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Advanced Topics in Distributed Systems
(Spring/Summer 2005)
Mobile Ad hoc Networking
Prof. Dr.-Ing. Ralf Steinmetz, Dr.-Ing. Matthias Hollick
Technische Universität Darmstadt,
Fachbereich Elektrotechnik und Informationstechnik, Fachbereich Informatik (Zweitmitglied),
Fachgebiet Multimedia Kommunikation – KOM, Tel.+49 6151 166158, Fax. +49 6151 166152
Merckstr. 25, D-64283 Darmstadt, [email protected]
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Slide 8.2Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
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Outline (1)
Introduction and Motivation
• Terminology and Basics
• Applications for Ad hoc Networks• Ad hoc vs. the Internet Model
Routing in Mobile Ad hoc Networks
• Characteristics of Ad hoc Networks• Ad Hoc Routing Paradigms
Selected Routing Protocols (1)
• Ad Hoc On-demand Distance Vector Routing (AODV)
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Slide 8.3Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
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Outline (2)
Selected Routing Protocols (2)
• Dynamic Source Routing (DSR)
• Location Aided Routing (LAR)
Performance Evaluation of Ad hoc Networks
• The Art of Performance Evaluation
• Analyzing Ad hoc Network Performance
Summary and Conclusion
Appendix
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Slide 8.4Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Motivation for Mobile Ad hoc Networks
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Slide 8.5Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Terminology and Paradigms
“Ad hoc”
• often improvised or impromptu; „an ad hoc committee meeting“
Wordnet
• formed or used for specific or immediate problems or needs; „ad hoc solutions“
• fashioned from whatever is immediately available: improvised;„large ad hoc parades and demonstrations“
Encyclopædia Britannica
“Spontaneous”
• arising from a momentary impulse
• controlled and directed internally; „self-acting“
• produced without being planted or without human labor;„indigenous“
• developing without apparent external influence, force, cause, ortreatment
Encyclopædia Britannica
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Slide 8.6Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Basics
(Mobile) Ad Hoc Communication Networks - MANET
• Historical successor of packet radio networks
• Self-organizing, mobile and wireless nodes • Absence of infrastructure, multi-hop routing necessary• Systems are both, terminals (end-systems) and routers (nodes)
• Constraints (dynamics, energy, bandwidth, link asymmetry)
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Slide 8.7Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Applications
Military applications
• Battlefield communication (soldiers, tanks, planes, …)
• Smart dust (sensor networks to detect chemical, biological threats)
Civilian applications
• Vehicular environment (telematics, car to car communication, taxi cab network, …)
• Entertainment (filesharing, gaming, ... in train, car, plane, school, …)
• Event support (conferences, sport-events, exhibitions, meetings, lectures)
• Home networking / Personal Area Networking (VCR, DVD, home entertainment, remote control, cell phone, laptop, watch, …)
• Disaster recovery (emergency services, ambulance, police, …)
• Smart dust (sensor networks for civilian applications)
• Ubiquitous computers with short-range interactions (embeddedsystems, smart buildings/artefacts, …)
• Cellular range extension, moveable base stations (UMTS, WLAN, WMAN, …)
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Slide 8.8Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Ad Hoc vs. The Internet Model
email WWW IPtel IMS...
SMTP HTTP RTP...
TCP UDP…
IP
ethernet
CSMA sonet...
copper fiber radio...
Spontaneous App. Behavior
Disconnected Operations
P2P App. Characteristics
User / Device Mobility
Wireless Communication
Distributed Medium Access
Service Discovery
Addressing
Name Resolution
Power Control
Gateway Discovery
New Apps.
Absence of Infrastructure
Ad Hoc Routing
User Demands
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Slide 8.9Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Peer to Peer vs. Ad Hoc
P2P
• Relevant resources located at nodes at the edges ("peers")
• Variable connectivity is the norm• e.g. does it support dial-up users with variable IP addresses
• Combined Client and Server functionality• for all end system nodes • also for intermediate nodes
• Peers with significant autonomy• e.g. storage / processing done by autonomous end-systems
• Direct data transfer between peers• e.g. more-or-less no central control
• Content locations widely distributed and most often replicated
Ad Hoc and P2P share paradigms
• Ad Hoc focuses on network level and below• P2P focuses on application level• Coexistence of Ad Hoc and P2P is possible / synergetic
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Slide 8.10Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Vendor Application Demo
Demo seen at www.meshnetworks.com (now Motorola)
Other companies include
• “Flarion”, “Radiant Networks”, “Invisible Networks”, “Green Packet Inc.”, “LocustWorld”, and some other companies …
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Slide 8.11Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
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Outline
Introduction and Motivation
• Terminology and Basics
• Applications for Ad hoc Networks• Ad hoc vs. the Internet Model
Routing in Mobile Ad hoc Networks
• Characteristics of Ad hoc Networks
• Ad Hoc Routing Paradigms
Selected Routing Protocols (1)
• Ad Hoc On-demand Distance Vector Routing (AODV)
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Slide 8.12Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Characteristics of Ad Hoc Communications
Characteristics are dominated by heterogeneity and variability
• Mobility characteristics • Speed, uniformity of movement, …
• Wireless characteristics • Broadcast nature, transmission errors, limited range, partitioning,
hidden and exposed terminals, …
• System characteristics • Distributed system, absence of infrastructure, high topology
dynamics, etc.
