H3C Technologies H3C S7500E Series Switches - Manual (Page 91)

3-9
RSVP-TE GR
RSVP-TE Graceful Restart (GR) preserves the soft state and label forwarding information when the
signaling protocol or control plane fails, so that LSRs can still forward packets according to forwarding
entries, ensuring continuous data transmission.
A device that participates in an RSVP-TE GR process plays either of the following two roles:
z
GR restarter, the router that gracefully restarts due to a manually configured command or a fault.
It must be GR-capable.
z
GR helper, neighbor of the GR restarter. A GR helper maintains the neighbor relationship with the
GR restarter and helps the GR restarter restore its forwarding capability. A GR helper must be
GR-capable.
The RSVP-TE GR function depends on the extended hello capability of RSVP-TE. A GR-capable
device advertises its GR capability and relevant time parameters to its neighbors by extended RSVP
Hello packets. If a device and all its neighbors have the RSVP GR capability and have exchanged GR
parameters, each of them can function as the GR helper of another device, allowing data to be
forwarded without interruption when the GR restarter is rebooting.
A GR helper considers that a GR restarter is rebooting when it receives no Hello packets from the
restarter in a specified period of time. When a GR restarter is rebooting, the GR helpers retain soft
state information about the GR restarter and keep sending Hello packets periodically to the GR
restarter until the restart timer expires.
If a GR helper and the GR restarter reestablish a Hello session before the restart timer expires, the
recovery timer is started and signaling packet exchanging is triggered to restore the original soft state.
Otherwise, all RSVP soft state information and forwarding entries relevant to the neighbor will be
removed. If the recovery timer expires, soft state information and forwarding entries that are not
restored during the GR restarting process will be removed.
S7500E series, can act as a GR restarter and a GR helper at the same time.
Traffic Forwarding
Even when an MPLS TE tunnel is available, traffic is IP routed if you do not configure it to travel the
tunnel. For traffic to be routed along an MPLS TE tunnel, you can use static routing, policy routing, or
automatic route advertisement.
Static routing
Static routing is the easiest way to route traffic along an MPLS TE tunnel. You only need to manually
create a route that reaches the destination through the tunnel interface.