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Optimized Link State Protocol

Optimized Link State Protocol. Version 2 Assaf Israel, Eli Nazarov, Asi Bross. OLSRv2 - Overview. Applicability mobile ad-hoc networks (MANET) dynamic topology 100%> reliable environment (WiFi, WiMax) nodes can be gateways to other networks Characteristics Table driven

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Optimized Link State Protocol

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  1. Optimized Link State Protocol Version 2 Assaf Israel, Eli Nazarov, Asi Bross

  2. OLSRv2 - Overview • Applicability • mobile ad-hoc networks (MANET) • dynamic topology • 100%> reliable environment (WiFi, WiMax) • nodes can be gateways to other networks • Characteristics • Table driven • proactive protocol • Build on top of MANET NHDP

  3. Terminology • node • 1-hop neighbor set • 2-hop neighbor set • bidirectional link • interface

  4. Mobile Ad-hoc NetworksNeighborhood Discovery Protocol • A solid base for the OLSRv2 protocol. • Objective - maintain 1-hop & 2-hop neighbors link state tables • Pros • Simplicity - only one type of messages • Generic - does not limit to type of connectivity technology • Cons • Effects bandwidth as messages are routinely transmitted

  5. Mobile Ad-hoc NetworksNeighborhood Discovery Protocol (cont.) • Local Information Base - per node • Active interface - IP tuples set • Removed interface - IP tuples set • Interface Information Base - per interface • Link Set • Current & Recently lost 1-hop neighbors to this interface • Connection quality • Validation time

  6. Mobile Ad-hoc NetworksNeighborhood Discovery Protocol (cont..) • Interface Information Base (Cont.) • 2-Hop Set • Each entry consist of 2-hop address & all of the addresses of the corresponding symmetric 1-hop neighbor • Each tuple records an address of recently lost 1-hop neighbor

  7. Mobile Ad-hoc NetworksNeighborhood Discovery Protocol (cont.) • Neighbor Information Base • Neighbor Set - Neighbor tuples • List all IP’s of a single 1-hop neighbor • Lost Neighbor Set - Lost Neighbor tuples

  8. “Hello” message • The only type of message in MANET NHDP • Generated by a node independently on each MANET interface • Identify the source interface but adds information of all other local interfaces • May be sent • Proactively - at a regular pre-defined interval • Dynamically - interval may be backed off to to congestion or network stability • Event driven - e.g new/lost/changed status link

  9. “Hello” message - Objectives • Advertise the router’s interface addresses to it’s 1-hop neighbors. • Advertise the router’s knowledge of each of its 1-hop neighbors.

  10. “Hello” message - Content • Must contain all of the Local Interface Set IPs • For each interface, and every pre-defined Refresh-Interval Must send all relevant information in the Interface Link Set & Neighbor Information Base. • Validity Time for which the information is considered valid • periodically should contain the Interval Time for which messages are sent from the interface.

  11. “Hello” message - Processing • Updates the receiver’s Interface Information Base • If an entry from the message source exists then the valid time is checked and updated accordingly • If an entry does not exist from the message source, a new one will be created • If a message contains information that a symmetrical link has been lost/created between the source and a third node the 2-hop neighbor, the 2-hop Set will be updated accordingly • Updates to the Neighbor Information Base may occur • Will cause generation of yet another Hello message • Hello message are not forwarded

  12. MANET Neighborhood Discovery Protocol Optional extensions • Link quality • Jitter

  13. OSLRv2 - Multi Point Relays • Multipoint Relays (MPR)- Set of 1-hop neighbors which broadcast node’s packets. • MPR must have bi-directional like with the node - avoid uni-directional link problems. • The union of all neighbors of MPRs give the group of 2-hop neighbors of the node.

  14. Multi Point Relays (Cont.) • OLSRv2 uses MPR’s to calculate routes to all known nodes. • Route is a sequence of hops through MPRs. • Last MPR is the target node or the target is a 1-hop neighbor of the last MPR. • MPR Selector is a neighbor that selected this node as a MPR.

  15. Signaling • Extends NHDP “Hello” messages to include the selected MPRs set of the source node. • For each 1-hop neighbor with symmetric link that is selected as MPR for this router. • TC messages • Includes a Set of all 1-hop neighbors that selected the sending node as an MPR. • Advertised Neighbor Set. • Attached Network Set.

  16. Message Processing & Forwarding • TC messages may be processed and/or forwarded • Hello messages are available to OLSRv2 after NHDP process - Never forwarded.

  17. OSLRv2 - Databases • All MANET NHDP Tables - with extensions • e.g flags to indicate MPR and MPR selector in Neighbor set. • Topology Information Base • Processing & Forwarding Information Base

  18. Topology Information Base • Advertised Neighbor Set • Includes addresses of neighbors that selected this node as MPR. • Symmetric 1-hop neighbors that are advertised through TC massages. • Derived from Neighbor Set. • Advertised Remote Router Set • Remote addresses of routers that transmits TC massages. • Contains all of their addresses.

  19. Topology Information Base (Cont.) • Topology Set • Topology information about the network. • Routing Set • Records a path to each destination.

  20. Topology Information Base (Cont.) • Attached Network Set • Records Information about networks attached to other routers or can be reached via those router.

  21. Processing & Forwarding Information Base • Used to ensure that each massage is processed and forwarded once, at most, per OLSRv2 interface • Before processing/forwarding a massage, we must first check that it wasn't processed/forwarded yet.This is done using the information stored in Processing & Forwarding Information Base.

  22. Processing & Forwarding Information Base • Received Set - per interface • Signatures of messages received on this interface. • Processed Set • Signatures of messages processed by the router. • Forwarded Set • Signatures of messages forwarded by the router. • Relay Set - per interface • Symmetric 1-hop neighbors which messages should be forwarded when received on that interface.

  23. “Hello” message process by OLSRv2 • Updates its Neighbor Information Base if it was chosen as a MPR for the originator router (MPR Selector) • In case of topology change the set of MPRs is recalculated.

  24. TC messages processing • When TC message received: • Topology Set is updated. • Advertised Remote Router Set is updated. • Attached Network Set is updated. • The Dijkstra algorithm can be used to construct the Routing Set

  25. Packet routing • When a packet needs to get from A to B it is sent to the next MPR as described in the Routing Set. • Each MPR will forward the packet to the next MPR in the route. MPR Target MPR MPR MPR Source MPR

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