Inherent heterogeneity
• Do nodes have identical capabilities, responsibilities, and constraints?
• Transmission ranges and radios may differ, battery life may differ, processing capacity may differ, … (asymmetry)
• Only some nodes may route packets, some nodes may act as leaders of nodes, e.g. cluster head (asymmetric responsibilities)
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Slide 8.13Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Example User Mobility: What is Realistic?
4000m x 3000m
10 nodes?100 nodes?1000 nodes?10000 nodes?
1000m x 1000m, 333 nodes
1 m/s 1000s5 m/s 200s20m/s 50s
1000m
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Slide 8.14Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Node Density Quiz: Street Lamps
Moving from mobile to stationary, more mesh like multihop scenarios:
What do you think:
How many street lamps are operated in Frankfurt (am Main)
(1) Please write your first guess on the provided post-it
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Slide 8.15Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Node Density Quiz: Street Lamps
Moving from mobile to stationary, more mesh like multihop scenarios:
What do you think:
How many street lamps are operated in Frankfurt (am Main)
(1) Please write your first guess on the provided post-it
Consider the following Information:~ 650.000 Residents (with ~330.000 cars)~ 248 square-km~ 1000 km streets
(2) Please write your second guess on the provided post-it
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Slide 8.16Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Macroscopic Workload / Mobility Model
Synthetic mobility models (see demo)
• Easy to use
• Strict separation from traffic models• Unrealistic for large scenarios (e.g. random waypoint)
Empirical workload / mobility models
• Data is hard to obtain• Can often not be separated in mobility vs. traffic
• Available for past scenarios (may not be generalized easily)
Hybrid workload / mobility model (synthetic traffic, empirical mobility) (see demo)
• Pros: flexibility, realism• Cons: lots of parameters, data is hard to obtain
• Trade-off
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Slide 8.17Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Demo of Mobility Models
Synthetic mobility model
• e.g. random walk, random waypoint
• Demo: ANSim, see http://www.i-u.de/schools/hellbrueck/ansim
Hybrid workload / mobility model
• Demo: MobQoS Model
• Seehttp://www.kom.tu-darmstadt.de/Research/MobQoS
• Developed together withSiemens Corporate Technology, Munich
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Slide 8.18Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Quiz on Ad Hoc Routing
Why do we need specialized ad hoc routing?
(A) To deal with topology dynamics induced by mobility
(B) To reach nodes that are no direct neighbors
(C) To match the characteristics of wireless communication
(D) To support spontaneous formation of the network
(E) To operate without fixed infrastructure
(F) Because all end-systems are also acting as routers
Correct answers are A, B, C, D, E, and F!
