Engineering FAQs

• What is NAT traversal?
NAT means Network Address Translation. When you connect to the Internet, information you send and receive is typically passed through a firewall, which protects your network infrastructure from hackers. Each individual network that is connected to the public Internet is identified by an IP address. Devices on the outside of your firewall see your publicly-routed IP Address; devices on the network inside of the firewall are addressed with private, non-routable IP addresses. When information passes through the firewall, it does so in the form of data packets. Each packet contains a header, telling it where it’s from and where it’s going. When a packet passes through the firewall to the public Internet, the private IP address is replaced with the publicly-routed IP address. When information passes from the public Internet through the firewall, the publicly-routed IP address is replaced with a private one and routed to the appropriate device.

• How is SIP affected by NAT traversal?
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, NextLevel Internet supports the Cisco ASA/PIX. Other firewalls, including Sonicwall, Edgwater and Ingate ALGs have this capability, but NextLevel Internet can only provide technical support for the Cisco ASA/PIX.

• How do I know that I’m having a NAT-traversal issue?
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 hosted Voice service, call NextLevel Internet’s support team at 858.836.0700.

• How do I handle a NAT-traversal issue?
NextLevel Internet has several different options to help you deal with technical difficulties. If you are having difficulties, please email support@nextlevelinternet.com . Please note that there may be a fee associated with NAT-traversal issues if NextLevel Internet engineering is required to fix the issue. If your network uses the Cisco ASA/PIX, or we should be able to troubleshoot your problems remotely. If you don’t currently use one of these NextLevel Internet-supported devices, there is another option. If you assign a public IP address directly to your phone, you will obviate any NAT-traversal issues, because there is no translation necessary. This option does, however, leave your system vulnerable to attack. NextLevel Internet does not recommend this option.

• Does NextLevel Internet support NAT Traversal devices?
NextLevel Internet supports Cisco ASA/PIX devices. Other devices capable of SIP packet translation are available, but NextLevel Internet does not offer technical support for their use.

• What is a SIP-aware firewall?
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. NextLevel Internet provides technical support for the Cisco ASA/PIX firewalls for SIP-packet translation.

• What is far-end NAT traversal?
Far-End NAT traversal is a method of accomplishing for more information on NAT traversal. NextLevel Internet does not utilize Far-End NAT Traversal, because doing so would introduce unnecessary delays and latency into our customers' voice traffic. NextLevel Internet places paramount importance on the voice quality of our service, and we feel that accomplishing NAT traversal on the customer's premise is a far more effective and efficient technique.

• What is call QoS?
QoS stands for Quality of Service. Quality of Service (QoS) is the idea that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance. Is the sound clear? Is there any jitter or latency? These are questions that determine the level of QoS. At NextLevel Internet, we pride ourselves on being an industry leader in QoS. Our engineers work tirelessly to ensure for our customers the highest possible level of QoS.

• How does NextLevel Internet ensure call quality?
There are a several methods of ensuring the highest possible call quality. NextLevel Internet recommends using a dedicated data connection of at least T1 speed, along with a properly-configured router using the latest QoS technologies.

• What is NextLevel Internet's philosophy of QoS?
NextLevel Internet is dedicated to providing the highest possible level of call quality. To that end, our experienced engineers and technicians develop and test the latest QoS techniques. NextLevel Internet VoICE service currently uses several techniques to ensure QoS.

• What is a Dedicated Voice Connection?
A dedicated voice connection is an Internet connection used solely for voice traffic. It carries no data packets, so traffic congestion, latency, and jitter are not issues. It is one of the best ways to ensure call quality, but it is generally not cost effective, because it requires the purchase of an additional T1-class Internet connection.

• What is TOS?
TOS stands for Type-of-Service splitting. It is a way of classifying and prioritizing the traffic on a data connection to give priority to voice traffic. If voice packets are held up by data traffic, latency and jitter issues can arise. Data packets, on the other hand, can handle slight delay far more easily.

• What is Voice Optimized Internet?
Voice Optimized Internet (VOA) is a technology NextLevel Internet offers to ensure call quality. Essentially, one circuit (T-1) is delivered to the customer site. The circuit is provisioned with two separate IP addresses one for data traffic and the other for voice traffic. Using this method, the voice traffic is prioritized from the customer premises all the way to our carrier network. This reduces the congestion for both inbound and outbound voice traffic.

• Are my Voice calls secure?
Voice 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 NextLevel Internet engineers, but none of the available technologies is yet universal.

• Is my hosted Voice system secure?
Your hosted Voice system is as secure as any other data leaving or entering your network. If you employ the use of a SIP-enabled firewall, your VoIP traffic is relatively secure. For someone to gain access to your VoIP calls, they would have to steal all of the packets leaving your network. The only way to do that is to be physically present at one of the points of transmission.

• What is TLS?
TLS is software with the ability to handle secure signaling, including SIP signaling, using secure certificates similar to the way some web sites use certificates to ensure secure financial transactions. Our engineers are currently testing TLS technology, but because it is not yet universal, it is not ready for implementation.

• What is SRTP?
SRTP is a way to encrypt the signals carrying the voice information over the Internet. It is still in the development stage; NextLevel Internet engineers are testing and monitoring its progress to determine whether it can be of use.