SIP and VoIP guides
How SIP registration, transports, RTP, SRTP, codecs and ports work, explained in plain language. General education, not SIPdia-specific documentation unless marked.
- Guides
Common SIP Ports and What They Do
SIP uses port 5060 for UDP and TCP and 5061 for TLS. RTP audio uses a range of UDP ports, and STUN uses 3478. Learn what each port carries, how to find the ports your PBX uses, and how to open them safely.
9 November 2026 · 5 min read
- Guides
Common SIP Security Risks and How to Reduce Them
An overview of the most common SIP threats: scanning, brute force, toll fraud, eavesdropping, spoofed caller ID, registration hijacking, SIP ALG problems and weak PBX defaults, with practical mitigations.
9 November 2026 · 6 min read
- Guides
How to Secure a SIP Account
Practical steps to protect a SIP account: strong unique secrets, a separate auth username, TLS and SRTP, IP allow-lists, VPN access, credential rotation and toll-fraud monitoring.
9 November 2026 · 7 min read
- Guides
How to Protect a PBX from SIP Scanning and Brute-Force Attempts
Keep SIP port 5060 off the public internet, use VPN or allow-lists, add fail2ban, set strong secrets, restrict international dialing, watch CDRs and keep the PBX updated.
9 November 2026 · 6 min read
- Guides
Understanding RTP and Audio Streams in VoIP Calls
RTP carries the voice in a SIP call. Learn the RTP packet structure, how ports are negotiated in SDP, what RTCP reports, how jitter buffers work, how DTMF travels as RTP events, and why one-way audio happens.
9 November 2026 · 6 min read
- Guides
SIP Client vs VoIP Phone: What Is the Difference?
A SIP client is software or hardware that speaks the SIP protocol. A VoIP phone is any device that makes calls over IP. Learn how the terms overlap, where they differ, and which fits your setup.
9 November 2026 · 5 min read
- Guides
SIP Codecs Explained: G.711, Opus and Other Common Options
A codec turns voice into data and back. Learn how G.711, Opus, G.722, G.729 and GSM compare in bandwidth, quality and licensing, how codecs are negotiated in SDP, and how to choose one for your PBX.
9 November 2026 · 6 min read
- Guides
SIP over TLS vs SRTP: What Each One Protects
TLS encrypts SIP signaling hop by hop; SRTP encrypts the audio stream. Learn why you need both, how SDES and DTLS-SRTP exchange keys, and what SIPdia offers.
9 November 2026 · 6 min read
- Guides
SIP over UDP, TCP and TLS: Key Differences
SIP can run over UDP, TCP or TLS. Learn how each transport affects reliability, NAT traversal, message size and privacy, which ports they use, and how to pick the right one for your PBX or provider.
9 November 2026 · 6 min read
- Guides
SIP Registration Explained
SIP registration is how a softphone tells the server where to reach it. Learn the REGISTER request, the 401 challenge, expiry and refresh, the Contact header, and why registration breaks behind NAT.
9 November 2026 · 6 min read
- Guides
What Is a SIP Account? Username, Auth ID, Domain and Password
A SIP account is the set of credentials a softphone uses to register with a SIP server. Learn what the username, auth ID, domain, password, server and outbound proxy fields mean and where each one comes from.
9 November 2026 · 6 min read
- Guides
What Is a SIP Softphone? A Practical Guide
A SIP softphone is an app that places and receives phone calls over the internet using the SIP protocol. Learn how it works, what you need to use one, and how it compares to a desk phone.
9 November 2026 · 5 min read
- Guides
What Is SIP and How Does SIP Calling Work?
SIP is the signalling protocol that sets up, changes and ends voice calls over IP networks. Learn the main SIP messages, how a call flows from INVITE to BYE, and how SIP works with SDP and RTP.
9 November 2026 · 5 min read
- Guides
What Is SRTP and How Does It Protect Voice Traffic?
SRTP is the Secure Real-time Transport Protocol. It encrypts and authenticates the RTP audio packets of a VoIP call. Learn how it works, how keys are exchanged with SDES or DTLS, and why it needs TLS signalling.
9 November 2026 · 5 min read
Get SIPdia for your Mac, iPhone or iPad
Bring the SIP account you already have. The Mac and iPhone apps are in release preparation; download links appear on the download page when each release is live.
