What are and how to use SIP Pings in VoIP

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This article discusses what SIP pings are, and how to use them in troubleshooting VoIP (Voice over IP) networking.

A SIP ping in VoIP is a diagnostic method used to check the availability and responsiveness of a SIP (Session Initiation Protocol) server or endpoint. It’s similar in concept to an ICMP ping, but it uses SIP signaling instead of IP packets. This does not preclude the use of ping:

Key Points of using SIP Ping:

  • Purpose: To verify that a SIP server (like a proxy, registrar, or UAS) is reachable and responsive on the SIP signaling level—not the media (RTP) level.
  • How it works:
    • A SIP OPTIONS request is sent to the target SIP device or server.
    • If the device is alive and reachable, it responds with a SIP 200 OK message.
    • No call is initiated—this is purely a signaling check.
  • Common uses:
    • Health checks in SIP trunking and hosted VoIP systems.
    • Monitoring and alerting by VoIP monitoring tools (e.g., to detect outages or high latency).
    • Pre-call validation of SIP endpoints or routes.
  • Command-line example using sipsak: sipsak -s sip:username@sipserver.com
    This sends a SIP OPTIONS request and waits for a response.

You can see in the command line example above, I used a tool called sipsak. If you want to learn more about sipsak, look here.

Example of a SIP Ping

Limitations of SIP Pings:

  • It only checks SIP signaling path availability—not media (RTP) quality or audio.
  • Some SIP servers may be configured to ignore or rate-limit OPTIONS pings.

Here’s a diagram and example SIP OPTIONS exchange, showing how a SIP ping works in VoIP:

SIP OPTIONS Ping Diagram

+-------------+                            +------------------+
| SIP Client  |                            |  SIP Server      |
| (Monitoring)|                            |  (or Proxy/UAS)  |
+-------------+                            +------------------+
       |                                              |
       |---- SIP OPTIONS ---------------------------->|
       |                                              |
       |<--- SIP 200 OK ------------------------------|
       |                                              |
  • SIP Client sends a SIP OPTIONS request to the SIP Server.
  • SIP Server responds with SIP 200 OK if it is reachable and operational.

SIP OPTIONS Request Example

sip
OPTIONS sip:server.example.com SIP/2.0
Via: SIP/2.0/UDP 192.168.1.10:5060;branch=z9hG4bK776sgdkse
From: "Monitor" <sip:monitor@client.example.com>;tag=1928301774
To: <sip:server.example.com>
Call-ID: a84b4c76e66710
CSeq: 63104 OPTIONS
Max-Forwards: 70
Content-Length: 0

SIP 200 OK Response Example

sip
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.1.10:5060;branch=z9hG4bK776sgdkse
From: "Monitor" <sip:monitor@client.example.com>;tag=1928301774
To: <sip:server.example.com>;tag=8321234356
Call-ID: a84b4c76e66710
CSeq: 63104 OPTIONS
Content-Length: 0
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO
Supported: replaces, timer
User-Agent: AcmeSIPServer/2.4.1

What You Can Learn from This Exchange:

  • Server is alive if it responds with 200 OK.
  • Capabilities (from the Allow: header).
  • User-Agent can indicate server software/version.
  • Network round-trip time can be measured between request and response.

Conclusion

Using a control plane verification for VoIP like SIP ping is a great troubleshooting checklist item when trying to find out why someone’s IP phone is not working properly. Plus using a tool that does this creates packet traffic that can be used to document and further troubleshoot the VoIP network.

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