OLSRv2 High Level Overview

New Methodologies for performance modeling of Routing Protocols in Wireless Networks

Carlos Rodrigo AponteOLSRv2High Level Overview1Overview of OLSROLSR is a link-state proactive routing protocol with four basic parts:Neighbor DiscoveryA node estimates its local topology.By local topology, we mean 1- and 2-hop topologySelector of Topology Information to DisseminateNot all links are needed to form shortest pathsAdvertising a subset of all links reduces total overheadTopology DisseminationOnce the link information to be advertised is determined, it must be disseminated over the networkRoute CalculationOnce the link advertisements are received, paths can be computed.

2Overview of OLSROLSR is a link-state proactive routing protocol with four basic parts:Neighbor DiscoveryA node estimates its local topology.By local topology, we mean 1- and 2-hop topologySelector of Topology Information to DisseminateNot all links are needed to form shortest pathsAdvertising a subset of all links reduces total overheadTopology DisseminationOnce the link information to be advertised is determined, it must be disseminated over the networkRoute CalculationOnce the link advertisements are received, paths can be computed.

3Neighborhood DiscoveryIn OLSR, Hello messages are used to estimate the local topologyTwo tasksEstimation the one-hop neighborsOne-hop neighbors are those with bidirectional linksLocal dissemination of the one-hop topology to estimate the two-hop topology4Task 1: Estimating one-hop neighborsS812346716121119181714151091351From the point of view of nodes S and 1Initially, neither of the nodes know about the topology5S812346716121119181714151091351Node S broadcasts a HELLO message.Task 1: Estimating one-hop neighbors (cont)6S812346716121119181714151091351Node 1 receives the HELLO message and learns:It can hear SThus a unidirectional link is discovered by 1Task 1: Estimating one-hop neighbors (cont)7S812346716121119181714151091351Node 8 broadcasts a HELLO message.Task 1: Estimating one-hop neighbors (cont)Source: 8Dest: BroadcastInfo: 8 has heard S8S8123467161211191817141510913511Node S receives the HELLO message, and learns:It was heard by 8It can hear 8Thus node S discovers a bidirectional link to 8Node 1 receives the HELLO message and learns:It can hear 8Thus a unidirectional link is discovered by 1Task 1: Estimating one-hop neighbors (cont)Source: 8Dest: BroadcastInfo: 8 has heard S9S8123467161211191817141510913511Node 1 broadcasts a HELLO message.Task 1: Estimating one-hop neighbors (cont)Source: 1Dest: BroadcastInfo: 1 has heard S and 810S81234671612111918171415109135111Node S receives the HELLO message, and learns:It was heard by 1It can hear 1Thus node S discovers a bidirectional link to 1Node 8 receives the HELLO message and learns:It was heard by 1It can hear 1Thus node 8 discovers a bidirectional link to 1Task 1: Estimating one-hop neighbors (cont)Source: 1Dest: BroadcastInfo: 1 has heard S and 811S81234671612111918171415109135111Node 18 broadcasts a HELLO message.Task 1: Estimating one-hop neighbors (cont)Source: 18Dest: BroadcastInfo: 18 has heard 1 and 812S81234671612111918171415109135111Node 1 receives the HELLO message, and learns:It was heard by 18It can hear 18Thus node 1 discovers a bidirectional link to 18Node 8 receives the HELLO message and learns:It was heard by 18It can hear 18Thus node 8 discovers a bidirectional link to 18Task 1: Estimating one-hop neighbors (cont)Source: 18Dest: BroadcastInfo: 18 has heard 1 and 813S81234671612111918171415109135111After a while, nodes 1 and S discover their entire 1-hop topologyTask 1: Estimating one-hop neighbors (cont)14S812346716121119181714151091351111Node 1 broadcasts a HELLO message, including information about its neighbors.Task 2: Estimating 2-hop Topology Source: 1Dest: BroadcastInfo: Neighbors: S,8,18,1915S812346716121119181714151091351111Node S receives the HELLO message, and learns:All 1-hop neighbors of node 1Part of its 2-hop topologyTask 2: Estimating 2-hop Topology (cont)Source: 1Dest: BroadcastInfo: Neighbors: S,8,18,1916S812346716121119181714151091351111Node S broadcasts a HELLO message, including information about its neighbors.Task 2: Estimating 2-hop Topology (cont)Source: SDest: BroadcastInfo: Neighbors: 1,2,3,4,5,6,7,817S812346716121119181714151091351111Node 1 receives the HELLO message, and learns:All 1-hop neighbors of node SPart of its 2-hop topology11Task 2: Estimating 2-hop Topology (cont)Source: SDest: BroadcastInfo: Neighbors: 1,2,3,4,5,6,7,818S81234671612111918171415109135Eventually, nodes 1 and S will discover their entire 2-hop neighborhoodTask 2: Estimating 2-hop Topology (cont)19S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Detecting bidirectional links20S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Node 1 received HELLO message from S

