Rong-Chang Chen

Performance improvement of vector quantization by using threshold

Vector quantization (VQ) is an elementary technique for image compression. However, the complexity of searching the nearest codeword in a codebook is time-consuming. In this work, we improve the performance of VQ by adopting the concept of THRESHOLD. Our concept utilizes the positional information to represent the geometric relation within codewords. With the new concept, the lookup procedure only need to calculate Euclidean distance for codewords which are within the threshold, thus sifts candidate codewords easily. Our scheme is simple and suitable for hardware implementation. Moreover, the scheme is a plug-in which can cooperate with existing schemes to further fasten search speed. The effectiveness of the proposed scheme is further demonstrated through experiments. In the experimental results, the proposed scheme can reduce 64% computation with only an extra storage of 512 bytes.

A hierarchical FLP model for broadband networks

In next generation networks (NGNs), broadband networks include various layer 2 and layer 3 devices, e.g., Ethernet switches and routers. When deploying broadband networks, how the devices are appropriately located is an important issue. The device location problem could be treated as a hierarchical facility location problem (FLP). We present detailed mathematical models for the hierarchical FLP encountered in broadband network planning. Through experiments based on real networks, we demonstrate that the linearity of the model could significantly improve both the computational complexity and the optimality.

Scalable IP routing lookup in next generation network

Ternary content-addressable memory has been widely used to perform fast routing lookups. It is able to accomplish the best matching prefix problem in O(1) time without considering the number of prefixes and its lengths. As compared to the software-based solutions, the Ternary content-addressable memory can offer sustained throughput and simple system architecture. It is attractive for IPv6 routing lookup. However, it also comes with several shortcomings, such as the limited number of entries, expansive cost and power consumption. Accordingly, we propose an efficient algorithm to reduce the required size of Ternary content-addressable memory. The proposed scheme can eliminate 98 percentage of Ternary content-addressable memory entries by adding tiny DRAM. We also address related issues in supporting IPv6 anycasting.

High-performance IP forwarding with efficient routing-table update

There has been an extensive study in constructing the routing tables during the past few years. Although the existing works have certain advantages, those approaches either use complicated data structures which result in large storage requirement and high complexity for updating/building the forwarding table or they are not scalable to fit in Internet protocol version 6 (IPv6). In this work, we propose a fast forwarding-table construction algorithm. With the modified multiway search tree, we can further reduce the depth of the tree and eliminate the storage for pointers. It leads to reduce the FT size and shorten the routing-table lookup time. While considering the route flaps, the forwarding performance will degrade by only 3.1% with 4000 BGP updates per 30 s in the worst case. Moreover, it is simple enough to fulfill the need of the fast packet forwarding. An extension approach to solve the IPv6 routing lookup is also presented for the future deployment.

Scalable Packet Classification for IPv6 by Using Limited TCAMs

It has been demonstrated that performing packet classification on a potentially large number of filters on key header fields is difficult and has poor worst-case performance. To achieve fast packet classification, hardware support is unavoidable. Ternary content-addressable memory (TCAM) has been widely used to perform fast packet classification due to its ability to solve the problem in O(1) time without considering the number of entries, mask continuity and their lengths. As compared to the software-based solutions, the TCAM can offer sustained throughput and simple system architecture. It is attractive for packet classification, especially for the ultimate IPv6-based networks. However, it also comes with several shortcomings, such as the limited number of entries, expansive cost and power consumption. Accordingly, we propose an efficient algorithm to reduce the required TCAM by encoding the address portion of the searchable entries. The new scheme could encrypt the 128-bit prefixes of the real-world IPv6 routing tables into 11 bits and still keeps the property of CIDR.