Fax
T.38
A real-time fax-over-IP protocol that relays fax data over IP networks, commonly using UDPTL instead of RTP audio passthrough.
Why It Matters
T.38 shows up in real troubleshooting because it helps narrow whether a problem belongs to DNS, routing, media, mail, security, or addressing. Use the related TraceRoo tools below to turn the definition into evidence.