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To achieve efficient device failover to the backup/secondary Application Server, the SBC uses the Address Reachability Service (ARS) to determine if a server is reachable, providing the ability to "blacklist" a server IP address if it is found to be unreachable, as well as the ability to remove the server from the blacklisted state. ARS profiles can be created to configure blacklisting and recovery algorithm variants.

These ARS profiles can be assigned to the services section of a SIP trunk group to enforce the blacklisting and recovery of any SIP peer(s) associated with the trunk group. If no recovery algorithm is specified when configuring a SIP ARS profile, the recovery algorithm default values are used as indicated below:

  • Recovery Alg Probe Duration: 1 second
  • Recovery Alg Probe Interval: 1 second
  • Recovery Alg Probe Method: sip-options
  • Recovery Alg Probe Num Responses: 1
  • Recovery Alg Timer Duration: 1 second
  • Recovery Algorithm: probe

Traffic is shared across all SBC Session Control Module (SCM) processes. For INVITE time outs, an IP Peer is blacklisted only when the same SCM process reaches the configured number of INVITE timeouts within the configured timeout duration.

For a single shot call scenario (i.e. lab testing), it may be necessary to gather additional timeouts to see an IP Peer get blacklisted. Once the peer is blacklisted, the same data is available across all SCM processes.

Similarly, when a peer is not blacklisted but is in the process of being blacklisted because of time outs, the 'show' command to check ARS Status may give inconsistent results depending upon the SCM process which responds first to the command.

Traffic is shared across all SBC SCM processes. For INVITE time outs,an IP Peer is blacklisted only when the same SCM process reaches the configured number of INVITE timeouts within the configured timeout duration.

To View Sip Ars Profile

On SBC main screen, go to Configuration > Profile Management > Category: Service Profiles > Sip Ars Profile.

The Sip Ars Profile window is displayed.

Figure : Profile Management - Service Profiles - Sip Ars Profile

 

To Edit Sip Ars Profile

To edit any of the Sip Ars Profile in the list, click the radio button next to the specific Sip Ars Profile name.

Figure : Profile Management - Service Profiles - Sip Ars Profile Highlighted

 

The Edit Selected Sip Ars Profile window is displayed below.

Figure : Profile Management - Service Profiles - Sip Ars Profile Edit Window

 

Make the required changes and click Save at the right hand bottom of the panel to save the changes made.

To Create Sip Ars Profile

To create a new Sip Ars Profile, click New Sip Ars Profile tab on the Sip Ars Profile List panel.

Figure : Profile Management - Service Profiles - Sip Ars Profile Fields

 

The Create New Sip Ars Profile window is displayed.

Figure : Profile Management - Service Profiles - Sip Ars Profile Create Window

 

The following fields are displayed:

Table : SIP Address Reachability Profile Parameters

 

Parameter

Description

Name

Specifies the name of the SIP ARS Profile.

Failure Response Codes

Use this parameter to define one or more response codes to treat as failure responses. Include one or more of the following values, separating each entry with a comma: - 400-699 - list codes individually

- all – include all response codes from 400-699

 - all4xx – include all 4xx response codes

 - all5xx – include all 5xx response codes

- all6xx – include all 6xx response.

The Failure Response Codes values for Path Check Profile and Sip Ars Profile within the same zone/TG has similar values to avoid unexpected behavior. For example, it is ill advised to set Path Check Profile Failure Response Code to "all" and Sip Ars Profile Failure Response Codes to "all4xx,all6xx".

In EMA, the Failure Response Codes are configured as comma separated values. In CLI, the values of the Failure Response Code are separated by space.

Blk List
Algorithms

Specifies the type of BLACKLISTING ALGORITHM for this ARS profile:
timeouts (default)—the timeout of the specified SIP message will be used for blacklisting the server. The algorithm TYPE, NUMBER OF TIMEOUTS, and DURATION attributes for this parameter must also be specified.
retryafter—use the BLACKLISTING RETRYAFTER ALGORITHM TYPE (trigger)
as the blacklisting criteria.

