reactive proactive protocols l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Reactive & proactive protocols PowerPoint Presentation
Download Presentation
Reactive & proactive protocols

Loading in 2 Seconds...

play fullscreen
1 / 42

Reactive & proactive protocols - PowerPoint PPT Presentation


  • 347 Views
  • Uploaded on

Reactive & proactive protocols. Reactive protocols Dynamic Source Routing (DSR) [Johnson96] Ad Hoc On-Demand Distance Vector Routing (AODV) [Perkins99Wmcsa] Link reversal algorithm [Gafni81] Proactive protocols Optimized Link State Routing (OLSR) [Jacquet00ietf,Jacquet99Inria]

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Reactive & proactive protocols' - elina


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
reactive proactive protocols
Reactive & proactive protocols
  • Reactive protocols
    • Dynamic Source Routing (DSR) [Johnson96]
    • Ad Hoc On-Demand Distance Vector Routing (AODV) [Perkins99Wmcsa]
    • Link reversal algorithm [Gafni81]
  • Proactive protocols
    • Optimized Link State Routing (OLSR) [Jacquet00ietf,Jacquet99Inria]
    • Destination-Sequenced Distance-Vector (DSDV) [Perkins94Sigcomm]
link reversal algorithm motivation
Link reversal algorithm: motivation
  • Find alternative routes when primary route fails
  • Desired properties
    • not by flooding
    • distributed algorithm
    • loop free
problem statement
Problem statement
  • single destination (can be relaxed)
  • links are bi-directional
  • but assume directions
    • routes from sources to destination: acyclic directed graph (ADG)
  • destination oriented ADG
    • every source has a route to destination
  • destination disoriented ADG
  • original graph: connected, destination oriented
  • problem: given a destination disoriented ADG, how to reverse link directions to get a destination oriented ADG?
problem illustration ii
Problem illustration (II)

A

B

F

Links are bi-directional

But algorithm imposes

logical directions on them

C

E

G

Maintain a directed acyclic

graph (DAG) for each

destination, with the destination

being the onlysink

This DAG is fordestination

node D

D

problem illustration iii
Problem illustration (III)

A

B

F

C

E

G

Link (G,D) broke

D

  • Node G has no outgoing links
  • Only C has route to D
two algorithms
Two algorithms
  • Full reversal
  • Partial reversal
  • both runs in iterations, stop when all nodes (excluding sink) has at least one outgoing link (why?)
full reversal
Full reversal

A

B

F

C

E

G

Link (G,D) broke

D

Any node, other than the destination, that has no outgoing links

reverses all its incoming links.

Node G has no outgoing links

full reversal9
Full reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Now nodes E and F have no outgoing links

full reversal10
Full reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Now nodes B and G have no outgoing links

full reversal11
Full reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Now nodes A and F have no outgoing links

full reversal12
Full reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Now all nodes (other than destination D) have an outgoing link

full reversal13
Full reversal

A

B

F

C

E

G

D

DAG has been restored with only the destination as a sink

full reversal discussion
Full reversal discussion
  • Will it ever stop?
  • Is it loop free?
  • Is it flooding?
  • If the graph is connected, then full reversal terminates after a finite # of iterations.
  • Directed graph at each iteration is a acyclic.
  • The direction of any link between two nodes that have a direct path to the destination in the initial ADG will never be reversed.
partial reversal
Partial reversal
  • A node reverses incoming links from only those neighbors who have not reversed links “previously”
    • If all neighbors have reversed links, then the node reverses all its incoming links
partial reversal16
Partial reversal

A

B

F

C

E

G

Link (G,D) broke

D

Node G has no outgoing links

partial reversal17
Partial reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

Represents a

node that has

reversed links

D

Now nodes E and F have no outgoing links

partial reversal18
Partial reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Nodes E and F do not reverse links from node G

Now node B has no outgoing links

partial reversal19
Partial reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Now node A has no outgoing links

partial reversal20
Partial reversal

A

B

F

C

E

G

Represents a

link that was

reversed recently

D

Now all nodes (except destination D) have outgoing links

partial reversal21
Partial reversal

A

B

F

C

E

G

D

DAG has been restored with only the destination as a sink

partial reversal discussion
Partial reversal discussion
  • Will it ever stop?
  • Is it loop free?
  • Is it flooding?
  • If the graph is connected, then partial reversal terminates after a finite # of iterations.
  • Directed graph at each iteration is a acyclic.
  • The direction of any link between two nodes that have a direct path to the destination in the initial ADG will never be reversed.
full reversal another description
Full reversal: another description
  • Routing as water flow
  • Each node has a “height”
    • node i has height αi
    • “water” flows from i to j if αi >αj
    • Reverse direction: reselect height
  • Destination-disoriented ADG
    • node w/o outgoing link: its height is local minimum
  • Full reversal
    • Node w/o outgoing link reselect height to become a local maximum
    • Broadcast new height
partial reversal another description
Partial reversal: another description
  • Through numbering scheme (“heights”)
  • More complicated
  • See paper
  • Proof of properties of full & partial reversal: see paper
link reversal algorithm advantages
Link reversal algorithm advantages
  • Not flooding
    • attempt to limit updates to routing tables at nodes in the vicinity of a broken link
    • Partial reversal tends to be better than full reversal
  • Each node may potentially have multiple routes to a destination
link reversal algorithm disadvantages
Link reversal algorithm disadvantages
  • Need a mechanism to detect link failure
    • hello messages may be used
    • but hello messages can add to contention
  • Broadcast of link reversal messages
  • If network is partitioned, link reversals continue indefinitely
link reversal in a partitioned network
Link reversal in a partitioned network

