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Ad Hoc and Wireless MeshNetworking

Laura Marie [email protected]

Datakommunikation III, HT 2006

Overview

Ad hoc and wireless mesh networksI Ad hoc network (MANet)

I operates independently of networkinfrastructure

I nodes cooperate to provide networkservices

I Mesh networkI supplements network infrastructureI nodes cooperate to provide Internet

access

Ad hoc network

mobile wireless network

capable of autonomous operation

Ad hoc network



I operates without base station

infrastructure

Ad hoc network




infrastructure

I nodes cooperate to provide connectivity

Ad hoc network




infrastructure


I every node is a router (no default

router)

Ad hoc network




infrastructure


I every node is a router (no default

router)

ad hoc routing problem

Ad hoc network



Ad hoc network



I operates without centralized

administration

Ad hoc network




administration

I nodes cooperate to provide services

Ad hoc network




administration


I address allocation (no DHCP)

Ad hoc network




administration


I address allocation (no DHCP)

I fairness and security

Example

network nodes (mobiles, laptops, PDA’s)

Example

wireless communication

Example

“equivalent” topology

Example

discover multihop route

Example

route failure due to mobility

Example

dynamic route repair

Example

extend infrastructure

Example

How is a MANET different from other

networks?

I Internet

I WLAN/Cellular

I MobileIP

Internet

default router

Internet routing(+ humans)

networkprovider

simple default router at edges

expertise managing core

WLAN/celluar

nodes communicate only with base-station

Mobile IP

correspondent

CN

MNhome

FA

MobileIP allows a node to change its point of

attachment to the network

Mobile IP

CNFA

HA

MN

home agent (HA) tunnels traffic to the node

Applications

I Military/rescue

(no infrastructure)

Applications

I Military/rescue

(no infrastructure)

I Disaster management

(damaged infrastructure)

Applications

I Military/rescue

(no infrastructure)



I Spontaneous networks

(meeting/conference room)

Applications

I Military/rescue

(no infrastructure)





I Personal area networks

Applications

I Military/rescue

(no infrastructure)





I Personal area networks

I Campus area networks

Applications

I Extend coverage

improve range or capacity in a building

Applications

I Extend coverage


I Community mesh networks

share network connectivity with

neighbors

Applications

I Extend coverage


I Community mesh networks

share network connectivity with

neighbors

I Developing countries

provide cheap communication

infrastructure

History

Not a new idea

I US DARPA (1970’s)

History

Not a new idea


I Amateur (ham) radio operators (1970’s)

“packet radio”

History

Not a new idea



“packet radio”

I renewed interest mid-1990’s

History

Not a new idea



“packet radio”


I IETF MANET working group (1997)

History

Not a new idea



“packet radio”


I IETF MANET working group (1997)

I startup companies (2000–)

Ad hoc routing

Outline

I challenges

I design choices

I protocol example

I wireless communication

Challenges

I distributed state in unreliable

environment

Challenges


environment

I changing topology

I limited communication capacity

I limited battery capacity

Challenges


environment

I changing topology

I limited communication capacity

I limited battery capacityI wireless communication

I variable link qualityI non-symetric linksI interference and collisions

CriteriaI effectiveness

I convergence/recoveryI scalability (number of nodes, density)



I performanceI data throughputI route latency (delay)I route optimality

(hops/stability/diversity)I overhead cost

(packets/bandwidth/energy)

Alphabet Soup

many proposed protocols:

AODV CEDAR ABR FSR

TORA GSR OLSR LANMAR

ZRP LAR DSR OSPF++

RDMAR CBRP DSDV WRP

TBRPF CGSR GPSR HSR

Design choices

protocols divided into a few main categories

I on-demand (reactive)

I table driven (proactive)

I hierarchical/cluster-based

I geographic/position-based

Reactive Routing

find routes as needed (on demand)

I advantagesI no overhead maintaining unused routes

I disadvantagesI high route latencyI optimization?

Proactive routing

table-based, more similar to conventional

routing

I advantagesI low route latencyI state information

I disadvantagesI high overhead (periodic table updates)I route accuracy depends on updates

AODV (DYMO)

Ad hoc On demand Distance Vector

Perkins et.al.

AODV (DYMO)


Perkins et.al.

conventional distance vector

I nodes exchange distance information (to

all nodes) with their neighbors

I periodic exchange and immediate

update for changes

I routing table selects shortest path

AODV (DYMO)


Perkins et.al.

conventional distance vector

I nodes exchange distance information (to

all nodes) with their neighborsI periodic exchange and immediate

update for changesI routing table selects shortest path

exchange a lot of information that is never

used

AODV (DYMO)

on-demand variant of conventional distance

vector

AODV (DYMO)


vector

I route request (RREQ) packet is flooded

through the network

AODV (DYMO)


vector


through the network

I route discovery creates (temporary)

reverse paths back to the source

AODV (DYMO)


vector


through the network

I route discovery creates (temporary)

reverse paths back to the source

I route reply (RREP) turns a valid reverse

path into a route

AODV (DYMO)

handling topology change

AODV (DYMO)