#RCVD_HELLO=1#RCVD_HELLOunheardNodeSource: SDest: BroadcastInfo:Detecting bidirectional links21S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Source: 1Dest: BroadcastInfo:Node S received HELLO message from 1

#RCVD_HELLO=1#RCVD_HELLOunheardNodeDetecting bidirectional links22S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Source: SDest: BroadcastInfo:Node 1 received HELLO message from S

#RCVD_HELLO=2#RCVD_HELLOunheardNodeDetecting bidirectional links23S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Source: 1Dest: BroadcastInfo:Node S received HELLO message from 1

#RCVD_HELLO=2#RCVD_HELLOunheardNodeDetecting bidirectional links24S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Node 1 received HELLO message from S

#RCVD_HELLO=#RCVD_HELLOunheardNode33Node S received HELLO message from 1

#RCVD_HELLO=#RCVD_HELLOunheardNode33Source: SDest: BroadcastInfo:44Source: 1Dest: BroadcastInfo:44555566667777U-1U-1U-1U-1Detecting bidirectional links25S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Source: SDest: BroadcastInfo:Node 1 received HELLO message from S

#RCVD_HELLO=#RCVD_HELLO=U=>AsymmetricLinkUUDetecting bidirectional links26S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Source: 1Dest: BroadcastInfo: AsymmetricLink with SNode S received HELLO message from 1

#RCVD_HELLO=#RCVD_HELLO=U=>SymmetricLinkUUDetecting bidirectional links27S81234671612111918171415109135In order to consider a link symmetric, a node has to receive U HELLOs from the neighbor.In OLSR, U=1.Source: SDest: BroadcastInfo: SymmetricLink with 1Node 1 received HELLO message from S

#RCVD_HELLO=#RCVD_HELLO>U=>SymmetricLinkU+1U+1Detecting bidirectional links28S8234671612111918171415109135In order to consider a link lost, a node has to lose D HELLOs from the neighbor.In OLSR, D=3.1Node 1 received HELLO message from S

#RCVD_HELLO=#RCVD_HELLO=U=>SymmetricLinkUUDetecting bidirectional links29S8234671612111918171415109135In order to consider a link lost, a node has to lose D HELLOs from the neighbor.In OLSR, D=3.Node 1 detected lost HELLO messages from S

#LOST_HELLO=#LOST_HELLOSymmetricLink001Source: SDest: BroadcastInfo: SymmetricLink with 11122334455D-1D-1DDNode 1 detected lost HELLO messages from S

#LOST_HELLO=#LOST_HELLO=D=>LostLinkDetecting bidirectional links30Event Counting (Generalization of RFC)When link is downParameters: U, D

When link is upUDHelloarrivalCk0102030405060708000.51HellosTransmission Probability0102030405060708001234HellosNumber of Sequential Success/Failures

OLSR v1: U=1 D=3. Generalized by UMD31Exponential Moving Average w/ Hysteresis (RFC)When link is downQk+1 = Qk + (1- ) 1{Received Hello k} Qk >TUp link is upWhen link is upQk+1 = Qk + (1- ) 1{Received Hello k} Qk >TDown link is downParameters: , Tup, Tdown

