ZyXEL Communications MAX-306M1, User Manual

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Chapter 9 The VPN Transport Screens
User’s Guide
101
9.3.2 Generic Routing Encapsulation
In order to transport the VPLS traffic over the WiMAX network, the WiMAX Modem
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 Modem and your service provider’s router.
It is necessary to encapsulate the Ethernet pseudowire since the WiMAX
connection is IP-only. MPLS information is carried in a packet’s Ethernet header
and, without encapsulation, would be stripped from the packet prior to the
packet’s transmission over the WiMAX link.
The following figure shows the VPLS connection between your WiMAX Modem (A)
and your service provider’s router (B), consisting of GRE-encapsulated Ethernet
pseudowire traffic.
Figure 37 VPLS Tunneling
ETHERNET PSEUDOWIRES
GRE
TUNNEL
WiMAX CONNECTION