Draytek Vigor 2950Gi User's Guide download pdf (Page 171)

igor2930 Series User’s Guide

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Local certificate and Trusted CA certificate for this router can be saved within one file.

Please click Backup on the following screen to save them. If you want to set encryption

password for these certificates, please type characters in both fields of Encrypt password

and Retype password.

Also, you can use Restore to retrieve these two settings to the router whenever you want.

Voice over IP network (VoIP) enables you to use your broadband Internet connection to

make toll quality voice calls over the Internet.

There are many different call signaling protocols, methods by which VoIP devices can talk

to each other. The most popular protocols are SIP, MGCP, Megaco and H.323. These

protocols are not all compatible with each other (except via a soft-switch server).

The Vigor V models support the SIP protocol as this is an ideal and convenient deployment

for the ITSP (Internet Telephony Service Provider) and softphone and is widely supported.

SIP is an end-to-end, signaling protocol that establishes user presence and mobility in VoIP

structure. Every one who wants to talk using his/her SIP Uniform Resource Identifier, “SIP

Address”. The standard format of SIP URI is

sip: user:password @ host: port

Some fields may be optional in different use. In general, "host” refers to a domain. The

“userinfo” includes the user field, the password field and the @ sign following them. This is

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/ISDN 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

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Draytek Vigor 2950Gi User's Guide Page 171