[cisco-voip] SIP Trunking Questions

[Ryan Ratliff]

Inline..

-Ryan

On Dec 7, 2010, at 6:17 AM, Nick wrote:

Hi All
 
I have a couple of questions regarding implementing a SIP trunk solution, this will be using a private MPLS network SIP trunking based service where the session border controllers are within the SIP trunking platform, therefore the CUCM SIP trunks point to the SBC's directly.
 
1) The SIP platform needs to point each SIP trunk to a specific IP address within the IP PBX, so if the platform is confgured so that specific channels within the trunk are reserved for say inbound or outbound calls then these will be configured as another SIP trunk and need to point to a different IP address. The cluster will only have two servers so if we have 2 trunks we would be ok, but if we need more than 2 trunks then how can this be configured to point to different IP addresses and then route to the CUCM, if this a function of a CUBE or is there any other product that could do this?
 
RR> Sounds like a convoluted configuration requirement on the SBC.  How would putting a CUBE (one IP address) in place of the CUCM cluster alleviate the need for more than 2 trunks? The word "if" in your first sentence implies that configuration is optional and I'd opt out of it unless you have a good reason for dedicating channels for inbound vs outbound calls. 

2) I understand the product can use either G.729 or G.711, however if say for instance another customer is using the same platform with a different codec and a call is placed between these two companies,  the SIP platform cannot negotiate the correct codec, is it possible that the CUCM can negotiate the correct codec and the complete the call?

RR> Depends on how the SBC presents the list of codecs to CUCM. If it presents both CUCM will try for G.711 as long as the region/party on the CUCM side supports it.  If the SBC just dumbly sends through what the other party sends then the CUCM and the party on the other side of the SBC should be able to do the negotiation.  If the SBC tries to be intelligent about it and fails then you could have issues.   This is the kind of thing that I would want to test the heck out of before deployment.
 
Regards
 
 
Nick
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