Sip Registration; Sip Outbound Proxy Server; Dns Lookup Of Sip Servers - Obihai OBi110 Administration Manual

SIP Registration

Device can be setup to periodically register with a SIP Proxy Server or SIP Registration Server. SIP Proxy Server and SIP
Registration Server can be different, although they are usually the same in practice. SIP Proxy Server is a required
parameter that must be configured on the OBi device. The Registration Server is optional and assumed to be the same as
the SIP Proxy Server if it is not configured on the device.
The main purpose of registration is to create and maintain a dynamic binding of the SIP account to the device's local contact
address. Service provider can also rely on this periodic message to infer if the device is online and functional. Each OBi
device takes only one local IP address that is either statically assigned in the device's configuration, or dynamically obtained
from a local DHCP server. The SPn service for n = 1, 2, 3, and 4, on the other hand each uses a different local contact port
for sending and receiving SIP messages (default is 5060, 5061, 5062, and 5063 respectively).
Note that dynamic address binding through periodic registration is not strictly necessary if the local IP address of the device
does not change; the device's contact address may be statically configured on the Registration Server.

SIP Outbound Proxy Server

An outbound proxy server can be configured on the device such that all outbound requests are sent via the outbound proxy
server instead of directly to the SIP Proxy Server or Registration Server.

DNS Lookup of SIP Servers

When sending out SIP requests to the server, the device looks up the IP address of the server using standard DNS query if
the server is specified as a domain name instead of an IP address. If Outbound Proxy Server is configured, it is used instead
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