32Cumulative Sum (CumSum) Link Detection

PerrUpPerrDownTHelloreceivedWhen link is downSk+1 = max(0, Sk - 1{Missed Hello} + PUp)Sk >T link is upWhen link is upSk+1 = max(0, Sk +1{Missed Hello} - PDown)Sk > T link is downParameters: Pup, Pdown, T33Overview of OLSROLSR is a link-state proactive routing protocol with four basic parts:Neighbor DiscoveryA node estimates its local topology.By local topology, we mean 1- and 2-hop topologySelector of Topology Information to DisseminateNot all links are needed to form shortest pathsAdvertising a subset of all links reduces total overheadTopology DisseminationOnce the link information to be advertised is determined, it must be disseminated over the networkRoute CalculationOnce the link advertisements are received, paths can be computed.

OLSR merges selector of Topology Information to Disseminate with Topology Dissemination. But in CBR, these are two different components34Topology DisseminationIn order to limit control traffic, only a subset of nodes (Multi-Point Relays: MPRs) forwards control packets

Two tasksDetermine the set of MPRsMPR Selection Objective: determine a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the messageFlood TC messages over the reduced graph35Topology DisseminationIn order to limit control traffic, only a subset of nodes (Multi-Point Relays: MPRs) forwards control packets

Two tasksDetermine the set of MPRsMPR Selection Objective: determine a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the messageFlood TC messages over the reduced graph36Why use MPRs?In traditional flooding, each node relays the messages.This approach typically results in each node receiving the message many times (i.e, it wastes bandwidth/ creates excess overhead)Retransmission node37Why use MPRs?By carefully selecting which nodes forward messages, the overhead can be reduced.This is the objective of MPR-based flooding(note there are many other ways to accomplish this goal )In traditional flooding, each node relays the messages.This approach typically results in each node receiving the message many times (i.e, it wastes bandwidth/ creates excess overhead)Retransmission node38Topology DisseminationIn order to limit control traffic, only a subset of nodes (Multi-Point Relays: MPRs) forwards control packets

Two tasksDetermine the set of MPRsMPR Selection Objective: determine a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the messageFlood TC messages over the reduced graph39Topology DisseminationIn order to limit control traffic, only a subset of nodes (Multi-Point Relays: MPRs) forwards control packets

Two tasksDetermine the set of MPRsMPR Selection Objective: determine a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the messageFlood TC messages over the reduced graph40Task 1:MPR selection algorithm : exampleS812346716121119181714151091351. Determine all 2-hop neighbors which are only reachable through just one 1-hop neighbor 2. Select those 1-hop neighbors as MPRs3. Determine C = reachable 2-hop nodes through the current set of MPRs.4. Let U = 2-hop neighbors which are not reachable through the MPRs.5. If U= , then doneElse Add the 1-hop node that has the highest number of neighbors in U to the set of MPRsGo to step 3From the perspective of node SMPR Selection Objective: each nodes determines a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the message41S81234671612111918171415109135

From the perspective of node STask 1:MPR selection algorithm: example (cont)MPR Selection Objective: each nodes determines a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the message1. Determine all 2-hop neighbors which are only reachable through just one 1-hop neighbor 2. Select those 1-hop neighbors as MPRs3. Determine C = reachable 2-hop nodes through the current set of MPRs.4. Let U = 2-hop neighbors which are not reachable through the MPRs.5. If U= , then doneElse Add the 1-hop node that has the highest number of neighbors in U to the set of MPRsGo to step 342S81234671612111918171415109135

1. Determine all 2-hop neighbors which are only reachable through just one 1-hop neighbor 2. Select those 1-hop neighbors as MPRs3. Determine C = reachable 2-hop nodes through the current set of MPRs.4. Let U = 2-hop neighbors which are not reachable through the MPRs.5. If U= , then doneElse Add the 1-hop node that has the highest number of neighbors in U to the set of MPRsGo to step 3From the perspective of node STask 1:MPR selection algorithm: example (cont)MPR Selection Objective: each nodes determines a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the message43S81234671612111918171415109135






