3Com MSR 50 Series Configuration Manual page 936

936 C 58: OSPF C
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ONFIGURATION
After the restart, the GR Restarter will send an OSPF GR signal to its neighbors that
will not reset their adjacencies with it. In this way, the GR Restarter can restore the
neighbor table upon receiving the responses from neighbors.
After reestablishing neighborships, the GR Restarter will synchronize the LSDB and
exchange routing information with all adjacent GR-capable neighbors. After that,
the GR Restarter will update its own routing table and forwarding table based on
the new routing information and remove the stale routes. In this way, the OSPF
routing convergence is complete.
TE and DS-TETE
OSPF Traffic Engineering (TE) provides for the establishment and maintenance of
Label Switch 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.
For OSPF TE configuration, refer to
IGP Shortcut and Forwarding Adjacency
IGP Shortcut and Forwarding Adjacency enable OSPF to use a 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
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outbound interface for a destination
If LGP Shortcut is enabled only, only the router enabled with it can use LSPs for
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routing.
For configuration of this feature, refer to
VPN
OSPF supports multi-instance, which can run on PEs in VPN networks.
In BGP MPLS VPN networks, multiple sites in the same VPN can use OSPF as the
internal routing protocol, but they are treated as different ASs. An OSPF route
learned by a site will be forwarded to another site as an external route, which
leads to heavy OSPF routing traffic and management issues.
"MPLS TE Configuration" on page
"MPLS TE Configuration" on page
1345.
1345.