Ju Hyoung Mun

Binary search on prefix lengths for IP address lookup

Address lookup is an essential function in the Internet routers that should be performed in wire-speed. A lot of address lookup algorithms have been widely studied. Among them, we have thoroughly investigated the binary-search-based address lookup algorithms. Most of the existing binary search schemes perform binary search on prefix values, and hence the lookup speed is proportional to the length of prefixes or the log function of the number of prefixes. The previous algorithm based on binary search on prefix lengths has superior lookup performance than others. However, the algorithm requires very complicated pre-computation of markers and best matching prefixes for internal nodes. This complicated pre-computation makes the composition of the routing table and the incremental update difficult. In this letter, a new IP address lookup scheme based on binary search on prefix lengths is proposed. The performance evaluation results show that the proposed scheme has very good performance in the lookup speed and the scalability

New Approach for Efficient IP Address Lookup Using a Bloom Filter in Trie-Based Algorithms

IP address lookup operation determines the longest prefix matching each incoming destination address. As a fundamental operation for packet forwarding at Internet routers, search speed for routing table lookup is the most important performance metric. Previous researches have shown that the search performance of trie-based algorithms can be improved by adding on-chip Bloom filters. In these algorithms, an on-chip Bloom filter identifies the membership of a node in an off-chip trie, and the number of trie accesses is reduced, because the Bloom filter can filter out accesses to non-existing nodes in the trie. In this paper, we propose a new method of utilizing a Bloom filter for the IP address lookup problem. In the previous Bloom filter-based approach, false positiveness has to be identified by accessing the off-chip trie for every positive result, since false positives can produce wrong results. In our proposed approach, the false positiveness of a Bloom filter is not necessarily identified by making false positives not mislead the search. Hence the number of off-chip trie accesses are significantly reduced. Simulation results show that the best matching prefix can be found with a single off-chip access in average and in the worst-case with the reasonable size of a Bloom filter in our proposed method.

NXG06-1: An Efficient IP Address Lookup Algorithm Using a Priority Trie

Fast IP address lookup in the Internet routers is essential to achieve packet forwarding in wire-speed. The longest prefix matching for the IP address lookup is more complex than exact matching because of its dual dimensions, length and value. By thoroughly studying the current proposals for the IP address lookup problem, we find out that binary search could be a low-cost solution while providing high performance. Most of the existing binary search algorithms based on trie have simple data structures which can be easily implemented, but they have empty internal nodes. Binary search algorithms based on prefix values do not have empty nodes, but they either construct unbalanced trees or create extra nodes. In this paper, a new IP address lookup algorithm using a priority trie is proposed. The proposed algorithm is based on the trie structure, but empty internal nodes are replaced by priority prefixes. The longest prefix matching in the proposed algorithm is more efficiently performed since search can be immediately finished when input is matched to a priority prefix. The performance evaluation results show that the proposed priority trie has very good performance in terms of the memory requirement, the lookup speed, and the scalability.

On Reducing False Positives of a Bloom Filter in Trie-Based Algorithms

Many IP address lookup approaches employ Bloom filters to obtain a high-speed search performance. Especially, it has been recently studied that the search performance of trie-based algorithms can be significantly improved by adding Bloom filters. In such algorithms, the number of trie accesses can be greatly reduced because Bloom filters can determine whether a node exists in a trie without actually accessing the trie. Bloom filters do not have false negatives but have false positives. False positives can lead to unnecessary trie accesses. The false positive rate must thus be reduced to enhance the performance of lookup algorithms applying Bloom filters. One important characteristic of trie-based algorithms is that all the ancestors of a node are also stored. The proposed algorithm utilizes this characteristic in reducing the false positive rate of a Bloom filter without increasing the size of the memory for the Bloom filter. When a Bloom filter produces a positive result for a node of a trie, we propose to check whether the ancestors of the node are also positives. Because Bloom filters have no false negatives, the negatives of any of the ancestors mean that the positive of the node is false. In other words, we propose to use more Bloom filter queries to reduce the false positive rate of a Bloom filter in trie-based algorithms. Simulation results show that querying one ancestor of a node can reduce the false positive rate by up to 67% with exactly the same architecture and the same memory requirement. The proposed approach can be applied to other trie-based algorithms employing Bloom filters.

