1. Mobile and Wireless Networking
Lecture 19 Dr. Xinbing Wang

2. AODV: Summary Routes need not be included in packet headers
Nodes maintain routing tables containing entries only for routes that are in active use
At most one next-hop per destination maintained at each node
DSR may maintain several routes for a single destination
Sequence numbers are used to avoid old/broken routes
Sequence numbers prevent formation of routing loops
Unused routes expire even if topology does not change
Dr. Xinbing Wang

3. Part 4: Other Wireless Networks
Ad hoc networks
Mobility and routing
Flooding routing algorithm
Dynamic source routing (DSR)
Ad hoc On-Demand Distance Vector Routing (AODV)
Location-Aided routing (LAR)
Quality of Service (QoS) in ad hoc networks
Sensor networks
Wireless PANs
Dr. Xinbing Wang

4. Location-Aided Routing (LAR) [Ko98Mobicom]
Exploits location information to limit scope of route request flood
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
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
Dr. Xinbing Wang

5. Expected Zone in LAR X = last known location of node D, at time t0
Y = location of node D at current
time t1, unknown to node S
r = (t1 - t0) * estimate of D’s speed X r Y
Expected Zone
Dr. Xinbing Wang

6. Request Zone in LAR Network Space Request Zone X r B A Y S
Dr. Xinbing Wang

7. LAR: Route Request
Only nodes within the request zone forward route requests
Node A does not forward RREQ, but node B does (see previous slide)
Request zone explicitly specified in the route request
Each node must know its physical location to determine whether it is within the request zone
Dr. Xinbing Wang

8. LAR: Route Discovery
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
Dr. Xinbing Wang

9. 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/accurate information, and may be smaller than the original request zone B S
Request zone adapted by B
Request zone defined by sender S
Dr. Xinbing Wang

10. LAR Variations: Implicit Request Zone
In the previous scheme, a route request explicitly specified a request zone
Alternative approach: A node X forwards a route request received from Y if node X is deemed to be closer to the expected zone as compared to Y
The motivation is to attempt to bring the route request physically closer to the destination node after each forwarding
Dr. Xinbing Wang

11. Part 4: Other Wireless Networks
Ad hoc networks
Mobility and routing
Flooding routing algorithm
Dynamic source routing (DSR)
Ad hoc On-Demand Distance Vector Routing (AODV)
Location-Aided routing (LAR)
Quality of Service (QoS) in ad hoc networks
Sensor networks
Wireless PANs
Dr. Xinbing Wang

12. Motivation Mobile ad hoc networks & QoS:
Limited wireless resources: low-capacity
Mobility: time-varying topology
Lack of infrastructure: fully-distributed
Low-capacity time-varying resources with a fully mobile infrastructure
Dr. Xinbing Wang

13. QoS Definition in MANETs
Has to be redefined !
To provide a set of parameters in order to adapt application to the quality of network while routing through the network
e.g. Adaptive application, and soft QoS
Parameters should represent:
available resources: low-capacity
stability of resources: time-varying topology
Protocols should be:
Adaptive: fully mobile infrastructure & low-capacity time-varying topology and resources
Dr. Xinbing Wang

14. A Cross-Layer QoS Model
A cross-layer model to deploy QoS:
ALMs-- Application Layer Metrics
NLMs-- Network Layer Metrics
MLMs-- MAC Layer Metrics
MLMs & NLMs determine the quality of links to generate paths with good quality
ALMs select one path which is more likely to meet application requirements
Adapt to the network quality if needed
Dr. Xinbing Wang

15. Parameters class I, delay class II, throughput class III, B-E
power level
buffer level
stability level
link SINR
At application layer
At network layer
At MAC layer
Dr. Xinbing Wang

16. Architecture Application Layer Metrics Network Layer Metrics
MAC
App. Requirement
QoS Class
D T B-E
Application Layer Metrics
Network Quality:
Stability/
Power/buffer
Network Layer Metrics
Link Quality:
Link SINRs
MAC Layer Metrics
Protocol Stack
QoS Extension
Dr. Xinbing Wang

17. Example: SWAN
SWAN: Service Differentiation in Stateless Wireless Ad Hoc Networks
General Idea:
Probe for bandwidth
Admit (or not) traffic as real time at source
Best Effort traffic rate controlled
Violation signaled via ECN (explicit congestion notification)
Design Philosophy
Stateless
Use existing best-effort MAC (in worst case)
Distributed control
Dr. Xinbing Wang

