--- title: "Joseph O'Shaughnessy (@josephoshaughnessy) | Hashnode" description: "Network engineer. Labs, packet captures and real-world troubleshooting. Read the latest articles by Joseph O'Shaughnessy on Hashnode." url: "https://hashnode.com/@josephoshaughnessy" --- @josephoshaughnessy # Joseph O'Shaughnessy @josephoshaughnessy · London, UK · Joined October 2026 Network engineer. Labs, packet captures and real-world troubleshooting. ### [Diagnosing Slow TCP Transfers](https://josephoshaughnessy.hashnode.dev/diagnosing-slow-tcp-transfers?utm_source=hashnode&utm_medium=feed) Packet loss or a slow app? How to tell the difference in Wireshark, using dup ACKs, fast retransmissions and zero windows. 10 min read · [josephoshaughnessy.hashnode.dev](https://josephoshaughnessy.hashnode.dev/diagnosing-slow-tcp-transfers?utm_source=hashnode&utm_medium=feed) [4d ago](https://hashnode.com/posts/diagnosing-slow-tcp-transfers/6aef9eb239a473d6c9cf169f) ### [Diagnosing DNS Failures with dig and tcpdump](https://josephoshaughnessy.hashnode.dev/dns-failures-dig-tcpdump?utm_source=hashnode&utm_medium=feed) Five ways DNS breaks, and how dig and a packet capture tell them apart 11 min read · [josephoshaughnessy.hashnode.dev](https://josephoshaughnessy.hashnode.dev/dns-failures-dig-tcpdump?utm_source=hashnode&utm_medium=feed) [Oct 31](https://hashnode.com/posts/dns-failures-dig-tcpdump/6ae53900ae02375f2968935f) ### [Finding an MTU Black Hole](https://josephoshaughnessy.hashnode.dev/mtu-black-hole?utm_source=hashnode&utm_medium=feed) Why big transfers hang when ping works, and three ways to fix it 12 min read · [josephoshaughnessy.hashnode.dev](https://josephoshaughnessy.hashnode.dev/mtu-black-hole?utm_source=hashnode&utm_medium=feed) [Oct 18](https://hashnode.com/posts/mtu-black-hole/6ad5323dd1a4c0ef2ace34a9) ### [Diagnosing a Failed TCP Handshake](https://josephoshaughnessy.hashnode.dev/tcp-handshake-wireshark?utm_source=hashnode&utm_medium=feed) Three ways a TCP handshake fails, and how to tell them apart in a packet capture 12 min read · [josephoshaughnessy.hashnode.dev](https://josephoshaughnessy.hashnode.dev/tcp-handshake-wireshark?utm_source=hashnode&utm_medium=feed) [Oct 18](https://hashnode.com/posts/tcp-handshake-wireshark/6ad50995b1413071e4d7e3c3)