The value of tmnxKeyChainKeyDirection is used to specify the
protocol-stream direction to encrypt.
A value of 'send' specifies that this key entry will be used to sign
protocol packets that are being sent by the router to another device.
A value of 'receive' specifies this key entry will be used to
authenticate protocol packets that are being received by the router.
A value of 'send-receive' specifies that this key will be used to sign
protocol packet that are being sent by the router to another device,
as well as to authenticate protocol packets that are being received by
the router.