7 Tips to VoIP Performance
Posted on 19/10/2007 @ 11:34 AM
1. Make sure you have enough bandwidth
A good rule of thumb is 25-30% of a typical company will be on the phone at any one time. So if you have a 20-user system, you’ll need roughly 180 Kbps on the G.729 codec. If you use G.711 you’ll need over 500 Kbps. Break this rule and you will start having problems.
2. Check your lowest common denominator
It’s not the headlining download rate that you need to check, but the upload speed of your ADSL. Most DSL services only work asymmetrically, with the upload speed being the slowest. The actual upload speed will vary depending on your distance from the exchange and type of service provided.
3. Be careful what you mix
Mixing data and voice on your LAN or ADSL can cause voice issues even before the packets have left the building. Everyone thinks the issue is with the DSL or on the Internet, but look closer to home, especially if you have a busy LAN with one big broadcast domain.
4. Not all DSL routers are created equal
If your DSL router costs less than your latest iPod, then you might want to rethink your priorities. We only use Cisco 800 routers at remote sites, as they fix most issues automatically, even before we know there is an issue. Higher-end routers provide a wealth of additional debugging information and can be configured to retrain before noisy lines start to cause issues. The bottom line is that a little upfront investment will stop many issues popping up that would become a major headache with cheaper residential routers.
5. Ask your provider how they connect to the PSTN
A lot of SIP providers connect their switches via the internet to the PSTN. This does provide another unknown. We use a combination of Tier 1 providers, including BT and Global Crossing over both IP and the London Carrier Ring. The additional delay these providers add into call is minimal, a few milliseconds.
6. How does your provider troubleshoot issues?
All networks have issues, what’s important is how issues are dealt with and if the provider helps identify problems even when they aren’t caused by the provider. The level of tracing that can now be achieved is staggering, full media streams can be captured and played back, allowing engineers to peer into a call and see the fault just as if the call was live.
7. Is your PBX system verified with your SIP provider?
A lot of providers say they have SIP, just make sure that it works with your PBX. Preferably use a manufacturer approved provider. This means you can push back issues between the PBX and SIP provider.
About VoiceFlex
VoiceFlex, a division of Frontier Systems, was established to provide advanced IP telephony (VoIP) services for UK businesses. Bringing the reliability of the Internet to the telephone, VoiceFlex is an advocate of SIP (Session Initiation Protocol) - the latest technology allowing voice calls to be made over the Internet. VoiceFlex uses its own SIP technology offering developed completely in-house, to provide low cost, ISDN replacement lines that provide the best possible call quality, inexpensively with the flexibility that comes from using the Internet. VoiceFlex can also port any telephone number regardless of geographic location. Products include SIP Trunks and SIP Centrex.
VoiceFlex offices are based in Piccadilly and Coventry. For further information, please visit: www.voiceflex.com or contact Paul Taylor on 0207 440 1811 or email ptaylor@voiceflex.com
If you require more information, please contact Paul Taylor on 020 3004 1990 or email ptaylor@voiceflex.com
www.voiceflex.com
A good rule of thumb is 25-30% of a typical company will be on the phone at any one time. So if you have a 20-user system, you’ll need roughly 180 Kbps on the G.729 codec. If you use G.711 you’ll need over 500 Kbps. Break this rule and you will start having problems.
2. Check your lowest common denominator
It’s not the headlining download rate that you need to check, but the upload speed of your ADSL. Most DSL services only work asymmetrically, with the upload speed being the slowest. The actual upload speed will vary depending on your distance from the exchange and type of service provided.
3. Be careful what you mix
Mixing data and voice on your LAN or ADSL can cause voice issues even before the packets have left the building. Everyone thinks the issue is with the DSL or on the Internet, but look closer to home, especially if you have a busy LAN with one big broadcast domain.
4. Not all DSL routers are created equal
If your DSL router costs less than your latest iPod, then you might want to rethink your priorities. We only use Cisco 800 routers at remote sites, as they fix most issues automatically, even before we know there is an issue. Higher-end routers provide a wealth of additional debugging information and can be configured to retrain before noisy lines start to cause issues. The bottom line is that a little upfront investment will stop many issues popping up that would become a major headache with cheaper residential routers.
5. Ask your provider how they connect to the PSTN
A lot of SIP providers connect their switches via the internet to the PSTN. This does provide another unknown. We use a combination of Tier 1 providers, including BT and Global Crossing over both IP and the London Carrier Ring. The additional delay these providers add into call is minimal, a few milliseconds.
6. How does your provider troubleshoot issues?
All networks have issues, what’s important is how issues are dealt with and if the provider helps identify problems even when they aren’t caused by the provider. The level of tracing that can now be achieved is staggering, full media streams can be captured and played back, allowing engineers to peer into a call and see the fault just as if the call was live.
7. Is your PBX system verified with your SIP provider?
A lot of providers say they have SIP, just make sure that it works with your PBX. Preferably use a manufacturer approved provider. This means you can push back issues between the PBX and SIP provider.
About VoiceFlex
VoiceFlex, a division of Frontier Systems, was established to provide advanced IP telephony (VoIP) services for UK businesses. Bringing the reliability of the Internet to the telephone, VoiceFlex is an advocate of SIP (Session Initiation Protocol) - the latest technology allowing voice calls to be made over the Internet. VoiceFlex uses its own SIP technology offering developed completely in-house, to provide low cost, ISDN replacement lines that provide the best possible call quality, inexpensively with the flexibility that comes from using the Internet. VoiceFlex can also port any telephone number regardless of geographic location. Products include SIP Trunks and SIP Centrex.
VoiceFlex offices are based in Piccadilly and Coventry. For further information, please visit: www.voiceflex.com or contact Paul Taylor on 0207 440 1811 or email ptaylor@voiceflex.com
If you require more information, please contact Paul Taylor on 020 3004 1990 or email ptaylor@voiceflex.com
www.voiceflex.com
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