関連ワード:  what is network layer in osi model    what is network layer in osi model with example    what is the network layer in osi model responsible for    what is function of network layer in osi model    what does network layer in osi model do    what is the use of network layer in osi model    what is the purpose of network layer in osi model    what is the primary function of network layer in osi model    which level is the network layer in osi model    network layer in osi model diagram