Windows Advanced Firewall: What does "Edge Traversal" mean?
Solution 1:
It looks like this Microsoft patent filing from earlier this year might tell you what you want to know.
From what I can gather, this flag allows firewall rules to apply to traffic that has been encapsulated by, for example, an IPv6 to IPv4 tunnel originating outside the border of the network. As patents often are, this one is written in such a generic manner as to apply to any different type of tunneling protocol, from what I can tell.
The payload of this encapsulated traffic would be opaque to the any firewall at the network on the other end of the tunnel. Presumably, these encapsulated packets would be passed through unfiltered to the internal host where the other end of the tunnel terminated. That host would receive the traffic, pass it through its own firewall, decapsulate the traffic (if allowed by its own firewall), and pass the decapsulated packets back its firewall. When the packet travels thru the firewall the second time (after decapsulation), it has an "this packet traversed the network edge" bit set such that only rules with the "edge traversal" bit also set will apply to the packet.
Figure 4 of that patent application appears to describe the process graphically, and the "Detailed Descriptions" section beginning on page 7 describes the process in painfully specific detail.
This basically permits a host-based firewall to have different rules for traffic that came in via a tunnel thru the local network's firewall, as opposed to traffic that was just sent unencapsulated by a tunnel directly through the local network's firewall.
I wonder if the iptables "mark" functionality would be prior art to this patent? It certainly seems like it does a very similiar thing, albeit in an even more generic fashion (since you can write user-land code to "mark" packets for virtually any reason if you want to ).
Solution 2:
An older post, but still worth adding to. It seems that in Windows Server 2012, this item simply means "allow packets from other subnets". At least that is the behavior I have observed. We have two offices connected with an IPSec VPN. The VPN connects the two routers, so as far as the Windows computers are concerned, it's simply traffic between two different private subnets. With the setting "Block Edge Traversal" Windows will not allow connections from the other subnet.
Solution 3:
Edge traversal occurs whenever you have a tunnel interface that goes to a less secure network, which is tunneled over another interface that is attached to a more secure network. This means that the host is bypassing (tunneling over) one of the security boundaries set up by the local network administrator. For example, with any tunnel to the Internet over a physical interface attached to the corporate network, you have “edge traversal”.
In Windows 7, Microsoft’s built-in NAT traversal technology, Teredo, can be configured to work through the firewall using rules that make use of Edge Traversal. In principle, 3rd party NAT traversing tunneling technologies could do so as well.