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Chapter 6 <br />

A DNS SRV answer may contain several records ordered by priority. Each record contains a<br />

proxy name. If a proxy is unavailable, requests are sent to the second proxy and so on. There<br />

is no need to configure the overflow through ARS.<br />

DNS SRV can also be used for registration. The service/name to resolve is the registrar name.<br />

Note 1:<br />

Alcatel-Lucent OmniPCX Office Communication Server does not perform the DNS A request alone. A<br />

DNS A request is always performed following a DNS SRV request.<br />

The figure: Process for Locating a SIP Server describes the process followed to locate a SIP<br />

server starting from a given URI.<br />

Note 2:<br />

Since only UDP transport protocol is supported, Alcatel-Lucent OmniPCX Office Communication Server<br />

does not perform NAPTR requests. For example, if "domain.com" is the domain name to resolve, a DNS<br />

SRV request for "_sip._udp_domain.com" is sent.<br />

6-44

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