Address Configuration in Adhoc Networks in IPv4. By Meenakshi Sundaram V

Problem Definition In a MANET, group of nodes dynamically form a network. No dedicated machine providing DHCP services. Providing an efficient addressing scheme for an infrastructure less network (adhoc). Existing adhoc literature bypass node configuration, assume nodes are configured prior.

DHCP

Network admin. assigns a range of IP addresses to DHCP client computer on the LAN has its TCP/IP software configured to request an IP address from the DHCP server when that client computer's network interface card starts up Request and grant process uses a lease concept. Dynamic reuse of IP address.

DHCP in ADHOC domain Centralized administration is an impossible task. Automated Dynamic assignment of IP address a desirable goal. Resolution of addresses when two or more partitions merge.

Characteristics for IP address protocol IP address valid only for the duration for for which node stays in network. Node departs, IP address should become reusable. Resolve if two nodes happen to have same address. could arise because of reusability.

Related Work Perkins et.al - Node i picks random address. Issues RREQ. if no reply beyond a timeout, address distinct. B A S E H C I [S] Figure 2.Using routing protocol’s flooding

Related Work IP address treated as shared resource. assignment of new IP address requires approval from all other nodes. Each node maintains list of used addresses. not scalable.[ Nesargi et.al] Zero Configuration Choose a random address and use ARP to check for duplication.

Basic Idea A distributed approach, extending the functionality of DHCP across all nodesin an adhoc network. Dynamically configure each new node also as a DHCP server. Add a small address space to each node, for it to allocate addresses.

Local link address Use the IPV4 local link address – /16 Use sub netting. Net[0].net[1].net[2].net[3]. Of the 16 host bits, set 13 bits for subnet. Theoretically number of hosts=2^13*8 adhoc nodes.

Sub netting. Address of the first node Subnet add: IP Address Subnet add: Address of the second node Subnet Allocated to second node

Node Configuration 1 st Node: IP: Subnet: nd Node: IP: Subnet Figure 3.Configuring Nodes.

Address request A new node broadcast’s a request with hop count=1 If more than one neighbor offer’s an address, use the one with least host part. The server-node, generates subnet_request packet, broadcasts.

New Subnet Request Includes its subnet value in the request. Every receiving node :  check if subnet value greater than in packet.  If so, replace with greater subnet in packet &forward.  Else if contains reusable subnets, append to packet and forward.  Else discard.  subnet allocated to the new node, using the reply generated.

State at Each node Each node i maintains: Client  Server’s address.  A lease timer. Server  For every allocated address, by node i: maintain subnet address, shutdown timer.  List of un-allocated addresses.  List of released subnet’s.

IP Renewal If timer expires at both client and server end & lease not renewed.  Add the address to the free pool at server end.  Subnet reusable after a recovery timeout.  Client sends a 1 hop address request again.  Acquire new address, subnet. Allot existing clients, new addresses & reset timer (s).

Split Network Split  Lease timer expires.  adjacent neighbor’s detected could be of original network or new network.  Irrespective, new address allocated. Network split gracefully handled.  If no neighbor, first node of new network.

Merger Network Merger  Assume Network Merger detected.  Node x and y in transmitting range of each other detect they belong to different networks  One node loses competition, gets new address and subnet from the other node.  Trigger’s further changes.  Merger is expensive.

Comments Quick node configuration. Eliminates random assignment of IP address. Until a merge occurs,address duplication not possible. Nodes belonging to multiple network segments. Proactive?

Questions?