Incident
State
Open
Open since
2026-09-09 06:05:37 UTC
Running
10 d
Consecutive probes
≥6
Newest failing probe
2026-09-18 06:03:02 UTC
Newest failing status
521
csdn.net answered our probe with a server error on at least 6 consecutive probes.
csdn.net
What our own request to this host returned, over the last 30 days. Nothing here was tested for weaknesses and nothing was captured from anyone else's traffic.
Last status
521
Answered
100% of 6 probes
Refused
none of 6 probes over 30 days
Median open time
1613 ms
Last seen
2026-09-18 06:03:02 UTC
“Answered” is how often our own request got a response, from one region at one probe per day. It is not an uptime figure and must not be read as one. A refusal is a response, so a refused probe counts as answered. "Refused" counts the probes whose answer was 403 or 429.
Transport
TLS
1.3
Certificate expiry
67 days left
Issuer
Xcc Trust OV SSL CA
Chain valid
valid
Name matches
matches
HTTP version
1.1
Cipher
TLS_AES_256_GCM_SHA384
Address family
v4
Headers and cookies
Header grade
not measured
HSTS
not measured
Mixed content
not measured
Cookie flags
not measured
Redirect hops
1
Exposure check
not measured
The request ended at https://www.csdn.net/. 6 of the 6 probes that got a response ended on a different host, so the fields above may describe that host rather than this one.
Where the time went
DNS (first request) 0 msConnect (first request) 258 msTLS handshake (first request) 0 msRedirects, then waiting for the first byte 1446 msTransfer 2 ms
1706 ms in total, across 2 requests — the first and 1 redirect. Transfer is the remainder after the first byte rather than a separately measured phase.
Only the first request’s DNS, connection and TLS are timed separately, so that segment is not server think-time alone: it carries the other request and anything else between the first connection and the first byte.
The TLS handshake reads 0 ms because the first request was plain HTTP, so there was no handshake to time. The TLS version and certificate above are from the HTTPS hop the origin redirected to, which is a different connection from the one timed here.
1,924 bytes returned, after 1 redirect.
Registration and published DNS
Domain registration
172 days left
Registrar
Alibaba Cloud Computing (Beijing) Co., Ltd.
Registered
1999-03-11
DNSSEC
not signed
Registry record read over RDAP on 2026-09-12. Neither involves a request to this host, and neither is a test: we read what the registry and the domain’s own DNS publish. A published policy is not evidence about what a mail receiver would actually do.
By observer region
Measured from one region. The per-region comparison §5.5 describes needs more than one, and the deployment has one today.
Incidents we have recorded for this host
1 open now · not live · lags probing by days
Open now
An incident opens when a domain answers 5xx — its own server erroring — on 2 probes in a row, and closes when a probe succeeds. A 4xx, a refusal included, is an answer and does not count.
Each record is one thing we measured: the host answered our probe — one request, from one vantage point — with a server error on the stated number of consecutive probes. It says nothing about what anyone else sees from anywhere else.
The status is the HTTP status the host answered our newest failing probe of that run with — 503, say. It is that one response to that one request, not a summary of the run, and not the newest probe's status: a host that has since answered normally still shows the status of the last probe that failed. A record that reads "not recorded" was opened before we began keeping it and has not failed again since; that is an absence of a measurement, not a status of zero.
Hosts we could not reach at all are not listed. Their incidents are recorded separately and not published here, because from one vantage point a host nobody can reach and a host refusing our prober look the same, and naming one as the other would be a false claim about a working site. So this list is a floor: it can only under-count.
Not live: an incident opens only after 2 failing probes in a row and the estate is swept in passes days apart, so a record appears here days after the errors begin, and a close appears only when a later probe succeeds.
All the incidents we have recorded, on the Radar board →