FAQ
on VoIP and SIP Trunking
Basic Guide to VoIP Troubleshooting
Diagram on the left showed the flow of VoIP in a Network and the Area of Problem Section.
Echo Problem
Echoing is one of the most common problems and is often the easiest to fix.
Symptoms – One or both parties hear one (or both) voices repeated, often faintly, with a slight delay.
Related Equipment – #1: The handsets or softphones; #10: Other party’s phone.
Cause – Echo is usually caused by ‘crosstalk. That’s when a phone’s microphone picks up the sounds from the phone’s earpiece because the volume is too high.
Resolutions – Have both parties turn down their handset volume.If using a softphone without a headset, turn down the volume, or better yet use a headset. This will keep the mic from picking up sound from the speaker.
Choppiness Problem
People usually say the call is “breaking up” when they hear choppy audio.
Symptoms – It sounds like words, or parts of words, are missing.
Related Equipment – #2: The router or switch on the LAN; #3: The firewall on the office’s LAN; #8: WAN; #9: WAN transmission towers.
Cause – Choppiness is caused by ‘packet loss’ which results from the ‘high jitter’ of an unstable connection.
Resolutions – Ensure the firewall is properly configured to allow for and prioritize VoIP traffic. If the office uses the same LAN for computers and VoIP, then ensure that no computers on the LAN are using more bandwidth than normal. Streaming video sites (such as Hulu and Netflix) and video conferencing are two common culprits.
You may need to perform some tests on the two network variables which most affect VoIP call quality, latency and jitter. These, along with packet loss, are the main variables by which network and connection quality are measured. They are defined as:
Latency: Latency is the amount of time it takes for packets to arrive, and it is measured in milliseconds (ms, meaning thousandths of a second). The maximum one-way latency (from one caller to the other) that can still allow for high-quality VoIP calls is around 150 ms. Latency is measured by doing a ping test.
Jitter: Jitter is the variation in the latency of arriving packets. Remember that packets often arrive having taken different routes, so some arrive more quickly than others. Jitter is measured by doing a traceroute test.
Packet loss: If some packets take too long to arrive, the others do not wait. The voice audio will be reassembled without the late or missing packets, resulting in packet loss.
Try an online connection speed test to verify that upload and download speeds are consistent with what your ISP is providing.
If necessary, consider increasing bandwidth from the ISP or switching to a Dedicated Voice broadband SIP Trunk.
Start with this list of questions to help you narrow down the problem’s source:
Are wireless headsets or handsets being used ?
See if the problem goes away when you try using a wired handset. There’s a long list of devices that can interfere with wireless phones. It includes, but is not limited to: microwave ovens, fluorescent lights, WiFi networks and cell phones. If you’re experiencing interference from one of these devices, try relocating the device, selecting a different channel for the wireless phone or switching to a wired handset.
Is the problem affecting all extensions in the office ?
Ask around, or try plugging the phone into a different LAN outlet to see if the problem goes away. If it does, then the wiring in (or to) the original LAN outlet is likely the problem.
Phone LAN wiring and LAN outlet connections can degrade over time. They can also be damaged during installation or renovations. Lastly, phone LAN wiring that runs alongside electrical wiring can pick up interference. It might require a trained technician to narrow down the culprit.
Are the Phones connected to dedicated LAN switch board ?
If the phones use the same LAN for computers and VoIP, then ensure that no computers on the LAN are using more bandwidth than normal, ensure prioritize VoIP traffic. For best result, Dedicate a Manage LAN Switch that support VoIP QoS for your VoIP device.
Are your Broadband Router and Bandwidth VoIP friendly ?
Ensure the firewall is properly configured to allow for and prioritize VoIP traffic. Upgrade the broadband router firmware if necessary.
Try an online connection speed test to verify that upload and download speeds are consistent with what your ISP is providing.
If necessary, consider increasing bandwidth from the ISP or switching to a Dedicated Voice broadband SIP Trunk.
Are Mobile Data (3G/4G) Broadband Router being used ?
If a digital mobile data signal becomes too degraded and enough data is lost in transit, then there is a high likelihood that the connection will be terminated and the call dropped. Also ensure the firewall is properly configured to allow for and prioritise VoIP traffic. Upgrade the broadband router firmware if necessary.
Try an online connection speed test to verify that upload and download speeds are consistent with what your ISP is providing.
If necessary, consider increasing bandwidth from the ISP or switching to a Dedicated Voice broadband SIP Trunk.
Questions on Fax over IP:
Can Faxees be sent over VoIP ?
Short answer, yes. But it’s not especially reliable, and therefore not advisable if you want to be confident that your fax will be delivered.
What are the requirement to use Fax ?
1. You need to have T.38 compatible protocol supported Fax Machine and ATA device.
2. You need to have a DID number dedicated to be Fax number use.
3. You need to dedicate a common email to receive Faxes to email.
Can Faxes be received by Email ?
Yes. You need to dedicate a common email to receive Faxes to email.
Questions on Global Phone numbers (a.k.a DIDs or DDIs ):
I live in Munich, Germany. Can I order a UK phone number?
Yes. See "Available DIDs".
If I purchase a DID in some country and the DID includes N free minutes, does that mean I have N free minutes to call telephone numbers in that country?
No. DID is inbound only service to call you from a regular phone. The N free minutes are incoming minutes only. All outgoing calls are charged according to the calling rates.
What does the DID parameter "channels" mean?
The channels parameter is the maximum number of simultaneous incoming calls the DID supports. To implement "call waiting" service, the DID has to support at least 2 channels. If the number of simultaneous incoming calls exceeds number of DID channels, the caller will get BUSY signal.
How do I buy a phone number?
You can request purchase from our sale by clicking the contact us below. In your content please indicate which country DID you are interested.