1. Determine all 2-hop neighbors which are only reachable through just one 1-hop neighbor 2. Select those 1-hop neighbors as MPRs3. Determine C = reachable 2-hop nodes through the current set of MPRs.4. Let U = 2-hop neighbors which are not reachable through the MPRs.5. If U= , then doneElse Add the 1-hop node that has the highest number of neighbors in U to the set of MPRsGo to step 3From the perspective of node STask 1:MPR selection algorithm: example (cont)MPR Selection Objective: each nodes determines a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the message49Local Topology Information is Required to Make RoutesMPRs advertise links to MPR selectors0812346716121119181714151091351 is a MPR for 0Legend:01Original Graph081234671612111918171415109135If only MPRMPR Selectors are used, then 7 could not reach 16 in one hop.50Overview of OLSROLSR is a link-state proactive routing protocol with four basic parts:Neighbor DiscoveryA node estimates its local topology.By local topology, we mean 1- and 2-hop topologySelector of Topology Information to DisseminateNot all links are needed to form shortest pathsAdvertising a subset of all links reduces total overheadTopology DisseminationOnce the link information to be advertised is determined, it must be disseminated over the networkRoute CalculationOnce the link advertisements are received, paths can be computed.

OLSR merges selector of Topology Information to Disseminate with Topology Dissemination. But in CBR, these are two different components51Selection of Topology Information to DisseminateSDCAHFEGBOriginator Node1-hop Neighbors2-hop NeighborsMPRsMPR SelectorsLinks Advertised by TC MessageSA,B,C,DE,F,G,HA,CA,B,C,DAS,HB,C,DSS,HBS,GA,C,DSNo TC message generatedCS,E,F,GA,B,DSS,E,F,GHELLO MessageTC Message

52Are Paths Composed of Advertised Links the Shortest Paths?Yes, they are.Suppose that D is N hops from SBut, S is not aware of a N-hop path to D. However, S is aware of N-1-hops paths to some of Ds neighbors, C1, C2, This means that there are neighbors of Cs, denoted by B1, B2, that are N-2 hops from the C1, C2,

Since S cant reach D in N hops, but can reach C1, C2, in N-1 hops, the links from C1, C2, to D are not advertisedThus, C1, C2, are not MPRs of D

This is cannot happen, one of the Ci must be a MPR for D.Otherwise, how will the two-hop neighbors (B1, B2, ) be covered?

Therefore, if there are shortest paths to all nodes N-2 and N-1 hops away, then there are shortest paths to nodes N hops away.

Clearly, there are shortest paths to nodes 1 hop away and to nodes 2 hops away (the set of MPRs guarantee this). So there are shortest paths to nodes 3 hops away, and therefore, there are shortest paths to node 4 hops away, .DC1SB1C2B2N-2N-1Length >N53Topology DisseminationIn order to limit control traffic, only a subset of nodes (Multi-Point Relays: MPRs) forwards control packets

Two tasksDetermine the set of MPRsMPR Selection Objective: determine a minimal set of neighbors such that if each neighbor relays the message then each node in the two-hop neighborhood receives the messageFlood TC messages over the reduced graph54Task 2: Topology Dissemination SDCAHFEGBOriginator Node1-hop Neighbors2-hop NeighborsMPRsMPR SelectorsLinks Advertised by TC MessageSA,B,C,DE,F,G,HA,CA,B,C,DACS,G,ESS,HBS,GA,C,DSNo TC message generatedCS,E,F,GA,B,DSS,E,F,G

Topology dissemination = deciding which nodes relay the topology informationRFC and INRIAs approach

55Task 2: Topology Dissemination Originator Node1-hop Neighbors2-hop NeighborsMPRsMPR SelectorsLinks Advertised by TC MessageSA,B,C,DE,F,G,HA,CA,B,C,DACS,G,ESS,HBS,GA,C,DSNo TC message generatedCS,E,F,GA,B,DSS,E,F,G

Topology dissemination = deciding which nodes relay the topology informationRFC and INRIAs approachSDCAHFEGBNode S Broadcasts a TC Message