We discuss these issues with selected protocols in a few minutes
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Slide 8.19Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Requirements for Ad Hoc Routing
The routing protocol needs to
• Converge fast
• Minimize signaling overhead
The routing strategy (algorithm) may include
• Shortest distance, Minimum delay, Minimum loss
• Minimum congestion (load-balancing), Minimal interference• Maximum stability of routes or maximal signal strength
• Minimum energy (power aware routing)
Standard Internet routing cannot fulfill these requirements
• Assumes infrastructure, assumes symmetrical conditions, assumes plenty of resources, converges slow, typically supports hop-count metric only, …
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Slide 8.20Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
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Outline
Introduction and Motivation
• Terminology and Basics
• Applications for Ad hoc Networks• Ad hoc vs. the Internet Model
Routing in Mobile Ad hoc Networks
• Characteristics of Ad hoc Networks
• Ad Hoc Routing Paradigms
Selected Routing Protocols (1)
• Ad Hoc On-demand Distance Vector Routing (AODV)
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Slide 8.21Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Features of the AODV protocol
Protocol operation
• Reactive routing protocol
• Route discovery cycle for route finding• Flooded / Broadcasted Route Request (RREQ)• Unicast Route Reply (RREP) along reverse path of RREQ• Unicast Route Error (RERR)
• No overhead on data packets
Protocol principles
• Based on distance vector routing
• Loop freedom is achieved through sequence numbers, also solves “count to infinity” problem
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Slide 8.22Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
• Broadcast flood acquisition using Route Request (RREQ)• Nodes set up reverse path pointing towards the source
Route acquisition process
• RREQ must never be broadcasted more than once by any node• Unicast Route Reply (RREP) propagation
AODV – Route Acquisition
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Slide 8.23Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
AODV – Route Error
Link failure reporting / repairing routes
• If X is unable to forward packets from S to D on link (X,Y)
X increments its Destination Sequence Number (N) for D
A Route Error (RERR) message is generated at X
The RERR includes N and is sent out based on precursor lists
Upon receipt of RERR, S initiates new route discovery for D using destination sequence number at least as large as N
SYX
D
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Slide 8.24Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
AODV – Route Maintenance
Timers to keep route alive
• A routing table entry maintaining a reverse path is purged after a timeout interval (Discuss: How long should interval be at least?)
• A routing table entry maintaining a forward path is purged if not used for the active_route_timeout interval
DB
E
CA
Here: Destination Sequence Number to determine freshness
• To avoid using old/broken routes
• To prevent formation of routing loops
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Slide 8.25Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Example
Parameters
AODV
25 nodesPure Flooding
Area = 836m*836m
Radio Range = 250mNode Density = 7
RREQ from #13 to #2
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Slide 8.26Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Other Features of AODV
Status
• Implementations available (for IPv4, IPv6)
• IETF Experimental RFC status issued (July 2003)
Target networks
• Where routing churn is high enough that proactively maintaining routes is unproductive & can absorb network wide broadcast rate
Multiple optimizations
• AODV-LR – Local Repair
• AODV-ESP – Expanding-Ring Search
• Multipath & Multicast extensions (AODVM, AOMDV, MAODV)
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Slide 8.27Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
AODV Optimizations – Gossiping (1)
Flooding is very inefficient, esp. if node density is high
• Probabilistic techniques are expected to better deal with the
highly dynamic and mobile characteristics of the network
• Probabilistic techniques may easily be adapted to network
density without breaking symmetric conditions
Gossiping as example of epidemiological algorithm
• Assume a large population of n people
• A rumor is initially transmitted to one member of the population
• This person passes (forwards) the rumor to a fixed number of
confidants with probability p, the rumor is kept secret with
probability 1- p (other modes possible)
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Slide 8.28Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
AODV Optimizations – Gossiping (2)
Gossip-variants
• Gossip (p1), Gossip (p1, k), Gossip (p1,k,m)
• General forwarding probability p1
• Number of neighbors n; probability p2 for n < n0 , p2 > p1
• Hop count k; forwarding probability p = 1 for k k0
• Number of overheard messaged m; p = 1 for m m0
Pseudo-Algorithm for Gossip (p1, k)upon reception of message m at node nif message m received for the first time then
if hop count k less or equal k0 then
broadcast(m) with probability 1else
broadcast(m) with probability p1
end if
end if
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Slide 8.29Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
AODV Extension – Multipath (AODVM)
Multipath variants for multiple protocols
• Easy for source routing algorithms
• Not trivial for optimized protocols like AODV• “Multipath” should NOT be mixed up with “Multicast”
AODVM
• Ad hoc On-demand Distance Vector Multipath (AODVM) Routing
• Instead of dropping duplicate RREQ packets, AODVM uses an RREQ table to store the redundant RREQ information.
Route Request (RREQ)
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Node M’s RREQ table
3ZS
J
Neighbor
3S
DistanceSource
Source: Zhenqiang Ye
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Slide 8.30Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
AODVM Explained
Path Discovery Procedure
• Destination initiates an RREP for each RREQ that is received (from different neighbors).
