Shulou(Shulou.com)06/01 Report--

In order to minimize communication costs and facilitate mobile office, the deployment of remote extensions is increasingly widespread, and the main methods currently implemented are as follows:

1. The headquarters applies for a fixed IP, which is the best, most convenient and most stable way at present, but the cost (fixed IP monthly rent) is higher.

2. Both the headquarters and the branch purchase ×× routers of the same brand (such as Xiannuo, etc., the price is about 1400) to apply for two dynamic domain names. You can set them on the routers of the two places respectively to form an ×× network (virtual local area network) in the two places. All calls are through the ××× network, which is relatively safe; the headquarters server needs to adopt dual network cards, and the data and voice are separated (currently adopted more frequently).

3, headquarters to apply for dynamic domain name (preferably a fee), set it on the soft phone or network phone, this solution is the most economical, but also the most unstable, mainly afraid of operators from time to time to block dynamic domain name and SIP port, and exposed port on the public network is also an unsafe practice (not recommended).

In order to ensure the quality of calls, it is recommended that headquarters apply for a dedicated broadband for voice calls, separate from computer Internet access. Please handle the specific implementation as appropriate.

How much bandwidth do I need to request for remote extension calls? The bandwidth occupied by a general one-way call is calculated as follows:

Bandwidth = packet length × packets per second

= package length × (1/packaging cycle)

=(Ethernet header +IP header +UDP header +RTP header + payload) × (1/packetization period)

=(208bit +160 bit +64 bit +96bit + payload) × (1/packing period)

=(528 bits +(packing period (s)× bits per second)) × (1/packing period)

=( 528 /packing cycle) + bits per second

According to the above calculation formula:

G711,20ms packet, bandwidth ( 528/20 + 64) kbit/s = 90.4

G729,20ms packet, bandwidth ( 528/20 + 8 ) kbit/s = 34.4

G723, 5.3k, 30ms packet, bandwidth ( 528/30 + 5.3 ) kbit/s =22.9

However, in actual use, it is found that when the interface bandwidth is limited to 64k or less on the router, there is still obvious distortion, no matter which coding method is used.

Therefore, it is suggested to calculate the bandwidth occupied by n concurrent calls according to the maximum of 96kb/channel or calculate the allowable number of concurrent calls from a certain bandwidth. (If ADSL uplink and downlink bandwidth asymmetry, it should be calculated by uplink bandwidth)

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