A Study of Link Buffering for OLSR Masato Goto, Sota Yoshida, - - PowerPoint PPT Presentation

▶
a study of link buffering for olsr
SMART_READER_LITE
LIVE PREVIEW

A Study of Link Buffering for OLSR Masato Goto, Sota Yoshida, - - PowerPoint PPT Presentation

Sep 28, 2023 9 likes •219 views

1 A Study of Link Buffering for OLSR Masato Goto, Sota Yoshida, Kenichi Mase, and Thomas Clausen Graduate School of Science and Technology Niigata University, JAPAN 04/09/30 Niigata University OLSR WorkShop in San Diego 2 Outlines

slide-1
SLIDE 1

04/09/30 OLSR WorkShop in San Diego

Niigata University

1

A Study of Link Buffering for OLSR

Masato Goto, Sota Yoshida, Kenichi Mase, and Thomas Clausen

Graduate School of Science and Technology Niigata University, JAPAN

slide-2
SLIDE 2

04/09/30 OLSR WorkShop in San Diego

Niigata University

2

Outlines

  • Background
  • Introduction of an extension for OLSR

– Link Buffering – Packet Restoration

  • Performance evaluation
  • Conclusion
  • Future work
slide-3
SLIDE 3

04/09/30 OLSR WorkShop in San Diego

Niigata University

3

Background

  • The hello-based detection of link disconnection is not enough

quick as required and it is difficult to keep accurate link information under high mobility environments.

  • Link layer notification method is defined as one of the methods

to detect link disconnection as fast as possible.

  • In high-mobility, high-density and high-loaded ad hoc networks,

it is difficult to keep high performance even if only link layer notification is used.

  • In order to improve performance in such a environment, we

propose an extension of OLSR. Degradation of packet delivery ratio

slide-4
SLIDE 4

04/09/30 OLSR WorkShop in San Diego

Niigata University

4

Link Layer Notification

Data Packet ACK

Node: A Node: B

  • Link layer notification is described

in section 13 of RFC 3626.

  • How is link disconnection detected ?

– When not receiving CTS after sending RTS. – When not receiving ACK after sending a data packet.

RTS CTS

slide-5
SLIDE 5

04/09/30 OLSR WorkShop in San Diego

Niigata University

5

Extension for OLSR

  • The

extension includes two mechanisms: – Link buffering – Packet restoration

  • They are used together with link layer

notification, that informs detection of link disconnection to upper layers.

slide-6
SLIDE 6

04/09/30 OLSR WorkShop in San Diego

Niigata University

6

Link Buffering (1/5)

When link disconnection is detected by link layer notification, the node conducts two actions. Action 1: The node changes all routes using the disconnected link to route_invalid state. Action 2: The node updates the neighbor table and routing table.

slide-7
SLIDE 7

04/09/30 OLSR WorkShop in San Diego

Niigata University

7

Link Buffering (2/5) Action 1

valid 5 7 valid 10 4 valid 5 3 State Next Hop Destination

  • Normally, a route entry is in the route_valid state.
  • When a node is informed of link disconnection, it changes

all routes using same next hop to route invalid state.

5

invalid invalid

slide-8
SLIDE 8

04/09/30 OLSR WorkShop in San Diego

Niigata University

8

Link Buffering (3/5) Action 2

Invalid

6 7 valid 10 4

invalid

5 3 State Next Hop Destination 6 7 5 No route valid

slide-9
SLIDE 9

04/09/30 OLSR WorkShop in San Diego

Niigata University

9

Link Buffer (4/5) Data packet forwarding

Packets

When a node receives a data packet, it behaves differently according to the route entry and its status.

  • No_route
  • Route_valid
  • Route_invalid

Stores in the link buffer

Forwards to next hop

Discards

slide-10
SLIDE 10

04/09/30 OLSR WorkShop in San Diego

Niigata University

10

Link Buffering (5/5)

  • Route state transition occurs in following cases:

– When a node receives control packets. – When a node is informed of link disconnection.

  • The node forwards all packets destined to a destination in the

link buffer if the route’s state changes to route_valid.

  • If a route for the destination is not updated within

BUFFERING_TIME, the node discards all packets destined to the destination in the link buffer and deletes the route entry in the routing table.

slide-11
SLIDE 11

04/09/30 OLSR WorkShop in San Diego

Niigata University

11

Packet Restoration

34

Next hop 6 Next hop 6 Next hop 27 Next hop 34 Next hop 34

MAC Queue ........

