as the 'default' WILL go 'down' BEFORE it switches to the other one, 
regardless of the criteria used.

Another plan would be to set up two routers at the site with two separate VPN 
tunnels across the two different links, both tunnels being always on. You could 
then use a SIP proxy or iptables magic to choose which tunnel was the best at 
any given time.

I would go for the wifi. Maybe because I want to do a long-shot link. Also 
because I want to go to the virgin islands :).

Good luck!

-Dave

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Re: [asterisk-users] network config

[Jeff LaCoursiere]

Hi David,

On Tue, 8 Dec 2009, David Gibbons wrote:

 snip
 A client has two offices in the Virgin Islands that MUST maintain data
 connectivity, and there are no available leased line options to run
 a P2P link between them.
 snip
 Is there line of sight? I've been wanting to do a long-shot wifi link and my 
 company would give it a shot if you want :).


Sadly no, because cruise ships park (dock?) directly in front of one the 
locations, which is directly between them.  Worse high intensity radar 
blasts seem to give any kind of wireless signal we have attempted lots of 
trouble.  If it weren't for the ships, this would work well I think, but 
as its happens the ships are the source of the client's revenue!

snip

 And finally - is there a device that will manage the tunnel such that a
 high water mark of latency will also cause the tunnel to switch to the
 other link, rather than actual packet loss?
 See above. Fail-over routers have to wait some criteria are met in order 
 to fail over (ping latency, ping loss, etc). This means that the 
 connection you're using as the 'default' WILL go 'down' BEFORE it 
 switches to the other one, regardless of the criteria used.

Hmm, an excellent point.  I suppose some amount of tweaking might cause 
the switch to happen before asterisk or the endpoint decides that the 
call is lost?  Are these SIP timers that we might play with?  Some amount 
of silent interruption might be tolerated during a switch, but a lost call 
is hard to accept.


 Another plan would be to set up two routers at the site with two 
 separate VPN tunnels across the two different links, both tunnels being 
 always on. You could then use a SIP proxy or iptables magic to choose 
 which tunnel was the best at any given time.


Hmm, another good thought.  Now its getting complicated :)

 I would go for the wifi. Maybe because I want to do a long-shot link. 
 Also because I want to go to the virgin islands :).


Heh.  Come on down!  Water is fine...

j

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