0	lelong		0xa1b2c3d4	pcap data (little endian),
>4	leshort		x		version %d
>6	leshort		x		rev %d,
>16	lelong		x		snap length %d,
>20	lelong		0		no link-layer encapsulation
>20	lelong		1		Ethernet
>20	lelong		2		Ethernet (3MB)
>20	lelong		3		AX25
>20	lelong		4		ProNET
>20	lelong		5		CHAOS
>20	lelong		6		IEEE 802
>20	lelong		7		ARCNET
>20	lelong		8		SLIP
>20	lelong		9		PPP
>20	lelong		10		FDDI
>20	lelong		11		LLC/SNAP encapsulated ATM
>20	lelong		12		raw IP


0	belong		0xa1b2c3d4	pcap data (big endian),
>4	beshort		x		version %d
>6	beshort		x		rev %d,
>16	belong		x		snap length %d,
>20	belong		0		no link-layer encapsulation
>20	belong		1		Ethernet
>20	belong		2		Ethernet (3MB)
>20	belong		3		AX25
>20	belong		4		ProNET
>20	belong		5		CHAOS
>20	belong		6		IEEE 802
>20	belong		7		ARCNET
>20	belong		8		SLIP
>20	belong		9		PPP
>20	belong		10		FDDI
>20	belong		11		LLC/SNAP encapsulated ATM
>20	belong		12		raw IP

