ZyXEL MAX-306 User Guide - Page 117
Multi-Protocol Label Switching, 9.3.2 Generic Routing Encapsulation, VLAN 10
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Chapter 9 The VPN Transport Screens interface is simply a set of information that takes frames from a VLAN and put them on an Ethernet pseudowire, and vice versa. In this example, the WiMAX Device takes frames tagged with two different VLAN IDs (10 and 20) and using the customer interfaces, assigns them to specific pseudowires (PW1 and PW2). Figure 49 Pseudowire Mapping VLAN 10 PW1 VLAN 20 PW2 10 20 PW1 1 WiMAX PW2 2 R The WiMAX Device has a default customer interface configured for frames that arrive at the WiMAX Device without VLAN tags. 9.3.1 Multi-Protocol Label Switching The WiMAX Device uses MPLS VPNs to create virtual private LANs. MPLS stands for Multi-Protocol Label Switching, and is a packet-switching technology that allows packets with different VLAN tags to be transported on different paths (known as LSPs, or Label Switched Paths). Each packet is identified by its VLAN tag and sent to a specific LSP for transport over the WiMAX network. Each LSP has a defined start-point and end-point. Since MPLS creates monodirectional paths (traffic flows in only one direction), each Ethernet pseudowire uses two LSPs so that traffic can flow both ways. One LSP carries upstream traffic, and the other carries downstream traffic. 9.3.2 Generic Routing Encapsulation In order to transport the VPLS traffic over the WiMAX network, the WiMAX Device uses the Generic Routing Encapsulation (GRE) protocol. Like MPLS, GRE is a tunneling protocol that has specified endpoints. The GRE tunnel is bi-directional, and transports both LSPs. The GRE tunnel runs across the WiMAX network between the WiMAX Device and your service provider's router. User's Guide 117