External Session Border Controllers
For releases earlier than 4.0, an external SBC is needed for operation behind NATs. In newer releases a A SBC is still recommended for most installations. This gets external SIP signalling signaling and media off of the server allowing the server to scale better and provide a more reliable connection for Trunks and Remote workers.
Remote worker configurations require both near-end and far-end NAT traversal assistance. Some products, such as the Frafos ABC SBC or Sangoma SBC or Ingate SIParator provide support for both. Therefore, at the far-end there is no special equipment required and phones connected behind a traditional firewall/router will work fine. Other products might require NAT traversal assistance at the far-end as well.
SIP Trunking requires both near-end NAT traversal as well as interoperability with the ITSP providing the SIP trunking service. An SBC is required and we have typically used Acme Packet (now Oracle), Sangoma or Ingate SIParators Frafos ABC SBC for this purpose.
sipXcom does not work unless DNS and DHCP services are properly configured. It is possible to use the sipXcom server for such network services. The single CD ISO installation disk provides for automated installation and configuration of such services. However, more often you already have DNS and DHCP services deployed on your network. Please consult the respective information on how to configure such services to work with sipXcom. sipXcom uses DNS SRV records, which requires proper setup. If you deploy sipXcom in a high-availability configuration the complexity of the DNS SRV configuration increases dramatically.