FAQs - VoIP Installation Q&A
VoIP FAQs - Installation questions
Installation of VoIP--------------------------------------------
Many DSL modems have NAT router functions incorporated, which most cable modems generally do not have. If the NAT router function of your DSL modem does not support SIP pass-through, or is not SIP friendly, you may need to configure the DSL modem to act as a bridge. This can also be true with modems that have certain built in firewall features, which prevent some VoIP signaling and voice traffic.
Connecting the active VoIP phone port directly into a wall outlet by using an RJ-11 phone cable can do this. The phone circuit that you connect to must have been disconnected from the previous telecom, which is done usually at the demarc, to prevent voltage from re-entering. See our information on Distributing VoIP throughout a House. With most VoIP systems a limitation on the amount of phones that can be made to ring exists, due to voltage limitations. This number is sometimes around 6 or 7 phones, depending on the individual phone voltage requirements.
Unfortunately, dial up modems will not work over a VoIP connection.
In some cases, VoIP is being used with satellite connections, but with varying degrees of success, depending on the ISP�s service and the Codec being used. Generally, there are quality issues and the connection will be much more degraded than over a more traditional broadband connection. Satellite connections have large built in latencies, due to the physical distances the signal travels. Generally, they also have low bandwidth, especially on the upload side and have what they call �burstable� bandwidth speeds. This burstable speed can create changes in the bandwidth where the fluctuation can cause problems for voice data. In many cases the end voice quality is poor and not acceptable to most users.
In some cases certain routers may not support SIP pass-through or the NAT that they use does handle SIP correctly. If you can have good two-way conversations with your VoIP ATA connected directly on the public network, but after putting it behind the router, it has one-way audio or does not connect at all, then the router is probably SIP unfriendly or you may need to configure the router for VoIP. In any event, you should upgrade your router's firmware to the latest version. Many manufacturers have newer firmware releases that may help solve some of these issues.
Phones that are meant to work with VoIP are ones that make an analog signal. If the phone says that it complies with Part 68 or Part 15 of the FCC requirements, then it should work with a VoIP connection. Some phones are like a PC and a phone and have the software and hardware to connect directly to an IP connection and make calls using VoIP. These phones are referred to IP phones and some well known manufacturers are Aastra, Grandstream and Polycom. Phones that will not connect to most VoIP services are ones that are specific to a manufacturer of PBX. These phones could be Nortel, Toshiba or many other manufacturers which were designed to be specific for a PBX phone system and are usually digital phones.
This is probably a firewall or NAT issue. First try to connect the IAD directly to the modem. If the audio is both ways, then a NAT router is probably between the original IAD location and the modem. If you experience one-way audio connected directly to the modem, the modem will need to be set to bridge mode and the router will need to have PPPoE with username and password configured on it.
Yes and it's called a Hosted PBX or business VoIP. Usually offering IP Polycom phones, some VoIP providers sell a more traditional business VoIP service with extension dialing, auto attendants, and other business features.
The best configuration for networking a Netgear router (or any router) with the Westell DSL modem is to set the Westell to "Bridged Ethernet" mode. This makes the Westell a pass-through and the Netgear router will handle the NAT, DHCP and routing functions. By configuring the Westell modem to Bridged Ethernet your network will Not be double-natted, which can result in one way audio or no VoIP connection at all. Instructions on bridging a Westell DSL Modem.
The answer to this question depends on several factors including, the upload and download bandwidth of your connection, the network infrastructure of both the LAN and WAN connections, and the calling environment. For most normal companies a per location limit would be in the range of 7 to 9 phones or SIP trunks.
If you are installing one VoIP phone connection, then QoS may not even be needed. It would be best to see how the quality of your calls are and troubleshooting before thinking QoS will solve the issue. On the other hand, if you are setting up multiple phones and have several PCs, then configuring QoS to prioritize VoIP would be something to consider during installation.
Certain models of routers can accept Tomato firmware, which is a Linux based open source firmware. Some models of the Linksys WRT54G model would be able to be flashed with Tomato. Tomato offers excellent QoS configurations and a router with Tomato installed is a good economical choice.
There are quite a few manufacturers of IP Phones, some which are excellent. The wide range of available phones include Polycom, Aastra and Grandstream, among others. Each manufacturer has different strengths and in each a number of differently priced models. See out information on IP Phones for more information and what might be best for you.
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