Traffic Forwarding - HP HSR6800 Configuration Manual

PSB, RSB and BSB timeouts
To create an LSP tunnel, the sender sends a Path message with a LABEL_REQUEST object. After
receiving this Path message, the receiver assigns a label for the path and puts the label binding in
the LABEL object in the returned Resv message.
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.
Sometimes, although a reservation request does not pass admission control on some node, you may
want to store the resource reservation state for it while allowing other requests to use the resources
reserved for the request. In this case, 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 blockade state 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 roles:
•
GR restarter—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 are
removed. If the recovery timer expires, soft state information and forwarding entries that are not
restored during the GR restarting process are removed.
An HSR6802/HSR6804/HSR6808 router that supports primary-secondary switchover, if configured
with RSVP-TE GR, can act as a GR restarter and a GR helper at the same time.
HSR6802/HSR6804/HSR6808 routers without secondary MPUs can act as only GR helpers when
they are configured with RSVP-TE GR.

Traffic forwarding

For traffic to travel along an LSP tunnel, you must perform the configuration after creating the MPLS
TE tunnel. Otherwise, traffic is IP routed.
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-based
routing, or automatic route advertisement.
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