RFC 4891:Using IPsec to Secure IPv6-in-IPv4 Tunnel...
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UDP


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... IP as the next layer protocol (like TCP or UDP) in traffic selectors. ...


... In both SPD entries, "IKE" refers to UDP destination port 500 and possibly also port ...


... Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC 3948prop ...


... "IKE" refers to UDP destination port 500 and possibly also port ...


... endpoints support IPsec NAT traversal extensions, UDP encapsulation can be enabled. ...
... can be enabled. More details about UDP encapsulation of IPsec-protected IP packets ...



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