H3C Technologies H3C S10500 Series Switches - Manual (Page 88)

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After an OSPF GR Restarter restarts, it must perform the following tasks.
• Obtain OSPF neighbor information
• Obtain the LSDB
Before restart, the GR Restarter negotiates GR capability with GR Helpers. During the restart of the GR
Restarter, GR Helpers still advertise their adjacencies with the GR Restarter. After restart, the GR Restarter
sends GR Helpers an OSPF GR signal so that the GR Helpers do not reset their neighbor relationships
with the GR Restarter. Upon receiving responses from neighbors, the GR Restarter creates the neighbor
relationships.
After that, the GR Restarter synchronizes the LSDB with GR-capable neighbors, updates its routing table
and forwarding table, and removes stale routes.
OSPF NSR
With OSPF NSR, the active MPU and standby MPU have consistent data information, which includes the
system operational data and OSPF-related static and dynamic data. Upon a failover, the standby MPU
takes over all services from the active MPU seamlessly, and no ongoing network services are interrupted.
TE and DS-TE
OSPF Traffic Engineering (TE) provides for the establishment and maintenance of Label Switched Paths
(LSPs) of TE.
When establishing Constraint-based Routed LSPs (CR LSPs), MPLS obtains the TE information of links in
the area via OSPF.
OSPF has a new LSA, Opaque LSA, which can be used for carrying TE information.
DiffServ Aware TE (DS-TE) provides for network resource optimization and allocation, flow classification,
and indication of network bandwidth consumption of each flow in a link. TE is implemented on the
classified type (thin granularity summarization type) rather than the summarized type (thick granularity
summarization type) to improve performance and bandwidth utilization.
To support DS-TE application in MPLS, OSPF supports Local Overbooking Multiplier TLV and Bandwidth
Constraint (BC) TLV.
NOTE:
For OSPF TE configuration, see MPLS Configuration Guide.
IGP shortcut and forwarding adjacency
IGP shortcut and forwarding adjacency enable OSPF to use an LSP as the outbound interface for a
destination. Without them, OSPF cannot use the LSP as the outbound interface.
Differences between IGP shortcut and forwarding adjacency:
• If forwarding adjacency is enabled only, OSPF can also use an LSP as the outbound interface for
a destination
• If IGP shortcut is enabled only, only the router enabled with it can use LSPs for routing.
NOTE:
For configuration of this feature, see MPLS Configuration Guide.