On Sun, 9 Dec 2007, jorain wrote:
Thanks for your replies.1.. Our connection mainly for voip, occasionally used for surfing websites. 2.. We are using codec g711u for local calls through TE120P, and g729 only if making international calls through our sip provider, which only allow g723 and g729. How can we get the license for g723? Which codec would you recommend?
g729 sounds better than g723. You get licences from Digium at $10 each, or depending on your country patent laws and enforement, you can get them for free if you look/google hard enough... Or you might be able to force all your phones to use g729 and install the g729 voice prompts then you might not need any liceses at all.
3.. That quality problems we are facing are jitter, latency and occasionally low volume. What cause these problems?
The first 2 are caused by "The Internet", the latter is possibly caused by the transcoding process at your end, or the SIP providers end, or your local phones.
4.. No QoS Settings as we are quite new to it. Are we suppose to give high priority to RTP in our router? What sort of QoS and traffic shapping would you recommend?
There's nothing you can reliably do to affect the traffic on the global Internet. The best you can do is limit your outgoing traffic with QoS/Shaping in your router. This is dependant on your router. You can't really make much difference to incoming traffic as it's too late to do anything about it by the time it's come over the wire to your router, there are some devices that claim to help though, but I'm not convinced myself.
5.. How many users can we expect to use voip(with good quality) with 512kbps outbound connection? Regards,
In theory with a good and uncontended connection, that can support about 6 G711 calls, and many more g729 calls. (And that's what I see in practice with my own connection, but I have 833Kb/sec upstream)
It sounds like you might have a rubbish ISP. Make sure you have a "business quality" ISP rather than a domestic one. Use the 'mtr' command to see how many hops it is to your SIP provider, and what sort of delays to expect over your Internet link to them. You might use this to pick a different SIP provider.
Actually, using a business quality ISP (if such a thing exists in your country) is the one thing I always tell my customers - there are many, many "domestic" quality ISPs in the UK, and I've seen some of them struggle because they have piss-poor internal networks, or are just cheapskates... However, listening to a business tell me how important their Internet connection is to their business, then proudly announce that they are saving money because they have a combined deal for phone line/broadband/mobile/tv all for £9.99 a month really makes me cringe ... (and I could whinge on for days about this!!!)
Good luck... Gordon
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