Routing Fairness in Mobile Ad-Hoc Networks: Analysis and Enhancement by ijcsiseditor

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									                        (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 9, December 2010



      Routing Fairness in Mobile Ad-Hoc Networks : Analysis and Enhancement

           MANIYAR SHIRAZ AHMED1, HAJI MOINUDDIN2, FAZEELATUNNISA 3
                  1
                    Lecturer, Department of Computer Science & Information Systems,
                                  Najran University, Najran, Saudi Arabia,
                               samaniyar@nu.edu.sa, shiruraz@yahoo.com
                  2
                    Lecturer, Department of Computer Science & Information Systems,
                                  Najran University, Najran, Saudi Arabia
                            haji.moinuddin@yahoo.com, hmaddin@nu.edu.sa
                                      http://www.hajimoinuddin.co.nr/
                  3
                    Lecturer, Department of Computer Science & Information Systems,
                                  Najran University, Najran, Saudi Arabia
                                ftshiraz@nu.edu.sa,fazeel_ab@hotmail.com

Abstract: With the rapid advances in wireless and semiconductor technologies mobile connectivity
became cheap and ubiquitous. One of the major challenges facing Mobile Ad-Hoc Networks (also known
as MANETs) is the absence of a proper routing protocol that provides good fairness and scalability, low
overhead, low end-to-end delays, seamless connectivity and good quality of service. This paper studies the
fairness of routing protocols for MANETS. In this paper we propose routing segments methods to solve
the problem of lack of fairness in routing.

Keywords: MANETS, Fairness, Segments, Scalability

I. INTRODUCTION                                                          Mobile routing protocols have been
                                                                 attracting the attention of a major section of the
        Wireless devices are becoming                            research community as is evident from the large
ubiquitous, with the ever increasing advances in                 number of ongoing projects at various
wireless and mobile computing. Improved                          universities and institutions on this topic.
protocols must be developed to support these                     Numerous architectures have been proposed
new mobile devices/ MANETS[3] and to see                         earlier
that these devices do not overload the existing
infrastructure network. The effort in this                       II. RELATED WORK
endeavor is to provide anytime, anywhere
connectivity for unlimited mobile devices                                Routing protocols form the heart of any
without overloading the associated infrastructure                MANET, which have not evolved as much to
networks.                                                        support a large amount of mobile units. The
        Most protocols in place suffer from low                  performance of most routing protocols degrades
quality of service and overload the network with                 with the increase in mobile nodes,[9] leading to
a large percentage of overhead (control data)                    higher end-to-end delay, more dropped packets
when compared to the data packets. Any                           and low quality of service (QoS).
improvement in the routing protocol should be an                         Dynamic routing protocols can be
extendable architecture to support high number                   classified in several ways. Basically it is
of mobile units and at the same time ensures a                   classified into two (a) exterior protocols versus
good quality of service.                                         interior protocols, and (b) distance-vector versus



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                                                                                           ISSN 1947-5500
                          (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 9, December 2010



link-state protocols.[4] The first classification is               and how they use the information to form their
based on where a protocol is intended to be used:                  routing tables. Most protocols fit into one of two
between your network and another's network, or                     categories.
within your network. The second classification
has to do with the kind of information the                         The first of these categories is distance-vector
protocol carries and the way each router makes                     protocols. In a distance-vector protocol, a router
its decision about how to fill in its routing table.               periodically sends all of its neighbor’s two pieces
                                                                   of information about the destinations it knows
   (a) Exterior vs. Interior Protocols                             how to reach. First, the router tells its neighbors
                                                                   how far away it thinks the destination is; second,
        Dynamic routing protocols are generally                    it tells its neighbors what direction (or vector) to
classified as an exterior gateway [1] protocol                     use to get to the destination. This direction
(EGP[2]) or an interior gateway protocol (IGP).                    indicates the next hop that a listener should use
An exterior protocol carries routing information                   to reach the destination, and typically takes the
between two independent administrative entities,                   form "send it to me, I know how to get there."
such as two corporations or two universities.                      For example, RIP route updates simply list a set
Each of these entities maintains an independent                    of destinations that the announcing router knows
network infrastructure and uses an EGP to                          how to reach, and how far away it thinks each
communicate routing information to the other.                      destination is. The receiver infers that the next
Today, the most common exterior protocol is the                    hop to use is the announcing router. However, an
Border Gateway Protocol (BGP). It is the                           update can also take the form "send it to this
primary exterior protocol used between networks                    other router who knows how to get there." This
connected to the Internet, and was designed                        second form is usually used only when the router
specifically for such purposes.                                    that should be used to reach the destination
                                                                   cannot (or will not) speak the routing protocol
In contrast, an interior protocol is used within a                 being used by the other routers. Not all routing
single administrative domain, or among closely                     protocols support this form of third-party route
cooperating groups. In contrast to the exterior                    update.
protocols, IGPs tend to be simpler and to require
less overhead in a router. Their primary                           The other part of the protocol, the distance, is
drawback is that they cannot scale to extremely                    where distance-vector protocols differ. In each
large networks. The most common interior                           case, the protocol uses some metric to tell the
protocols in IP networks are the Routing                           receiving routers how far away the destination is.
Information Protocol (RIP), Open Shortest Path                     This metric may be a true attempt at measuring
First (OSPF), and the Enhanced Interior Gateway                    distance (perhaps using a periodic measure of the
Routing Protocol (EIGRP). The first two are                        round trip time to the destination), something
open standards adopted or developed by the                         that approximates distance (such as hop count),
Internet community, while the third is a                           or it may not measure distance at all. Instead, it
proprietary protocol designed by Cisco Systems                     may attempt to measure the cost of the path to
for use on their routers.                                          the destination. It may even involve a complex
                                                                   computation that takes into account factors like
   (b) Distance-Vector vs. Link-State                              network load, link bandwidth, link delay, or any
       Protocols                                                   other measure of the desirability of a route.
                                                                   Finally, it may include an administrative weight
Another way to classify dynamic routing                            that is set by a network administrator to try to
protocols is by what the routers tell each other,                  cause one path to be preferred over another.



