Routing Protocol classification
Ad-Hoc Routing Protocols
Proactive
Topology-based Geographic
Reactive Basic Greedy
Partial Flooding DFS-based
Stateless
Energy aware Remark 1: Topology control is typically
achieved by a localized algorithm.
Remark 2: In this lecture we do not consider topology control so much; just a few
examples while explaining routing.
non-localized localized
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
• Destination-Sequenced Distance-Vector Routing (DSDV)
• Optimized Link State Routing (OLSR)
• Ad-Hoc On-Demand Distance Vector Routing (AODV)
• Dynamic Source Routing (DSR)
Geographische Routingprotokolle
13
Topology-Based Routing Overview
Topology-Based Routing Protocols
Proactive (Table-driven)
Reactive
(Source-initiated on-demand)
DSDV OLSR … AODV DSR TORA …
DSDV: Main Idea
A B C
A A B B C B
A A B B C C
A B B B C C
15
DSDV: Table Maintenance
A B C
A A B B C ? D E E E
A A B B C C D C E A
A B B B C C D D E D
E D
A A B B C C D C E A A A B B C C D C E A A A
B B C B D E E E
DSDV: Shortest Paths
A
B
C
A A B B C C D C E C F ?
A B B B C C D D E E F D
E
D
A A B B C E D E E E F E
F
F => A or C ?
A B B B C C D D E E F D A A
B B C E D E E E F E
17
DSDV: Shortest Paths
A
B
C
A A 1
B B 0
C C 1
D C 2
E C 2
E
D
F
A B 2
B B 1
C C 0
D D 1
E E 1
F D 2
A A 0
B B 1
C E 2
D E 3
E E 1
F E 4
A B 2
B B 1
C C 0
D D 1
E E 1
F D 2
A A 0
B B 1
C E 2
D E 3
E E 1
F E 4
DSDV: Topology Changes
B C
D A
A A 1
B B 0
C C 1
D C 2
A B 2
B B 1
C C 0
D D 1
A A 0
B B 1
C B 2
D B 3
A C 3
B C 2
C C 1
D D 0
A A inf
B B 0
C C 1
D C 2
A A 0
B B inf C B inf D B inf
A B ?
B B 1
C C 0
D D 1
A C ?
B C 2
C C 1
D D 0
19
DSDV: Topology Changes
B C
D
A
A A inf
B B 0
C C 1
D C 2
A A 0
B B inf C B inf
A B inf
B B 1
C C 0
D D 1
A C inf
B C 2
C C 1
D D 0
A A 0
B B inf C B inf
A C 3
B B 0
C C 1
D C 2
A D 2
B B 1
C C 0
D D 1
A A 1
B C 2
C C 1
D D 0
A A 0
B D 3
C D 2
DSDV: Sequence Numbers
A
C
B
D
B => D C => D
C => D or B => D ?
21
S = 41 DSDV: Sequence Numbers
A
C
B
D
B => D, S = 43 C => D, S = 42
B = > D ! S = 42S = 43
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
• Destination-Sequenced Distance-Vector Routing (DSDV)
• Optimized Link State Routing (OLSR)
• Ad-Hoc On-Demand Distance Vector Routing (AODV)
• Dynamic Source Routing (DSR)
Geographische Routingprotokolle
23
Proactive protocols – OLSR
Combine link-state protocol & topology control
Optimized Link State Routing (OLSR)
Topology control component: Each node selects a minimal dominating set for its two-hop
neighborhood
• Called the multipoint relays
• Only these nodes are used for packet forwarding
• Allows for efficient flooding
Link-state component: Essentially a standard link-state algorithm on this reduced topology
• Observation: Key idea is to reduce flooding overhead
(here by modifying topology)
25 Multipoint Relays
MPR Concept
• Subset M of neighbors of given node S which covers all 2-hop neighbors of S
• Node A is covered if it can receive message from S either directly or via 1-hop neighbor
• Nodes in subset M are called relay point
Minimum-size multipoint relay is of interest for energy efficient broadcasting
• Reduce number of broadcast relays but
• Cover all nodes by the broadcast
Example for node S
• 1-hop neighbors: A, B, C, D, E, F
• 2-hop neighbors: U, V, W, X
• A multipoint relay: {A, B, D, E}
• A minimum-size multipoint relay: {C, F}
