Browsing by Author "Chan, CT"

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A distributed end-to-end rate control scheme for ABR service
(1998)
Chen, JR
;
Chen, YC
;
Chan, CT
;
資訊工程學系
;
Department of Computer Science
In ATM networks, the ABR service allows both the source and the destination to function simply, this means that we may need a certain complexity in the switch. To provide robust ABR service, policing and discarding functions are usually required. ABR rate control schemes such as UT [4] and OSU [5][7] can achieve high utilization, but they suffer the oscillation of transmission rate. We propose an End-to-End Rate Control Algorithm (EERCA), which performs the monitoring function in end systems, and achieves max-min fairness naturally. Our scheme relies on the round-robin discipline in combination with per-VC queuing for cell scheduling, it also covers the policing function. EERCA resolves the oscillation problem that is quite common in existing explicit rate schemes, as well as features very low cell loss ratio with much smaller buffer size.
A fast IP routing lookup scheme
(2000)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
A major design issue for the next generation routers is the 1P lookup mechanism. The router needs to perform a longest prefix matching on the address lookup for each incoming packet to determine the next hop. Currently, the process is done in software and has become a major performance bottleneck of the router. In this paper, we propose a fast IP lookup mechanism in which the forwarding table is small enough to fit in SRAM with very low cost. It also can be implemented in hardware using the pipeline technique. A large routing table with 45,000 routing prefixes can be compressed to a forwarding table with about 430 Kbytes in size by using our proposed method. In the worst case, the number of memory accesses for a lookup is three. When implemented in pipeline technique, the proposed mechanism can achieve one routing lookup per memory access. With current ions SRAM, this mechanism provides approximately 100 million routing lookups per second. Futhermore, the lookup speed can be improved linearly through the speedup of the memory access.
A fast IP routing lookup scheme
(2001-03-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
A major issue in router design for the next generation Internet is the fast IP address lookup mechanism. The existing scheme by Huang et al. performs the IP address lookup in hardware in which the forwarding table can be compressed to fit into reasonable-size SRAM, and a lookup can be accomplished in three memory accesses. In this letter, we claim that with a little extra memory, it is able to further reduce the lookup time to two memory accesses.
A fast packet classification by using enhanced tuple pruning
(2002)
Wang, PC
;
Chan, CT
;
Tseng, WC
;
Chen, YC
;
資訊工程學系
In the packet classification, the route and resources allocated to a packet are determined by the destination address as well as other header fields of the packet such as source/destination address, TCP and UDP port numbers. It has been demonstrated that performing packet classification on a potentially large number of fields is difficult and has poor worst-case performance. In this work, we proposed an enhanced tuple pruning search algorithm called "Tuple Pruning +" that provides fast two-dimension packet classification. With reasonable extra filters added for Information Marker, only one hash access to the tuples is required. Through experiments, about 8 MB memory is required for 100K-filter database and 20 million packet per second (MPPS) is achievable. The results demonstrate that the proposed algorithm is suitable for high-speed packet classification.
A fast table update scheme for high-performance IP forwarding
(2002-01-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In the previous work, Lampson et al. proposed an IP lookup algorithm which performs binary search on prefixes (BSP) [1]. The algorithm is attractive, even for IPv6, because of its bounded worst-case memory requirement. To achieve fast forwarding, it may need to slow down the insertion speed. Although this can be justified, the routing-table reconstruction in BSP is too time-consuming to handle the frequent route updates. In this work, we propose a fast forwarding-table construction algorithm which can accomplish more than 4,000 route updates per second. Moreover, it is simple enough to fulfill the need of fast packet forwarding. With the enhanced multiway search tree, we further reduced the depth of the tree and eliminated the pointer storage; this reduces the forwarding table size and shortens the lookup time.
