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Understanding Phone System NAT Traversal
The NAT Challenge
Network address translation allows multiple devices to share public IP addresses, but it complicates VoIP communication. SIP signaling and RTP media streams contain IP address information that NAT modifies, potentially breaking call setup and audio transmission.
How NAT Affects VoIP
When phone systems register through NAT, the IP addresses embedded in SIP messages differ from the addresses visible to the network. Registration may succeed while media fails, resulting in one-way audio or no audio at all.
Traversal Techniques
Session border controllers solve NAT traversal by rewriting address information in SIP messages. STUN servers help phones discover their public addresses. TURN servers relay media through public servers when direct connection fails. ICE protocols combine these approaches automatically.
Cloud-Based Solutions
Cloud phone platforms handle NAT traversal centrally. Phones behind enterprise firewalls register to cloud services that manage address translation. This approach eliminates NAT configuration challenges for individual deployments.
Configuration Best Practices
Organizations should configure firewalls to allow SIP signaling and RTP media traffic. Port range definitions should accommodate concurrent calls. Testing verifies that NAT traversal works correctly for both internal and remote extensions.
Conclusion
NAT traversal is a common challenge in VoIP deployment that requires proper configuration to resolve. By understanding traversal techniques and implementing appropriate solutions, organizations ensure reliable phone communication across network boundaries.
Redstone Systems, Inc. founded in Delaware, USA in December 2002, has been the ODM vendor for many well-known communications companies, serving the Southeast Asian market. In 2020, Redstone Systems will begin to return to the North America market with its self-developed brand.
Redstone has a complete product line of intelligent voice gateways, providing IP-PBXs, analog VoIP gateways (FXS/FXO), digital VoIP gateways (E1/T1), border appliances, and session boundary controllers (SBCs).
With advanced technology in digital signal processor (DSP), speech coding and speech processing, as well as efficient operational tools such as cloud remote management, auto provisioning, Redstone gateways are widely used in markets of enterprise communications, cloud communications, call centers, operators’ IMS/SIP trunks, bringing users friendly, efficient and reliable communication experience.
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