関連ワード:  define network layer in osi model    what is network layer in osi model    explain network layer in osi model    what is network layer in osi model with example    definition of network layer in osi model    what is the network layer in osi model responsible for    what is function of network layer in osi model    what is the work of network layer in osi model    what is the use of network layer in osi model    explain the role of network layer in osi model and its associated protocols