# Technical Specifications

**SIP**

Learn about SIP setup, IP ranges, ports, encryption, codecs, and DTMF support.

[General SIP Information](sip.html)

**Call Logs & Response Codes**

View and interpret call log response codes to troubleshoot call issues.

[SIP Response Codes in Call Logs](call-logs-response-codes.html)

**Caller ID Formats**

Learn about supported Caller ID formats (RAW, E.164, LOCAL) and how to customize them per trunk using CLI Prefix.

[Caller ID Formats](caller-id-formats.html)

**Failover**

Learn how DIDWW handles SIP failover and load balancing using DNS SRV and trunk groups for high availability.

[Service Failover and Load Balancing](failover.html)

**Fax Services**

Set up fax over IP using T.38 or G.711 protocols.

[FAX Services](fax-services.html)

**STIR/SHAKEN**

Learn about caller ID authentication and STIR/SHAKEN compliance.

[STIR/SHAKEN](stir-shaken.html)

**Toll-Free Dialing Format**

View country-specific formats for dialing Toll-Free DIDs.

[Inbound Toll-Free DID Dialing Format](tfdialscheme.html)

**UIFN Dialing Format**

View country-specific dialing formats for Universal International Freephone Numbers.

[Universal International Freephone Number (UIFN) Dialing Format](uifndialscheme.html)

**CPC Usage**

Understand CPC values for toll-free calls and their role in call routing and billing.

[CPC Usage](cpc-usage.html)

**Inbound Call Redirection Methods**

Redirect inbound calls using 30x and REFER methods.

[Inbound Call Redirection Methods](redirecting-calls.html)