Enabling QoS in Stateful Auto-configuration Protocol used in IPv6 based MANETs Punitha.R, puni.ravi22@gmail.com Reshmi.T.R reshmi.engg@gmail.com Murugan.K murugan@annauniv.edu Abstract The Mobile Ad-Hoc NETworks (MANETs) is an easy deployable, infrastructure-less networks. In IPv6 based MANETs the address configuration is done either with a stateless mechanisms or with the help of server like Dynamic Host Configuration Protocol version 6 (DHCPv6). The DHCPv6 server initially resides on the node which acts as the Internet gateway (IGW) in the network and later on each of the configured nodes will become a server. The node which enters the network, will request for an IP address and the server distributes a unique IP address and an address pool. Formerly the new node identifies the server using a random selection algorithm and this method faces many QoS issues due to the usage of the random selection algorithm. The proposed technique addresses the issues using a QoS enabled algorithm, which reduces the address acquisition delay and packet drops in the network, and thereby enhancing the performance of the network. The proposed technique is simulated and compared with the random selection algorithm using Network Simulator Version 2 (NS2). Keywords MANET, IPv6 address, Address configuration, DHCPv6. I. Introduction Mobile Ad-hoc Networks (MANETs) are the collection of mobile devices so called nodes, which shapes a network without any permanent infrastructure and are linked by wireless media. Each node communicates with other node within the transmission range through a wireless medium (the communicating nodes should be in the same transmission range). Devices that are out of the transmission range require the prolong help of the corresponding neighbor devices. A mobile node in MANET environment, act as both a host which produce data and also as a router which send, receive and forward messages to other nodes. The topology in MANET is of dynamic which incurs rapid changes in the network (frequent change of topology in MANET) which requires the nodes to update the routing table periodically. Wireless communication medium is the fundamental functionality of Ad-hoc networks. As such, before the topology connection of the nodes, physical linking should carry out in the network as in case of fixed network. But in case of wireless scenario this progress is not carried out since the communicating nodes are within the transmission range may form the link between them. Communication of mobile node requires message exchange to other neighboring nodes, due to the regular topology change of MANETs. MANET normally performs the operations of broadcast and multicast in order to flood the messages. A wide range of MANET applications, such as disaster management, rescue process with reformation of fixed network during emergency services, data tracking in sensors networks, address discovery with address management, route discovery in order to broadcast the messages to other nodes. In MANET the send and receive mechanism (exchange of messages) between the nodes is necessary for Autoconfiguration. The Transmission Control Protocol/Internet Protocol (TCP/IP) protocol provides the permission to the nodes in the entire network to communicate with a unique Internet Protocol (IP) address to each node of the MANET. There is server node which allocates these IP addresses in case of both wired and wireless with an infrastructure. On the other hand, the Mobile ad hoc networks do not have such a centralized server to perform this functionality. Hence, there is necessity for the protocol to perform the network configuration in a dynamic way. As such, the nodes which are the part of the network will act as the server and also manages the IP addresses. Due to the frequent change in the topology of mobile ad hoc networks the nodes that can link and leave the network frequently and even concurrently. Auto-configuration protocols are attempted with various issues in allowing network partitioning and merging and assuring the uniqueness of IP addresses. To ensure the accurate implementation of the network, the protocols try to achieve the following goals, 1 Unique IP addresses assignment: Ensure the uniqueness of the IP address and assure that no other nodes possess the same IP address.
