The network system that includes a first server and a first switch is provided. The first server includes a first virtual machine. The first virtual machine (VM) is configured to provide a first VM packet including a first VM identifier (ID) to the first server. The first server is configured to acquire a tenant identifier corresponding to the first VM according to the first VM identifier, to convert the tenant identifier to a first feature data, and to encapsulate the first VM packet to generate and output a first server packet containing the first feature data. The first switch is configured to receive the first server packet, to acquire a service instance identifier (I-SID) according to the first feature data, to acquire a backbone VLAN identifier according to the I-SID, and to encapsulate the first server packet to generate and output a switch packet.
