Thanks for the information. If I understand this correctly, the client would have to convince the owner of each and every router hop along the way to disable PMTU discovery if he insists on dropping all ICMP packets? And Scott hit the nail on the head with this comment: > Sometimes you can't be so hard headed when you are dealing with customers. You > usually are trying to get them to give money to YOU, not your competitor. > If I told my customers that "It is your problem", I would no longer have > customers to worry about! If you've ever dealt with with one of these paranoid Mordac-type security managers you know exactly what I'm talking about. In our case the path of least resistance was to disable pmtu discovery, and tell the customer that we've done all we possibly can to alleviate the issue on our end. Hopefully they come to their senses and allow ICMP packets like every major ISP and mail provider on the Internet.