Unexpected TCP retransmissions

I am trying to debug a network using wireshark. I have a few VMs running on virtualbox. One of the VM is connected to the host using a "host only" interface. The host runs OVS through which all the VMs communicate. I ran wireshark on one of the VMs and the corresponding port on OVS and I see a number of TCP retransmissions. What can cause this?

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retransmissions tcp wireshark

asked 13 Aug '12, 17:13

Abhishek Chanda
21●1●2●3
accept rate: 0%

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I see the following, possible reasons:

a bug in the OpenFlow dissector (see also error message in the screenshot)
a bug in Open vSwitch
some kind of overload in your virtual environment, leading to drops within the Open vSwitch or one of the VMs
a bug in yor OS/application that handles the HTTP connection
any other strange problem, wich is unpredictable without further information about your system and software versions used.

Regards
Kurt

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answered 14 Aug '12, 03:28

Kurt Knochner ♦
24.8k●10●39●237
accept rate: 15%

This turned out to be a problem with Virtualbox. I changed to KVM and its gone.

(23 Aug '12, 16:06) Abhishek Chanda

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Question tags:

wireshark ×1,620
tcp ×752
retransmissions ×104

question asked: 13 Aug '12, 17:13

question was seen: 4,872 times

last updated: 23 Aug '12, 16:06

Unexpected TCP retransmissions

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You have a trillion packets.

You need to see four of them.

Don't have Wireshark?

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