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G711 trunk transcoding

Discussion in '3CX Phone System - General' started by Dr Evil, Mar 14, 2017.

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  1. Dr Evil

    Mar 14, 2017
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    Hi All,
    Hopefully a simple one, although I have been unable to find a concise answer thus far:

    Single SIP trunk from provider configured on 3cx VM at the data centre.
    3 remote sites with roughly 10 Yealink phones each connecting to the data centre 3cx via STUN.

    So here's the question(s):
    1. The sites have low latency and only around 8 hops to get to the data centre being on full fibre leased lines. Is STUN ok in this instance or would a 3cx SBC at each site be of benefit?

    2. As the SIP trunk provider is sending/receiving only g.711 and the Yealink phones don't support g.711, presumably the 3cx VM at the data centre is transcoding the audio both ways for external calls through the SIP trunk. If 3cx SBC's are added to each site, would the SBC's then do the transcoding at each site to/from the trunks g.711 to the Yealink phones PCMA/PCMU?

    I hope this makes some sense and thanks in advance for any direction on this one.

    DSXDATA New Member

    Oct 20, 2015
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    Note: G711a/u is the same as PCMA/U.
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  3. YiannisH_3CX

    YiannisH_3CX Support Team
    Staff Member 3CX Support

    May 10, 2016
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    Hello Dr. Evil,

    The use of an SBC in your scenario would simplify the firewall configuration on the remote sites but would require extra hardware for the SBC to run on. Also the SBC can act a proxy and take some load off the PBX as the extensions at each remote site would be able to talk to each other directly. (if PBX delivers audio is off and call recording is off). If you plan to add more extensions is the future at each site i would recommned an SBC. But for the most part i would say that it depends on you and your needs as to what you will use.
    And as DSXDATA noted the codecs are a non issue as G711a/u is the same as PCMA/U
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