Page 236 7750 SR OS Services Guide
SAP Encapsulations and Pseudowire Types
The7750 SR 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 the7750 SR Epipe service:
• Ethernet null
• Ethernet dot1q
•QinQ
• SONET/SDH BCP-null
• SONET/SDH BCP-dot1q
• ATM VC with RFC 2684 Ethernet-bridged encapsulation (see Ethernet Interworking VLL
on page 198)
• FR VC with RFC 2427 Ethernet-bridged encapsulation (see Ethernet Interworking VLL
on page 198)
Note that while different encapsulation types can be used, encapsulation mismatching can occur if
the encapsulation behavior is not understood by connecting devices and 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 will be 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)
signalling 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, i.e., SDP vc-type, are available:
• PWE3 N-to-1 Cell Mode Encapsulation
• PWE3 AAL5 SDU Mode Encapsulation
The endpoints of Frame Relay VLLs 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.
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