Fact: Finding a minimum-size multipoint relay is NP complete
Approximations required! Example greedy approximation …
F U
X
D B
A
E V
W
S C
Multipoint Relays
Greedy approximation
• Repeat selecting node B which maximizes set of not so far covered nodes
Example
• (1) Maximum provided either by C or F; select C
• (2) Maximum provided then by F
• (3) All nodes covered; result {C, F}
F U
X
D B
A
E V
S C
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
• Destination-Sequenced Distance-Vector Routing (DSDV)
• Optimized Link State Routing (OLSR)
• Ad-Hoc On-Demand Distance Vector Routing (AODV)
• Dynamic Source Routing (DSR)
Geographische Routingprotokolle
27
AODV: Main Idea
S
D
RREQ
RREQ
RREQ
RREQ
RREQ RREQ
RREQ
RREQ RREQ
RREQ
AODV: Main Idea
S
D RREQRREP
29
AODV: Main Idea
S
D 1
2 3
1 2 3
1 2 3
AODV: Node Mobility
S
D
RREQ RREQ RREQ
31
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
• Destination-Sequenced Distance-Vector Routing (DSDV)
• Optimized Link State Routing (OLSR)
• Ad-Hoc On-Demand Distance Vector Routing (AODV)
• Dynamic Source Routing (DSR)
Geographische Routingprotokolle
DSR route discovery procedure
Search for route from 1 to 5
1
7
6
5 4 3
2
[1]
[1] 1
7
6
5 4 3
2
[1,7]
[1,7]
[1,4]
1
7
6
5 4 3
2 [1,7,2]
[1,4,6]
[1,7,3]
1
7
6
5 4 3
2
Node 5 uses route information recorded in RREQ to send back, via source routing, a route reply
[5,3,7,1]
33
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
Geographische Routingprotokolle
• Greedy-Routing und Planar-Graph-Routing
• Konstruktion von planaren Graphen
• Lokales Multicasting
• Beispiel MSTEAM
35 Localized Geographic Unicast Forwarding
Assumptions:
Localization system
Nodes know position of
• Themselves
• Their neighbors
• The destination source node
destination node
Geographic Greedy Routing
T S
A
(a)
F B
D C
E
Strategy: select from nodes closer to the destination the one which minimizes a local cost metric
B
E T S
(b)
?
A
C
D F
G
Problem: greedy routing failure
37 Recovery based on Planar-Graph Routing
source node
destination node
Planar Graph Routing Example
T S
P
F
39 Planar Graph Routing Example
T S
Q
F
P
Planar Graph Routing Example
T S
F
P
41 Planar Graph Routing Example
T S
P
F
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
Geographische Routingprotokolle
• Greedy-Routing und Planar-Graph-Routing
• Konstruktion von planaren Graphen
• Lokales Multicasting
• Beispiel MSTEAM
43 We need a Planar Graph
U V U V
Gabriel Graph (GG) Relative Neighborhood Graph (RNG)
W
U
V
Delaunay
Triangulation (DT)
We need a UDG or QUDG
UDG: Localized GG and RNG versions based on 1-hop neighbors
UDG: Localized DT version based on 2-hop neighbors (and less)
QUDG: Sort of localized GG (possibly the same for RNG)
Quasi unit disk graph (QUDG)
U V
Unit disk graph (UDG)
rmin rmax
U
45 Problems and Limitations
Locally constructing a planar graph in arbitrary networks is impossible
Even worse: localized unicast routing is impossible in arbitrary graphs
Localized single path algorithms deviation from shortest paths
• Let k be the hop/Euclidean length of the shortest path connecting s and t
• Localized single path algorithms may produce paths of length O(k2)
• Some even worse but some exist which are upper bounded by O(k2) u
x v
y
t s
Localized Unicast Routing in Practice!
Wireless network graph has structure!