2 Address management during network merging and partitioning: A node restrain an IP address for the moment that it is reserved in the network. When there is network partitioning (i.e. a node leaves the network), the IP address of the node should be accessible for the connection to another node. 3 Availability assurance usage: Any node with a free IP address in the network can provide the IP address to the requesting node without making an allowance for the hop limit or multihop. Thereby assuring availability of free addresses in network 4 Authenticate the reality of rival appeal for an IP address: The intelligence of the protocol should be such a way that it should follow the management that the same IP address is not given to two nodes in the network which request an IP address at the same time. 5 Accomplish synchronization: The dynamic topology of the network should be adapted by the protocol so that the synchronization should be updated periodically in order to ensure the configuration of the network. The protocols like Stateless Address Auto- Configuration (SLAAC) and Distributed Dynamic Host Configuration Protocol (DDHCP) are used in the Autoconfiguration. SLAAC is used in case of stateless and it is a standard that permit the routine auto-configuration of an Internet Protocol version 6 (IPv6) address without the availability of a router. There by, a Neighbor Discovery Protocol (NDP) is used to gather the information in order to convey the messages and to identify its neighbors. An IPv6 address is generated automatically as and when the node is a part of its host and by broadcasting the NDP messages to the neighboring nodes, a Duplicate Address Detection (DAD) has been processed. The configured IPv6 address to the node is not distinct, the Auto-configuration process will discontinue and it will be carried out manually. On the other hand, if the assigned address is distinct, it will have to ask for the network prefix through NDP messages and, then, it confirms with DAD for its uniqueness of IPv6 address. This protocol have inadequate applicability in mobile ad hoc networks since the NDP protocol is used to send the messages and it believe that all the nodes in the network are connected to each other. Therefore, it supports only one-hop (distance between two nodes) communication, whereas mobile ad-hoc networks are most repeatedly supports multihop transmission. A Dynamic Host Configuration Protocol version 6 (DHCPv6) message is sent by the node in the network which is in need of IPv6 address in order to obtain an address from a DHCP server. Based on the DHCPv6, its applicability is limited in mobile ad hoc networks. Therefore, an assumption has carried, that all the nodes in the network can connect to a server called DHCPv6 either directly or by several hop limits. However, there is no frequent direct connection to the DHCPv6 server through server hops due to the MANET topology, and it even make the server unreachable. Due to the dynamic topology in MANETs, a node cannot be configured by using a centralized server. There by, a Distributed Dynamic Host Configuration Protocol (DDHCP) which is of dynamic in nature is used in MANETs. In this paper, the node which avails the unique IP address will further act as DHCP server. The proposed solution is targeted towards the QoS enabled selection of the server node in order to obtain the IPv6 address and address pool. The proposed protocol is performed with IPv6 networks and not compared with the IPv4 networks. The residue of the paper is organized as follows: Section 2 presents the related work. Section 3 provides the proposed methodology. The performance evaluation is described in Section 4, followed by the conclusion and future work in Section 5. 2 Related Works There are many proposed works which concentrated on the issues faced during IP address assignment in MANETs. Few of the works are discussed below. Mansoor Mohsin and Ravi Prakash [1] used a proactive scheme for dynamic allocation of IP addresses in MANETs. The solution used the concept of binary split and considered some of the previously unsolved issues like partitioning and merging and abrupt departure of nodes from the system. The solution was scalable but have complexity induced during the protocol functioning. The major issue of this protocol is that consistent transmission for the synchronization of address blocks. Sonia Mettali Gammar et al. [2] proposed a distributed IP address configuration approach for MANET. The solution provided a unique IP address allocation for each node in the network. The various network conditions like node failures, network partitioning and merging are assured under address assignment. The distributed nature of the protocol caused complexity and overhead to the network. Mansi Ramakrishnan Thoppian and Ravi Prakash [3] proposed a distributed protocol for dynamic IP address assignment to nodes in MANETs. The solution of this protocol provided a unique IP address assignment under a variety of network conditions including message losses, network partitioning and merging. However, a high