You may configure either or both of these blacklisting criteria.

Blk List Alg
Timeouts Type

Specifies the TYPE of timeout trigger for the blacklisting TIMEOUTS algorithm:
sip-invite—use SIP INVITE messages as a timeout trigger.

Blk List Alg
Timeouts Num Timeouts

Specifies the number of timeout events that must occur before black listing the address. Must be 1-3600; default value is 1.

Blk List Alg Timeouts Duration

Specifies the DURATION (in seconds) in which the specified number of timeouts should occur. Must be 1-3600. SIP-INVITE timeout is the only event that is supported as of now.

Blk List Alg Retry After Type

Specifies the SIP status code which has a Retry After value:
sip-503

Mid Dialog ARS Screen Level

Use this parameter to control when to apply ARS to a mid-dialog request.

  • Always - ARS is applied to all mid-dialog requests in a call.
  • Never (default) - ARS is not applied to mid-dialog requests.
  • Only If Not Black List Due to 503 - ARS is applied to mid-dialog requests unless blacklist due to 503 is encountered.

Recovery
Algorithm

Specifies the type of recovery algorithm used after an IP address has been blacklisted:
probe (default)—the ARS initiates an active "ping" to the blacklisted server until it gets a response. Once a response is received, the address is removed from the blacklist. The METHOD, INTERVAL, NUMBER OF RESPONSES, and DURATION attributes for the this parameter must also be specified.
timer—the ARS removes the entry for the blacklist after a configured duration.

Recovery Alg
Timer Duration

Specifies the DURATION (in seconds), for which the IP address will remain blacklisted. Must be 1-3600.

Recovery Alg
Probe Method

Specifies the probe (ping) METHOD for blacklist recovery:
sip options—use a SIP OPTIONS request

Recovery Alg
Probe Interval

Specifies the probe INTERVAL (in seconds) for blacklist recovery. Must be 1 - 600 (default is 1).

Recovery Alg Probe Num Responses

Specifies the number of consecutive responses that must occur before removing an entry from the black list. Must be 1 - 32 (default is 1).

Recovery Alg
Probe Duration

Specifies the DURATION (in seconds) in which the specified number of probe responses should occur. Must be 1-3600 (default is 1).

Note

Sonus recommends to not configure Path Check Profile and SIP ARS Profile on the same peer to avoid unexpected results. As a general rule, the Path Check Profile is configured on the access leg where there is less traffic, and the ARS Profile is configured on the peer leg where there is continuous traffic. 

To Copy Sip Ars Profile

To copy any of the created Sip Ars Profile and to make any minor changes, click the radio button next to the specific Sip Ars Profile to highlight the row.

Figure : Profile Management - Service Profiles - Sip Ars Profile Highlighted

 

Click Copy Sip Ars Profile tab on the Sip Ars Profile List panel.

Figure : Profile Management - Service Profiles - Sip Ars Profile Fields

 

The Copy Selected Sip Ars Profile window is displayed along with the field details which can be edited.

Figure : Profile Management - Service Profiles - Sip Ars Profile Copy Window

 

Make the required changes to the required fields and click Save to save the changes. The copied Sip Ars Profile is displayed at the bottom of the original Sip Ars Profile in the Sip Ars Profile List panel.

To Delete Sip Ars Profile

To delete any of the created Sip Ars Profile, click the radio button next to the specific Sip Ars Profile which you want to delete.

Figure : Profile Management - Service Profiles - Sip Ars Profile Highlighted

 

Click Delete at the end of the highlighted row. A delete confirmation message appears seeking your decision.

Figure : Profile Management - Service Profiles - Sip Ars Profile Delete Confirmation

 

Click Yes to remove the specific Sip Ars Profile from the list.

 

 

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