Next hop 34

  • The node doesn’t drop the packet with same

next hop in MAC queue.

  • The node repeats wasteful data transmission

to disconnected link.

  • Simple restoration
  • Full restoration
slide-12
SLIDE 12

04/09/30 OLSR WorkShop in San Diego

Niigata University

12

Simple Restoration

34

Next hop 6 Next hop 6 Next hop 27 Next hop 34 Next hop 34

MAC Queue ........ .....

Next hop 34

link buffer

Next hop 34

Packet Clearance

slide-13
SLIDE 13

04/09/30 OLSR WorkShop in San Diego

Niigata University

13

Full Restoration

Next hop 6 Next hop 6 Next hop 27 Next hop 34 Next hop 34 Next hop 34

MAC Queue ........ ..... link buffer 34

Next hop 34 Next hop 34 Next hop 34

slide-14
SLIDE 14

04/09/30 OLSR WorkShop in San Diego

Niigata University

14

Table 1: Simulation model and parameters

CBR: 4 packets /sec, 64 [byte] Traffic type 50 MAC queue size IEEE802.11 MAC protocol Random way point, Pause time = 0 [sec] Mobility model 11 Mbps Bandwidth 100 [m] Power range Two-ray ground Propagation model 100 Number of nodes 300 × 1500 [m] Terrain range 900 [sec] Simulation time

Value Parameter

slide-15
SLIDE 15

04/09/30 OLSR WorkShop in San Diego

Niigata University

15

Table 2: Parameters of OLSR and Link buffering

3 [sec] BUFFERIUNG_TIME Unlimited Link buffer size 3 [sec] Holding time of topology information 1 [sec] Holding time of neighbor information 1 [sec] TC interval 1 [sec] Hello interval

Value Parameter

slide-16
SLIDE 16

04/09/30 OLSR WorkShop in San Diego

Niigata University

16

Various version of OLSR

  • OLSR-C: OLSR with packet clearance.
  • OLSR-SB: OLSR with packet clearance and link

buffer.

  • OLSR-SR: OLSR with packet clearance, link

buffer and simple restoration.

  • OLSR-FR: OLSR with packet clearance, link

buffer and full restoration.

slide-17
SLIDE 17

04/09/30 OLSR WorkShop in San Diego

Niigata University

17

20 30 40 50 60 5 10 15 20 25 30 35 40 45 50 Number of flows Packet delivery ratio [%] OLSR-FR OLSR-SR OLSR-LB OLSR-C

  • Fig. 1 Packet delivery ratio with 100 nodes and 20~40 m/s.
slide-18
SLIDE 18

04/09/30 OLSR WorkShop in San Diego

Niigata University

18

  • Fig. 2 Packet delivery time with 100 nodes and 20~40 m/s.

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 5 10 15 20 25 30 35 40 45 50 Number of flows Packet delivery time [s]

OLSR-FR OLSR-SR OLSR-LB OLSR-C

slide-19
SLIDE 19

04/09/30 OLSR WorkShop in San Diego

Niigata University

19

  • Fig. 3 Packet delivery time with 100 nodes and 30 flows.

20 30 40 50 60 70 80 5-10 10-20 20-40 30-60

Node speed [m/s] Packet delivery ratio [%]

OLSR-FR OLSR-SR OLSR-LB OLSR-C

slide-20
SLIDE 20

04/09/30 OLSR WorkShop in San Diego

Niigata University

20

  • Fig. 4 Packet delivery time with 100 nodes and 30 flows.

0.1 0.2 0.3 0.4 0.5 0.6 0.7 5-10 10-20 20-40 30-60

Node speed [m/s] Packet delivery time [s]

OLSR-FR OLSR-SR OLSR-LB OLSR-C

slide-21
SLIDE 21

04/09/30 OLSR WorkShop in San Diego

Niigata University

21

  • We need to evaluate the performance of OLSR in various

environment (low mobility).

  • We need to improve the mechanism how to retransmit the

packet in link buffer.

Conclusion

  • We proposed “Link buffering” and “Packet restoration”,

which are used with link layer notification and evaluated their performance.

  • OLSR-LB has little effect when node density is relatively

high, since a new route can be instantly recalculated in OLSR when link disconnection is detected.

  • OLSR-SR and OLSR-FR significantly outperform OLSR

without link buffering and packet restoration.

Future work