Topology dissemination = deciding which nodes relay the topology informationRFC and INRIAs approachSDCAHFEGBOnly nodes that have not previously received the message will update the Information Base


Topology dissemination = deciding which nodes relay the topology informationRFC and INRIAs approachOnly nodes that have not previously received the message and that have the transmitter as an MPR Selector, will forward the messageNodes that have S as an MPR SelectorSDCAHFEGB


Topology dissemination = deciding which nodes relay the topology informationOLSR-D and Qualnets approachSDCAHFEGBNode S Broadcasts a TC Message


Topology dissemination = deciding which nodes relay the topology informationOLSR-D and Qualnets approachSDCAHFEGBOnly nodes that have not previously processed the message will update the information base


Topology dissemination = deciding which nodes relay the topology informationOLSR-D and Qualnets approachOnly nodes that have not already forwarded the message and that have the transmitter as an MPR Selector, will forward the messageSDCAHFEGBNodes that have S as an MPR Selector

61Comparison of Flooding Techniques620214536789Sample Topology62Comparison of Flooding Techniques630214536789MPRs4 is the only MPR for 0 (0 had degree 5, but only one MPR!)6 and 9 are MPRs for 41 is the MPR for 3 (2 is an MPR for 5)

63RFC/INRIA Method640214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator64RFC/INRIA Method650214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 have received the TC message65RFC/INRIA Method660214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 have received the TC message4 is a MPR for 066RFC/INRIA Method670214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 have received the TC message4 is a MPR for 06, 7, 8, and 9 have received the TC message67RFC/INRIA Method680214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 have received the TC message4 is a MPR for 06, 7, 8, and 9 have received the TC message6 and 9 are MPRs for 468RFC/INRIA Method690214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 have received the TC message4 is a MPR for 06, 7, 8, and 9 have received the TC message6 and 9 are MPRs for 4All nodes have received the TC message69RFC/INRIA Method700214536789

Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 have received the TC message4 is a MPR for 06, 7, 8, and 9 have received the TC message6 and 9 are MPRs for 4All nodes have received the TC messageNote, while 3 is a MPR for 6, it has already received the TC message, and does not forward it70OLSRd/Qualnet Method710214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator

71OLSRd/Qualnet Method720214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 0

72OLSRd/Qualnet Method730214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 04 is the MPR or 0

73OLSRd/Qualnet Method740214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 04 is the MPR or 06, 7, 8, and 9 received the TC message from 6

74OLSRd/Qualnet Method750214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 04 is the MPR or 06, 7, 8, and 9 received the TC message from 66 and 9 are MPRs of 4

75OLSRd/Qualnet Method760214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 04 is the MPR or 06, 7, 8, and 9 received the TC message from 66 and 9 are MPRs of 4All nodes have received the TC message

76OLSRd/Qualnet Method770214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 04 is the MPR or 06, 7, 8, and 9 received the TC message from 66 and 9 are MPRs of 4All nodes have received the TC message3 is a MPR for 6 (5 is a MPR for 9)

77OLSRd/Qualnet Method780214536789Originator of TC messageReceived TC messageRelayed TC message0 is the originator1, 2, 3, 4, and 5 received TC message from 04 is the MPR or 06, 7, 8, and 9 received the TC message from 66 and 9 are MPRs of 4All nodes have received the TC message3 is a MPR for 6 (5 is a MPR for 9)1 is a MPR for 3 (2 is a MPR for 5)

What is the difference between MPR-based flooding and full flooding?!78Hazy-Sighted Topology DisseminationNote: hazy sighted dissemination does not work. But the idea is as followsIdea: Topology information from far away links is not important for making local forwarding decisionsWhen forwarding a packet, one only needs to move the packet in the right direction. This does not require detailed topology information

Idea (which turns out to be incorrect)potential next-hopThe potential next hop is a next hop for any destination in this region pktThis node does not need to travel very far in order to exit the next-hop regionThis node must travel further in order to exit the next-hop regionMore up-to-date information is required to reach destinations that are close than to reach destinations that are far.

Conclusion, topology information should not be flooded over the entire region.