• Nodes overhear the RREP packets• A node that is assigned to a route is deleted from its neighbors’
RREQ tables
3ZS
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Neighbor
3S
DistanceSource
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Node M’s RREQ table
CG
Route Request (RREQ)
Route Reply (RREP)
Source: Zhenqiang Ye
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Slide 8.31Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
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Outline
Selected Routing Protocols (2)
• Dynamic Source Routing (DSR)
• Location Aided Routing (LAR)• Optimized Links-State Routing (OLSR)
Current Research Challenges in Mobile Ad hoc Networking
• Dependable Routing in Ad hoc Networks• Modeling the AODV Route Acquisition Process
Summary and Conclusion
Appendix
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Slide 8.32Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Dynamic Source Routing (DSR)
Shares some principles with AODV
• When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery
• Source node S floods Route Request (RREQ)
• Each node appends own identifier when forwarding RREQ
• Following an example for a route discovery from source S to destination D
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Slide 8.33Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
B
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Represents a node that has received RREQ for D from S
Source: Nitin Vaidya
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Slide 8.34Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
B
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F
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D
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G
I
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YBroadcast transmission
M
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[S]
Represents transmission of RREQ
[X,Y] Represents list of identifiers appended to RREQ
Source: Nitin Vaidya
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Slide 8.35Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
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A
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[S,E]
[S,C]
Node H receives packet RREQ from two neighbors:
potential for collision
Source: Nitin Vaidya
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Slide 8.36Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
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[S,C,G]
[S,E,F]
Node C receives RREQ from G and H, but does not forward
it again, because node C has already forwarded RREQ once
Source: Nitin Vaidya
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Slide 8.37Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
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[S,C,G,K]
[S,E,F,J]
Nodes J and K both broadcast RREQ to node D
Since nodes J and K are hidden from each other, their
transmissions may collideSource: Nitin Vaidya
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Slide 8.38Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
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A
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F
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[S,E,F,J,M]
Node D does not forward RREQ, because node D
is the intended target of the route discovery
Source: Nitin Vaidya
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Slide 8.39Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Discovery in DSR
Route Reply (RREP)
• Destination D on receiving the first RREQ, sends a (RREP)
• RREP is sent on a route obtained by reversing the route appended to received RREQ
• RREP includes the route from S to D on which RREQ wasreceived by node D
• Route Reply can be sent by reversing the route in Route Request (RREQ) only if links are guaranteed to be bi-directional
• If unidirectional (asymmetric) links are allowed, then RREP may need a route discovery for S from node D
• Unless node D already knows a route to node S
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Slide 8.40Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Route Reply in DSR
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RREP [S,E,F,J,D]
Source: Nitin Vaidya
Represents RREP control message
Node S on receiving RREP, caches the route included in the RREP
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Slide 8.41Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Data Delivery in DSR
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DATA [S,E,F,J,D]
Source: Nitin Vaidya
Packet header size grows with route length
When node S sends a data packet to D, the entire route is included in the packet header (hence the name source routing)
Intermediate nodes forward according this route
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Slide 8.42Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Location-Aided Routing (LAR)
Exploits location information to limit scope of flooding for route request
• Location information may be obtained using GPS
Expected Zone is determined as a region that is expected to hold the current location of the destination node (D)
• Expected region determined based on potentially old location information, and knowledge of the destination’s speed
Route requests limited to a Request Zone that contains the Expected Zone and location of the sender node (S)
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Slide 8.43Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Expected Zone in LAR
S = Source node, D = Destination node
X = last known location of node D, at time t0
Y = location of node D at current time t1, unknown to sender S
r = (t1 - t0) * estimate of D’s speed
X
Y/D
r
SExpected Zone
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Slide 8.44Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Request Zone in LAR
Xr
S
Request Zone
Network Space
BA Y/D
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Slide 8.45Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Operation of LAR (1)
Only nodes within the request zone forward route requests
• Node A does not forward RREQ, but node B does
• Request zone explicitly specified in the route request• Each node must know its physical location to determine whether
it is within the request zone
Xr
S
BA
Request Zone
Y/D
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Slide 8.46Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Operation of LAR (1)
Only nodes within the request zone forward route requests
If route discovery using the smaller request zone fails to find a route, the sender initiates another route discovery (after a timeout) using a larger request zone
• the larger request zone may be the entire network
Rest of route discovery protocol similar to DSR (will be discussed later)
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Slide 8.47Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
LAR Variations: Adaptive Request Zone
Each node may modify the request zone included in the forwarded request
• Modified request zone may be determined using more recent information and may differ from original request zone
S
B
Request zone adapted by B
Request zone defined by sender S
Until now a route request explicitly specified a request zone
• Implicit Request Zone: A node X forwards a route request received from Y if node X is deemed to be closer to the expectedzone as compared to Y
• The motivation is to attempt to bring the route request physically closer to the destination node after each forwarding
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Slide 8.48Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Location-Aided Routing
The basic proposal assumes that, initially, location information for node X becomes known to Y only during a route discovery
• This location information is used for a future route discovery• Each route discovery yields more updated information which is
used for the next discoveryVariations
• Location information can also be piggybacked on any message from Y to X
• Y may also proactively distribute its location information
LAR Summary – Advantages• Reduces the scope of route request flood• Reduces overhead of route discovery
LAR Summary – Disadvantages• Nodes need to know their physical locations• Does not take into account possible existence of obstructions for
radio transmissions
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Slide 8.49Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
LAR-Optimization Query Localization
Limits route request flood without using physical information
• Route requests are propagated only along paths that are close tothe previously known route
• The closeness property is defined without using physical location information
Path locality heuristic: Look for a new path that contains at most k nodes that were not present in the previously known route
• Old route is piggybacked on a Route Request• Route Request is forwarded only if the accumulated route in the
Route Request contains at most k new nodes that were absent in the old route
• This limits propagation of the route request
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Slide 8.50Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
??