overhead is generated during IP address allocation. The latency and communication overhead is also increased with increase in the node population. K.Weniger[4] came up with a proposed work PACMAN, which was the believed to be the best proposed work in Address Autoconfiguration of MANETs. It used a variable length addressing method to reduce the overhead of the protocol during routing. The protocol worked with minimum address acquisition delay. The protocol was even tried by Carlo at al. [5] in Wireless Mesh Networks (WMN) to check the performance. The main issue of PACMAN is the complexity involved during duplicate address detection (DAD) and the incompatibility for IP oriented services. E. Baccelli et al. [6] described a model for configuring IP addresses and subnet prefixes on the interfaces of routers which connect to links with undetermined connectivity properties. The IP address configuration and network interface determines the exact performance of routing protocols. The determination of the network topology and configuration of IP address interface was obtained by considering the various performance metrics like, geographical topology, address blocks, traffic patterns etc. Sanghyun Ahn et al. [7] described an address configuration mechanism in MANET based on the address pool allocation. The Internet gateway (IGW) acts as a DHCP (Dynamic Host Configuration Protocol) server and assigns a unique address and a part of its address pool to an address requesting node and, then, the node can act as a server and assign a part of its address pool to its neighbor nodes. The server is selected randomly without any decisive factor. The requestor chooses the server arbitrarily and gains the unique IPv6 address. This solution does not consider the complexity and QoS issues caused by the protocol during the server selection and address pool allocation. Reshmi et al [8] describes a distributed addressing protocol which analyses the QoS issues faced during the address configuration and address a technique to reduce the impact of selfish nodes during the functioning of the protocol. The proposed work concentrates only on the QoS issues due to selfish nodes. The issues like address buffer size; node performance, network throughput etc are not considered. 3 QoS enabled stateful Auto-configuration in MANETs 3.1 Basic Mechanism. The Internet Gateway (IGW) router periodically broadcasts Router Advertisement (RA) messages to the entire MANET and the MANET nodes receiving the RA message can request for addresses to the IGW by unicasting a DHCP_Request message. Any intermediate node receiving the DHCP_Request message intercepts the message and allocates a part of its address pool of the IGW, if its address pool is big enough to allocate by unicasting a DHCP_Reply message to the address requesting node. Otherwise, it forwards the DHCP_Request message to the IGW. Once the IGW receives the DHCP_Request message, the IGW allocates a part of its address pool to the address requesting node by sending a DHCP_Reply message. The node with the allocated address pool assigns one address to its interface and keeps the rest of its address pool for later allocation to other MANET nodes requesting addresses. During MANET initialization, there will be only one node in the network that has the entire pool of IP addresses. When an un-configured node wishes to join a network, it requests the nearest configured neighbor node for an IP address. Nearby node assigns the requesting node an IP address from its pool of IP addresses. It also divides the set of IP address pool and gives a part of the pool to the requesting node. A node can leave the network either gracefully or suddenly. When node leaves a network gracefully, it gives its pool of IP addresses to any neighboring node. Nodes have the responsibility to handle the set of IP addresses, it can either keep this chunk of IP addresses with itself or it can find the next neighboring node (i.e. the node whose IP address block is a near to node IP address block) and forward this chunk of IP addresses to the neighboring node. Nodes coordinate is carried out from time to time in order to keep track of the IP addresses assigned and detect any drip in the available pool of IP addresses. 3.2 QoS enabled IP Address Allocations in MANETs The DHCPv6 server here called the allocator, will assign the IP addresses to the newly entering node in the mobile network and also afford part of the address pool to the node. Thereafter the newly entered node will act as the DHCPv6 server. Likewise each node in the network acquiring IP address and address pool will act as DHCPv6 server. A newly entering node, here called requestor, will throw the DHCP_Request message to all its neighboring nodes that are in 1-hop and 2-hop distance in order to avail the IP address. The neighboring nodes are identified with the Neighborhood discovery protocol (NDHP) [10]. The allocator is chosen based on an algorithm which considers the factors like the address pool size, distance from the requestor and service time for a request from the neighbor node. The neighboring node chosen as the allocator receives the DHCP_Request from the requestor