A

B

F

C

E

G

D

This DAG is fordestination node D

full reversal in a partitioned network
Full reversal in a partitioned network

A

B

F

C

E

G

D

A and G do not have outgoing links

full reversal in a partitioned network29
Full reversal in a partitioned network

A

B

F

C

E

G

D

E and F do not have outgoing links

full reversal in a partitioned network30
Full reversal in a partitioned network

A

B

F

C

E

G

D

B and G do not have outgoing links

full reversal in a partitioned network31
Full reversal in a partitioned network

A

B

F

C

E

G

D

E and F do not have outgoing links

full reversal in a partitioned network32
Full reversal in a partitioned network

A

B

F

In the partition

disconnected from

destination D, link

reversals continue, until

the partitions merge

Similar scenario can

occur with partial

reversal method too

One solution:

Temporally-Ordered Routing

Algorithm (TORA)

C

E

G

D

reactive proactive protocols33
Reactive & proactive protocols
  • Reactive protocols
    • Dynamic Source Routing (DSR) [Johnson96]
    • Ad Hoc On-Demand Distance Vector Routing (AODV) [Perkins99Wmcsa]
    • Link reversal algorithm [Gafni81]
  • Proactive protocols
    • Optimized Link State Routing (OLSR) [Jacquet00ietf,Jacquet99Inria]
    • Destination-Sequenced Distance-Vector (DSDV) [Perkins94Sigcomm]
classical link state routing
Classical link state routing
  • Each node periodically floods status of its links
  • Each node re-broadcasts link state information received from its neighbor
  • Each node keeps track of link state information received from other nodes
  • Each node uses above information to determine next hop to each destination
optimized link state routing olsr
Optimized Link State Routing (OLSR)
  • Reduce link state information flooding
  • A broadcast from node X is only forwarded by its multipoint relays (MPRs)
  • MPR of node X are its neighbors s.t. each two-hop neighbor of X is a one-hop neighbor of at least one MPR of X
    • Each node transmits its neighbor list in periodic beacons, s.t. all nodes can know their 2-hop neighbors, in order to choose the MPRs
optimized link state routing olsr36
Optimized Link State Routing (OLSR)
  • Nodes C and E are multipoint relays of node A

F

B

J

A

E

H

C

K

G

D

Node that has broadcast state information from A

optimized link state routing olsr37
Optimized Link State Routing (OLSR)
  • Nodes C and E forward information received from A

F

B

J

A

E

H

C

K

G

D

Node that has broadcast state information from A

optimized link state routing olsr38
Optimized Link State Routing (OLSR)
  • Nodes E and K are multipoint relays for node H
  • Node K forwards information received from H
    • E has already forwarded the same information once

F

B

J

A

E

H

C

K

G

D

Node that has broadcast state information from A

destination sequenced distance vector dsdv
Destination-Sequenced Distance-Vector (DSDV)
  • Each node maintains a routing table
    • next hop towards each destination
    • a cost metric for the path to each destination
    • a destination sequence number that is created by the destination itself
    • Sequence numbers used to avoid formation of loops
  • Each node periodically forwards the routing table to its neighbors
    • Each node increments and appends its sequence number when sending its local routing table
    • This sequence number will be attached to route entries created for this node
destination sequenced distance vector dsdv40
Destination-Sequenced Distance-Vector (DSDV)
  • Assume that X receives routing information from Y about a route to Z
  • S(X): destination sequence # for node Z as stored at node X
  • S(Y): destination sequence # sent by Y with its routing table to node X

Z

X

Y

destination sequenced distance vector dsdv41
Destination-Sequenced Distance-Vector (DSDV)
  • Node X takes the following steps:
    • If S(X) > S(Y), then X ignores the routing information received from Y
    • If S(X) = S(Y), and cost of going through Y is smaller than the route known to X, then X sets Y as the next hop to Z
    • If S(X) < S(Y), then X sets Y as the next hop to Z, and S(X) is updated to equal S(Y)

Z

X

Y

other schemes
Other schemes
  • Asymmetric responsibilities
    • giving special responsibilities to a subset of nodes (even if all nodes are physically identical)
  • Hybrid protocols
    • Proactive & reactive routing
  • Geographic routing
    • Utilizing geographic information
  • Many more…