B.REVATHI

M.Tech(CSE)

Guided By

SS.RajaKumari

TRANSFER RELIABILITY AND CONGESTION CONTROL STRATEGIES IN OPPORTUNISTIC NETWORKS A SURVEY

Abstract• Opportunistic networks are a class of mobile ad hoc networks

(MANETs) where contacts between mobile nodes occurunpredictably and a complete end-to-end path between Sourceand destination rarely exists at one time

• There are two important functions provided by the transport layer

a. ensuring reliable data transmission between source anddestination

b. ensuring that the network does not become congested withtraffic

• These functions are ineffective in opportunistic networks

• Opportunistic networks require different approaches to thoseadopted in the more common intermittently connected networks

Introduction• MOBILE ad hoc networks (MANETs) are infrastructure less

networks where nodes can move freely.

• One node can directly communicate with another if they arewithin radio communication range.

• A node can simultaneously serve both as a source or destination ofa message and as a relay for other messages.

• A message traverses the network by being relayed from one nodeto another until it reaches its destination (multi-hopcommunication)

Challenges in MANET’S• Nodes will be moving, the network topology regularly changes so

finding a delivery path to a destination is a challenging task.

• Constructing end-to-end delivery paths and ensuring robustmessage delivery in the face of dynamic topology is anotherchallenging task

Delay- or Disruption Tolerant Networks (DTN)• In some scenarios complete end-to-end paths rarely or never exist

between sources and destinations within the MANET, due to highnode mobility or low node density.

• These networks may experience frequent partitioning, with thedisconnections lasting for long periods.

• As a consequence, the end-to-end transfer delays in theseintermittently connected networks (ICNs)

Existing System • Existing storage congestion management proposals can be divided

into two categories

1. Those that use economic models to determine whether

custody of a message should be transferred to a new node

2. Those that analyze network traffic levels to make this

decision

Disadvantage:

• One drawback of the greedy scheme is that it does not considerthe cooperation between the neighboring nodes and hence itsperformance may be limited

Proposed System• Reliable data transfer and congestion control are the two functions to be

achieved

• Potential mechanisms for transfer reliability service are hop-by-hopcustody transfer and end-to-end return receipt.

• The requirements for storage congestion control are identified andcategorize based on the number of message copies distributed in thenetworks

• The principal storage congestion control mechanisms for single-copyforwarding are storage congestion management and congestionavoidance mechanisms, for multiple-copy forwarding, replicationmanagement and drop policy

Modules• Data replication

• The One –To-One optimization(OTOO)scheme

• The Reliable Neighbor (RN) Scheme

• Reliable Grouping (RG) Scheme

Data Replication• Data replication has been extensively studied in the Web

environment and distributed database systems

• In a MANET, mobile nodes collaboratively share data.

• Multiple nodes exist in the network and they send query requeststo other nodes for some specified data items.

• Each node creates replicas of the data items and maintains thereplicas in its memory (or disk) space.

• During data replication, there is no central server that determinesthe allocation of replicas, and mobile nodes determine the dataallocation in a distributed manner.

The One-To-One Optimization (OTOO) Scheme• It considers the access frequency from a neighboring node to improve

data availability.

• It considers the data size, the data item with smaller size is given higherpriority for replicating because this can improve the performance whilereducing memory space.

• It gives high priority to local data access, and hence the interested datashould be replicated locally to improve data availability and reduce querydelay.

• It considers the impact of data availability from the neighboring nodeand link quality. Thus, if the links between two neighboring nodes arestable, they can have more cooperation’s in data replication.

The Reliable Neighbor (RN) Scheme• Reliable Neighbor (RN) scheme contributes more memory to

replicate data for neighboring nodes.

• In this scheme, part of the node’s memory is used to hold data forits Reliable Neighbors.

• If links are not stable, data on neighboring nodes have lowavailability and may incur high query delay.

• Cooperation in this case cannot improve data availability andnodes should be more “selfish” in order to achieve betterperformance.

Reliable Grouping (RG) Scheme• To further increase the degree of cooperation, we use the reliable

grouping (RG) scheme.

• It shares Replicas in large and reliable groups of nodes, whereasOTOO and RN only share replicas among neighboring nodes.

• The basic idea of the RG scheme is that it always picks the mostsuitable data items to replicate on the most suitable nodes in thegroup to maximize the data availability and minimize the dataaccess delay within the group.

• The RG scheme can reduce the number of hops that the data needto be transferred to serve the query.

Interaction of transfer reliability and congestion control strategies in opportunistic networks

Congestion-aware forwarding module in opportunistic network nodes

Congestion control strategies for opportunistic networks

SYSTEM SPECIFICATION

Hardware Requirements

• System : Pentium IV 2.4 GHz.

• Hard Disk : 80 GB.

• Monitor : 15’ VGA Colour.

• Mouse : Optical Mouse

• RAM : 512 MB.

Software Requirements

• Operating system : Windows 7 32 Bit.

• Coding Language : C#

• Data Base : SQL Server 2008

UML Diagrams

Conclusion• The nature of opportunistic networks is such that some

conventional end-to-end transport functions have to beadditionally supported within the network.

• Transfer reliability and congestion control mechanisms have to beimplemented in the network on a per-hop basis

• The main focus is on high message delivery ratio or low deliverylatency