[Asterisk-Users] Cisco Call Manager & Asterisk for Voicemail

[Paul Davidson]

On 5/26/05, Scott Herrick <scott at angvall.com> wrote:
> My environment is a standard Cisco Call Mangler VoIP solution that has
> reached the capacity of the Unity VM system.  The cost of another Unity
> box is enough to prompt the decision makers to look for other solutions.
> 
> All the calls come into a Cisco 6509 and then to the CM.
> 
> The more I look at the H.323 the less I like it.  Rather, I didn't know
> how much I didn't know.   And I thought SIP was a thick protocol.
> 
> I have not thought this through but would SCCP on the * box help?  Might
> there be a way to have * "talk" SCCP to CM for VM and MWI?
> 
> Back to the books
> Scott

My environment could be a practical clone of yours. Truth be told,
under CCM, h.323 is the best option out there, at least until you get
to CCM 4.0.  I share your trepidation with SIP- and it's not really an
option under CCM 3- but SIP and H.323 share many of the same problems
regarding NAT traversal, etc.  H.323 is more of a logical descendant
from ISDN, however, and as such is a little more robust- but it's
still pretty cryptic.

SCCP will not help at all.  CCM uses SCCP only for communication with
handsets, and to my knowledge, the protocol was not designed to handle
server to server communication.  MGCP would be an option, except it's
possibly worse than h.323, and Asterisk doesn't yet support it in the
way CCM would need to see Asterisk as an MGCP gateway.

As an interesting aside, we just learned from Cisco that later
generation FXO modules for the router VIC modules support Caller-ID
back to Callmanager- but *ONLY* if you define the VIC as an h.323
gateway- MGCP doesn't support passing the fields back to CCM.  Store
that one away, those of you who are using CCM.

MWI, on the other hand, is one area that I think Cisco got right, at
least from an implementation standard under CCM.  If you want to turn
on the MWI, simply place a call to a extension of your choosing, while
setting caller ID info for the call to be the extension you want to
turn on- CCM does the rest.  So, a simple call file will take care of
the whole mess- off, on.. that's what Shaun spent the time putting
together.  It requires at least a signalling handshake between CCM and
Asterisk- it actually doesn't need a voice channel setup from Asterisk
to CCM, but of course, if you can do signalling, having voice is more
than a bonus.

The good news?  You don't really have to know all that much about
h.323 or sip to configure the trunks and get Asterisk and CCM humming
to the same tune.  You've already got a strong networking environment
(6509s are nice iron), so connecting CCM and Asterisk really isn't
much of a process- follow Shaun's example to the letter, possibly with
my modification if it helps you, and you're golden- once you've got it
configured, many other things will start to click.

Good luck.