In this section:
Ribbon recommends using the Transparency Profile to configure transparency on the SBC Core Core for new deployments, as well as applying additional transparency configurations to existing deployments. Do not use IP Signaling Profile flags in these scenarios because the flags will be retired in upcoming releases. Refer to the SBC SIP Transparency Implementation Guide for additional information.
IMPORTANT
Preconditions Interworking
The The This feature supports ISUP-SIP and SIP-SIP preconditions interworking, and provides transparency by dropping/adding of preconditions attributes between supporting or non-supporting peers. The preconditions are configured from the The SBC Core completes the ingress preconditions when the call terminates at the PSX script. Users can configure the list of script names (in the NOTE: The SBC allows a maximum of three script names to configure. The configurable script name is the same as the script name that the PSX returns. The The SBC adds a P-Charging-Vector header with the NOTE: The Unable to show "metadata-from": No such page "_space_variables" provides a preconditions support feature to reserve network resources as a preventative measure to minimize chances of session failure due to lack of resources before alerting the called party. This prevents a "ghost ring" where the called party is alerted before the call is set up.Unable to show "metadata-from": No such page "_space_variables" supports preconditions interworking functionality only when one leg of a call supports preconditions and other does not. The Unable to show "metadata-from": No such page "_space_variables" supports preconditions functionality on either of the legs (egress or ingress). With this feature, preconditions interworking is decided based on the precondition profile configuration, present in the Common IP Attributes of the IP Signaling Profile (IPSP).Unable to show "metadata-from": No such page "_space_variables" at the SIP Trunk Group level using the parameters “preconditions” (for incoming requests) and “transmitPreconditions” (for outgoing requests).psxScriptProfile) for which the SBC performs ingress preconditions interworking. The ingress preconditions trigger when one of the configured script names matches with the PSX returned script name. The script execution continues after the ingress preconditions are met.pemInterworking flag inhibits sending the P-Early Media header in the first 18x response for the ingress preconditions interworking scenario.termIOI parameter to the 18x response sent to the ingress network. The termIOI parameter sends the terminating networking identifier to the ingress network. The SBC creates and sends the termIOI parameter when there is no egress network, which occurs when the call is terminated in the script. When there is an egress network, the termIOI parameter is received from the egress network.termIOI parameter is configured in the Signaling SIP Trunk Group.
The CLI syntax is shown below:
% set addressContext <addressContext_name> zone <zone_name> sipTrunkGroup <sipTrunkGroup_name> services preconditions [none | required | supported] % set addressContext <addressContext_name> zone <zone_name> sipTrunkGroup <sipTrunkGroup_name> services transmitPreconditions [none | required | supported]
Info
Refer to SIP Trunk Group - Services - CLI for configuration details.
Preconditions Interworking Properties
The preconditions interworking is provided based on a new Preconditions Profile (PP), and the interpretation of what IPTG configuration to apply is driven by the ingress/egress PP configuration. This is required to provide flexibility for environments where mixed combinations of functionality is required as shown in the following table:
Preconditions Interworking Properties
| Ingress | Egress | Preconditions Interworking |
|---|---|---|
| IPTG-1 | IPTG-2 | Requires preconditions interworking in one direction, but not the other direction |
| IPTG-1 | IPTG-3 | Does not require preconditions interworking |
| IPTG-1 | IPTG-4 | Requires preconditions interworking for all calls |
Interworking functionality is triggered, and ingress/egress PP is evaluated only under the following two circumstances:
- Ingress session offer has precondition attributes and egress TG PP
SupportIfEgressIPTGis disabled. - Ingress session offer has no precondition attributes and egress TG PP
SupportIfEgressIPTGis enabled.
Note
Under any other circumstances, precondition interworking is not present and the Preconditions Profile does not have any effect.
Precondition Profile Flags Interaction and Outcome
Refer to the table below for flags interactions between the ingress and egress trunk groups. For a description of the flags, go to .
Case 1:
Ingress session offer has precondition attributes and egress TG PP SupportIfEgressIPTG is disabled.
