The following encapsulation service options are available on Ethernet ports:
null—supports a single service on the port; for example, where a single customer with a single service customer edge (CE) device is attached to the port.
dot1q—supports multiple services for one customer or services for multiple customers (see Figure: Multiple SAPs on a single port). For example, dot1q could be used when the Ethernet port is connected to a multi-tenant unit device with multiple downstream customers. The encapsulation ID used to distinguish an individual service is the VLAN ID in the IEEE 802.1Q header.
Figure: Multiple SAPs on a single port
