The Epipe service is designed to carry Ethernet frame payloads, so it can provide connectivity between any two SAPs that pass Ethernet frames. The following SAP encapsulations are supported on the 7450 ESS, 7750 SR, and 7950 XRS Epipe service:
Ethernet null
Ethernet dot1q
QinQ
SONET/SDH BCP-null for the 7450 ESS and 7750 SR
SONET/SDH BCP-dot1q for the 7450 ESS and 7750 SR
ATM VC with RFC 2684 Ethernet bridged encapsulation. See Ethernet Interworking VLL) for the 7750 SR.
FR VC with RFC 2427 Ethernet bridged encapsulation. See Ethernet Interworking VLL) for the 7450 ESS and 7750 SR.
While different encapsulation types can be used, encapsulation mismatching can occur if the encapsulation behavior is not understood by connecting devices, which are unable to send and receive the expected traffic. For example, if the encapsulation type on one side of the Epipe is dot1q and the other is null, tagged traffic received on the null SAP is double-tagged when it is transmitted out of the dot1q SAP.
ATM VLLs can be configured with both endpoints (SAPs) on the same router or with the two endpoints on different 7750 SRs. In the latter case, Pseudowire Emulation Edge-to-Edge (PWE3) signaling is used to establish a pseudowire between the devices, allowing ATM traffic to be tunneled through an MPLS or GRE network:
Two pseudowire encapsulation modes, that is, SDP vc-type, are available:
PWE3 N-to-1 Cell Mode Encapsulation
PWE3 AAL5 SDU Mode Encapsulation
The endpoints of Fpipes must be Data-Link Connection Identifiers (DLCIs) on any port that supports Frame Relay. The pseudowire encapsulation, or SDP vc-type, supported is the 1-to-1 Frame Relay encapsulation mode.