This a very usefull link for me. You can find the vendor of every network device 😀
• Use better faster DNS servers, like OpenDNS.org (188.8.131.52, 184.108.40.206).
• Connect directly to DNS servers to avoid DNS forwarding through your router (acting as a DNS proxy).
• Turn off IPv6 DNS lookups in Firefox/Camino (references: mozilla.org).
• If DNS forwarding is required, change the DNS servers directly on the router.
• Update your router’s firmware (references: jungledisk.com, ubuntu.com) for better SRV and IPv6 handling.
• Below are detailed instructions on applying these fixes to slow dns lookups/slow Internet on Leopard