SIP & Network
The SIP response code indicating the call was declined outright, commonly returned when a carrier blocks a call rather than failing to connect it.
603 Decline means the far end explicitly refused the call, as opposed to 486 Busy Here or 404 Not Found. Carriers frequently use 603 — sometimes with a reason header — to signal an intentional block.
Because 603 is a global failure response, it terminates the fork rather than allowing the call to be tried on another route.
A rising 603 rate on a customer's traffic is usually the first machine-readable sign that downstream carriers have started blocking them.
The signaling protocol used to set up, modify, and tear down voice and video calls over IP networks.
Analytics-driven tags such as 'Scam Likely' or 'Spam Risk' that terminating carriers and handsets apply to inbound calls.
The SIP header that carries the signed PASSporT token proving a call's caller ID was authenticated by the originating provider.
The percentage of call attempts that are actually answered, used as both a route-quality measure and a fraud indicator.
SipShield scores live SIP traffic with patented AI so the controls behind this term run automatically — and leave the audit trail regulators expect.