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                                                                                             ISSN 1947-5500
                         (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 9, December 2010



In any case, the metric allows a router that hears                traverse the link. For example, a given link might
about a destination from multiple routers to                      not be allowed to carry confidential information.
select the best path by comparing the "distance"
of the various alternatives. How the comparison                   Distance-vector and link-state protocols have
is made depends heavily upon how metric is                        their own strengths and weaknesses. In a
computed. For example, the metric in RIP route                    properly functioning and configured network,
updates is defined to be a hop count, in which                    either type yields a correct determination of the
one hop is supposed to represent handling by one                  best path between any two points.
router. A destination with a hop count of 16 is
considered unreachable. When a router receives
RIP updates from different routers referring to                   III. PROPOSED PROTOCOL
the same destination network, it selects the router
that is announcing the lowest metric. If this                              Binding refers to keeping the network
metric is lower than the metric for the route that                together, issuing routing updates, keeping track
is currently in its routing table, the router                     of nodes entering and exiting the network etc. As
replaces its routing table entry with the new                     the size of the MANET increases, the control
information from the other router.                                traffic also increases. When nodes are tasked
                                                                  with binding the network as well as data transfer,
In contrast, in a link-state protocol, a router does              bottlenecks are created within the network
not provide information about destinations it                     leading not only to battery drain out but slow
knows how to reach. Instead, it provides                          network performance and unfairness in routing.
information about the topology of the network in                  Hence it is critically important to disassociate
its immediate vicinity. This information consists                 both of these functionalities to prevent node
of a list of the network segments, or links, to                   failures due to bottle necks and also unfairness
which it is attached, and the state of those links                and low power conditions. We also have to solve
(functioning or not functioning). This                            the problem of scalability.
information is then flooded throughout the                                 This can be done by managing the manets
network. By flooding the information throughout                   based on the routing and must implement routing
the network, every router can build its own                       fairness in order to prevent early partitioning of
picture of the current state of all of the links in               the ad hoc network into disjoint network
the network. Because every router sees the same                   segments.
information, all of these pictures should be the                           Routing fairness [5] in MANETS is
same. From this picture, each router computes its                 essential as it discourages large volume of
best path to all destinations, and populates its                  disjoint network segments. Each sector can have
routing table with this information. How a router
                                                                  two motes (sensor mote and base and Sensor
determines which path is best is up to each
protocol. In the simplest case, a router may                      motes gather data and send to central mote(base
simply compute the path with the least number of                  station). Motes too far from base station requires
hops. In a more complex protocol, the link-state                  intermediate motes to relay, or route, data.
information may include additional information                    Routing structure formed is a tree, rooted at the
to help a router determine the best path. Such                    base station.
information may again include the bandwidth of
the link, the current load on the link,
administrative weights, or even policy
information restricting which packets may




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                                                                                            ISSN 1947-5500
                        (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 9, December 2010



