H3C Technologies H3C SR8800 - Manual (Page 59)

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The LABEL_REQUEST object is stored in the path state block (PSB) on the upstream nodes, while the
LABEL object is stored in the reservation state block (RSB) on the downstream nodes. The state stored in
the PSB or RSB object times out and is removed after the number of consecutive non-refreshing times
exceeds the PSB or RSB timeout keep-multiplier.
You may sometimes want to store the resource reservation state for a reservation request that does not
pass the admission control on some node. This however should not prevent the resources reserved for the
request from being used by other requests. To handle this situation, the node transits to the blockade state
and a blockade state block (BSB) is created on each downstream node. When the number of
non-refreshing times exceeds the blockade multiplier, the state in the BSB is removed.
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:
• GR restarter, the router that gracefully restarts due to a manually configured command or a fault. It
must be GR-capable.
• 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 LFIB information. 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 specific 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.
NOTE:
If configured with RSVP-TE GR, the router 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 still 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-based 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.