Resilience And Survivability - Siemens OpenStage 40 Administration Manual

3.5.9

Resilience and Survivability

To allow for stable operation even in case of network or server failure, OpenStage phones have
the capability of switching to a fallback system. The switchover is controlled by various
configurable check and timeout intervals.
Survivability is achieved in 3 different ways:
1. With firmware V2, DNS SRV can be used for enhanced survivability, either in a scenario
with a survivability proxy, or in a scenario with multiple primary SIP servers. The DNS serv-
er provides the phone with a prioritized list of SIP servers via DNS SRV. The phone fetches
this list periodically from the server, depending on the TTL (time to live) specified for the
DNS SRV records.
To enable DNS SVR requests from the phone, please make the following settings:
• Specifiy the IP address of the DNS server that provides the server list via DNS SRV.
The web interface path is Network > IP configuration > Primary DNS. For details, see
Section 3.3.6.2, "DNS Servers".
• Enable the use of an outbound proxy for routing outbound requests. The web interface
path is System > SIP interface > Outbound proxy. For details, see Section 3.5.7.1,
"Outbound Proxy".
• Set the SIP gateway port to 0. The web interface path is Network > Port configuration
> SIP gateway. Alternatively, if the SIP server otherwise specified in System > Regis-
tration > SIP server address is to be configured by DNS SRV, set the SIP erver port to
0. The web interface path is Network > Port configuration > SIP server. For details, see
Section 3.5.5.2, "SIP Ports".
• As SIP gateway address, enter the DNS domain name for which the DNS SRV records
are valid. The web interface path is System > Registration > SIP gateway address. Al-
ternatively, if the SIP server otherwise specified in System > Registration > SIP server
address is to be configured by DNS SRV, set the mentioned parmeter to the DNS do-
main name for which the DNS SRV records are valid. For details, see Section 3.5.5.1,
"SIP Addresses".
A survivability proxy acts as a relay between the phone and the primary SIP server. Thus,
the address of the survivability proxy is specified as gateway or SIP server at the phone
(see Section 3.5.6, "SIP Registration"). When the TLS connection between the survivability
proxy and the SIP server breaks down, e. g. because of server failure, the survivable proxy
itself acts as a replacement for the primary SIP server. Vice versa, in case the phone can
not reach the survivability proxy itself, it will register directly with the primary SIP server,
provided that it is specified in the DNS SRV server list.
The survivability proxy notifies the phone whenever the survivability changes, so it can in-
dicate possible feature limitations to the user. Furthermore, to enhance survivability, the
phone will be kept up-to-date about the current survivability state even after a restart.
A31003-O1010-M100-17-76A9, 09/09/2010
OpenScape Voice - OpenStage Family, Administration Manual
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