SIP-SIPI IWF Using Session Translation
You can use a feature called Number Translation function to perform simple changes to calling or called numbers for SIP-SIPI IWF calls. Number Translation uses session-translation elements to specify these translations. You use session-translation elements for SIP-SIPI IWF similarly to number translation to manipulate SIP-SIPI interworking information. Refer to "Number Translation" to for an extended explanation of how Number Translation works and for additional instruction on session-translation configuration.
The session-translation element presents the list of SIP and ISUP objects that you can manipulate with session translation:
- rules-asserted-id—Manipulates the SIP P-Asserted-Id header
- rules-redirect—Manipulates the SIP History-Info & Diversion headers
- rules-isup-cdpn—Manipulates the ISUP Called Party Number parameter
- rules-isup-cgpn—Manipulates the ISUP Calling Party Number parameter
- rules-isup-gn—Manipulates the ISUP Generic Number parameter
- rules-isup-rdn—Manipulates the ISUP Redirecting Number parameters
- rules-isup-ocn—Manipulates the ISUP Original Called Number parameters
As with number translation, the configuration steps you take for this processing include:
- Define translation-rules.
- Apply translation-rules to the appropriate session-translation parameters.
- Apply the applicable session-translation object on session-agents or realms. Apply these translations based whether you are targeting ingress or egress calls (in-translationid / out-translationid) and based on whether the call leg is SIP or SIPI.
Refer to "SIP-ISUP IWF Operational Detail" for processing sequences to ensure you are performing session-translation based on the expected state of each message object.
ISUP Session Translation and NOA Interworking
The SBC builds the ISUP-based number before translation referring to the ISUP nature of address. Procedures performed at the SIPI egress include:
- Regardless of ISUP session
translation configuration:
- If the received URI userpart starts with +, the SBC removes it and sets the NOA to International.
- When you have configured
any ISUP session translation:
- If the received URI userpart starts with 0 (zero), the SBC removes it and sets the NOA to National.
- If the received URI userpart does not starts with either + or 0, the SBC does not make any change to the NOA. This case would most likely be a SIPI to SIPI interworking wherein the incoming NOA is neither national or international.
| Nature of address | Example number | Number before translation |
|---|---|---|
| International | 1234 | +1234 (starts with +) |
| National | 1234 | 01234 (starts with zero) |
| Other | 1234 | 1234 (others) |
After the translation, the ISUP parameters are filled back with the right nature of address.
| Number after translation | New nature of address | Number in ISUP |
|---|---|---|
| +1234 (starts with +) | International | 1234 |
| 01234 (starts with zero) | National | 1234 |
| 1234 (others) | Do not change (keep previous one) | 1234 |
Review the following conversion example.
| Source ISUP called party number | Translation-rule #1 (convert to NATIONAL) called from rules-isup-cdpn | Result |
|---|---|---|
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