Configure SIP Server Reachability

SIP Keepalive Messages

Configure SIP keepalive messages:

Enable keepalive messages for active server

Select the check-box to enable keepalive messages for active server.

The Survivability module sends SIP OPTIONS messages to the Active softswitch at regular intervals and monitors the replies to establish availability of the softswitch.

Time Between Keepalive Messages

Enter the number of seconds between consecutive keepalive messages sent to the softswitch to determine connectivity.

Note: This field only controls the time between keepalives sent to the active server. When the server is marked unavailable, a backoff algorithm is used for the time interval between keepalives to this server.

Number of Missed Messages To Declare Alarm

Number of received messages to clear alarm

Enter the number of consecutively received keepalive messages required for the system to declare successful connectivity to the remote softswitch.

Interpret error codes as success

Enter the error response codes (maximum of up to 5) to be treated as successful responses (range 300-699). Responses with successful return codes (range 200-299) are always accepted.

Choose the behavior of keepalive messages when a SIP server becomes unavailable. The following options control the behavior of these keepalive messages when no response is received. Once a response is received, the system resets the interval to the default initial value (5 seconds).

• Regular—Keepalive messages to the failed server are started immediately after unavailability is detected. If the system does not receive any response to the keepalive messages, it doubles the interval for the next message until it reaches a maximum. The maximum interval is 40 seconds when in local mode and 160 seconds when in remote mode.

• Random—Keepalive messages are not immediately started. The system waits for a random period between 3 seconds and the maximum configured value, Tmax, before starting the OPTIONS pings. If the system does not receive any response to the keepalive messages, it continues to wait for a randomly selected period between 3 seconds and Tmax seconds before sending the next OPTIONS message.

Maximum backoff interval

Enter the maximum back off interval when you choose the Random option for the No-response back off algorithm.

Reachability holdoff

Enter the minimum number of seconds to wait after the reachability algorithm detects that a higher priority server has become reachable before marking the server active.

This is used to help prevent flip-flopping of the available server when an SBC responds to keepalives but the actual SIP server is not ready to handle registrations. Most installations use a default value of 0 seconds.

Ignore holdoff when local

Select the checkbox to instruct the system not to apply the Reachability Holdoff delay when the system is running in local mode. This prevents unnecessary delay when switching from local mode to remote SIP servers.

Monitor SIP Messages

Select the check-box to monitor SIP requests sent to the active server. When this option is selected, the system monitors the SIP requests sent to the active server (excluding keepalive messages generated by the system). If no response is received within the specified time, that server is marked as unavailable.

Time for declaring SIP messages lost (seconds)

Enter the number of seconds to wait for a reply to a SIP request. If no request is received within this time interval, the softswitch is declared unreachable.

Monitor Inbound SIP Transactions

Monitors SIP requests from the active SIP server trigger cancellation of the “Monitor SIP Messages” timer.

Disabled—The cancellation of the SIP messages timer on request received from active SIP server is disabled.

All SIP Requests—Monitor all SIP requests to cancel the SIP messages timer.

All except SIP OPTIONS—Monitor all SIP requests except OPTIONS to cancel the SIP messages timer.

Ignore response codes

Enter response codes that ignore SIP request timeout messages once the Session Border Controller (SBC) has received 100 Trying responses.

Enter a comma separated list of response codes. For example, if the list is “100,404,” Survivability ignores a 100 Trying response and 404 Not Found response when determining whether a SIP message has been responded to.

Ignore other responses when INVITE/NOTIFY pending

Select the check-box to ignore SIP request timeout messages that have an INVITE pending.

The Ignore options are useful in environments that have an SBC in the network that responds directly to certain SIP messages. In particular, REGISTER messages are handled by the SBC. Other messages, INVITES in particular, are handled by the SS.

In this configuration, the Survivability algorithm might not detect a failure, if the Softswitch went down, but the SBC kept running. It would see responses from the REGISTER messages, but no responses from INVITES. Depending on how they were intermixed, it would at least delay entry into Survivability, and potentially not go into Survivability at all.

With the Ignore options set, the Survivability algorithm ignores any response traffic except for non-100 INVITE responses.

Remote Responses

Immediate Failover on Remote 5xx codes

This function provides SIP message response 5xx detection for the current SIP servers availability. When the active SIP server sends a SIP message response, for example, 500 Server Internal Error or 503 Service Unavailable the system will immediately determine this SIP server is unavailable and mark this server status as Unavailable. The system will now mark the Idle SIP server as Active and send new SIP messages to the Active SIP server until the unavailable SIP server becomes Active.

This feature is not dependent on SIP Keepalive messages or SIP Requests features being enabled however, the feature works with both SIP Server Reachability features to provide more reliable SIP server detection of when a SIP server has become unstable for processing SIP calls.

Configure the 5xx Server Failure response messages to indicate this server is currently unavailable by a comma delimiter.

For example: 500,503

Register user with softswitch

Select the Register user with softswitch check-box to enable the SBC to recognize OPTIONS sent to the softswitch by registering the “From” username of the OPTIONS message.

Authorization User name

Enter the username to be used in authorization response.

Password (Status)

Read-only field to show the status of the password.

Enter the authentication password.

Confirm password

Confirm password by re-entering it.

Enter the realm string for the server where the above credentials are to be used.

The realm string can be set to any base64 value to identify the secure area and may used by HTTP clients to manage passwords. For example: “aHR0cHdhdGNoOmY=”

If this field is left blank, the credentials are used for all realms. If a realm string value is provided, the password is not saved in clear text in the configuration file.