This seems like such a good idea that many military systems are using this approachHazy-Sighted Topology DisseminationSet TTL for the number of hops that a topology control (TC) message will travel.Adjust the TTL for each TC message so that the TTL 2k every 2k periodsTTL 1 every periodTTL 2 every 2 periods (i.e., periods 2, 4, 6, )TTL 4 every 4 periods (i.e., period 4, 8, 12, 16, )TTL 8 every 8 periods (i.e., period 8, 16, 24, 32, )TTL 16 every 16 periods (i.e., period 16, 32, )The time between TC messages from a distance k is 2ceil(log2(k))Topology information 7 hops away will be received every 2ceil(log2(7)) = 2ceil(2.8) = 23 = 8 periods

This approach could potentially reduce the overhead, especially for large topologiesNote that each TC message is forwarded by most nodes. For large networks, topology dissemination can consume much of the available bandwidth

periodTTL1122314451627188911021111241311421511616Problems with Hazy-SightedThe basic idea has the critical flaw in that the path to a destination does not only depend on the location of the destination, but also depends on the other nodes in the network.Thus, a path can be impacted not only by the destination moving, but by nodes between the source and destination moving I guess this is obviousA correct model considers all linkspotential next-hoppktThis node does not need to travel very far in order to exit the next-hop regionThis node must travel further in order to exit the next-hop regionChange in topology that causes neighbor to stop being a next-hopDuration that the originator is unaware of the topology change and forwards the pkt to a node that is no longer a suitable next hop.T(kL ) = average durationThe fraction of the number line covered by the PS region is approximately the rate of topology changes the average duration, T (another approximation is exp(-rate*T) )Performance of Hazy-Sighted Dissemination82Performance of Hazy-Sighted DisseminationLet be the rate that a link breaks (or form).Let NL(kL ,kD) be the number of links kL away given the destination is kD hops awayWhy does the number of links kL away depend on kD?Suppose that a destination is very far away, like 100 hops. Then, NL(90,100)>1 (otherwise, the dest cant be 100 hops away).So, given a destination is kD hops away, the rate that any link breaks kL hops away is NL(kL, kD).Here we assume that is independent of kL and kDLet F(kL,kD) be the probility of PS when the break is at kL and the destinations is kD hops awayNL(kL,kD)F(kL,kD) is the rate of PS events from links kL away, given that the destination is kD awaySumming over all values of kLExpected value over all distances to destinations

83Path Stretch CalculationIn the hazy-sighted case, T(kL) = Ths 2ceil(log2(kL))In regular case, T(kL) = To

By adjusting THS and To we can make the path stretch the same for both cases

soOverhead

Overhead Ratio

Conclusion: In order to keep path stretch the same as with regular flooding, hazy-sighted results in higher overhead.One must focus on the intermediate nodes, not just the destination.Overview of OLSROLSR is a link-state proactive routing protocol with four basic parts:Neighbor DiscoveryA node estimates its local topology.By local topology, we mean 1- and 2-hop topologySelector of Topology Information to DisseminateNot all links are needed to form shortest pathsAdvertising a subset of all links reduces total overheadTopology DisseminationOnce the link information to be advertised is determined, it must be disseminated over the networkRoute CalculationOnce the link advertisements are received, paths can be computed.

87Update Topology SetCheck all advertised addresses that came in the message.These addresses are from the nodes that selected the originator node as an MPR.

88Update Topology Set (cont)Check all Topology Tuples in the Information Bases and verify if it exists an entry with the information just received.

89Update Topology Set (cont)If no information is stored in the Data Bases, create a new tuple.Existing or new tuple has to update its sequence number and holding time.

90Removing Topology TuplesTo remove a Topology Tuple on of two things must occur:The timer (tuple holding time) has to expire.A TC message has to explicitly remove a tuple. (i.e. notify that a link is broken)91The height of the text box and its associated line increases or decreases as you add text. To change the width of the comment, drag the side handle.

Adjust width of box to change paragraph width. Box's height adjusts according to text.

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OLSRv2 High Level Overview

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