Motorola 68338 User Guide - Page 24

WAN Adapter RFC1294 Multiprotocol Encapsulation Overview RFC1294 encapsulation is used for the IP and RIP protocols. RFC1490 extends RFC1294 to handle SNA protocols. For IP and IPX, however, RFC1294 and RFC1490 are identical. All protocols are encapsulated using the NLPID format for IP. How the WAN Adaptor Handles RFC 1294 The WAN adapter handles RFC1294 encapsulation as follows: 1) The WAN Adapter creates an RFC1294 header and places it in the packet in front of the data before the packet is passed to the WAN protocol stack. 2) The RFC1294 header is passed as data by the WAN protocol stack and is processed and stripped from the packet by the receiving WAN Adapter. 3) The packet is passed to the Routing forwarder. Note The Vanguard does not support the RFC1294 encapsulation of bridge data. If a WAN Adapter LAN Connection record has the parameter LAN Forwarder Type of BRID or BROUT, then the Encapsulation Type must be CODEX (not RFC1294); otherwise, bridge data will be lost. If bridge traffic will be sent over an FRI port, then the encapsulated bridge traffic can be sent over an Annex G station on the port. Packet Format Figure 2-3 shows the two main WAN packet formats in use for Frame Relay connections. RFC1294 Encapsulation Bypass Station Flag Q9.22 Q9.22 NPLID Protocol Packet CRC CRC Flag Note: The RFC1204 encapsulation to a Bypass FR station is used for interoperability with non-Motorola routers. Figure 2-3. Packet Formats Codex Encapsulation Annex G Station Flag Q9.22 Q9.22 OxCC ADDR CTL LGN LCN CTL LAPB Header X25 Packet Header Protocol Packet Type=0 Flags Codex Trailer CRC CRC Flag Note: Motorola to Motorola links are recommended to use Codex encapsulation over Annex G-type Frame Relay stations. 2-8 Vanguard Routing Model