server is not responding on SYN packetsWhy would a server not send a SYN/ACK packet in response to a SYN packetWhy would a server not send a SYN/ACK packet in response to a SYN packetserver dosnt produce syn-ackDuplicate syn packets sent from Windows server 2003 sp2Windows server closes TCP connection immediately after sending SYN+ACKNo response to some SYN packets when timestamps are enabledWhat happens if a machine gets a SYN/ACK packet without sending initial SYN packet?Server sends ACK in response to SYN causing a reset in TCP request from the clientServer send TCP ACK with wrong number after receiving SYNEstablishing TCP Connections by hping3SYN packets never responded to with SYN/ACK
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server is not responding on SYN packets
Why would a server not send a SYN/ACK packet in response to a SYN packetWhy would a server not send a SYN/ACK packet in response to a SYN packetserver dosnt produce syn-ackDuplicate syn packets sent from Windows server 2003 sp2Windows server closes TCP connection immediately after sending SYN+ACKNo response to some SYN packets when timestamps are enabledWhat happens if a machine gets a SYN/ACK packet without sending initial SYN packet?Server sends ACK in response to SYN causing a reset in TCP request from the clientServer send TCP ACK with wrong number after receiving SYNEstablishing TCP Connections by hping3SYN packets never responded to with SYN/ACK
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On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client is trying to establish two TCP connections from different src ports, so both connections should have been established. After 4 retries the client changed its src port from 13158 to 2352, and the TCP connection succeeded.
Is this an issue on the client or server side?
Similar article below doesn't seem to be related.
Why would a server not send a SYN/ACK packet in response to a SYN packet
TCP Dump (client IP masked):
tcp tcpip wireshark tcpdump packet-capture
edited Apr 13 '17 at 12:14
Community♦
1
asked Feb 17 '15 at 9:05
VladimirVladimir
11
add a comment |
On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client is trying to establish two TCP connections from different src ports, so both connections should have been established. After 4 retries the client changed its src port from 13158 to 2352, and the TCP connection succeeded.
Is this an issue on the client or server side?
Similar article below doesn't seem to be related.
Why would a server not send a SYN/ACK packet in response to a SYN packet
TCP Dump (client IP masked):
tcp tcpip wireshark tcpdump packet-capture
edited Apr 13 '17 at 12:14
Community♦
1
asked Feb 17 '15 at 9:05
VladimirVladimir
11
add a comment |
On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client is trying to establish two TCP connections from different src ports, so both connections should have been established. After 4 retries the client changed its src port from 13158 to 2352, and the TCP connection succeeded.
Is this an issue on the client or server side?
Similar article below doesn't seem to be related.
Why would a server not send a SYN/ACK packet in response to a SYN packet
TCP Dump (client IP masked):
tcp tcpip wireshark tcpdump packet-capture
edited Apr 13 '17 at 12:14
Community♦
1
asked Feb 17 '15 at 9:05
VladimirVladimir
11
On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client is trying to establish two TCP connections from different src ports, so both connections should have been established. After 4 retries the client changed its src port from 13158 to 2352, and the TCP connection succeeded.
Is this an issue on the client or server side?
Similar article below doesn't seem to be related.
Why would a server not send a SYN/ACK packet in response to a SYN packet
TCP Dump (client IP masked):
tcp tcpip wireshark tcpdump packet-capture
tcp tcpip wireshark tcpdump packet-capture
edited Apr 13 '17 at 12:14
Community♦
1
asked Feb 17 '15 at 9:05
VladimirVladimir
11
edited Apr 13 '17 at 12:14
Community♦
1
asked Feb 17 '15 at 9:05
VladimirVladimir
11
edited Apr 13 '17 at 12:14
Community♦
1
edited Apr 13 '17 at 12:14
Community♦
1
edited Apr 13 '17 at 12:14
Community♦
1
1
asked Feb 17 '15 at 9:05
VladimirVladimir
11
asked Feb 17 '15 at 9:05
VladimirVladimir
11
asked Feb 17 '15 at 9:05
VladimirVladimir
11
11
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Seems to be an issue on the server side. The client retransmitted the initial packet around 16:30:44 (the black sequence of lines on your screenshot) and the server finally replied. So it appears the very first packet was either lost on the server side, or server could not handle it properly for some reason (listen queue overflow, not enough workers, CPU saturation or something else).
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
add a comment |
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Seems to be an issue on the server side. The client retransmitted the initial packet around 16:30:44 (the black sequence of lines on your screenshot) and the server finally replied. So it appears the very first packet was either lost on the server side, or server could not handle it properly for some reason (listen queue overflow, not enough workers, CPU saturation or something else).
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
add a comment |
Seems to be an issue on the server side. The client retransmitted the initial packet around 16:30:44 (the black sequence of lines on your screenshot) and the server finally replied. So it appears the very first packet was either lost on the server side, or server could not handle it properly for some reason (listen queue overflow, not enough workers, CPU saturation or something else).
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
add a comment |
Seems to be an issue on the server side. The client retransmitted the initial packet around 16:30:44 (the black sequence of lines on your screenshot) and the server finally replied. So it appears the very first packet was either lost on the server side, or server could not handle it properly for some reason (listen queue overflow, not enough workers, CPU saturation or something else).
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
Seems to be an issue on the server side. The client retransmitted the initial packet around 16:30:44 (the black sequence of lines on your screenshot) and the server finally replied. So it appears the very first packet was either lost on the server side, or server could not handle it properly for some reason (listen queue overflow, not enough workers, CPU saturation or something else).
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
answered Feb 17 '15 at 9:26
drookiedrookie
6,19011219
6,19011219
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
add a comment |
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Server finally replied only after the client changed src port# and after existing connection was tiered down. Even if there is an existing TCP connection between client and server, new SYN packet should be accepted with no issues right?
– Vladimir
Feb 18 '15 at 3:07
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
Yup. I don't see a connection between client port changing and successful handshake (but may be there is, like bad packet filter rule), so I'd insist on packet losses, because it's way more usual.
– drookie
Feb 18 '15 at 10:36
add a comment |
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