arin.net - ARIN (IP address and ASN registry for North America)
iana.org - IANA protocol numbers (moved from isi.edu)
ieee802.org - IEEE 802 LAN/MAN Standards Committee (Ethernet, Wi-Fi)
ietf.org - Internet Engineering Task Force (Internet standards)
packetizer.com - Packetizer (H.323, SIP and ITU-T standards)
rfc-editor.org - RFC Editor (every RFC)rfc-editor.org/rfc9260 - RFC 9260: SCTP (Stream Control Transmission Protocol; replaces RFC 2960)
w3.org - W3C (World Wide Web Consortium)
arista.com - Arista Networks
cisco.com - Cisco
juniper.net - Juniper Networks (now part of HPE)
atlas.ripe.net - RIPE Atlas (global ping and traceroute measurements)
bgp.he.net - Hurricane Electric BGP Toolkit (looking glass, ping and traceroute)
bgp.potaroo.net - BGP routing table size reports (Geoff Huston)
iperf.fr - iPerf (TCP, UDP and SCTP bandwidth testing)
nmap.org - Nmap (free network scanner, from insecure.org)
peeringdb.com - PeeringDB (networks and internet exchange points)
wireshark.org - Wireshark (free protocol analyzer; formerly Ethereal)
amazon.com - Search Amazon.com for data networking books
experts-exchange.com - Experts Exchange (IT questions and answers)iponeverything.net - IP On Everything (networking links and notes)
networklessons.com - NetworkLessons (Cisco and networking tutorials)
serverfault.com - Server Fault (network and sysadmin Q&A)
cisa.gov - CISA (US Cybersecurity and Infrastructure Security Agency)
openssh.com - OpenSSH (free SSH)
sans.org - SANS Institute (security training and research)
ssh.com - SSH Communications Security (ssh.fi now goes here)info-zip.org - Info-ZIP (free Zip and UnZip)libpng.org - Introduction to PNG
zlib.net - zlib technical details (CRC and Adler-32 checksums; moved from info-zip.org)