?
?
?
?
Outline
Selected Routing Protocols (2)
• Dynamic Source Routing (DSR)
• Location Aided Routing (LAR)• Optimized Links-State Routing (OLSR)
Performance Evaluation of Ad hoc Networks
• The Art of Performance Evaluation• Analyzing Ad hoc Network Performance
Summary and Conclusion
Appendix
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Slide 8.51Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
The Art of Performance Evaluation (1)
“That which is monitored improves.”
—unknown Source
The quotes in this lecture part are taken from [Jain1991]
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Slide 8.52Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
The Art of Performance Evaluation (2)
Basics Terms
• Performance Analysis = Analysis + Computer Systems
• System – any collection of hardware and software• Metrics – the criteria used to evaluate the system performance• Workloads – the requests made by the users of the system
Is performance analysis is an art?
• Successful evaluation cannot be produced mechanically• Every evaluation requires a large set of skills
• Given the same data, two analysts may interpret them differently
Example
• 2 systems, which one is the best?
• Throughputs of two systems A, B measured in transactions/second
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Slide 8.53Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
The Art of Performance Evaluation (3)
Possible Solutions
• (1) Compare the average: both systems are equal
• (2) Compare the ratio with system B as base
• (3) Compare the ratio with system A as base
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Slide 8.54Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Common Mistakes & How-to Avoid Them (1)
1. No Goals
2. Biased Goals
• Any endeavor without goals is bound to fail!
• There is no such thing as a general-purpose model!• Goals correct metrics, workloads, and methodology!
• “To show that OUR system is better than THEIRS” ?
• Analysts = Jury!
(Source www.zeit.de)
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Slide 8.55Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Common Mistakes & How-to Avoid Them (2)
3. Unsystematic Approach
4. Analysis without understanding the problem
5. Incorrect Performance Metrics
6. Unrepresentative Workload
… see Appendix for othercommon mistakes
3. Unsystematic Approach
• Arbitrary selection of workload Inaccurate conclusions!
4. Analysis without understanding the problem
• “A problem well stated is half solved”!
5. Incorrect Performance Metrics
• Chosen to be easily computed rather to be relevant?
6. Unrepresentative Workload
• Should represent the actualusage of the system!
(Source www.zeit.de)
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Slide 8.56Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
So Everything Went Wrong …
(Source www.zeit.de)
How-to do it correct from the beginning?
How to Analyze (Mobile Ad hoc) Networks?
Best practice, since there is no perfect solution!
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Slide 8.57Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Systematic Performance Evaluation
Again: systematic approach to performance evaluation
(adopted from [Jain1991])
1. The definition of the system (boundaries), goals, and services2. The selection of the performance metrics
3. The definition of the parameters to study4. The selection of the factors/elements of the parameter set5. The choice of the evaluation technique
6. The development of the model and selection of the workload7. The design and conducting of the individual experiments
8. The analysis and interpretation of the obtained data9. The presentation of the results
“Important Files”
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Slide 8.58Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Example: Ad hoc Network Performance
Scenario
??
?
??
?
Challenge
• Qualify and quantify the
effects of node misbehavior
on the overall performance of
the routing system
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Slide 8.59Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
2. Selection of the Performance Metrics (2)
What do we expect?
• Criteria to compare the performance (so-called metrics)
• Metrics relate to the speed,accuracy, and availability of services
Network size
Mobility
Avg.E2Edelay
RoutingMessages
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Slide 8.60Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
2. Selection of the Performance Metrics (3)
Some “realistic?” results
only useful in combination with
other metricsLeB
eP
e2003
PeR
oD
aM
A2001
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Slide 8.61Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
5. Choice of Evaluation Technique
• Real world observations• no large scale MANET, expensive, only deployed technologies
• Emulation / Testbed experiments • only small scale, expensive, complicated (modeling mobility?)
