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DiPIT : a Distributed Bloom-Filter based PIT Table. Authors: Wei You, Bertrand Mathieu, Patrick Truong, Jean-Francois Peltier ,and Gwendal Simon Publisher: ICCCN 2012 Presenter: Chai-Yi Chu Date: 2013/04/10. Outline. Introduction DiPIT Architecture PITi shared Bloom filter
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DiPIT: a Distributed Bloom-Filter based PIT Table Authors: Wei You, Bertrand Mathieu, Patrick Truong, Jean-Francois Peltier ,and GwendalSimon Publisher:ICCCN 2012 Presenter: Chai-Yi Chu Date: 2013/04/10
Outline • Introduction • DiPITArchitecture • PITi • shared Bloom filter • Evaluation
Introduction • Propose a new implementation for one of the main components of CCN nodes, the Pending Interest Table (PIT). • PIT needs a large memory space to store the pending Interests. • Cut the PIT table into several sub-tables, which we call PITi. • Call DiPITfor Distributed PIT
DiPIT Architecture • Use counting Bloom filters • faster than hash tables for lookup and update operations. • be more efficient in memory space. • deal with information removal. • when a Data packet is forwarded, the related Interest entry should be deleted from the PIT table.
PITi: One Bloom filter per CCN face • works independently. • records in a counting Bloom filter the footprints of the Interests packets that come from the associated face. • Incoming Data packets are checked in parallel on all PITis and forwarded on the faces when the associated PITi has a matching footprint.
A shared Bloom filter: Deal with false positive • Adding another filter after the first Interest verification process. • The total false positive ratio is the product of the two individual false positive ratios of the two filters. • Returned Data packets do not remove entries in the shared Bloom filter • refresh the shared Bloom filter sometimes. • The number of inserted elements reaches a threshold • A regular basis
Main DiPITalgorithms • Incoming Interest: • (1) a negative result means that the Interest never came in. It is forwarded to the FIB and its footprint is added in the filter; • (2) a positive result means that either the Interest has already come, or it is a false positive. It is then checked in the secondary shared Bloom filter; • (2a) if the second filter gives a negative answer, the Interest is forwarded to the FIB and its footprint is added in the second filter; • (2b) on the contrary, a positive result means that this Interest is a duplicated emission, the CCN node blocks it.
Incoming Data: • Being verified in all the PITis, except the one where the Data comes. • If a PITicontains a matching Interest footprint, the Data packet is forwarded through this face and the footprint should be deleted from the PITi.
Evaluation • Assume one networking line card holding 16 interfaces. • The average Interest arrival rate ranges from 20 Mpcksto 200 Mpcks.(Million packet per second) • Data packet RTT time as 80 ms. • 5 hash functions for the counting Bloom filters, each counter has 3 bits. • The shared Bloom filter has a size of 1 Mbits. • Acceptable false positive in the range from 0.1% to 1%.
According to Little’s Law, the biggest number of elements in the PIT table is , which can be represented by . • Thus for the centralized hash table we used H-bit of 28 bits. We also add 32 bits H-bit in the valuations. • Assume 40 Bytes Interest packet. • Take the middle value and give 128 bits for each ContentName matching in hash table. • 2 Bytes to memorize the incoming interface identifiers.