Virtual trees routing protocol for an ATM-based mobile network
First Claim
1. A method for routing cells in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
- forming a set of VPI primary trees by determining all-pairs shortest paths for said nodes within said network, said set of primary trees including one tree rooted at each node in said network; and
determining a set of secondary trees rooted at each node in said network for given destination nodes.
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Abstract
The present invention is a system and method for routing cells in a wireless communications network, wherein the communications network includes a plurality of switching nodes and the cells are routed according to destination-rooted virtual path identifier (VPI) trees. The present invention includes a routing protocol for determining preestablished VPI trees rooted at each destination node. The routing protocol manages the routes of these trees, while ensuring that there are at least two VPI trees from each source to each destination for reliability reasons, and that each destination node has multiple VPI trees for load-balancing reasons. The routing protocol includes an off-line procedure for the determination of the initial VPI trees. In order to handle changes in network traffic and conditions, the routing protocol updates the routes of the VPI trees in a dynamic and distributed fashion. These update procedures are triggered by congestion, link/node failures and link/node additions.
218 Citations
40 Claims
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1. A method for routing cells in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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forming a set of VPI primary trees by determining all-pairs shortest paths for said nodes within said network, said set of primary trees including one tree rooted at each node in said network; and determining a set of secondary trees rooted at each node in said network for given destination nodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A wireless communications network including a plurality of switching nodes adapted to route cells in said network according to destination-rooted virtual path identifier (VPI) trees, said network configured according to the steps of:
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forming a set of VPI primary trees by computing all-pairs shortest paths for said nodes within said network, said set of primary trees including one tree rooted at each node in said network; and including a set of secondary trees rooted at each node in said network for given destination nodes. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A method for dynamically updating routing paths for cells traveling in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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detecting a trigger condition at a node i in said communications network indicative of a requirement to update one or more of said VPI trees, said trigger condition being a congested link in said communications network; updating route structures and route states of said VPI trees in said communications network in response to said trigger condition; and determining a candidate set of said VPI trees for redirection, said candidate set including "empty" VPIs, wherein an empty VPI has no assigned virtual channel identifiers (VCIs) thereon, said step of determining further including the substeps of; creating a set of all VPIs using said congested link; referencing a record of connections at said node i having been admitted with quality of service (QoS) guarantees to thereby rule out any non-empty VPIs.; communicating with a root node of each potentially empty VPI to determine if a best-effort connection without QoS guarantees has been admitted on said VPI. - View Dependent Claims (20, 21, 22, 23, 24, 25, 37, 40)
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26. A method for dynamically updating routing paths for cells traveling in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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detecting a trigger condition at a node i in said communications network indicative of a requirement to update one or more of said VPI trees, wherein said trigger condition is a failed link, wherein all VPIs traversing said failed link are considered empty, an empty VPI having no assigned virtual channel identifiers (VCIs) thereon; and updating route structures and route states of said VPI trees in said communications network in response to said trigger condition. - View Dependent Claims (27, 28)
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29. A method for dynamically updating routing paths for cells traveling in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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detecting a trigger condition at a node i in said communications network indicative of a requirement to update one or more of said VPI trees wherein said trigger condition is the addition of a link in said network to replace a previously failed link; updating route structures and route states of said VPI trees in said communications network in response to said trigger condition; determining a set of VPIs that were inactivated by a selective freeze procedure when said the link failure occurred; activating said set of VPIs previously inactivated; updating a data table at node i to indicate that a VPI from said set of VPIs previously inactivated is active; sending selective unfreeze messages in a chained fashion to neighbor nodes downstream of a selected VPI in said communications network, wherein each node informs a root node of its activation; and updating a data table at said root node to reflect new activation of said set of VPIs and thereby incorporate the restored link in said network.
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30. A method for dynamically updating routing paths for cells traveling in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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detecting a trigger condition at a node i in said communications network indicative of a requirement to update one or more of said VPI trees, wherein said trigger condition is the addition of a link in said network between two ports not previously connected; updating route structures and route states of said VPI trees in said communications network in response to said trigger condition; selecting a set of empty VPIs that pass through other links in said network; and redirecting said other links onto the new link being added.
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31. A method for dynamically updating routing paths for cells traveling in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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detecting a trigger condition at a node i in said communications network indicative of a requirement to update one or more of said VPI trees, wherein said trigger condition is the addition of said node i into said network; updating route structures and route states of said VPI trees in said communications network in response to said trigger condition; communicating with neighbor nodes in said network to determine a set of VPI trees to join as a leaf node; and joining said set of VPI trees as a leaf node. - View Dependent Claims (32, 33, 34, 35)
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36. A method for dynamically updating routing paths for cells traveling in a wireless communications network, said communications network including a plurality of switching nodes and said cells being routed according to destination-rooted virtual path identifier (VPI) trees, said method comprising the steps of:
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detecting a trigger condition at a node i in said communications network indicative of a requirement to update one or more of said VPI trees, wherein said trigger condition is a congestion incident, said congestion incident being defined as C-U<
T for a period of τ
, where C represents bandwidth capacity of a connection, U represents usage and T represents a reserved capacity to absorb bursts when needed; andupdating route structures and route states of said VPI trees in said communications network in response to said trigger condition. - View Dependent Claims (38, 39)
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Specification