On reducing false positives of a bloom filter in trie-based algorithms

Many IP address lookup approaches employ Bloom filters to obtain a high-speed search performance. Especially, the search performance of trie-based algorithms can be significantly improved by adding Bloom filters, because Bloom filters can determine whether a node exists in a trie without accessing the trie. The false positive rate of a Bloom filter must be reduced to enhance the lookup performance. One important characteristic of a trie is that all the ancestors of a node are also stored. The proposed IP lookup algorithm utilizes this characteristic in reducing the false positive rate of a Bloom filter without increasing the Bloom filter size. When a Bloom filter produces a positive result for a node of a trie, we propose to check whether the ancestors of the node are also positives. Because Bloom filters have no false negatives, the negative of the ancestor means that the positive of the node is false. Simulation results show that the false positive rate is reduced up to 67% using the exact same amount of memory. The proposed approach can be applied to other trie-based algorithms employing Bloom filters.

Utilizing 2-D leaf-pushing for packet classification

This paper proposes a 2-dimensional leaf-pushing.The application of leaf-pushing into a 2-D trie improves classification performance.An implementation method using a Bloom filter and a hash table is presented.A refined structure of the leaf-pushing trie is also proposed.Simulation results supporting our proposition are provided. Packet classification is one of the most challenging functionalities performed by routers at wire-speed for every incoming packet. For search spaces composed of multiple rules represented geometrically, various space decomposition algorithms have been studied to provide effective search methods. While an area-based quad-trie (AQT) provides a simple and intuitive way of mapping the geometrical search space into a two-dimensional (2-D) trie structure, it does not provide high-speed classification performance because the mapping is incomplete. This paper proposes the application of leaf-pushing into the 2-D trie to improve the classification performance of the AQT. The leaf-pushing AQT provides a more effective method of searching rules covering each input packet in the decomposed space. We also discuss an efficient implementation technique for our algorithm using a Bloom filter and a hash table. Simulation results show that our proposed leaf-pushing AQT improves the packet classification performance up to 37 times for sets with up to 100,000 rules compared with the AQT. To be compared with other space decomposition algorithms, a refined structure of the leaf-pushing AQT is also proposed. Simulation results show that the proposed refined structure provides an effective space decomposition method as well as the balance between memory requirements and classification speed, while most of other space decomposition algorithms show a trade-off between them.

Cache sharing using bloom filters in named data networking

In recently emerged Named Data Networking (NDN) technology, each router has a cache to store and provide frequently requested contents. Hence, an efficient cache management scheme is essential for effective content distribution and high cache utilization. As a new cache management scheme, this paper proposes the sharing of cache summaries with neighboring routers to increase the diversity of cached contents in NDN. Our proposed scheme defines a summary packet using a Bloom filter and a method to share the summary. When a Data packet is received, a router makes the decision of whether or not to save the Data depending on query results of the cache summaries of neighboring routers. If any of the neighboring routers have the Data, the Data has not necessarily been saved. When an Interest packet is received, a router can forward the Interest to a neighboring router that has the requested content by checking the summaries. The proposed scheme is evaluated using ndnSIM, which is an NS-3 based Named Data Networking simulator. Simulation results show that the sharing of cache summaries enhances the content diversity and accordingly the cache hit ratio, and reduces the average content delivery time.

Cache Sharing Using a Bloom Filter in Named Data Networking

In Named Data Networking (NDN), routers have caches to store frequently requested contents, and hence cache management scheme becomes a key factor for efficient content delivery. In this paper, we propose the sharing of cache summaries using a Bloom filter among neighboring routers for efficient content delivery and high cache utilization at NDN. When an Interest packet is received, a router can forward the Interest to a neighboring router which has the high potential of the requested content. The proposed scheme is evaluated by using ndnSIM, which is a NS-3 based named data networking simulator. Simulation results show that the summary sharing using our proposed method is beneficial in content diversity and average content delivery time.

A new Bloom filter structure for identifying true positiveness of a Bloom filter

Bloom filters have been employed in various fields because of its simple and effective structure in identifying the membership of an input. Since a Bloom filter can produce false positives, the positive results of a Bloom filter should be identified whether the positives are true or not by accessing the original database. A complement Bloom filter (C-BF) was introduced to identify the true positiveness of a given Bloom filter without accessing the original database. A critical problem of the C-BF is that every element included in the complement set of the given set should be programmed into the C-BF. Since the number of elements included in the complement set can be considerably large, the C-BF would require the significant amount of memory. In this paper, we claim that the elements that produce negative results from the given Bloom filter are not necessarily programmed into the C-BF, since Bloom filters never produce false negatives. In other words, we propose the Petit-BF (P-BF) which programs only the elements that cause false positives from the given Bloom filter. Simulation results and theoretical analysis show that the proposed method can achieve the same performance using a considerably smaller amount of memory.