• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.5B
• /
• pp.465-475
• /
• 2004

Transport Control Protocol (TCP) has been implemented in software running on CPU in end systems, and the protocol processing has appeared as a new bottleneck due to advanced link technology. TCP processing is a critical issue in Storage Area Network (SAN) such as iSCSL, and the overall performance of the Storage Area Network heavily depends on speed of TCP processing. TCP Engine implemented in hardware reduces the load of CPU in end systems as well as accelerates the protocol processing, and hence high speed data processing is achieved. In this paper, we have proposed a hardware engine for TCP processing. TCP engine consists of three major block, TCP Connection block Rx TCP block and Tx TCP block TCP Connection block is responsible for managing TCP connection states. Rx TCP block is responsible for receive flow which receives packets from network and sends to CPU. Rx TCP performs header and data processing and sends header information to TCP connection block and Tx TCP block It also assembles out-of-ordered data to in-ordered before it transfers data to CPU. Tx TCP block is responsible for transmit flow which transfers data from CPU to network. Tx TCP performs retransmission for reliable data transfer and management of transmit window and sequence number. Various test-cases are used to verify the TCP functions. The TCP Engine is synthesized using 0.18 micron technology and results in 51K gates not including buffers for temporal data storage.

• International Journal of Internet, Broadcasting and Communication
• /
• v.15 no.1
• /
• pp.1-7
• /
• 2023

TCP is considered a major candidate transport protocol even for constrained IoT networks due to its ability to integrate into the existing network infrastructures. Since TCP implementations such as uIP TCP often allow only a single TCP segment per connection to be unacknowledged at any given time due to resource constraints, the congestion control relies only on RTO management. In our previous work, to address the problem that uIP TCP performs poorly particularly when a radio duty cycling mechanism is enabled and the hidden terminal problem is severe, we proposed a RTO scheme for uIP TCP and validated the performance through Cooja simulation. In this study, we investigate the effect of other factors that were not considered in our previous work. More specifically, the effect of traffic intensity, the degree of the hidden terminal problem, and RDC is investigated by varying the offered load and the transmission range, and the RDC channel check rate. Simulation results imply that we need to further investigate how to improve TCP performance when the radio duty cycling mechanism is used.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2000.04a
• /
• pp.629-632
• /
• 2000

현재 사용하고 있는 HTTP/1.0은 각각의 트랜잭션마다 별개의 TCP 연결 설정을 해야함으로서 야기되는 잦은 RTT지연과 Slow Start로 인해 성능상의 문제점을 야기하고 있다. IETF의 HTTP-NG은 이런 문제점을 포함하여 다각적인 요구를 수용할 수 있도록 HTTP/1.1(RFC 2616)을 발표하였다. HTTP/1.1은 이 문제점을 지속적인 연결(Persistent Connection) 개념을 도입하여 개선하고 있다. 그러나, 연결 해제 시점을 명확하게 정의하고 있지 않기 때문에 이로 인해 서버의 자원 낭비를 줄이는 효율적인 연결 관리 방법을 제시하지 못하고 있다. 본 논문은 하나의 TCP 연결 위에 다중의 요구들을 실행할 수 있는 HTTP/1.1의 지속적인 연결 개념에, 클라이언트 측에서 적절한 TCP 연결 해제 시점을 지원하여 서버 자원을 효율적으로 사용할 수 있는 알고리즘을 제안한다.

• Journal of Information Technology Services
• /
• v.8 no.1
• /
• pp.193-202
• /
• 2009

Cloud computing emerges as a new computing paradigm which targets reliable and customizable services. The term builds on decades of research in virtual machine, distributed and parallel computing, utility computing, and more recently networking, web service, and software as a service. In this paper, we provide a seamless connection migration of web services. This is useful for cloud computing environment in which many client terminals have mobility. With the wireless internet facility, those mobile users can move place to place during internet communication. Therefore, we provide solutions to the two major problems in current virtualization based migration: communication failure problems and connection re-establishment. Communication channel flushing by zero window notification helps to resolve the communication failure problems and TCP port inheritance prevents connection re-establishment errors during socket reconstruction. Thus, our web service migration facility is now able to preserve open network connections, and even for server sockets. This is a highly transparent approach, in that we did not Introduce additional messages for channel flushing and did not make any modification to the TCP protocol stack. Experimental results show that the overhead due to connection migration of web services is almost negligible when compared with time to take the conventional web service migration.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.7
• /
• pp.22-29
• /
• 2002

The Gauranteed Frame Rate service category was proposed by the ATM Forum as an enhancement to the UBR service. This service aims to support minimum cell rate gaurantee for each virtual connection and allow any excess bandwidth in the network to be shared among the contending VCs in a fair manner. We propose a new buffer management algorithm for GFR service through FIFO queuing discipline. Proposed scheme can provide minimum bandwidth guarantee for GFR VCs as well as improve the fairness among the competing GFR VCs on a single FIFO queue. From simulation results, we demonstrate the proposed scheme fulfills the requirement of GFR service as well as improves the TCP throughput.

