Jan 29, 2017 · In Wireshark, I see TCP duplicate ACK packets sent from the receiver to the sender. What does it mean? Does it imply packet loss? Thank you.

Mar 3, 2020 · In this case you have to find the Selective ACKs - which are shown as "Dup-Acks" in Wireshark. If you delve into the packet detail of the Dup-ACKs, you'll see the "left edge" and "right edge" values that identify them as SACKs.

By default, Wireshark’s TCP dissector tracks the state of each TCP session and provides additional information when problems or potential problems are detected. Analysis is done once for each TCP packet when a capture file is first opened.

I'm getting excessive TCP Dup ACK and TCP Fast Retransmission on our network when I transfer files over the MetroEthernet link. The two sites are connected by one sonicwall router, so the sites are only one hop away. Here is a screenshot from wireshark, and here is the entire capture.

May 7, 2013 · In response to the unnecessary "spurious" retransmission (#194), the receiver sends a Duplicate-SACK (D-SACK, #195). A D-SACK is the use of the SACK mechanism to inform the sender that it has sent duplicate data (#194 = #150). Note the "Left Edge = 23361 & Right Edge = 24062" in the TCP Options/SACK detail. D-SACKs are also Dup-ACKs.

May 6, 2011 · While forming the "(A-B) range ack" packet - server has to specify the last-acked part (0) in TCP header. Wireshark marks the range-acks (SACKs) as [TCP Dup ACK ...] because all those range-acks have same last-acked part value in TCP header (Ack=872619 in Your case).

Duplicate ACKs are sent when the receiver sees a gap in the packets it receives. They're not just used for fast retransmissions, it is the other way around (sort of): fast retransmissions use a counter for duplicate ACKs to trigger a retransmission faster than by …

Dec 16, 2024 · In Wireshark, the keyword for duplicate ACKs is “TCP Dup ACK”, and for fast retransmission, it is “TCP Fast Retransmission”. The following image shows an example of a fast retransmission occurring after 51 duplicate ACKs:

Traffic towards 192.168.10.5 seems to be looping (L3) and forking. This causes each IP packet to 192.168.10.5 to reach 192.168.10.5 mutiple times (with descending TTL's). This causes DSACK messages from 192.168.10.5 telling 192.168.10.100 that it …

Apr 29, 2021 · Wireshark displays TCP ACKed unseen segment and TCP spurious Retransmission, which is apparently due to a slow capturing device (which applies to the client side). It seems the client side capture is having a different …