Hello Robert,

thanks for hint. The trace:

curl http://localhost:8453/trace/connectivity.samsung.com.cn
[iterat][4123608.00]   'connectivity.samsung.com.cn.' type 'A' new uid was assigned .01, parent uid .00
[cache ][4123608.01]   => no NSEC* cached for zone: samsung.com.cn.
[cache ][4123608.01]   => skipping zone: samsung.com.cn., NSEC, hash 0;new TTL -123456789, ret -2
[cache ][4123608.01]   => skipping zone: samsung.com.cn., NSEC, hash 0;new TTL -123456789, ret -2
[zoncut][4123608.01]   found cut: samsung.com.cn. (rank 010 return codes: DS 1, DNSKEY 1)
[resolv][4123608.01]   => NS is provably without DS, going insecure
[select][4123608.01]   => id: '61652' choosing: 'dns1.esamsungchina.com.cn.'@'27.106.204.42#00053' with timeout 10000 ms zone cut: 'samsung.com.cn.'
[resolv][4123608.01]   => id: '61652' querying: 'dns1.esamsungchina.com.cn.'@'27.106.204.42#00053' zone cut: 'samsung.com.cn.' qname: 'coNNECTIVitY.SAMSunG.com.CN.' qtype: 'A' proto: 'tcp'
[worker][4123608.01]   => connecting to: '27.106.204.42#00053'
[worker][4123608.01]   => connection to '27.106.204.42#00053' failed (internal timeout)
[select][4123608.01]   => id: '61652' noting selection error: 'dns1.esamsungchina.com.cn.'@'27.106.204.42#00053' zone cut: 'samsung.com.cn.' error: 4 TCP_CONNECT_TIMEOUT
[iterat][4123608.01]   'connectivity.samsung.com.cn.' type 'A' new uid was assigned .02, parent uid .00
[select][4123608.02]   => id: '65410' choosing to resolve AAAA: 'dns1.esamsungchina.com.cn.' zone cut: 'samsung.com.cn.'
[plan  ][4123608.02]   plan 'dns1.esamsungchina.com.cn.' type 'AAAA' uid [4123608.03]
[iterat][4123608.03]     'dns1.esamsungchina.com.cn.' type 'AAAA' new uid was assigned .04, parent uid .02
[cache ][4123608.04]     => no NSEC* cached for zone: esamsungchina.com.cn.
[cache ][4123608.04]     => skipping zone: esamsungchina.com.cn., NSEC, hash 0;new TTL -123456789, ret -2
[cache ][4123608.04]     => skipping zone: esamsungchina.com.cn., NSEC, hash 0;new TTL -123456789, ret -2
[zoncut][4123608.04]     found cut: esamsungchina.com.cn. (rank 010 return codes: DS 1, DNSKEY 1)
[resolv][4123608.04]     => NS is provably without DS, going insecure
[select][4123608.04]     => id: '29392' choosing: 'dns.esamsungchina.com.cn.'@'27.106.204.41#00053' with timeout 10000 ms zone cut: 'esamsungchina.com.cn.'
[resolv][4123608.04]     => id: '29392' querying: 'dns.esamsungchina.com.cn.'@'27.106.204.41#00053' zone cut: 'esamsungchina.com.cn.' qname: 'DNS1.ESAMsUNgchiNa.coM.cN.' qtype: 'AAAA' proto: 'tcp'
[worker][4123608.04]     => connecting to: '27.106.204.41#00053'
[worker][4123608.04]     => connection to '27.106.204.41#00053' failed (internal timeout)
[select][4123608.04]     => id: '29392' noting selection error: 'dns.esamsungchina.com.cn.'@'27.106.204.41#00053' zone cut: 'esamsungchina.com.cn.' error: 4 TCP_CONNECT_TIMEOUT
[iterat][4123608.04]     'dns1.esamsungchina.com.cn.' type 'AAAA' new uid was assigned .05, parent uid .02
[cache ][4123608.05]     => no NSEC* cached for zone: esamsungchina.com.cn.
[cache ][4123608.05]     => skipping zone: esamsungchina.com.cn., NSEC, hash 0;new TTL -123456789, ret -2
[cache ][4123608.05]     => skipping zone: esamsungchina.com.cn., NSEC, hash 0;new TTL -123456789, ret -2
[select][4123608.05]     => id: '16382' choosing: 'dns1.esamsungchina.com.cn.'@'27.106.204.42#00053' with timeout 10000 ms zone cut: 'esamsungchina.com.cn.'
[resolv][4123608.05]     => id: '16382' querying: 'dns1.esamsungchina.com.cn.'@'27.106.204.42#00053' zone cut: 'esamsungchina.com.cn.' qname: 'DNs1.esamSUNgcHiNA.COM.cn.' qtype: 'AAAA' proto: 'udp'
[select][4123608.05]     => id: '16382' noting selection error: 'dns1.esamsungchina.com.cn.'@'27.106.204.42#00053' zone cut: 'esamsungchina.com.cn.' error: 1 QUERY_TIMEOUT
[worker][4123608.00] internal timeout for resolving the request has expired
[resolv][4123608.00] request failed, answering with empty SERVFAIL
[resolv][4123608.05]     finished in state: 8, queries: 0, mempool: 114752 B