Tag Archives: three-way handshake

DNS Capture: UDP, TCP, IP-Fragmentation, EDNS, ECS, Cookie

It’s not always this simple DNS thing such as “single query – single answer, both via UDP”. Sometimes you have some more options or bigger messages that look and behave differently on the network. For example: IP fragmentation for larger DNS answers that do not fit into a single UDP datagram (hopefully not after the DNS flag day 2020 anymore), or DNS via TCP, or some newer options within the EDNS space such as “EDNS Client Subnet” (ECS) or DNS cookies.

I won’t explain any details about those options, but I am publishing a pcap with that kind of packets along with some Wireshark screenshots. Feel free to dig into it.

Continue reading DNS Capture: UDP, TCP, IP-Fragmentation, EDNS, ECS, Cookie

PAN Blocking Details

One of my readers sent me this question:

We have an internal discussion about whether it is possible to block the 3 way hanshake TCP but allow the JDBC application protocol. In other words we would like to block the test of the port with the command “telent address port” but we would like that the connections via JDBC continue to work. is it possible to do this theoretically? Is it possibile to do it with paloalto firewall?

Let’s have a look:

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