Title: MANETconf: Configuration of Hosts in a Mobile Ad Hoc Network
1 MANETconf Configuration of Hosts in a Mobile Ad Hoc Network
Authors Sanket Nesargi Ravi Prakash
Originally Published IEEE INFOCOM 02 New York June 2002
Presented By Michael Pincott
Date July 1 2003
Related / Previous Work
Making MANETconf Robust
3 Background Information
Received M.S. and Ph.D. in CS at University of Texas at Dallas
Worked at Nortel for a few years
Mobile Computing/Wireless Networks
Network Service Protocols
Protocol Design Frameworks
Transport/Network Layers in Fixed and Wireless Networks
Moving from Hair Metal into Pink Floyd Led Zeppelin Rainbow Deep Purple
Rides a Kawasaki Ninja ZX 6 motorcycle
Loves his BMW 323i
4 Background Information
Received Ph.D. in CS at The Ohio State University in 1996
Checkpointing and Recovery
Causally and Totally Ordered Message Delivery
Clocks and Dependency Tracking
Big Robert De Niro fan
Toastmaster International Member
He comes in peace and wants to make the world a happy place.
5 MANETs Primer
Typical Wireless Networks
Wireless Server Assigns DHCP IPDNS netmask
Data is routed through server
Wireless Server may be Internet gateway
6 MANETs Primer
MANET (Mobile Ad Hoc Network)
Group of mobile wireless nodes working cooperatively and spontaneously
Devoid of fixed infrastructure or central administration
7 System Model
Without centralized servers unconfigured nodes joining the MANET must be assigned a unique IP addresses.
Hosts already in the MANET must be responsible for uniquely configuring hosts wishing to join the MANET.
Hosts in the MANET must be responsible for allowing graceful and abrupt host departures.
8 System Model
In IPv4 the MANET can use
Nodes communicate through the exchange of IP packets.
Hosts of edges of MANET may not be directly reachable. MANET nodes must behave as routers and forward packets from the source to the destination.
9 Related/Previous Work
Zeroconf Working Group
Attacks similar problem of network configuration with the lack of dedicated servers.
Assigns unique IPs to nodes in
Single network segments where all nodes can directly communicate.
Multiple segments connected to the same router.
Limits the flexibility of Ad Hoc Networks
10 Related/Previous Work
PMWRS (Perkins Malinen Wakikawa Royer Sun)
Similar to Zeroconf.
Performs duplicate address detection through multiple rounds of MANET-wide flooding.
Uses AREQ and AREP.
Tied to underlying routing protocol as it specifies the routes to be used by its messages.
Uses 169.254.. IP block. Routers drop packets! This limits hosts ability to route packets after configured.
Network selects a candidate IP for the host joining the network. Checks for conflicts by polling hosts in the network. Timeout delays and retry constants are limiting when the size/shape of network is unknown.
If multiple hosts request an IP concurrently PMWRS may assign two hosts the same IP.
Much of the 169.254.. address block is reserved by IETF for future use.
11 Related/Previous Work
Hardware Based Addressing
Use the unique hardware address of a card to help uniquely assign IPs (MAC address in Ethernet Adapters).
Hardware Based Addressing Limitations
MANET nodes not restricted to NICs with unique MAC addresses.
Not all NICs have unique addresses.
Some devices allow for the reprogramming of the MAC address.
Nodes can be easily determined by tracking the MAC. Security
12 MANETconf Concept
Assign unique IP addresses to hosts despite dynamic topology by employing a mutual exclusion algorithm.
A node proposes an IP address for an incoming host.
If proposed IP is accepted by all other hosts the incoming host is assigned that IP.
Proposed solution is a modified version of the Ricart-Agrawala algorithm.
RA Algorithm modification include the ability to be flexible to changing network topology and a changing number of users in the network.
RAs inflexibility for topology changes is the motivation for MANETconf.
13 MANETconf Operation
Requestor broadcasts its Neighbor_Query message and starts its Neighbor_reply_timer.
Very first requestor will not receive any replied.
When timer expires the requestor will try again and if there is still no response it assumes it is the first node in the MANET.
14 MANETconf Operation
New Node Joining the MANET
Node i wishes to join the network. Node j is currently the only node in the network.
i broadcasts the Neighbor_Query message.
j responds before the timer expires.
i selects j as its initiator and ignores any other Neighbor_Replies it may receive.
i sends j a Requester_Request message.
15 MANETconf Operation
New Node Joining the MANET (contd)
j polls other nodes in the network asking if IP x is available for use. Other nodes check their Allocated IP and Allocated_pending lists.
If all responses to j are affirmative j
Assigns IP x to node i.
Adds IP x to its Allocated IP list.
Floods this information throughout the MANET so other hosts can also transfer IP x to their Allocated IP lists.
If at least one host responses with a negative the entire process is repeated with a new IP (x).
Process is repeated until node i is assigned an IP or the initiator_request_retry number is exceeded. j then notifies i with a failure message stating that no resources are available.
16 MANETconf Operation
Concurrent Address Initiation
Nodes a and e wishes to concurrently join the network.
