There are a number of fundamental reasons why simple NAT and PAT are insufficient to resolve NAT traversal issues for VoIP traffic in general and for SIP signaling specifically. A small subset of the reasons:
The SIP Standard requires a number of header fields to be specified, some of which need to contain the IP Address where responses need to be sent to. Since NAT and PAT operate only on the IP headers, and not on the UDP Payload, the WAN-to-LAN device does not address this issue at all.
SIP does not only perform the tasks of setting up, adjusting calls, and tearing down calls, but also incorporates the media codec negotiation phase inside an embedded protocol called SDP (Session Description Protocol). Again, the WAN-to-LAN device does not address this additional content at NAT or PAT level.
The BVoIP SBC is a carrier grade solution that can provide service to tens of thousands of endpoints. Phones or other SIP devices will have a configuration field for a “SIP proxy” server and port – when pointed to the SBC, all SIP packet rewriting for NAT support is handled automatically. This eliminates the need to use STUN, sbc2TURN, ICE, VPN, Tunnel or any other method to handle NAT.
The Session Border Controller allows VoIP sessions to succeed when one or more VoIP endpoints (such as analog phone adapters, gateways or IP phones) are in a NAT environment. It takes all of the mess out of connecting remote devices back to a SIP server and greatly simplifies your deployment! This offering is designed to work as an intermediary between endpoint devices made by Yealink, Cisco, Snom, Polycom, Fanvil and more!
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