Wireshark mailing list archives
Interpretation of "summary" TCP/IP packets?
From: "Templin (US), Fred L" <Fred.L.Templin () boeing com>
Date: Tue, 3 Jul 2018 19:42:37 +0000
Hi, On a pair of Ubuntu linux laptops (call them A and B) connected via a 1Gbps link, I am running “iperf3 –c” on node A and “iperf3 –s” on node B. Also on node B I am running wireshark on B’s “eth0” interface to capture the traffic. When I start the wireshark capture, and then start the iperf3 test, the capture shows “summary” TCP/IP packets instead of the “real” packets. I call them “summary” packets because their length is much larger than 1500 bytes (the MTU of the link connecting A and B). For example, I see packets with lengths like 20338, 29026, etc. When I use wireshark to examine the IP headers of these “summary” packets, the IP length field reflects these larger values and shows the packets as non-fragmented IP packets, which makes no sense because the largest non-fragmented IP packet possible is only 1500 bytes. When I put a router (call it R) between nodes A and B and run wireshark on R, what I see is the “summary” packet followed by N 1500 byte packets that cover the same sequence number space as for the summary packet. This begins to make sense to me because the smaller packets fit inside the path MTU. But, the “summary” packet sill shows up in the wireshark capture. Can someone explain to me what is going on here? Thanks - Fred
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Current thread:
- Interpretation of "summary" TCP/IP packets? Templin (US), Fred L (Jul 03)
- Re: Interpretation of "summary" TCP/IP packets? Guy Harris (Jul 03)
- Re: Interpretation of "summary" TCP/IP packets? Templin (US), Fred L (Jul 03)
- Re: Interpretation of "summary" TCP/IP packets? Guy Harris (Jul 03)