and responds to it with DHCP_Reply message. The node provides a unique IP address and distributes IP address pool to the requestor. The requesting node uses an QoS enabled algorithm to select an allocator for IP address allocation. Based on the algorithm a routing table is calculated which prioritize the neighboring nodes based on their QoS factors. The pseudocode of the algorithm is given below Algorithm 1: Qos enabled allocator selection BEGIN Declare a variable req_n // req_n is the requestor node. Declare a variable all_n Declare a variable hc Declare a variable addr_buff size node. Declare a variable all_s node. Declare a variable n Declare a variable m set threshold value for counter=1 to n 4 Simulation results and analysis 4.1 Simulation Environment // all_n is the allocator node. // hc is the hop count. // addr_buff is the address buffer // all_s is the status of the allocator // n is the number of nodes. // m is the shortlisted allocator if [all_s! =0] && [addr_buff >= threshold] then shortlist m to allocator list find hc sort hc in ascending order sort addr_buff in descending order if m [addr_buff] = max &&hc=1 then select the node as all_n if (m [addr_buff] = m-1 [addr_buff]) && hc=1 then calculate the response time of the node select the node with less response node as all_n if (m [addr_buff] = max && hc=2) and m-1[addr_buff] < max && hc=1)then END select m as all_n update allocator list endfor req_n sends address request and waits for t time if req_n receives response then else address assigned selects the next node in the allocator list repeat the process The performance of the proposed scenario of IPv6 address configuration is implemented and tested in Network Simulator 2 (NS-2). The Optimized Link State Routing (OLSR) protocol is a routing protocol. The OLSR is optimized as an IP routing protocol in mobile ad-hoc networks, and also used as a routing protocol for other wireless domain. PARAMETER TYPES Number of Nodes Mobility Model Simulation Area Simulation Time Speed Pause Time Table 1: Simulation Parameters VALUES 30-110 (variable) Random Waypoint 1250 m x 1250 m 50 s 10 m/s MAC Protocol IEEE 802.11 Transmission Range Routing Protocol 4.2 Performance Metrics 5s 250 m OLSR The QoS enabled allocator selection algorithm is implemented in OLSR protocol and is compared with the Random allocator selection algorithm. The comparison of the above mentioned algorithms are done considering the following performance metrics. 4.3 Results Address Acquisition Delay: The address acquisition delay is the time taken to configure an IP address in a newly entering node after issuing an Address request. Packet Delivery Ratio: The delivery ratio is the ratio between the number of packets originated from the source and the number of packets received by the destination. The QoS of the network will be increased if the packet delivery ratio is high. Overhead: The average number of routing packets required to deliver a single data packet is analyzed. This metric gives an idea of the extra bandwidth consumed by overhead to deliver data traffic. The address acquisition delay caused by a newly entering node in various scenarios has been compared and shown in the fig.2. Here RANBAD represents Random based addressing protocol and QOSEAD represents QoS enabled addressing protocol. The results show that the address acquisition delay caused by QoS enabled addressing protocol is less when compared to the Random based allocator selection.
5 CONCLUSIONS AND FUTURE WORK Fig.2 Address Acquistion Delay The fig.3 shows the packet delivery ratio during the protocol functioning in the network. The results shows that the packet delivery ratio of QoS enabled protocol is high when compared to Random based protocol. The QoS enabled allocator selection algorithm performs well when compared to the Random based allocator selection. The proposed algorithm inbuilt protocol improves the network bandwidth usage and reduces the overhead caused by the addressing protocols. The address acquisition delay caused by the proposed protocol is comparatively less and hence the newly entering node can be a member of MANET to avail and provide services. The proposed algorithm was implemented and analyzed in a pro-active link state protocol..in future the algorithm can be tried in reactive protocols to get better network performance during the functioning of stateful IP addressing protocols. REFERENCES [1] Mansoor Mohsin and Ravi Prakash, IP Address Assignment In A Mobile Ad Hoc Network, MILCOMM 2002 Military Communication Conference Proceedings, pp. 1 6. [2] Sonia Mettali Gammar, Elabidi Amine, Farouk Kamoun Distributed address auto configuration protocol for Manet networks, Springer, Telecommun Syst, 44, pp. 39-48, November 2009. [3] Mansi Ramakrishnan Thoppian and Ravi Prakash, A Distributed Protocol for Dynamic Address Assignment in Mobile Ad Hoc Networks IEEE Transactions On Mobile Computing, Vol. 5, No. 1, Pp. 4 19, January 2006. Fig.3 Delivery Ratio The fig.4 shows the overhead incurred during the protocol functioning in various scenarios. The results show that the overhead due to the implantation of QoS enabled protocol is less due to the appropriate allocator selection. [4] K.Weniger, PACMAN: Passive Autoconfiguration for Mobile Ad Hoc Networks, IEEE Journal on Selected Areas in Communications, Vol. 23, No. 3, pp. 507 519, March 2005. [5] Carlos J. Bernardos, Maria Calderon, Ignacio Soto, AnaBeatriz Solana, Kilian Weniger, Building an IP-based community wireless mesh network: Assessment of PACMAN as an IP address autoconfiguration protocol, Elsevier, Journal on Computer Networks 54, pp. 291 303, August 2009. [6] E. Baccelli, Ed. M. Townsley, Ed. IP Addressing Model in Ad Hoc Networks RFC5889, IETF September 2011. [7] Sanghyun Ahn, Yujin Lim MANET Address Configuration using Address Pool, Internet Draft, January 2011. [8] Reshmi.T.R et al Trust based Dynamic Distributed IP addressing protocol for MANETs using Fuzzy rule set, World Congress on Information and Communication Technologies (WICT 2012) Proceedings, pp 931-936. November 2012. [9] T.Clausen, C.Dearlove, J.Dean Mobile Ad-Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP), Internet Draft, April 2011. Fig.4 Overhead