Aim at localized unicast approaches with high delivery rate
Method of choice: sorts of clustering
arbitrary graph wireless network graph
47 Geographic Clustering
Geographic Clustering
49 Geographic Clustering
Geographic Clustering
51 K-Hop Clustering
K-Hop Clustering
53 K-Hop Clustering
K-Hop Clustering
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
Geographische Routingprotokolle
• Greedy-Routing und Planar-Graph-Routing
• Konstruktion von planaren Graphen
• Lokales Multicasting
• Beispiel MSTEAM
55
Localized Multicast Forwarding Problem
Assumptions:
Location system
Nodes know position of
• Themselves
• Their neighbors
• The destinations source node
destination node destination node
destination node
destination node
57
Building Blocks
T1
T3
T2 S
B A
D C
Building Blocks – Message Split
T1
T3
T2 S
B A
D C
59
Building Blocks – Next Hop Selection
T1
T3
T2 S
B A
D C
?
Building Blocks – Recovery
T1
T3
T2 S
B A
D C
?
?
Übersicht
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
Geographische Routingprotokolle
• Greedy-Routing und Planar-Graph-Routing
• Konstruktion von planaren Graphen
• Lokales Multicasting
• Beispiel MSTEAM
61
EMST Backbone Assisted Localized Routing
T9
T7
T6
T1
T3 S
T8
T5
T2 T1,…,T9
63 EMST Backbone Assisted Localized Routing
T8 T9
T7
T6
T5
T4
T1
T2
T3 S
EMST(S,T1,…,T9)
EMST Backbone Assisted Localized Routing
T8 T9
T7
T6
T5
T1
T2
T3
D1
D2 D3
S
65 EMST Backbone Assisted Localized Routing
T8 T9
T7
T6
T5
T4
T1
T2
T3 A
B
C
S
T7,T8,T9
T1,T2,T3 T4,T5,T6
The Cost over Progress Framework
T3
T1
W V
T2 S
Which one is the better next hop node?
T1,T2,T3
67 The Cost over Progress Framework
Approximate expected number of hops H(S,V)
H(S,V) |EMST(S,T1,T2,T3)| / (|EMST(S,T1,T2,T3)| - |EMST(V,T1,T2,T3)|)
Approximate expected cost C(S,V) = cost(S,V) * H(S,V)
Select node X which provides progress and minimizes C(S,X) T3
T1
W V
T2 S
MSTEAM & MFACE
S T6
T5
T4
T1
T2
F1
F2
69
MSTEAM & MFACE
S T6
T5
T4
T3
T1
T2
F1
F2
MSTEAM & MFACE
S
U
V W
F1 F2
F3
T1
T2 T3
71
MSTEAM & MFACE
S
U
V W
F1 F2
F3
T1
T2 T3
MSTEAM & MFACE
S
U
V W
F1 F2
F3
T1
T2 T3
73
MSTEAM & MFACE
S
U
V W
F1 F2
F3
T1
T2 T3 p
MSTEAM & MFACE
S
U
V W
F1 F2
F3
T1
T2
75
MSTEAM & MFACE
S
U
V W
F1 F2
F3
T2
Zusammenfassung
Untersuchte Netzstruktur und Problemstellungen
Topologie-basierte Routingprotokolle
Geographische Routingprotokolle
Zusammenfassung
Wir betrachteten hier: drahtlose Vernetzung ohne aufwendige (und kostenpflichtige) Infrastruktur
Abdeckung größerer Gebiete trotz limitierter Kommunikationsreichweite Multihop-Kommunikation
Wir haben es hier somit hauptsächlich mit einem Netzwerkproblem zu tun
Wesentliche Probleme: Routing und Topologiekontrolle
Anpassung traditioneller Routing-Verfahren: Topologie-basiertes Routing
Neuer Routing-Ansatz auf der Basis von Knotenkoordinaten
Dieser Ansatz erlaubt ganz neue Formen der Datenkommunikation und generell ganz neue Formen von Netzorganisation
Generelles Paradigma, um mit der Dynamik solcher infrastrukturlosen Multihop- Netze umzugehen: lokale Algorithmen/Verfahren
Dieses Paradigma ist auch zur Beherrschung von komplexen und dynamischen Internet-Overlay-Topologien anwendbar
Mit den hier behandelten lokalen Verfahren wurde nur ein kleiner Ausschnitt eines interessanten Forschungsfeldes betrachtet
Mehr in der Vorlesung „Lokale Netzstrukturen“
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