One important thing to considere when switching wholesale traffic is to hide your vendors, to avoid loosing customers ! well unless you route the media to very expensive devices, it sounds tricky to do, but not with some open source applications !
We lately discovered how a back-to-back user agent called sippy (b2bua.org), if combined with RTP Proxy, can definitely hide all your vendors ! How scalable is it, you would ask ? well a descent server such as a core2duo with 1GB of RAM can easily switch over 5M minutes/month. The good thing of RTP Proxy is that it can be distributed accross several servers – regular checks are performed by the b2bua to validate the availability of the proxies and discard unresponsive ones from the pool.
Once again this is a great peace of open source software, that can achieve fonctionalities only reserved to high end type of switches, for a fraction of the cost !
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