prefixkit Ask an engineerAsk RU

SIP response codes

SIP 181 Call Is Being Forwarded

The call is being forwarded. The request is being processed; more responses will follow.

181
Name
Call Is Being Forwarded
Class
1xx · Provisional
Defined in
RFC 3261

The request is being processed; more responses will follow.

What the response looks like

SIP/2.0 181 Call Is Being Forwarded
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK776asdhds
From: <sip:101@pbx.example>;tag=1928301774
To: <sip:+15551234567@pbx.example>
Call-ID: a84b4c76e66710@203.0.113.10
CSeq: 2 INVITE
Content-Length: 0

More tools: voip & telephony

AI voice agent cost newRetell, ElevenLabs, Vapi, Bland vs human agents.AI agent ↔ PBX over SIP newAsterisk and FreeSWITCH configs for AI agents.VoIP pcap analyzerCalls, voice quality and why they dropped.SIP log analyzerLadder, SDP, NAT, DTMF and STIR/SHAKEN from a log.SIP server checkSRV, TCP/TLS and a SIP OPTIONS ping.SIP trunk generator newAsterisk pjsip.conf, FreeSWITCH gateway, Kamailio.IVR builder newVoice menu and hours for Asterisk and FreeSWITCH.PBX audio converter newPrompts to 8 kHz WAV, A-law, µ-law; TTS.STIR/SHAKEN decoder newIdentity header: attestation, numbers, checks.MOS calculatorVoice quality from delay, jitter and loss.VoIP bandwidthBandwidth per call with all headers and VPN.Erlang B & CTrunk channels and call-centre agents needed.SIP response codesWhat every code means and what to check.Q.850 causesCall release causes and their SIP mapping.