Precondition Profile Flags Interaction and Outcome
| Scenarios | Ingress Flags Assumptions | Egress Flags Assumptions | SBC Behavior |
|---|---|---|---|
| 1 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled/Enabled Preconditions Strength Mandatory: Policy: Disabled Preconditions Strength Mandatory: Priority: 2 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled Preconditions Strength Mandatory: Policy: Enabled Preconditions Strength Mandatory: Priority: 1 | As Egress Preconditions Strength Mandatory: Priority has highest value, its policy is considered Interworking is desired |
| 2 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled/Enabled Preconditions Strength Mandatory: Policy: Disabled Preconditions Strength Mandatory: Priority: 1 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled Preconditions Strength Mandatory: Policy: Enabled Preconditions Strength Mandatory: Priority: 2 | As Ingress Preconditions Strength Mandatory: Priority has highest value, its policy is considered Interworking is not desired. As Egress IPTG has preconditions: Transparent is configured, Preconditions Parameters is transparently sent to Egress |
| 3 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled/Enabled Preconditions Strength Mandatory: Policy: Disabled Preconditions Strength Mandatory: Priority: 1 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled Preconditions Strength Mandatory: Policy: Enabled Preconditions Strength Mandatory: Priority: 1 | As priority is same Ingress Preconditions Strength is considered Interworking is not desired As Egress IPTG has preconditions: Transparent is configured, Preconditions Parameters is transparently sent to Egress |
Note
Priority 1 (lowest value) has the highest priority.
Case 2:
Ingress session offer has no precondition attributes and egress TG PP “Preconditions Support If Egress IPTG” = Enabled.
Precondition Profile Flags Interaction and Outcome
| Scenarios | Ingress Flags Assumptions | Egress Flags Assumptions | SBC Behavior |
|---|---|---|---|
| 1 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled/Enabled Preconditions Strength Mandatory: Policy: Enabled/Disabled Preconditions Strength Mandatory: Priority: 2 Use UPDATE when Signaling Preconditions Locally Met: Policy:Enabled Use UPDATE when Signaling Preconditions Locally Met: Priority:2 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Enabled Preconditions Strength Mandatory: Policy: Enabled/Disabled Preconditions Strength Mandatory: Priority: 1 Use UPDATE when Signaling Preconditions Locally Met: Policy: Disabled Use UPDATE when Signaling Preconditions Locally Met: Priority: 1 | As Egress Preconditions Support If Egress IPTG: Enabled Irrespective of Preconditions Strength Mandatory: Policy/Priority Interworking is desired and Outgoing Offer will have preconditions with preconditions strength as "mandatory"
As value is disabled in initial outgoing Invite local: met is sent |
| 2 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Disabled/Enabled Preconditions Strength Mandatory: Policy: Enabled/Disabled Preconditions Strength Mandatory: Priority: 2 Use UPDATE when Signaling Preconditions Locally Met: Policy: Enabled Use UPDATE when Signaling Preconditions Locally Met: Priority:1 | IPTG Flags: Preconditions: Transparent 100rel Support: Enabled IPSP PP flags: Preconditions Support If Egress IPTG: Enabled Preconditions Strength Mandatory: Policy: Enabled/Disabled Preconditions Strength Mandatory: Priority: 1 Use UPDATE when Signaling Preconditions Locally Met: Policy: Disabled Use UPDATE when Signaling Preconditions Locally Met: Priority: 2 | As Egress Preconditions Support If Egress IPTG: Enabled Irrespective of Preconditions Strength Mandatory: Policy/Priority Interworking is desired and Outgoing Offer will have preconditions with preconditions strength as "mandatory"
As value is Enabled in initial outgoing Invite local: not met is sent |
NOTE:
- If Preconditions interworking is configured as “Use UPDATE”, configure the Allow UPDATE flag as well.
- If Preconditions interworking is configured as “Use UPDATE” but a 183 from the peer does not have UPDATE in the Allow header, the Unable to show "metadata-from": No such page "_space_variables"will not send an UPDATE and does not take any other action, thus a call timeout timer generates to terminate the call.
- Do not set Preconditions to "Required" for interworking scenarios.
During an ingress precondition interworking scenario, if the remote precondition is met in PRACK, the
Unable to show "metadata-from": No such page "_space_variables"processes it and sends the INVITE towards the egress.
