Hidden Problems with the Hidden Node Problem

Transcription

1 Hidden roblems with the Hidden Node roblem Hidden Node roblem Hidden node Outside the TX range of sender but within the range of receiver. C is hidden node! Throughput is decreased. Larger data packets are more vulnerable. Solution in IEEE Solution in IEEE For unicast packets it s a solved problem Four-way handshake //DT/CK For unicast packets it s a solved problem Four-way handshake //DT/CK Solution in IEEE Formally For unicast packets it s a solved problem Four-way handshake //DT/CK Duration field DT Sender CK lue/red Node Virtual CS 1

2 roblem I: rohibiting arallel TX [1] roblem I: rohibiting arallel TX [1] lue nodes can transmit in arallel Yellow nodes can Receive in arallel Red nodes are helpless! Detecting Opportunities For arallel TX Detecting Opportunities Does not help! Duration field DT If a node receives only Can transmit in parallel If a node receives only Can Receive in parallel If a node receives both + Can do nothing Sender lue/red Node CK Virtual CS Solution MC- [1] Solution MC- [1] Transmitting in arallel What is missing? / Source Dest T DT T CK 1. time gap between / and Data so that potential nodes for parallel transmission can also exchange - R Master Transmission T DT T CK DT 2. Consequently, an indication in - packets about the start time of Data and CK packets T DT T DT T CK T CK DT CK T DT T CK CK R 2

3 Solution MC- [1] Transmitting in arallel rinciple for arallel transmission / Source Dest T DT T CK Z Master Transmission There can be at most one transmitter within the reception range of a receiver T DT T CK DT T DT T CK CK DT Z CK MC- erformance Comparison MC- erformance Comparison MC- limitations: roblem II: /-induced congestion [2] acket size for non-master transmission should be less than that of master transmission. Designed for static network. For Mobile Network enabling parallel transmission is still an open problem! 3

4 roblem II: /-induced congestion [2] locked Node -MC layer takes certain number of attempts and then drops. - It looks like congestion although buffer may still have space. C locked D False blocking False blocking may propagate! C locked C locked D E Falsely blocked G F E D seudo deadlock seudo deadlock 4

5 Solution Validation roblem III: Virtual Jamming [3] REL JMMING (Continuously generate interfering signals) DoS ttack VIRTUL JMMING (retend that you are transmitting) Way of V. Jamming Second kind of attack Duration field Format of / packet Large value on Duration field. Solution! Duration field is a 16 bit integer number. Deny access -ut for as a high large cap. as 32,767 micro second. -Ignore anything Roughly 30 (30 X 32,767 = 983,010 microsec) packets per second above a is threshold. enough for full Denial of service! ttacker lue/red Node Special scenario Simulation Model Modified existing implementation of IEEE in NS2. TR range equals CS range. acket size 1024 bytes. Destination is within one-hop i.e. no routing protocol. No error model. 5

6 Effect on throughput Solution: Validation Without ttack With ttack Validate by sensing the channel (ackward compatible!) When to validate?? ttacker Carrier Sense lue/red Node X X artial Virtual Jamming Solution: Random Validation Validate by sensing the channel (ackward compatible!) When to validate?? Validate by sensing the channel (ackward compatible!) When to validate?? Carrier Sense Carrier Sense ttacker ttacker lue/red Node Node 1 Node 2 Throughput after Random validation More Experimental result Throughput With ttack With Random Validation 6

7 More Experimental result Future Direction Delay Experiment with random scenarios. Lone is a great problem! How about in mobile environment? Can we tell with reasonable confidence that the hidden node problem is a solved problem?? Refernces [1] MC-: MC for Concurrent transmissions in Multi-hop Wireless Networks, rup charya, archan Misra and Sorav ansal. [2] /-Induced Congestion in d Hoc Wireless LNS, Saikat Ray, Jeffrey. Carruthers and David Starobinski. [3] rotecting Wireless Networks against a Denial of Service ttack ased on Virtual Jamming, Dazhi Chen, Jing Deng, and ramod K. Varshney. [4] Denial-of-Service ttacks: Real Vulnerabilities and ractical Solutions, John ellardo and Stefen Savage. End! 7