Dynamic Source Routing DSR

1
Dynamic Source Routing (DSR)

• Sandeep Gupta
• M.Tech - WCC

2
Overview

• Used in multihop wireless ad-hoc networks
• Completely self-organizing and self-configuring
• Completely On-Demand
• Composed of two mechanisms Route Discovery
  Route Maintenance

3
Assumptions

• All nodes willing to forward packets
• Diameter of network will often be small ( 5 to 10
  hops)
• Nodes can detect errors discard packets
• Nodes move at a moderate speed
• Unidirectional links may be present
• Each node has single IP address

4
Route Discovery
A
A,B
A,B,C
A,B,C,D
A
B
C
D
E

• Source checks route cache for route to
  destination
• If no route available, source transmits ROUTE
  REQUEST

5
Route Discovery
A
A,B
A,B,C
A,B,C,D
A
B
C
D
E

• ROUTE REQUEST gets propagated in the network
• When it finally reaches destination, it sends
  ROUTE REPLY using same or different path

6
Route Discovery
A
A,B
A,B,C
A,B,C,D
A
B
C
D
E

• Destination may piggyback other data like TCP SYN
  with ROUTE REPLY

7
Route Maintenance
A
B
C
D
E

• Each node originating or forwarding a packet
  confirms receipt of packet by next hop
• Link Level ack
• Passive ack
• Software ack

8
Route Maintenance
A
B
C
D
E

• If receipt is not confirmed, ROUTE ERROR is sent
  to original sender
• Sender removes this broken link, leaving
  retransmission to upper layers

9
Route Maintenance
A
B
C
D
E

• When retransmitting, sender may use another route
  to destination in its cache or starts a fresh
  route discovery

10
Route Discovery Additional Features

• Caching overheard routing information
• Replying to ROUTE REQUEST using cached routes
• ROUTE REQUEST hop limit
• Preventing ROUTE REPLY storms

11
Preventing ROUTE REPLY storm
C
D
A
B
G
E
F

• Delay d H x (h 1 r)
• h length of number of hops
• r random no. between 0 1
• H small constant delay

12
Route Maintenance Additional Features

• Packet salvaging
• Automatic route shortening (gratuitous ROUTE
  REPLY)
• Piggybacking ROUTE ERROR message in next ROUTE
  REQUEST

13
Support for Heterogeneous Networks Mobile IP
4
1
1
2
2
A
B
C
D

• Each interface is assigned a unique identifier
• Routes include Node address interface ID
• IF_INDEX_MA IF_INDEX_ROUTER indexes are used
  for Mobile IP support

14
Simulation results
50 nodes with 20 active connections Simulation
length in seconds 19.84 Number of nodes
50 Number of sending nodes 47 Number of
receiving nodes 50 Number of generated packets
3481 Number of sent packets 3414 Number of
forwarded packets 0 Number of dropped packets
1206 Number of lost packets 0 Minimal packet
size 28 Maximal packet size 644 Average packet
size 83.0361 Number of sent bytes 359450 Number
of dropped bytes 135396
50 nodes with 10 active connections Simulation
length in seconds 19.49 Number of nodes
50 Number of sending nodes 41 Number of
receiving nodes 50 Number of generated packets
2295 Number of sent packets 2283 Number of
forwarded packets 0 Number of dropped packets
810 Number of lost packets 0 Minimal packet
size 28 Maximal packet size 612 Average packet
size 82.5206 Number of sent bytes 231830 Number
of dropped bytes 103914
15
Conclusion

• Dynamic Source Routing adapts quickly to
  routing changes when node movement is frequent,
  yet requires little or no overhead during periods
  in which nodes move less frequently. Though DSR
  overhead increases when traffic is heavy or
  number of nodes are more but this should still be
  less compared to distance vector protocols like
  DSDV where a complete picture of the whole
  network is present at every node even though it
  might not require it.

16
References

• Ad Hoc Networking, Edited by Charles E Perkins,
  Addison-Wesley
• 1st sem project report - Simulating IEEE 802.11
  with Dynamic Source Routing (DSR) in NS