The following lists encapsulation service options 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. The encapsulation ID is always 0 (zero).
Dot1q — Supports multiple services for one customer or services for multiple customers (Figure 1 and Figure 1). For example, the port is connected to a multi-tenant unit (MTU) device with multiple downstream customers. The encapsulation ID used to distinguish an individual service is the VLAN ID in the IEEE 802.1Q header.
QinQ — The QinQ encapsulation type adds a IEEE 802.1Q tag to the 802.1Q tagged packets entering the network to expand the VLAN space by tagging tagged packets, producing a double tagged frame.
There are several 7750 SR encapsulation service options on SONET/SDH channels:
Internet Protocol Control Protocol (IPCP) — Supports a single IP service on a SONET/SDH port or a single service per channel (if the interface is channelized). This is typically used for router interconnection using point-to-point protocol (PPP).
Bridging Control Protocol (BCP-null) — Supports a single service on the SONET/SDH port or a single service per channel (if the interface is channelized). This is used for bridging a single service between two devices using PPP over SONET/SDH. The encapsulation ID is always 0 (zero).
Bridging Control Protocol (BCP-dot1q) — Supports multiple services on the SONET/SDH port/channel. This encapsulation type is used for bridging multiple services between two devices using PPP over SONET/SDH. The encapsulation ID used to distinguish services is the VLAN ID in the IEEE 802.1Q header in the BCP-encapsulated frame.
ATM — ATM, ATM-FR, ATM SAP-bridge encapsulation termination Epipe and VPLS.
Frame Relay — Supports the switched data link layer protocol that handles multiple virtual circuits.
There are several 7450 ESS encapsulation service options on SONET/SDH channels:
Internet Protocol Control Protocol (IPCP) — Supports a single IP service on a SONET/SDH port. This is typically used for router interconnection using point-to-point protocol (PPP).
Bridging Control Protocol (BCP-null) — Supports a single service on the SONET/SDH port. This is used for bridging a single service between two devices using PPP over SONET/SDH. The encapsulation ID is always 0 (zero).
Bridging Control Protocol (BCP-dot1q) — Supports multiple services on the SONET/SDH port. This encapsulation type is used for bridging multiple services between two devices using PPP over SONET/SDH. The encapsulation ID used to distinguish services is the VLAN ID in the IEEE 802.1Q header in the BCP-encapsulated frame.
Frame Relay — Supports the switched data link layer protocol that handles multiple virtual circuits.
Figure 1. 7750 SR/7950 XRS and 7450 ESS multiple SAPs on a single port/channel