Huawei Quidway NetEngine80E Configuration Manual page 290

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
When a network runs the OSPF protocol, you can enable OSPF local Multicast-Topology (MT)
to solve the problem of multicast traffic interruption caused by the conflict between multicast
and the TE tunnel. After local MT is enabled, multicast packets can be correctly forwarded. If
the outgoing interface of the calculated route is a TE tunnel interface of IGP-Shortcut type, a
router adds a route of the physical outgoing interface to the MIGP routing table. Multicast uses
routes in the MIGP routing table to forward packets.
OSPF GR
When a router restarts or performs the active/standby switchover, it directly ages all routing
entries in the Forward Information Base (FIB) table. This results in route interruption. In
addition, neighboring routers remove this router from the neighbor list, and notify other
routers. This causes the re-calculation of SPF. If this router recovers within a few seconds, the
neighbor relationship becomes unstable. This results in route flapping.
After being enabled with OSPF Graceful Restart (GR), a router can ensure continuous packet
forwarding if it restarts just for abnormities. In such a case, route flapping is avoided during the
short restart of the router.
When a router restarts OSPF, the GR Restarter does not age the forwarding information. At the
same time, the GR Helper keeps the topology information or routes obtained from the GR
Restarter for a period. This ensures that traffic forwarding is not interrupted when protocol restart
occurs.
OSPF and DS-TE
OSPF TE supports the establishing and maintaining of the Label Switch Path (LSP) of the TE.
When constructing constraint-based routed LSP (CR LSP), MPLS needs information about the
traffic attributes of all the links in the area. With the help of the OSPF, MPLS obtains traffic
engineering information about the links.
OSPF supports a new type of LSAs called opaque LSA. The opaque LSA can carry TE
information. You can use the related commands to configure OSPF to support or not support
the originating and handling of the opaque LSA that carries TE information.
Difference service aware TE (DS-TE) is primarily used to optimize and assign network
transmission resources, classify the traffic, and specify the percentage of each traffic to the link
bandwidth. Traffic engineering is implemented based on each divided class (aggregated class
with fine granularity) instead of an aggregated class (aggregated class with coarse granularity).
This enhances the performance and utility of the bandwidth.
To support DS-TE in MPLS, OSPF supports Local Overbooking Multiplier TLV and bandwidth
constraint (BC) TLV.
Issue 02 (2014-09-30)
NOTE
For details of local MT, refer to the chapter "IP Multicast Overview" in the HUAWEI NetEngine80E/
40E Router Feature Description - IP Multicast.
NOTE
Unless otherwise specified, "protocol restart" in this document refers to restarting OSPF in GR mode.
NOTE
For details of OSPF TE configurations, refer to the HUAWEI NetEngine80E/40E Router Configuration
Guide - MPLS.
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