• Simulation studies • medium scale (~50-1000 nodes), restricted to chosen scenarios
• Analytical models • assume ideal protocols, mainly for capacity / connectivity on L2
Current investigation methods (boundaries not fix)
Abstraction Level vs. Generality of Results
Emulation(Testbed)
Analysis Simulation Real World
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Slide 8.62Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
System and Model
Real World
AnalysisSimulation
Emulation(Testbed)
Various degrees of abstraction
Observation
Workload CalculationsSimulation results
Measurements
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Slide 8.63Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Degrees of Abstraction (1)
Real World
Emulation(Testbed)
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Slide 8.64Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Degrees of Abstraction (2)
Abstraction Level vs. Generality of Results
Analysis Simulation Emulation(Testbed)
Real World
L5Application
Layer
L4Transport
Layer
L3Network
Layer
L2Data Link
Layer
L1Physical
Layer
L5Application
Layer
L4Transport
Layer
L3Network
Layer
L2Data Link
Layer
L1Physical
Layer
L5Application
Layer
L4Transport
Layer
L3Network
Layer
L2Data Link
Layer
L1Physical
Layer
L3Network
Layer
Scope of Modeling
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Slide 8.65Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
6. Workload
7. Design and Conducting of Experiment
“Would you tell me, please, which way I ought to go from here?”
“That depends a good deal on where you want to get to,” said the Cat.
“I don’t much care where —” said Alice.
“Then it doesn’t matter which way you go,” said the Cat.
— Lewis Carroll, Alice’s Adventures in Wonderland
Workload is crucial
• Services exercised, Level of detail• Representativeness, Timeliness
• Also consider load level!
Experimental Design
• Simple Designs (vary one factor at a time)
• Full/ Fractional Factorial Designs (utilizes full/partial combination of levels of all factors)
• How many experiments?• Given k factors,
with the i th factorhaving ni levels
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Slide 8.66Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
7. Design and Conducting of Experiments (2)
Workload inExample
• Moderate
• Artifical
• 8% of nodes are sources (random)
• We use constant bitrate traffic over UDP.
Factors that are kept constant (250 node setup)• Average node density = 9; Area = (2334m)2; Simulation time = 900s• Link layer = IEEE 802.11b with Distributed Coordination Function (DCF)• Network layer = Ad hoc On-demand Distance Vector Routing, IPv4 • Transport/Application layer = Constant Bit-Rate (CBR) flows over UDP
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Slide 8.67Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
8. Analysis and Interpretation of Data (1)
A man with one watch knows what time it is.
A man with two watches is never sure.
— Segal’s Law
Steps contd.
• The analysis only produces results and not conclusions• Based on these results the analysts/decision makers can draw
conclusions
• Outcomes of measurements/simulations are random quantities• They change with each replication
• Take into account the variability of the results
• Simply comparing the means can lead to inaccurate conclusions• Proper statistics are basis for a unbiased analysis
• Each analysts will probably draw different conclusions are giventhe same set of results …
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Slide 8.68Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
8. Analysis and Interpretation of Data (2)
2800500050008000
1000010000200006000075000
100000100000100000100000100000150000180000250000250000300000400000500000500000550000
15000001500000
17000000
“Then there is the man who drowned crossing a stream with an average depth of six inches.”
— W. I. E. Gates
Some statistics …
How many street lamps are operated in Frankfurt (am Main) …
• First guess vs. “educated” guess, N = 26 participants• The correct solution was ~ 64,000 to 65,000 (or 42 ;-)
• First guesses range from 2,800 to 17,000,000Mean = 914,454, 95% Confidence interval = +/- 437,160Median = 100,000, = 3,304,848
• Educated guesses range from 3,500 to 750,000Mean = 113,392, 95% Confidence interval = +/- 20,590Median = 57,500, = 155,656
32007000800015000200002000020000250003000040000400005000050000650008000099999100000100000100000125000200000200000200000300000300000750000
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Slide 8.69Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
8. Analysis and Interpretation of Data (4)
Tell me what you see:
(A)
(B)
(E)
(C)
(D)
(C)
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Slide 8.70Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
8. Analysis and Interpretation of Data (5)
Observations for Selfish Nodes
Packet loss increases …
• … nearly linearly with the number of selfish nodes
• … with node mobility
Routing overhead increases
15%42%
i.e. 40 out of 250 nodes
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Slide 8.71Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
8. Analysis and Interpretation of Data (6)
Observations for Black Holes
Successful communication only in close proximity
Packet loss …
• … is extremely high, even for few black holes• … increases with node mobility
49%78%
i.e. 10 out of 250 nodes
Increase inmalicious nodes
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Slide 8.72Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Closing the Art of Performance Evaluation
“Do not plan a bridge capacity by counting the number
of people who swim across the river today.”