18. SWAN Architecture
Source: [2]
Dr. Xinbing Wang

19. Differentiated Services & ECN Fields in IP
| DS FIELD, DSCP | ECN FIELD |
DSCP: Differentiated Services Codepoint
ECN: Explicit Congestion Notification
Codepoint for the best effort packets is '000000‘
Codepoint for real time MUST be assigned.
Source: [1]
Dr. Xinbing Wang

20. Bandwidth Probe Message
| Type | PROBE ID | Bottleneck Bandwidth
| Source IP Address
| Destination IP Address
Source: [1]
Type 0 (Bandwidth Probe Request)
1 (Bandwidth Probe Reply)
2 (Regulate Message with Source based Algorithm)
3 (Regulate Message with Network based Algorithm)
PROBE ID Sequence number for probe
Bottleneck Bandwidth
Bandwidth (Kbps) along path. Updated by node if
bandwidth at that node is < existing value
Hop-by-hop – uses existing MANET route or initiates
on-demand routing
Dr. Xinbing Wang

21. Admission Control Solely at source nodes For Real Time flows (UDP)
Uses Bandwidth Probe
Each node knows real-time traffic bandwidth by eavesdropping
Bavailable < Bthresh – Bcurrent
Dr. Xinbing Wang

22. Rate Control of Best Effort Traffic
Best Effort traffic is rate controlled to ensure bandwidth available for Real Time traffic and keep total below threshold
Independently done at each node
AIMD (Additive Increase and Multiplicative Decrease):
Increase best-effort rate by C every T until
Delay > D is detected (MAC Feedback)
Then reduce rate R%
See more parameter info in:
G.-S. Ahn, A. T. Campbell, Andras Veres and Li-Hsiang Sun, "Supporting Service Differentiation for Real-Time and Best Effort Traffic in Stateless Wireless Ad Hoc Networks (SWAN)", IEEE Transactions on Mobile Computing, September 2002.
Dr. Xinbing Wang

23. ECN Regulation of Real Time Traffic
Each node monitors rt utilization
When overload noted, mark ECN in real-time traffic before sending to destination
Destination sends regulate message
Control message causes real-time traffic to re-probe and re-admit…
…Or NOT!!!!
Dr. Xinbing Wang

24. Problem 1 – False Admission
Reply1 bb=10
Probe1 10
Reply1 bb=10
Probe1 bb=10
Probe1 bb=10
Reply1 bb=10 10 10 A
Reply2 bb=10
Probe2 bb=10
Probe2 bb=10
Reply2 bb=10 10
Reply2 bb=10
Probe2 R
Bavailable =10
Bavailable =10 B
Bavailable =0
Bavailable =0
Dr. Xinbing Wang

25. Problem 1 – False Admission
Regulate 1 10
ECN 10
ECN 10 1 10
Regulate1,
Regulate 2
Regulate1,
Regulate 2
Regulate 2 D 2
Dr. Xinbing Wang

26. Problem 2 – How to mark ECN
WHEN a violation occurs
IF all flows packets marked ECN
THEN all re-probe at about the same time
Potential for massive, synchronized false admissions
Dr. Xinbing Wang

27. Solutions Source-Based Regulation Algorithm
All real-time packets marked ECN
Source waits random time before re-probing
Network-Based Regulation Algorithm
DON’T mark all packets
Mark a random “congested set” of sessions
Mark sessions for T seconds, then pick another set
Dr. Xinbing Wang

28. Simulation Results (ns-2)
1500m x 300m
AODV
50 Nodes
2-5 hops / flow
Traffic:
5x (+/-) FTP – infinite
5x (+/-) Web – pareto
4x VoIP – 32KBps CBR
4x Video – 200KBps CBR
Random Waypoint (up to 72km/h)
Real-time delay
TCP “Goodput”
Source: [3]
Dr. Xinbing Wang

29. Questions How a MANET node connects to the Internet?
How to find an Internet Gateway?
What issues to concern for interworking security?
QoS support for MANET and the Internet convergence.
Dr. Xinbing Wang

30. References
[1] G-S. Ahn, A. T. Campbell, A. Veres, L. Sun, "SWAN", Internet Draft, draft-ahn-swan-manet-00.txt, MANET Working Group Internet Draft, October 2002.
[2] G-S. Ahn, A. T. Campbell, A. Veres, L. Sun, "Supporting Service Differentiation for Real-Time and Best Effort Traffic in Stateless Wireless Ad Hoc Networks (SWAN)," IEEE Transactions on Mobile Computing, September 2002.
[3] G-S. Ahn, A. T. Campbell, A. Veres, L. Sun, "SWAN: Service Differentiation in Stateless Wireless Ad Hoc Networks," Precedings of IEEE INFOCOM '02, 2002.
Dr. Xinbing Wang