A fast table update scheme for high-performance IP forwarding
(2001)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
There has been an extensive study in constructing the routing tables during the past few years. Although the existing works have certain advantages, ho,vel er, those approaches either use complicated data structures which result in large storage requirement and high complexity updating/building the forwarding table, or they are not scalable refit in IPv6. Lampson et al. proposed an IP lookup algorithm which performs binary search on prefixes (BSP) [11] The algorithm is attractive, even for IPv6, because of its bounded worst-case memory requirement. For achieving fast forwarding the cost paid is the slowing down insertion. Although this can be justified, the performance of routing-table reconstruction in BGP is too time-consuming,ring to handle the frequent route updates. In this work, we propose a fast forwarding-table construction algorithm which can handle more than 4,000 route updates per second. Moreover; it is simple enough to fufil the need of fast packet forwarding. With the modified multiway search tree, we can further reduce the depth of the tree and eliminate the storage for pointers, this reduces the fowarding table size and shorten the lookup time.
A FIFO-based buffer management approach for the ATM GFR services
(2000-06-01)
Chan, CT
;
Hu, SC
;
Wang, PC
;
Chen, YC
;
資訊工程學系
We investigate the TCP packet transmission over the ATM Guaranteed Frame Rate (GFR) service using a selective packet-discard with buffer vacancy tracking strategy and a packet-based push-out buffering scheme. Our approach is based on FIFO queueing discipline, it features fair sharing of available resources as well as feasibility in hardware implementation.
A novel transient characterization technique to investigate trap properties in HfSiON gate dielectric MOSFETs - From single electron emission to PBTI recovery transient
(2006-05-01)
Wang, TH
;
Chan, CT
;
Tang, CJ
;
Tsai, CW
;
Wang, HCH
A positive bias temperature instability (PBTI) recovery transient technique is presented to investigate trap properties in HfSiON as high-k gate dielectric in nMOSFETs. Both large and small-area nMOSFETs are characterized. In a large-area device, the post-PBTI drain current exhibits a recovery transient and follows logarithmic time dependence. In a small-area device, individual trapped electron emission from HfSiON gate dielectric, which is manifested by a staircase-like drain current evolution with time, is observed during recovery. By measuring the temperature and gate voltage dependence of trapped electron emission times, the physical mechanism for PBTI recovery is developed. An analytical model based on thermally assisted tunneling can successfully reproduce measured transient characteristics. In addition, HfSiON trap properties, such as trap density and activation energy, are characterized by this method.
An adaptive priority traffic control approach for guaranteed services in ATM networks
(1997)
Chen, YC
;
Chan, CT
;
Hu, SC
;
資訊工程學系
;
Department of Computer Science
This paper presents an adaptive priority traffic control approach which uses a dynamic buffer allocation scheme, and an adaptive priority queuing technique for handling the delay-sensitive traffic in ATM networks. The former adjusts the buffer size based on the real traffic demand, while the latter adaptively change the priority. The simulation results show that diverse delay-sensitive traffic achieve satisfied performance through our approach. It may fulfill the emerging needs of guaranteed services.
An efficient IP routing lookup by using routing interval
(2001-12-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Nowadays, the commonly used table lookup scheme for IP routing is based on the so-called classless interdomain routing (CIDR). With CIDR, routers must find out the best matching prefix (BMP) for IP packets forwarding, this complicates the IP lookup. Currently, this process is mainly performed in software and several schemes have been proposed for hardware implementation. Since the IP lookup performance is a major design issue for the new generation routers, in this article we investigate the properties of the routing table and present a new approach for IP lookups, our approach is not based on BMP and significantly reduces the complexity, thus the computation cost of existing schemes can be significantly reduced. We also propose an efficient IP lookup algorithm, with which we improve the binary search on prefixes to 30 millions of packets per second (MPPS) and 5,000 route updates/s under the same experiment setup with an even larger routing table.
