Tunnel Routing
Load Balancing & Fault Tolerance
Tunnel Routing
Tunneling
is a technique to perform data transmission for a foreign protocol over a incompatible network; such as
running IPv6 over IPv4, and the transmission of data for use within a private, corporate network through a public
network. Tunneling is done by encapsulating and decapsulating data and information of the particular protocol within
the incompatible transmission units symmetrically.
Traditional tunneling is established over single WAN link which is a lack of load balancing and fault tolerance.
FortiWAN's Tunnel Routing (TR) is a technique that builds a special connection between two FortiWAN units to deliver
link aggregation
and
fault tolerance
over multiple WAN links ideally tailored for multinational intranet systems.
Different to Auto Routing distributing sessions over WAN links, Tunnel Routing breaks further a session down to
packets over multiple WAN links and allows data to be prioritized during transfer while boosting the performance of
critical services such as VPN and live video streaming while avoiding delays and data loss.
Basically, FortiWAN's Tunnel Routing implies routing packets of a session over tunnels (WAN links), which contains
the two elements -
Tunnels
and
Routing
.
GRE Tunnel
FortiWAN's Tunnel Routing sets up proprietary tunnels between symmetric FortiWAN sites (local and remote) with
GRE (Generic Routing Encapsulation) protocol. GRE (Generic Routing Encapsulation) Protocol packs the Payload
(Original Packet) with Delivery Header and GRE Encapsulation Header. Physically, a point-to-point GRE tunnel for
Tunnel Routing is the transimission of GRE packets via a pair of WAN links predefined on the symmetric FortiWAN
sites (a WAN link on the local FortiWAN, and another one on the remote FortiWAN) (See "Tunnel Group" and "Group
Tunnel" in "
").
Routing
With the multiple WAN links on each FortiWAN, Tunnel Routing distributes (routes) GRE packets of a session over the
GRE tunnels (a tunnel group) according the balancing algorithms and tunnel status detection. This is what the load
balancing and fault tolerance Tunnel Routing provides for tunneling. Moreover, with proper policy setting, Tunnel
Routing can route GRE packets over multiple sites (more than two sites) without full-mesh connections between the
sites (See "Default Rule", "Routing Rule" and "Persistent Rules" in "
How to set up routing rules for Tunnel Routing
").
Briefly, it performs routing of GRE packets over multiple tunnels and multiple sites.
Next we introduce Tunnel Routing in the following topics:
How to set up routing rules for Tunnel Routing
FortiWAN Handbook
Fortinet Technologies Inc.
137
