Draytek Vigor2710 Series, Руководство пользователя

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Vigor2710 Series User’s Guide 56
very similar to a URL so some may call it “SIP URL”. SIP supports peer-to-peer direct
calling and also calling via a SIP proxy server (a role similar to the gatekeeper in H.323
networks), while the MGCP protocol uses client-server architecture, the calling scenario
being very similar to the current PSTN network.
After a call is setup, the voice streams transmit via RTP (Real-Time Transport Protocol).
Different codecs (methods to compress and encode the voice) can be embedded into RTP
packets. Vigor V models provide various codecs, including G.711 A/µ-law, G.723, G.726
and G.729 A & B. Each codec uses a different bandwidth and hence provides different levels
of voice quality. The more bandwidth a codec uses the better the voice quality, however the
codec used must be appropriate for your Internet bandwidth.
Usually there will be two types of calling scenario, as illustrated below:
z
Calling via SIP Servers
First, the Vigor V models of yours will have to register to a SIP Registrar by sending
registration messages to validate. Then, both parties’ SIP proxies will forward the
sequence of messages to caller to establish the session.
If you both register to the same SIP Registrar, then it will be illustrated as below:
The major benefit of this mode is that you don’t have to memorize your friend’s IP
address, which might change very frequently if it’s dynamic. Instead of that, you will
only have to using
dial plan or directly dial your friend’s account name if you are
with the same SIP Registrar.
z
Peer-to-Peer
Before calling, you have to know your friend’s IP Address. The Vigor VoIP Routers
will build connection between each other.