In order to achieve efficient device fail-over to a backup/secondary Application Server, the SBC uses
uses the Address Reachability Service (ARS) to determine if a server is reachable. This allows the
SBC to to “blacklist” a server IPv4 or IPv6 address if it is deemed unreachable, and address subsequent requests to that destination appropriately. In summary, ARS interface provides following configurable capabilities:
- Use INVITE requests timeout(s) to determine if an address is unreachable.
- Add unreachable addresses to a ‘blacklist’ file. Once an address is in the blacklist, no new calls are placed to that destination until address is removed from the blacklist.
- Provide two mechanisms to remove an unreachable server IP address from the blacklist:
- Use OPTIONS request to probe the blacklisted IP address until the server is once again visible (alive).
- Passively remove an address from the blacklist after a pre-configured period of time.
- View addresses deemed unreachable.
- Allow configuration of up to 32 ARS profiles and the monitoring of up to 1,023 endpoints.
- Allow an endpoint to be marked as blacklisted if a 503 with a Retry-After header is received. In this scenario, the recovery mechanism automatically runs a timer for the length specified in the Retry-After Header. For example, a Retry-After duration of”120” automatically removes the endpoint to from the blacklist two minutes after receiving the Retry-After header.
Internal to the SBC
, multiple call processing modules exist; traffic is shared across these modules. An IP Peer is blacklisted only when the same call processing module reaches the configured number of INVITE timeouts within the configured timeout duration (this is not an absolute value). 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 call processing modules.
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% set profiles services sipArsProfile TestARSProfile blkListAlgRetryAfterType sip-503
% set profiles services sipArsProfile TestARSProfile blkListAlgTimeoutsNumTimeouts 45
% set profiles services sipArsProfile TestARSProfile blkListAlgTimeoutsType sip-invite
% set profiles services sipArsProfile TestARSProfile blkListAlgorithms timeouts
% set profiles services sipArsProfile TestARSProfile blkListAlgTimeoutsDuration 34
% set profiles services sipArsProfile TestARSProfile recoveryAlgorithm probe
% set profiles services sipArsProfile TestARSProfile recoveryAlgTimerDuration 456
% set profiles services sipArsProfile TestARSProfile recoveryAlgProbeMethod sip-options
% set profiles services sipArsProfile TestARSProfile recoveryAlgProbeInterval 78
% set profiles services sipArsProfile TestARSProfile recoveryAlgProbeNumResponses 6
% set profiles services sipArsProfile TestARSProfile recoveryAlgProbeDuration 546
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See Refer to SIP ARS Profile - CLI or Service Profiles - Sip Ars Profile (EMA) for configuration details.
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> show status addressContext ac-1 zone SipZone sipArsStatus
sipArsStatus 2 0 {
sigPortNum 2;
endpointIpAddress FC00::3200:0:0:241:2;
endpointIpPortNum 20302;
endpointArsState blacklisted;
endpointStateTransitionTime 2011-12-09T16:25:21.000009Z; |
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| SRS_Reachability |
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| SRS_Reachability |
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