Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Supported L2TPv3 PayloadsL2TPv3 supports the following Layer 2 payloads that can be included in L2TPv3 packets tunneled overthe pseudowire:• Frame Relay• Ethernet• 802.1q (VLAN)• HDLC• PPP• ATM• IPv6 Protocol DemultiplexingNoteEach L2TPv3 tunneled packet includes the entire Layer 2 frame of the payloads described in this section.If sequencing is required (see the section “Sequencing”), a Layer 2-specific sublayer (see the section“Pseudowire Control Encapsulation”) is included in the L2TPv3 header to provide the Sequence Numberfield.Frame RelayL2TPv3 supports the Frame Relay functionality described in the following sections:• Port-to-Port Trunking• DLCI-to-DLCI Switching• PVC Status Signaling• Sequencing• ToS Marking• CIR Guarantees• Binding L2TPv3 Sessions to Multilink Frame Relay InterfacesPort-to-Port TrunkingDLCI-to-DLCI SwitchingPort-to-port trunking is where two CE Frame Relay interfaces are connected as by a leased line (UTI rawmode). All traffic arriving on one interface is forwarded transparently across the pseudowire to the otherinterface.For example, in Figure 1, if the two CE routers are connected by a virtual leased line, the PE routerstransparently transport all packets between CE R3 and CE R4 over a pseudowire. PE R1 and PE R2 donot examine or change the DLCIs, and do not participate in the LMI protocol. The two CE routers areLMI peers. There is nothing Frame Relay-specific about this service as far as the PE routers areconcerned. The CE routers should be able to use any encapsulation based on HDLC framing withoutneeding to change the provider configuration.Frame Relay DLCI-to-DLCI switching is where individual Frame Relay DLCIs are connected to createan end-to-end Frame Relay PVC. Traffic arriving on a DLCI on one interface is forwarded across thepseudowire to another DLCI on the other interface.41