Preconditions Interworking Using 183 Response
The Unable to show "metadata-from": No such page "_space_variables" supports preconditions interworking for generic call flows based on the ingress IPTG or on the message content of the same IPTG. A new SIP Message Manipulation (SMM) variable is used to determine the applicable IPTG configurables for an initial INVITE, SUBSCRIBE, REGISTER, or an Out-Of-Dialog request.
If support of an IPTG prefix-based Call Admission Control (CAC) together with SMM-based ingress IPTG selection is desired, use IPTGs which are selected based on the SMM. The SMM rules in the same profile are used for the selection, and each profile is associated with an IP prefix (by virtue of being attached to an IPTG which is selected based on IP prefix). A Parent IPTG is defined covering all such SMM-based IPTGs, and the parent IPTG CAC corresponds to the IP prefix-based IPTG.
Note
The presence, absence, or value of a SIP information element such as a proprietary Header or a proprietary Parameter are examples of the type of message contents that trigger the enhanced preconditions.
The message content policy selection is supported through Flexible Policy.
The Unable to show "metadata-from": No such page "_space_variables" Flexible Policy supports the selection of the IPTG for the ingress leg though SIP SMM rules. The IPTG that is selected using SMM configuration is applied to all the incoming initial INVITE, initial SUBSCRIBE, initial REGISTER, and/or Out-Of-Dialog request. The CAC is applied to both the IP-prefix based IPTG and the SMM based IPTG.
Support of a IPTG prefix based CAC, along with SMM based ingress IPTG selection, it is accomplished as follows:
- IPTGs selected based on the SMM, uses the SMM rules in the same profile for selection and each profile is associated with an IP prefix (since it is attached to an IPTG, which is selected based on an IP prefix).
- A parent IPTG is defined as covering all the SMM based IPTGs, and the parent IPTG CAC corresponds to the IP prefix based IPTG.
Note
- If an IPTG configured using SMM, and configured in the system, the call is rejected with a code 488 "Request not acceptable here" message.
- The IPTG is not validated while configuring via SMM; it is validated at the time of execution since IPTGs can be added/deleted in between SMM.
The
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also provides preconditions support for 183 responses using following CLI syntax, (This flag is for specific call flows and is not intended for generic use)% set addressContext <addressContext_name> zone <zone_name> sipTrunkGroup <sipTrunkGroup_name> services preconditionIntwkUsing183 <disable|enable>
NOTE:preconditionIntwkUsing183 are configured, the Preconditions Profile takes a higher precedence. Settings of “preconditions=transparent”/”100rel support=yes” on both legs is the only supported configuration for proper precondition interworking functionality.preConditionIntwkUsing183 when End-to-End Prack is configured.
P - Early Media Preconditions Interworking
The parameter pemInterworking is added to the Trunk Group Signaling configuration to control when to send the PEM header during ingress Preconditions interworking for SIP-SIP calls.
For SIP - SIP / SIP-SIP-T with preconditions interworking
The
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does not add P-early media in the first 183 which is sent to ingress as a part of preconditions interworking. The Unable to show "metadata-from": No such page "_space_variables"
relays P-early media received from Egress peer except for the case where the Unable to show "metadata-from": No such page "_space_variables"
provides Ringback Tone (RBT). Note that the Unable to show "metadata-from": No such page "_space_variables"
must create and send 180 ringing with PEM sendrecv before providing the RBT. If P-early media is not received in 180 ringing coming from the Egress peer, the Unable to show "metadata-from": No such page "_space_variables"
needs to create and add P-early media sendrecv to the 180 ringing sent to ingress. For SIP–ISUP with preconditions interworking
The
Unable to show "metadata-from": No such page "_space_variables"
does not add P-early media in the first 183 which is sent to ingress as a part of preconditions interworking. The Unable to show "metadata-from": No such page "_space_variables"
needs to create and add P-early media sendrecv to the 180 ringing sent to ingress upon receipt of ACM/CPG from Egress ISUP network before providing the RBT. Call Flows
This feature supports the following call flows:
Mobile — “SIP” —
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— “GWGW” — GSX — “ISUP” — PSTNMobile — “SIP” —
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— “GWGW” — Unable to show "metadata-from": No such page "_space_variables"
— “SIP-I/T” — C5IMSMobile — “SIP” —
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— “SIP-I/T” — C5IMS
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