An efficient traffic control approach for GFR services in IP/ATM internetworks
(1998)
Chan, CT
;
Chen, YC
;
Wang, PC
;
資訊工程學系
;
Department of Computer Science
The Guaranteed Frame Rate (GFR)/UBR+ service has been proposed to support traffic streams with a minimum packet level guarantee for packets not exceeding the maximum size. In addition, the service also specifies that the excess traffic of a user should have access to a fair share of available resource. In this paper, we investigate a packet-discard strategy in combination with the push-out scheme, which alleviates the effect of fragmentation and supports GFR services efficiently. The simulation results show that our proposed method achieves the requirements of GFR service as well as improves the TCP throughput using the common FIFO cell scheduling. Moreover, it is feasible in implementation.
An efficient traffic control scheme for TCP over ATM GFR services
(2002-04-05)
Chan, CT
;
Wang, PC
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In ATM networks, the guaranteed frame rate (GFR) service category has been defined to support user applications which are neither able to specify the range of traffic parameter values, nor able to comply with the behavior rules. It provides a packet-level rate guarantee with a given maximum packet size. The service specifies that the excessive traffic from a user should share the available resource fairly. In this paper, we investigate TCP/IP packet transmission over ATM by using a selective packet-discard strategy with tracking of the available buffer space and a packet push-out buffering scheme to accommodate the GFR service. The simulation results show that our proposed method fulfills the requirements of GFR service as well as improves the TCP throughput under the common FIFO scheduling. A feasible implementation approach is also addressed. (C) 2001 Elsevier Science B.V. All rights reserved.
An enhanced congestion avoidance mechanism for TCP vegas
(2003-07-01)
Chan, YC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in traditional schemes. It has been demonstrated that TCP Vegas achieves much higher throughput than TCP Reno. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs in the backward path. In this letter, we propose an enhanced congestion avoidance mechanism for TCP Vegas. By distinguishing whether congestion occurs in the forward path or not, it significantly improves the connection throughput when the backward path is congested.
An intelligent buffer management approach for GFR services in IP/ATM internetworks
(2000-08-30)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
In ATM networks, the Guaranteed Frame Rate (GFR) service has been proposed to accommodate non-real-time traffic with packet size not exceeding a maximum length, such as TCP/IP based traffic. The GFR service not only guarantees a minimum throughput at the frame level, but also supports a fair share of available resources. In this article, we propose a buffering strategy called Intelligent Fair Buffer Allocation (IFBA) that provides minimum cell rate (MCR) guarantees and fair sharing to GFR virtual circuits (VCs). From the simulation results, we demonstrate that IFBA fulfills the requirements of GFR service as well as improves the TCP throughput using the FIFO scheduling. (C) 2000 Elsevier Science B.V. All rights reserved.
Anatomy of zero-norm states in string theory
(2005-04-01)
Chan, CT
;
Lee, JC
;
Yi-Yang
;
電子物理學系
;
Department of Electrophysics
We calculate and identify the counterparts of zero-norm states in the old covariant first quantized (OCFQ) spectrum of open bosonic string in two other quantization schemes of string theory, namely, the light-cone Del Giudice-Di Vecchia-Fubine zero-norm states and the off-shell Becchi-Rouet-Stora-Tyutin (BRST) zero-norm states (with ghost) in the Witten string field theory (WSFT). In particular, special attention is paid to the interparticle zero-norm states in all quantization schemes. For the case of the off-shell BRST zero-norm states, we impose the no-ghost conditions and recover exactly two types of on-shell zero-norm states in the OCFQ string spectrum for the first few low-lying mass levels. We then show that off-shell gauge transformations of WSFT are identical to the on-shell stringy gauge symmetries generated by two types of zero-norm states in the generalized massive sigma-model approach of string theory. The high-energy limit of these stringy gauge symmetries was recently used to calculate the proportionality constants, conjectured by Gross, among high-energy scattering amplitudes of different string states. Based on these zero-norm state calculations, we have thus related gauge symmetry of WSFT to the high-energy stringy symmetry of Gross.
