Copyright 2010-2015 Obihai Technology, Inc.
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If the Outbound Proxy Server is provided, server redundancy is applied to the Outbound Proxy Server instead of the
REGISTRATION server. Server redundancy behavior is enabled by enabling the parameter
ITSP Profile X –
SIP
::
X_ProxyServerRedundancy
(which is disabled by default).
Another requirement for using the server redundancy feature is that the underlying server must be configured in the
device as a domain name instead of an IP address. This allows the OBi to collect a list of candidate servers based on
DNS query. The domain name may be looked up as DNS A record or DNS SRV record. For A records, all the IP addresses
returned by the DNS server are considered to have the same priority. For SRV records, the hosts returned by the DNS
server can be each assigned a different priority.
After a list of candidate servers are obtained, the OBi device will first look for a working server according to the stated
priority. A
working server
means one that the device can successfully register with. This is known as the
Primary Server
.
Subsequently, the device maintains registration with the primary server the usual way. However, if no working server is
found after traversing the entire list, device takes a short break and repeats the search in the same order.
While maintaining registration with the Primary Server, the OBi will continually attempt to fallback to one of the
candidate servers that has higher priority than the primary server, if any. The list of candidate servers that the device is
trying to fallback on is known as the
primary fallback list
, which may be empty.
In addition, an OBi device can be configured to maintain a secondary registration with a server that has lower or equal
priority than the primary server. Secondary registration can be enabled by setting the parameter
X_SecondaryRegistration
to
true
. If
X_ProxyServerRedundancy
is
false
, however,
X_SecondaryRegistration
does not take any effect. If this feature is enabled, as soon as a primary server is found,
the OBi will search for a working secondary server in the same manner from the list of candidate servers that are of
lower or equal priority than the primary server. Similarly, once a secondary server is found, the OBi forms a
secondary
fallback list
to continually attempt to fallback on if the list is not empty.
The interval for checking the primary fallback list and the secondary fallback list are configured in the parameter
X_CheckPrimaryFallbackInterval
and
X_CheckSecondaryFallbackInterval
respectively. These parameters
are specified in seconds and the default value is 60 for both.
Notes:
-
Secondary server exists implies primary server exists.
-
If the secondary server exists, it immediately becomes the primary server when the current primary server
fails; the device then starts searching for a new secondary server if the candidate set is not empty.
-
The candidate list may change (lengthened, shortened, priority changed, etc.) on every DNS renewal (based on
the entry’s TTL). Device will rearrange the primary and secondary servers and fallback lists accordingly,
whichever is applicable.
If the server redundancy feature is disabled, the device resolves only one IP address from the server’s domain name
and will not attempt to try other IP addresses if the server is not responding.
SIP Privacy
The OBi device observes inbound caller privacy and decodes the caller’s name and number from SIP INVITE requests by
checking the FROM, P-Asserted-Identity (PAID for short), and Remote-Party-ID (RPID for short) message headers. All
these headers may carry the caller’s name and number information.
If PAID is present, the device takes the name and number from it. Otherwise, it takes name and number from RPID if it
is present, or from the FROM header otherwise. RPID, if present, will include the privacy setting desired by the caller.
The privacy setting may indicate one of the following options:
-
off
= no privacy requested; the OBi will show name and number.
-
full
= full privacy requested; the OBi will hide both name and number.
-
name
= name privacy requested; the OBi will show the number but hide the name.
-
uri
= uri privacy requested; the OBi will show the name but hide the number.