Not sure if this is really related. But several months back my ISP sent me a new/re-conditioned DSL modem. The instructions were to authenticate using PPPoE. However, it caused all sorts of fragmentation for me. Max packet size was <1464 if i recall correctly. The fragmentation caused me problems first at my firewall because I wasn't letting all the fragments through, and second on the other end of an authentication to a Windows/Kerberos server. A post I googled suggested Kerberos doesn't like fragments. Anyhow I changed my DSL modem setting to PPPoA. Supposedly it wasn't supported by my ISP, but it is. It cleared up issues I was having.
