| Bidirectional TTs (BTTs) |
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| When two TTs are logically coupled, one TT, called the
forward TT, carries traffic from an originating node to a
destination node. The other TT, called the backward TT,
carries traffic from the destination node to the originating node.
This set is called a BTT if the following conditions hold: |
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- Both TTs are instantiated through an atomic action at one
LSR called the originator node, or through an atomic action at
a network management station.
- Neither of the composite TTs can exist without the other. Both
are instantiated and destroyed together.
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| A BTT is "topologically symmetric"
if its constituent TTs are routed through the same physical path, and
it is "topologically asymetric" if its components are routed through
different physical paths. |
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| Basic operation on TTs |
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- Establish: to create an instance of a TT.
- Activate: to cause a TT to start passing traffic. Establishment and
Activation are logically separated events. However, they may be
implemented as one atomic action.
- Deactivate: to cause a TT to stop passing traffic.
- Modify Attributes: to cause the attributes of a TT to be
modified.
- Reroute: to cause a TT to change its route. This can be
done through administrative action or automatically by the underlying
protocol.
- Destroy: to remove an instance of a TT from the network
and reclaim all resources allocated to it.
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