Why IPsec ?

proprietary methods should not used.
we should choice an open standard.
it is not easy to design security protocols for each application.
some closed environments might choice this way.
SSL, SSH might not be used.
these methods only protect the communication on TCP.
asymmetric cryptography could not be suitable for home appliances.
IPsec
it could protect the communication on IP.
however it requires some light key configuration methods for home appliances.
other protection method could be used on IPsec or without using IPsec.