US Patent 8379638 Security encapsulation of ethernet frames

A technique for encapsulating data packets at a Data Link Layer to provide security functions. The technique first encrypts a payload to provide an encrypted payload. The encrypted payload is inserted in an output encapsulated frame. Also added to the output encapsulated frame is an encapsulation header that includes security information, such as a security packet index (SPI) value used to identify a security association (SA). Because the output encapsulated frame may now be longer than maximum allowed Ethernet Path Maximum Transmission Unit (PMTU), the encapsulation header also preferably includes a fragmentation field. The fragmentation field supports the ability to fragment the encrypted datagrams into smaller pieces.