What causes tcp retransmition and header error checksum?

Question

My boss complained that his pc is too slow to access network. I had a quick nothing seemed obvious.

To see behind scenes, l installed wireshark. There is a lot of fragmentation and retransmition going on from his pc and destination server.

What can it be?

Answer 1

It turns out it was jumbo packets mismatch settings.

Comments

you beat me to the answer.... it usually means some mismatch - i wasnt going to say jumbo frames but it often points at some network setup discrepancy - eg poor cabling between specific switches etc

Fragmentation happens specifically when you are trying to transmit packets that are bigger than the path MTU - which basically means if you send a package bigger than 1500 bytes in most cases, with jumbo frames, its not just your device that needs to support it, its the switch and the target end

jumbo frames can cause problems if the switch doesnt support it or filters jumbo frames silently

---

A lot of things goes behind the scene!!