IEEE802.3 CSMA/CD

Since many local nets with access to the internet via standard gateway using common SNAT are all still based on IEEE802.3 with medium access control CSMA/CD (CSMA/CA CSMA/CR) this could have terrible risks in some cases.

The topology before the gateway to the Internet and the backbone (provider) architecture / topology exactly after this gateway, as well as the topology after the 1st real Internet router are critical!
If there is an internet exchange common backbone for all providers (that all regional or most providers share), this is the next critical area issue!

http://www.ieee802.org/3