If the two initiators (b and d) chose unique IPs for a and e there is no conflict.
If initiators b and d happen to chose the same IP for a and e the initiators IP will be used to set priority. The higher priority initiator will receive the affirmative ack and the lower priority initiator will receive the negative ack.
17 MANETconf Operation
Graceful Departure of Node
Node i wishes to depart the network and relinquish its IP before leaving the network.
i broadcasts the Address_Cleanup message.
All nodes in the network remove the used IP from their Allocated IP list.
18 Making MANETconf Robust
Abrupt or Ungraceful Node Departure
Node a crashes or ungracefully leaves the network.
Node e wishes to join the network. It selects node d as its initiator.
During node ds initialization process it sends Initiator_Request messages to all the IPs in its Allocated IP list.
Node a will fail to respond to the Initiator_Request message.
Node d then sends an individual Initiator_Request message to just node a. Node d will wait until its request_reply_timer expires again. It will retry again based on the threshold set by request_reply_retry.
With no response from node a node d sends an Address_Cleanup message throughout the MANET to release node As IP.
19 MANETconf Operation
Node a wishes to join the network. It selects b as its initiator.
Node a migrates and is unable to communicate with b. Node a now chooses c as its initiator.
Node a informs c of its previous attempt to request an IP from b.
Node c sends node b a message informing b of node as migration.
Node b still queries for an IP for node a. When node b arrives at a valid IP for node a the result is sent to node c and node c initiates node a.
20 Making MANETconf Robust
Node a wishes to join the network. It selects b as its initiator.
In the middle of the configuration process node b crashes.
Eventually node as Address_allocation_timer will timeout. Node a will then perform another Neighbor_query and select a new initiator if one can be reached.
Any other nodes that reserved an IP from node bs address request will eventually time out and the IP will be flushed from the Allocated_Pending lists.
21 Making MANETconf Robust
The link between nodes c and d fails. The network splits into two networks.
All nodes in one partition can assume that the nodes in the other partition have departed ungracefully and cleaned up accordingly.
22 Making MANETconf Robust
During a network split what prevents an entering node on one partition from assuming the IP of a node on a second partition
Partitions keep two identifiers lowest partition IP address and UUID.
One partition has the node with the lowest IP address. Nodes in this parent partition clean up the addresses from the second partition.
Clean up is also performed in the second partition if a node requests an IP address. As the lowest IP in the parent node are unobtainable nodes in the second partition determine what IP address is the lowest number. This lowest IP address node then floods the partition and all nodes in that partition then know which node is the partition identifier.
23 Making MANETconf Robust
Partition Detection (contd)
If no IP address assignment is initiated on the second partition a clean up is never triggered and the split is not detected.
In this case if the lowest IP in tables become unreachable after a number of retries a cleanup can be initiated.
Methods work even if network is partitioned into multiple partitions.
24 Security Issues
Susceptible to DOS attacks
A rogue node could act as an initiator and effectively allocate all free IPs to phantom nodes and prevent valid nodes from joining the network.
The rogue node can also respond to requests on behalf of the phantoms to prevent clean ups.
Susceptible to Malicious Clean up Messages
A rogue node could clean up the IPs of valid nodes and disconnect them from the network. If this happens to an initiator duplicate IPs could exist.
Authors claim that their proposed solution is only as insecure as other solutions and protocols such as ARP and RARP.
Resolution to the above attacks can be achieved with the use of digital certificates from a trusted Authentication Server.
Performed on ns-2 (ver2.1b6a) with CMU extensions to support ad hoc networks.
Simulations for related approaches (Zeroconf etc) are not performed due to their deterministic latency and number of messages that can be computed theoretically.
Simulations do not implement support for handling partitioning.
MANET is modelled with moving nodes. Nodes pick a random coordinate move at a speed of 5 m/s stop at the destination for 10s then repeat the process.
Maximum number of nodes is 40 50 60 and 80.
Maximum node density is one node per 0.02km2.
For 40 60 and 80 node simulations simulations are started with 25 35 and 45 pre-configured nodes respectively.
Node arrival times uniformly distributed in the range 0 70s.
Node lifetime varies between 0-1000s 0-2000s and 0-15000s.
Graceful departures varied between 75 and 100.
Underlying routing protocol is DSDV.
No arrivals accepted in the first 200s to allow nodes to set up routing tables.
75 graceful and 25 abrupt departures.
Most addresses are allocated in under 0.5s
5s allocation attempts correspond to unanswered initiator requests and are consistent with the numbers set in the initiator_request_timer field.
10s allocation attempts correspond to situations where abrupt departure nodes were cleaned up.
100 graceful departures.
Latency is high for some address allocation attempts due to packet loss.
Only the results of the samples that are not dropped are shown.
Time required for address allocation increases with the number of nodes in the network.
Other Flood Messages
Messages sent to nodes that fail to respond to Initiator_Request messages.
All communications directed back to the initiator.
MANETconf allows for dynamic allocation of IPs in a Mobile Ad Hoc Network without the need for a centralized server running DHCP.
Proposed solution is tolerant to splits and merges and can tolerate message loss.
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