—Heard at a presentation
The quotes in this lecture part are taken from [Jain1991]
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Slide 8.73Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
??
?
?
?
?
Outline
Selected Routing Protocols (2)
• Dynamic Source Routing (DSR)
• Location Aided Routing (LAR)• Optimized Links-State Routing (OLSR)
Performance Evaluation of Ad hoc Networks
• The Art of Performance Evaluation• Analyzing Ad hoc Network Performance
Summary and Conclusion
Appendix
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Slide 8.74Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Summary
Mobile ad hoc networks (MANET)
• Self-organizing, mobile and wireless nodes
• Absence of infrastructure, multi-hop routing necessary• Systems are both, terminals (end-systems) and routers (nodes)• Constraints (dynamics, energy, bandwidth, link asymmetry)
Characteristics include
• Mobility, wireless, application / traffic, and system characteristics
Routing is a central problem in ad hoc networks
• A large set of routing protocols exists• Open issues persist: QoS, Security, Scalability, Heterogeneity, …
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Slide 8.75Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Taxonomy of Routing Protocols
• The above mentioned protocols are only a selection!
• AODV, DSR, OLSR, and TBRPF are currently moved towards Experimental RFC (within IETF)
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Slide 8.76Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Some Routing Protocols / Frameworks
AODV - Ad Hoc On Demand Distance Vector (Perkins, NOKIA; Belding-Royer, UCSB; Das, UC)
CEDAR - Core-Extraction Distributed Ad Hoc Routing
DREAM - Distance Routing Effect Algorithm for Mobility
DSDV - Destination-Sequenced Distance Vector
DSR - Dynamic Source Routing (Johnson, CMU)
FSR - Fisheye State Routing
LANMAR - Landmark Ad Hoc Routing
LAR - Location Aided Routing
OLSR - Optimized Link State Routing (Clausen, Jacquet, INRIA)
TBRPF - Topology Broadcast based on Reverse-Path Forwarding (Ogier,Templin, SRI)
Tora / IMEP - Temporally-Ordered Routing Algorithm / InternetManet Encapsulation Protocol
ZRP - Zone Routing Protocol (Haas, Cornell)
… see also http://www.wikipedia.org/wiki/Ad_hoc_protocol_list
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Slide 8.77Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Mobile Ad Hoc Network = MANET = Manet?
There is even more to the name MANET
• Édouard Manet (1832 – 1883)
• “Godfather” of impressionisms
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Slide 8.78Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Acknowledgements
Acknowledgements for inspirations to the ad hoc tutorial go to:
• N. Vaidya @ UIUC
• C. Perkins @ Nokia• S. Corson @ UMD• P.R. Kumar @ UIUC• D. Johnson @
• Zhenqiang Ye @ UCR
• Raj Jain @ Ohio State • Jens Schmitt @ Universität Kaiserslautern• A. Wolisz @ TU Berlin
• Matthias Kropff @ KOM, TUD• The other colleagues of the Mobile Networking Group @ KOM
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Slide 8.79Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Contact – Feedback
Prof. Dr.-Ing. Ralf Steinmetz
Dept. of Electrical Engineering and Information TechnologyMultimedia Communications Lab · KOM
Merckstr. 25 · 64283 Darmstadt · GermanyPhone (+49) 6151 – 16 6150Fax (+49) 6151 – 16 [email protected]://www.kom.tu-darmstadt.de
Matthias Hollick
Mobile Networking
Dept. of Electrical Engineering and Information TechnologyMultimedia Communications Lab · KOM
Merckstr. 25 · 64283 Darmstadt · GermanyPhone (+49) 6151 – 16 6158Fax (+49) 6151 – 16 [email protected]://www.kom.tu-darmstadt.de
Further information• http://www.kom.tu-darmstadt.de
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Slide 8.80Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
??
?
?
?
?
