Question on VoIP security

Hello list,

I am currently facing an Intranet VoIP project (will be restricted to
1 organization's Intranet, geographically disperse), from the security
standpoint. So, I have to propose a security architecture for a
SIP-based VoIP deployment. Vendor is still a variable, so it should be
as vendor-independent as possible (but it will probably be Cisco /
Nortel).

Does anyone have information on the currently security practices used
to protect the confidentiality, integrity and guarantee access control
in the VoIP services network?

If you can provide me with general principles, and perhaps links to
documents describing the security problems I should consider, these
would be more than welcome.

Thanks in advance and best regards,
Rodrigo.

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