I link failure causes route error (RERR)

I destination managed sequence number

ensures loop freedom

AODV (DYMO)


I link failure causes route error (RERR)

I destination managed sequence number

ensures loop freedom

AODV is RFC 3562 (experimental)

DYMO is IETF Internet draft

AODV (simplified)

7

1

2

6

11

13103

5

12

4

8

914

route from node 1 to node 14

AODV (RREQ)

1479

8

4

12

5

3 10 13

11

6

1

2

14?1 hop

broadcast flooding of route request

wireless multicast advantage

AODV (RREQ)

5

1hop

41−>14: via 1

8

1hop

914

1−>14: via 1

3

6

7

111hop

13

1

101−>14: via 1

212

node from which RREQ was received defines

reverse path to source

AODV (RREQ)

14?

2 hops

2

6

1

14

11

13103

5

12

4

8

97

2 hops

2 hops

14?

14?

RREQ is flooded though the network

AODV (RREQ)

2hop

6

14

1

1310

2

3

5

12

4

8

97

1−>14: via 3

1−>14 (via 1)

1−>14 (via 1)

1 hop

1 hop

1−>14 (via 1)

1 hop

1−>14: via 3

1−>14 (via 5)2hop

2hop

2hop

1−>14: via 2

11

reverse paths are recorded

AODV (RREQ)

14?

3 hops

3 hops 14

3

7

1

6

3 hops

1310

5

12

4

8

9

3 hops

11

2 14?

14?

14?

unreliable broadcast

destination managed sequence number, ID

prevent looping

AODV (RREQ)

3hop

79

8

4

12

5

3 10 13

1

14

6

11

1−>14: via 3

1−>14 (via 1)

1−>14 (via 1)

1 hop

1 hop

1−>14 (via 1)

1 hop

1−>14: via 3

1−>14 (via 5)2hop

2hop

2hop

1−>14: via 22hop

1−>14: via 83hop

1−>14: via 83hop

1−>14: via 7

2


AODV (RREQ)

4 hops

4 hops2

14

3

7

1

6

11

1310

5

12

4

8

9

4 hops14?

14?

14?

broadcast collision problem (jitter)

AODV (RREQ)

4hop

6

14

1

2

13103

5

12

4

8

97

1−>14: via 3

1−>14 (via 1)

1−>14 (via 1)

1 hop

1 hop

1−>14 (via 1)

1 hop

1−>14: via 3

1−>14 (via 5)2hop

2hop

2hop

1−>14: via 22hop

1−>14: via 8

1−>14: via 83hop

1−>14: via 73hop

3hop

1−>14 via 10

1−>14 via 104hop

11


AODV (RREQ)

14?

3

7 14

13

1

6

11

10

5

12

4

8

9 5 hops

5 hops14?

2

broadcast flooding is very expensive

AODV (RREQ)

5 hops

79

8

4

12

5

3 10 13

1

14

6

11

1−>14: via 3

1−>14 (via 1)

1−>14 (via 1)

1 hop

1 hop

1−>14 (via 1)

1 hop

1−>14: via 3

1−>14 (via 5)2hop

2hop

2hop

1−>14: via 22hop

1−>14: via 8

1−>14: via 83hop

1−>14: via 73hop

3hop

1−>14 via 10

1−>14 via 104hop

4hop

14!2

RREQ arrives at the destination

two routes are discovered

AODV (RREP)

14

7

3

14

1

6

11

10

2

5

12

4

8

9

13

destination sends unicast RREP (sets

sequence number)

“activate” reverse path

AODV (RREP)

14

27

3

14

1

6

11

10

5

12

4

8

9

13

destination sends unicast RREP (sets

sequence number - not shown)

AODV (RREP)

11

6

1

9

3

7

1314

14

14 via 13

214

8

4

12

5

10

RREP messages “activates” reverse path

AODV (RREP)

2

5

12

14

4

148

14

79

13

14

via 13

1

3

6

1114

10

via 10

RREP messages “activates” reverse path

AODV (RREP)

via 8

9

8

4

12

5

10

11

6

1

14

3

7

1314

14

14 via 13

via 101414

2

RREP reaches source – route discovery

complete

AODV (RREP)

via 5

9

8

4

12

5

10

11

6

1

14

3

7

1314

14

14 via 13

14 via 10via 814

2

source adopts destination sequence number

AODV

via 10

9

8

4

12

5

10

11

6

1

14

3

7

1314

14 via 5 via 814

14 via 13

14

2

traffic flows along forward route

reverse path information times out

AODV(RERR)

via 10

9

8

4

12

5

10

11

6

1

14

3

7

1314

14 via 5 via 814

14 via 13

14

2

link failure

how to be sure?

AODV(RERR)

10

14

5

12

via 5

4 14

8

via 13

9

3

14

7

via 8

13

1

6

14

11

2

14

node generates route error message (RERR)

AODV(RERR)

via 13

9

8

4

12

5

10

11

6

1

14

3

7

1314

14 via 5

14

2

forwarded to source

AODV(RERR)

4

12

5

10

11

6

1

14

8

7

1314 via 13

14 via 1014?