Outline
Selected Routing Protocols (2)
• Dynamic Source Routing (DSR)
• Location Aided Routing (LAR)• Optimized Links-State Routing (OLSR)
Performance Evaluation of Ad hoc Networks
• The Art of Performance Evaluation• Analyzing Ad hoc Network Performance
Summary and Conclusion
Appendix
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Slide 8.81Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Appendix: Additional Readings (1)
Research Papers
• See course download page for selected research papers
• Laura M. Feeney, A Taxonomy for Routing Protocols in Mobile
Ad Hoc Networks, Technical Report 1999• Young Bae-Ko and Nitin Vaidya, Location-Aided Routing (LAR)
in Ad Hoc Networks, Infocom 1998
IETF Standardization
• MANET WG http://www.ietf.org/html.charters/manet-charter.html
• AODV: http://www.ietf.org/rfc/rfc3561.txt• DSR: http://www.ietf.org/internet-drafts/draft-ietf-manet-dsr-10.txt• OLSR: http://www.ietf.org/rfc/rfc3626.txt• TBRPF: http://www.ietf.org/rfc/rfc3684.txt
• The papers/standards are not mandatory for the course but you might find them interesting
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Slide 8.82Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Appendix: Additional Readings (2)
Books
• Raj Jain: "The Art of Computer Systems Performance Analysis:
Techniques for Experimental Design, Measurement, Simulation,
and Modeling" (ISBN 0-471-50336-3)
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Slide 8.83Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Common Mistakes & How-to Avoid Them (2)
3. Unsystematic Approach
4. Analysis without understanding the problem
5. Incorrect Performance Metrics
6. Unrepresentative Workload
… see Appendix for othercommon mistakes
3. Unsystematic Approach
• Arbitrary selection of workload Inaccurate conclusions!
• Systematic approach is key to solve performance problem!
4. Analysis without understanding the problem
• The “world” model is the goal No!• “A problem well stated is half solved”!
5. Incorrect Performance Metrics
• Chosen to be easily computed rather to be relevant?
6. Unrepresentative Workload
• Should represent the actualusage of the system!
(Source www.zeit.de)
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Slide 8.84Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Common Mistakes & How-to Avoid Them (3)
7. Wrong Evaluation Technique
8. Overlooking Important Parameters
9. Ignoring Significant Factors
10. Inappropriate Experimental Design
11. Inappropriate Level of Detail
7. Wrong Evaluation Technique
• Use the technique you know best vs. the appropriate one?
• Methods are measurement, (emulation), simulation, analysis!
8. Overlooking Important Parameters
• Just do it?• Make a list of all system/workload characteristics!
9. Ignoring Significant Factors
• Vary only well-understood parameters?• Use the factors that impact the performance most!
10. Inappropriate Experimental Design
• Naïve: each factor changed one by one cross-influences?• Improper selection Waste of time!
11. Inappropriate Level of Detail
• Too narrow vs. too broad …
• Slight variations to study detailed model!
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Slide 8.85Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Common Mistakes & How-to Avoid Them (4)
12. No (bad) Analysis
13. Erroneous Analysis
14. No Sensitivity Analysis
15. Ignoring Errors in Input
16. Improper Treatment of Outliers
12. No (bad) Analysis
• Measure, measure more, ... you’ve just produced tons of data!
• Produce summary, include analysis + measurement background!
13. Erroneous Analysis
• Average of ratios (example earlier)?• Too short simulations?
14. No Sensitivity Analysis
• Fact vs. evidence! very much depends on workload!• Clarify relative importance of parameters!
15. Ignoring Errors in Input
• Uncertainty because of inaccurate measurements?• Biased input?
16. Improper Treatment of Outliers
• Too high or too low values? real system phenomenon or outlier needs to be clarified!
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Slide 8.86Matthias Hollick, Ralf Steinmetz, Mobile Networking (WS2004/2005)05. Jan. 2005
Common Mistakes & How-to Avoid Them (5)
17. Assuming No Change in the Future
18. Ignoring Variability
19. Too Complex Analysis
20. Improper Presentation of Results
21. Ignoring Social Aspects
22. Omitting Assumptions and Limitations
17. Assuming No Change in the Future
• Future is same as past? carefully limit assumptions!
18. Ignoring Variability
• Analyze only the mean performance?• E.g. take only daily average of load demands if peak hours exist?
19. Too Complex Analysis
• Reality: the more complex the model the “easier” to publish …
• Simple models are beneficial for day-to-day purposes!
20. Improper Presentation of Results
• Right metric to measure performance of analyst is not number of analyses performed but number of helpful analyses!
21. Ignoring Social Aspects
• Underestimation of presentation? social skills important!
22. Omitting Assumptions and Limitations
• Missing assumptions in report? results are falsely transferred!