                                                                    IV. ROUTING FAIRNESS

                                                                            To be fair in routing, at base station, same
                                                                    number of packets should receive from each
                                     Sensor mote                    mote. Within each period of time (or epoch),
Base station                                                        transmit number of packets from each sub tree
                                                                    equal to size of that sub tree.
         The problems with this kind of routing
structures can be like motes closer to the base                                                                      Within 1 epoch, send 1
station has to transmit packets generated locally                                                                    from A, 10 from B,
as well as those generated by downstream motes,                                                                      1000 from C, and 1
                                                                                                                     from myself
these motes likely to become bottlenecks in the
system which results in more packets originating
further away being dropped (unfairness) loss of
packets due to queue overflow and interference
during transmission (congestion. unfairness may
result in network not retrieving sufficient data
from faraway motes to meet application                                Subtree A        Subtree B          Subtree C
requirements. congestion wastes scarce energy                         Size = 1         Size = 10          Size = 1000
resources.
         The problem of packets being dropped
(unfairness) and be solved by determining                           For this we require per child queue (does not
maximum application data generation rate and by                     depend on size of sub tree, so can be small and
implementing hop-by-hop Automatic Repeat                            constant), FIFO queues, sub tree size (obtained
Request (ARQ).[7] since motes generate data at a                    as before).Then we should check for proof of
rate network can handle, congestion (queue                          correctness (by induction).
overflow) should not occur. ARQ ensures all
packets ultimately reach the base station. BUT                                                           A’s Queue      B’s Queue C’s Queue

difficult to obtain maximum rate for every                                        A                           A            E
network configuration underestimation of                                                                                   D             C
                                                                           B               C
generation rate reduces effective bandwidth.                                                                               F
                                                                D
                                                                                  E

                                                                                       F




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                                                                                           ISSN 1947-5500
                        (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 9, December 2010



V. ENHANCEMENT OF FAIRNESS                                       VII. PROTOCOL IMPLEMENTATION

        The proxies alleviate the unfair advantage                       If data needs to be transferred from one
that shorter connections have over longer                        end of the MANET to the other, the source sends
connections. For this we can split longer                        a request to its adjacent TCP segment. This TCP
connections into shorter segments. The                           segment then forwards the request to the
throughput of longer connections, however,                       respective TCP segment. The TCP segment
cannot equal that of shorter connections due to                  which to participate in the data transfer reply
interactions between segments. The packets                       back with node addresses of nodes that are active
cannot be sent and received at the proxy at the                  and willing to participate in the route.
same time, so the adjacent TCP[6] segments                               Propagation of the route establishment
have to transport data in stages                                 request is between the TCP segments only,
                                                                 which decide on the basis of the instantaneous
        We can improve fairness by having                        information able to them. By limiting the
Multiple TCP connections with varying lengths                    propagation of the route request to the segments
in terms of hop count. Because the Longer                        only the traffic is greatly reduced, because as
connections achieve lower throughput than                        seen in other protocol the request keeps on
shorter ones, we have to introduce proxies[8]                    propagating due to retransmission from nodes
which improves throughput. For a connection of                   throughout the network until the TTL of the
length 16 hops, the throughput improves from                     request has expired causing considerable traffic.
around 22 Kbps to 27 Kbps. Thus there will be                            Before the source transmits data, it must
improvement in fairness                                          setup proper segments to be used by the
                                                                 respective protocols. Firstly, depending upon the
VI. ROUTING                                                      routing information and number of proxies
                                                                 received for its route, this segment is utilized by
        Routes can be of two types; first spanning               the intersegment DSR protocol. Next the source
just longer segment, and the second, spanning                    adds intra-segment routing information for the
shorter segments. In the case of routes spanning                 packet to reach the first gateway node.
longer segments, the entire route is divided into                        By adding segments and proxies in this
shorter segments. This active route is                           fashion two purposes are served. First CGRS
hierarchically managed using two routing                         gets the route to the nearest gateway. Second the
protocols; one at the inter-segment level and the                DSR protocol gets the next hop to inter-segment
other at the intra-segment level.                                gateway node. The inter-segment header gets
        The entire route from the source to the                  reduced with each hop where as the intra-
destination has nodes involving multiple                         segment is renewed at each gateway node. A new
segments divided into shorter segments.                          inter-segment is appended while entering a new
        A segment is the route between two                       segment. Inter-segment routing (DSR) occurs at
gateway nodes or the route between the gateway                   the gateway nodes while the intersegment
node and the source node or the destination node.                routing occurs at both gateway nodes and
In other words, a route is a connection of one or                segment nodes until the data packet reaches the
more segments and segment has a segment-head.                    destination.




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                                                                                           ISSN 1947-5500
                        (IJCSIS) International Journal of Computer Science and Information Security, Vol. 8, No. 9, December 2010



VIII. CONCLUSION

        This paper studies the dynamic routing
fairness for mobile adhoc networks and describes
the different existing dynamic routing protocols.
Different from existing works, this work
considers the routing segments to improve
fairness in the routing. We show our
assumptions that can be implemented to get more
fairness in routing. We proposed routing segment
method. The problems in routing fairness and
proposed solutions have been discussed.

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      outing_ protocols



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