Transcript Dynamic Source Routing in Ad

Mobile Ad-hoc Networks
-- Overview and a case study
Yinzhe Yu
Oct. 8, 2003
Contents
Introduction on MANET
Recent research topics
Case study: Dynamic Source Routing
What is a MANET ?
Mobile nodes, wireless links
Infrastructure-less: by the nodes,…
Multi-hop routing: …,and for the nodes
Minimal administration: no hassles
Application Example – The Simpson's
Be home early,
Homer.
Hi, Marge.
I miss you.
Dad, you can use
Nelson if I am
too fast.
Yes. What are
you doing,
Nelson?
I can hear u, Lisa.
Can u hear me?
Hmm, A MANET
makes sense.
Why a MANET?
Fast deployment of ad-hoc networks
Special events/conference, military
combat/emergency rescue
What about also cheaper ?
sensor dust, home networking
What’s unique about a MANET ?
Moving nodes  ever changing topology
Wireless links
 various and volatile link quality
Pervasive (cheap) devices
 Power constraints
Security
 Confidentiality, other attacks
MANET Protocol Zoo
Topology based routing
Proactive approach, e.g., DSDV.
Reactive approach, e.g., DSR, AODV, TORA.
Hybrid approach, e.g., Cluster, ZRP.
Position based routing
Location Services:
DREAM, Quorum-based, GLS, Home zone etc.
Forwarding Strategy:
Greedy, GPSR, RDF, Hierarchical, etc.
Recent Research Topics
Routing
Better metric, higher throughput
A high-throughput path metric for multi-hop wireless routing. MobiCom 03.
Transport Layer
TCP performance: throughput, fairness, etc.
Enhancing TCP fairness in ad-hoc networks using neighborhood RED. MobiCom 03.
Improving fairness among TCP flows crossing wireless ad-hoc and wired networks.
MobiHoc 03.
MAC Layer
MAC protocol for directional antennas
A MAC protocol for full exploitation of directional antennas in ad-hoc wireless
networks. MobiHoc 03.
Recent Research Topics (cont.)
Security
Reliable routing against malicious nodes
Ariadne: A secure on-demand routing protocol for ad-hoc networks. MobiCom 2002.
Power Management
Power saving and power control
Asynchronous wakeup for ad hoc networks. MobiHoc 2003.
A power control MAC protocol for ad hoc network. MobiCom 2002.
A Case study: Dynamic Source Routing
On-demand
Source Routing
Route Discovery
Route Request
Route Reply
Route Maintenance
Assumption:
Cooperative nodes
Relatively small network diameter (5-10
hops)
Detectable packet error
Unidirectional or bidirectional link
Promiscuous mode (optional)
Route Discovery
B
RREQ FORMAT
Initiator ID
A-B-D-G
A-B-D-G
Initiator seq#
G
Target ID
A-B
A
A-B-D-G
A-B-D
D
A
Partial route
A-C-E
A
H
E
A-B-C
A-C-E
A-C-E
C
A-C
Route Request (RREQ)
A-B-C
F
Route Reply (RREP)
Route Discovery is issued with exponential back-off intervals.
Route Discovery: at source A
A need to send to G
Lookup Cache for route A to G
Start Route
Discovery
Protocol
wait
Route
Discovery
finished
no
Buffer
packet
Continue
normal
processing
Route
found
?
yes
yes
Packet
in
buffer
?
Write route in
packet header
no
don
e
Send
packet to
next-hop
Route Discovery: At an intermediate node
<src,id> in
recently
seen
requests
list?
Accept route
request
packet
yes
Discard
route
request
no
Host’s
address
already in
patrial
route
Append
myAddr to
partial route
Store <src,id>
in list
Broadcast packet
no
no
myAdd
r=targ
et
yes
Send route
reply packet
done
yes
Discard
route
request
Route Maintenance
B
RERR
RERR
G
D
G
A
Route Cache (A)
G: A, B, D, G
G: A, C, E, H, G
F: B, C, F
H
E
C
F
Additional feature #1: Caching Overheard Routes
Node C Cache
E:
E:C,
C,D,
D,EE
A: C, B, A
Z: C, X, Y, Z
V: C, X, W, V
Node A Cache
E: A, B, C, D, E
A
B
C
D
E
V
W
X
Y
Z
Additional feature #2: RREP with Cached Routes
B
RERR
RERR
RREQ
(! D-G)
D
G
A
Route Cache (A)
G: A, B, D, G
F: B, C, F
G:A,C,E,H,G
RREQ
(! D-G)
RREQ
(! D-G)
H
E
RREP
C
Route Cache (C)
G: C, E, D,
H, G
F
Additional feature #3: Packet Salvage
B
RERR
RERR
G
D
A
G
Route Cache (D)
G: D, E, H, G
H
E
C
F
Caution: No double salvage allowed !!!
A Summary of DSR
Entirely on-demand, potentially zero control message
overhead
Trivially loop-free with source routing
Conceptually supports unidirectional links as well as
bidirectional links
High packet delays/jitters associated with on-demand
routing
Space overhead in packets and route caches
Promiscuous mode operations consume excessive
amount of power