H.323 and SIP security issues

["John Scheidemantel" <jds () intrinsictech net>]

I am looking at implementing VoIP in our network and need to know the
security issues and best practices of implementing
H.323 and SIP across our intranet and internet. I know that VoIP uses UDP as
its transport. How does one design the network to overcome running UDP
through the firewall?

John Scheidemantel