SIP messages, which are carried inside of data packets, also include IP address information. Traditional NAT does not open the packet to change the IP information inside the SIP message. Therefore, the VoIP provider will not be able to send the call to the appropriate location. SIP requires a device to open the packet and adjust the IP information as it passes through the firewall.
Some firewall devices, known as Application Layer Gateways (ALGs), have the ability to make this change inside the SIP message. Though several ALGs are capable of SIP NAT traversal, TOTLCOM supports the Ingate SIParator router. Other firewalls, including Sonicwall and Cisco ASA/PIX, have this capability, but TOTLCOM can only provide technical support for the Ingate ALGs.
NAT-traversal problems manifest themselves in several easy-to-identify ways. If you are experiencing any of the following problems, you may have a NAT-traversal issue:
1. Are you having one-way audio?
2. Is the call setting up (ringing), but missing sound?
3. Are calls not setting up in the first place?
If you are experiencing any of these issues with your VoIP service, call TOTLCOM’s Customer Care Specialists at 1-800-300-5500.
ALG stands for Application Layer Gateway. An ALG is a device that handles translation of the packet IP addresses (and for TOTLCOM VoIP service, the SIP IP information inside the packet) as they traverse the firewall. TOTLCOM supports the use of the Ingate SIParator ALG.
It is important to remember that ALG devices are designed to handle a specific number of concurrent calls. Be sure to purchase an ALG that fits your business needs. TOTLCOM’s Account Executives can help you determine which ALG is right for you. Call 800-300-5500 to speak with an Account Executive today.
Another name for ALG, a SIP-aware firewall is a device capable of handling the translation of SIP-packet IP addresses as the packets traverse the firewall. TOTLCOM provides technical support for the Ingate SIParator firewall for SIP-packet translation.
TOTLCOM is dedicated to providing the highest possible level of call quality. To that end, our experienced engineers develop and test the latest QoS techniques. TOTLCOM VoIP service currently uses several techniques to ensure QoS, including TOS-splitting, traffic shaping, and voice-optimized internet (on some phone systems).
Traffic shaping is a technology used to enhance call quality. Traffic shaping software can differentiate between voice and data traffic. The software then “throttles back” the speed on the data traffic to make room for the voice traffic to proceed on the network unimpeded.
VoIP traffic is as secure as any other data traffic you send out onto the public internet. There are ways of making the system more secure, including some technologies currently undergoing testing by TOTLCOM engineers, but none of the available technologies is yet universal. The best way to ensure security for your VoIP traffic is to employ the use of a SIP-enabled firewall.
TOTLCOM is great and your staff is awesome. You have a good crew and I rest assured you guys have my back and I still to this day recommend your company to others. – William – CKC Labs
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