OPTIONS200
SIP reachability
OPTIONS pings over UDP, TCP, and TLS with real transaction timers. Any answer below 500 counts as alive — SBCs reply 405 or 486 by design, and we know that.
SIP monitoring, done by SIP people
Know before your customer calls.
Generic uptime tools can't read a 503. SIP Sentry probes your trunks, registrars, and SBCs with real OPTIONS, REGISTER, TLS, and DNS SRV checks — and pages you only when something is actually wrong.
Free tier · no card · probe IPs published for allowlisting
sipsentry-probe · eu-west
probesbc01.acme-telecom.nl:5061
OPTIONS sip:acme-telecom.nl
Via: SIP/2.0/TLS · SNI acme-telecom.nl · Max-Forwards: 70
SIP/2.0 200 OK
Allow: INVITE, ACK, CANCEL, BYE, OPTIONS · Server: SBC/9.2
up11 mscert 58 dSRV oknext check in 60 s
Check types
Checks that speak SIP, not just TCP
A port being open tells you nothing about whether calls complete. Each check exercises the protocol layer where telephony really fails.
REGISTER401→200
Registration path
A real REGISTER with digest auth (MD5 and SHA-256) against a dedicated test extension. Exercises the auth path that actually breaks — then removes its own binding.
TLS58 d
Certificate expiry
Handshake with correct SNI, expiry countdown, chain and hostname verification. Still reports expiry on self-signed SBC certs instead of choking on them.
NAPTR/SRVok
DNS discovery chain
Validates the full RFC 3263 chain: NAPTR, SRV per service, and A/AAAA for every target — not just the one a phone would pick. Broken SRV kills trunks silently.
ICMP4 ms
Network baseline
Round-trip latency and packet loss to your edge. When ICMP is filtered, it measures TCP connect time instead — and tells you which one it measured.
RTP / MOS
Test calls with quality scoring
Automated calls with estimated MOS from jitter, loss, and latency (ITU-T G.107). On the roadmap — tell us if you need it sooner.
coming soon
Alerting you can trust
Built for the 3 AM shift
A monitoring product earns exactly one thing: trust. These rules are wired into the state machine, not written on a values page.
Timeout is not down
SBCs drop OPTIONS from unknown sources by policy. Every monitor chooses whether a timeout means down or degraded, so a firewall rule never pages your on-call.
Unknown is not down
If our probes lose coverage, your monitors go unknown and no customer alert fires. You will never page a customer because our infrastructure had a bad night.
No flap, no noise
N consecutive failures before an alert, M successes before recovery — per monitor. One lost UDP datagram is a statistic, not an incident.
Alerts cannot get lost
Every notification is queued in the same transaction as the state change and retried with backoff. A crash mid-send delays an alert; it never deletes one.
Probe architecture
Probes that run anywhere — including inside your network
Probes connect outbound over WebSocket. No inbound ports, no VPN, no firewall tickets. Use our vantage points, or run the same single binary next to the SBC that only accepts SIP from known addresses.
- ▸One static binary or container, no local state, no stored credentials
- ▸Results buffered through connection loss, deduplicated on arrival
- ▸Cloud probe IPs published for SBC allowlisting
# run a private probe
$ docker run -d \
-e API_URL=wss://api.sipsentry.io/probe/v1/connect \
-e PROBE_TOKEN=••••••••••••• \
sipsentry/probe
probe connected · region=ams-dc2 · checks=5
status.acme-telecom.nl
All systems operational
SIP trunkUp
RegistrarUp
TLS certificateUp
For MSPs
A status page for every customer you manage
Group monitors per customer, route alerts per customer, and give each one a public status page with 90 days of uptime history. White-label it with their name and logo on the MSP plan — your customers see their voice platform, not your tooling.
Alerts go where your team lives: email, signed webhooks, Slack, Telegram, and SMS.
Your first monitor is two minutes away
Three monitors free, forever. Point one at your trunk and see the first OPTIONS result before your coffee is done.