2

14

9

3

initiate new route discovery (RREQ)

AODV(RERR)

97

3

14

1

6

11

10

2

5

12

4

8

13

discover new route (latency)

AODV(RERR)

14?

7

3

14

1

6

2

11

10

5

12

4

8

9

14

14 via 5 via 814

14

14 via 10

via 1313

what about a local repair?

initiate RREQ from point of failure

AODV(RERR)

14?

7

3

14

1

6

2

11

10

5

12

4

8

9

14

14 via 5 via 814

14

14 via 10

via 1313

what about a local repair?

initiate RREQ from point of failure

AODV(RERR)

via 10

7

3

14

1

6

2

11

10

5

12

4

8

9

14

14 via 5 via 814

14

14 via 10

via 13

14

13

lower latency

AODV(RERR)

via 10

7

3

14

1

6

2

11

10

5

12

4

8

9

14

14 via 5 via 814

14

14 via 10

via 13

14

13

lower latency but longer routes

AODV(DYMO)

I (over)-simplified description here

I further complexities and optimizations

I AODV-UU implementation is

well-known






OLSR

Optimized Link State Routing

Clausen et.al

OLSR


Clausen et.al

conventional link-state routing

I beacon to determine neighbors

I for each node, disseminate its links to

all other nodes

I use SPF algorithm to generate routing

table

OLSR


Clausen et.al

conventional link-state routing

I beacon to determine neighborsI for each node, disseminate its links to

all other nodesI use SPF algorithm to generate routing

table

high overhead, exchange information for links

that are never used

OLSR

variant of conventional link state routing

OLSR


I for each node, disseminate only some of

its links

I for each node, only disseminate

information received via some links

I use SPF to generate routing table

OLSR


I for each node, disseminate only some of

its links

I for each node, only disseminate

information received via some links

I use SPF to generate routing table

“some links” = multipoint selector set

OLSR

IETF RFC 3626 (experimental)

2-hop Neighborhood

broadcast periodic “hello” messages

I each message contains a list of

neighbors

I each node discovers its 2-hop

neighborhood

I discovers failed links

I discovers bi-directional links

Bi-directional Links

HELLO(3)={1,2,4,7}

HELLO(6)={2,3,7}

6

4

3

14

1

2

13

129

10

11

7

85

Bi-directional Links

NBR(3)={1,2,4,7}

NBR(3)={1,2,4,7}HELLO(6)={2,3,7}

5

3

14

1

2

13

129

10

11

7

8

6

4

Multipoint Relay

multipoint relay set (MPR): subset of a

node’s 1-hop neighbors, such that each of its

2-hop neighbors is a 1-hop neighbor of a

node in the MPR set

Multipoint Relay




node in the MPR set

minimum set of 1-hop neighbors that results

in the same set of 2-hop neighbors

Multipoint Relay




node in the MPR set

minimum set of 1-hop neighbors that results

in the same set of 2-hop neighbors

each node has an MPR set (not a “network”

MPR set)

Multipoint Relay(MPR set)

12

1

2

6

9

10

1185

3

7

4

14

13

1-hop and 2-hop neighbors of node 4 ode 5

is not needed in the multipoint relay set

Multipoint Relay(MPR set)

12

1

2

6

9

10

1185

3

7

4

14

13

node 5 is not needed in the multipoint relay

set

Dense Network

12

1

2

6

9

10

1185

3

7

4

14

13

with greater node density, the proportion of

relay nodes is smaller

Dense Network (MPR set)

{3,8}

{4,10}

{10}

{1,4,8}

{8,10}

{4,7}

{1,3}

{3,5}

{7,8,12} {9,10}

{10}{7,8}

{6,4,10}

{2,7}

9

13

14

1

5

11

10

127

32

4

8

6

nodes which are not in the MPR set are in

some sense redundant

Dense Network (MS set)

9

13

14

1

5

11

10

127

32

4

8

6

multipoint selector (MS) set is the inverse of

MPR set

i.e. nodes that have selected this node as an

MPR

Dense Network (OLSR)

Operation:


Operation:

I each node uses HELLO messages to find

and announce its MPR set


Operation:


and announce its MPR setI a node sends link state information only

for nodes in its MS set (for which it is

an MPR)


Operation:




an MPR)I each node computes SPF routes using

all received messages


Operation:




an MPR)I each node computes SPF routes using

all received messagesI a node only rebroadcasts link state

messages from nodes in its MS set

OLSR

only disseminate link data for green nodes

only rebroadcast data from green nodes1: 4 2 3 5 2: 1 3 6 3: 1 2 4 6 74: 1 3 5 7 8 5: 1 5 8 6: 2 3 77: 3 4 6 9 10 8: 4 5 9 10 11 9: 7 10 1210: 7 8 9 11 12 13 11: 8 10 13 12: 9 10 13 1413: 10 11 12 14 14: 10 12 13






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