Comparison of oxide breakdown progression in ultra-thin oxide silicon-on-insulator and bulk metal-oxide-semiconductor field effect transistors
(2004-09-15)
Chen, MC
;
Ku, SH
;
Chan, CT
;
Wang, TH
;
電子工程學系及電子研究所
Enhanced oxide breakdown progression in ultra-thin oxide silicon-on-insulator p-type metal-oxide-semiconductor field-effect transistors is observed, as compared to bulk devices. The enhanced progression is attributed to the increase of hole stress current resulting from breakdown induced channel carrier heating in a floating-body configuration. Numerical analysis of hole tunneling current and hot carrier luminescence measurement are performed to support our proposed theory. This phenomenon is particularly significant to the reliability of devices with ultra-thin oxides and low operation gate voltage. (C) 2004 American Institute of Physics.
Comparison of oxide breakdown progression in ultra-thin oxide SOI and bulk pMOSFETs
(2004)
Chan, CT
;
Kuo, CH
;
Tang, CJ
;
Chen, MC
;
Wang, TH
Accelerated oxide breakdown progression in ultra-thin oxide (1.4nm) SOI pMOSFETs is observed, as compared to bulk devices. The accelerated progression is explained by the increase of hole stress current as a result of breakdown induced channel carrier heating in a floating-body configuration. Numerical simulation of hole tunneling current and hot carrier luminescence measurement are carried out to justify the proposed theory.
CPn model on fuzzy sphere
(2002-03-18)
Chan, CT
;
Chen, CM
;
Lin, FL
;
Yang, HS
;
電子物理學系
We construct the CPn model on fuzzy sphere. The Bogomolny bound is saturated by (anti-)self-dual solitons and the general solutions of BPS equation are constructed. The dimension of moduli space describing the BPS solution on fuzzy sphere is exactly the same as that of the commutative sphere or the (noncommutative) plane. We show that in the soliton backgrounds, the number of zero modes of Dirac operator on fuzzy sphere, Atiyah-Singer index, is exactly given by the topological charge of the background solitons. (C) 2002 Elsevier Science B.V. All rights reserved.
Design and analysis of delay control for CBR services in ATM networks
(1998-05-15)
Chen, YC
;
Chan, CT
;
Hu, SC
;
資訊工程學系
;
Department of Computer Science
Asynchronous transfer mode (ATM) networks are designed to provide end-to-end transport of user data via virtual connections with specified quality of services (QOS), which is expected to be satisfied through effective traffic control mechanisms. This paper presents an adaptive delay-jitter control (ADJC) method that guarantees the delay bounds of constant bit rate (CBR) services in ATM networks. Our proposed method is based on a node-by-node time-frame scheme. Through both mathematical derivation and simulation, we have demonstrated that ADJC features a significant improvement over existing approaches in jitter delay, which can be reduced to one time-frame from end-to-end for CBR traffic. Simulation results have shown that CBR services receive satisfactory delay performance using our approach. (C) 1998 Elsevier Science B.V.
Design and analysis of traffic control for guaranteed services on the Internet
(2000-05-01)
Wang, PC
;
Chan, CT
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Real-time communications services will be one of the most promising applications on the Internet. Real-time traffic usually utilizes a significant amount of resources while traversing through the network. To provide guaranteed service for delay-sensitive real-time applications, both resource reservation and effective traffic control are necessary. The resource reservation protocol (RSVP) was developed to deal with the former problem while various approaches have been proposed to solve the latter one. It is crucial for guaranteed services to maintain satisfactory performance through effective traffic control, which must be implemented in a feasible way and be able to work with RSVP. In this article, we present a flexible and effective traffic-control approach with a resource reservation scheme to accommodate delay-sensitive services on the Internet. We demonstrate that our approach features proven bounded end-to-end queueing delay for delay-sensitive applications and good resilience for resource allocation. In addition, our packet transmission discipline achieves significant improvement in end-to-end delay control.