• Journal of KIISE:Information Networking
• /
• v.32 no.4
• /
• pp.443-451
• /
• 2005

Stateful inspection devices must maintain flow information. These devices create the flow information also for network attack packets, and it can fatally inflate the dynamic memory allocation on stateful inspection devices under network attacks. The memory inflation leads to memory overflow and subsequent performance degradation. In this paper, we present a guideline to set the flow entry timeout for a stateful inspection device to remove harmful embryonic entries created by network attacks. Considering Transmission Control Protocol (TCP) if utilized by most of these attacks as well as legitimate traffic, we propose a parsimonious memory management guideline based on the design of the TCP and the analysis of real-life Internet traces. In particular, we demonstrate that for all practical purposes one should not reserve memory for an embryonic TCP connection with more than (R+T) seconds of inactivity where R=0, 3, 9 and $1\leqq{T}\leqq{2}$ depending on the load level.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.10e
• /
• pp.403-405
• /
• 2002

지금까지 TCP 혼잡 제어를 위한 여러 종류의 메커니즘들이 Connection을 적응성 있게 제어하기 위하여 사용되어 왔지만, TCP 혼잡 제어 메커니즘들은 성능상의 여러 문제점을 가지고 있는게 사실이다. 이에 IETF에서는 AQM(Active Queue Management) 메커니즘으로 RED 알고리즘을 권고했다. 그러나 이 또한 상이한 네트워크에서는 파래메터 설정에 따른 문제점이 있어, 네트워크 상황에 적절하게 대응하지 못하는 단점이 있다. 이러한 RED알고리즘의 문제점을 극복하고, 효율성을 개선하기 위해서 SRED, BLUE, FRED, DRED 등 다양한 AQM 메커니즘들이 제시되고 있다. 본 논문에서는 네트워크 트래픽 상황에 따라 적응성을 갖고 Threshold의 변경에 사용되는 패킷 손실율을 구하는데 있어 트래픽을 고려한가중치를 줌으로써 트래픽 상황을 반영하도록 했고, Threshold 설정에 있어 적응성 있는 단계를 통하여 큐 안정성을 개선하도록 하였다. 제안한 알고리즘의 성능 분석은 NS 시뮬레이터를 사용하였고, 제안한 Load Adaptive DRED 알고리즘과 DRED 알고리즘의 버퍼 관리 기법의 성능 비교 분석을 통하여 큐 안정성의 개선된 성능을 확인하였다.

• Journal of Communications and Networks
• /
• v.10 no.3
• /
• pp.338-350
• /
• 2008

The differentiated services (DiffServ) is proposed to provide packet level service differentiations in a scalable manner. To provide an end-to-end service differentiation to users having a connection over multiple domains, as well as a flow marker, an intermediate marker is necessary at the edge routers, and it should not be operated at a flow level due to a scalability problem. Due to this operation requirement, the intermediate marker has a fairness problem among the transmission control protocol (TCP) flows since TCP flows have intrinsically unfair throughputs due to the TCP's congestion control algorithm. Moreover, it is very difficult to resolve this problem without individual flow state information such as round trip time (RTT) and sending rate of each flow. In this paper, to resolve this TCP fairness problem of an intermediate marker, we propose a fair scalable marker (FSM) as an intermediate marker which works with a source flow three color marker (sf-TCM) operating as a host source marker. The proposed fair scalable marker improves the fairness among the TCP flows with different RTTs without per-flow management. Through the simulations, we show that the FSM can improve TCP fairness as well as link utilization in multiple domain DiffServ networks.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.6
• /
• pp.1610-1618
• /
• 1998

In this paper, we present the FB(Fair Buffering) mechanism for the efficient support of TCP traffic over UBR connections in the subnet ATM model. We show that both throughput and fairness may be improved with the FB mechanism. The FB mechanism is founded on the observation that the performance of TCP over UBR connections is optimal when the buffer space is allocated in proportion to the connection's bandwidth-delay product. We compare through simulation the performance of the existing drop-tail, EB(Equal Buffering) and the proposed FB buffer management schemes, with and without RR(Roung-Robin) scheduling, and demonstrate that the proposed FB mechanism is most effective when used in conjunction with the RR scheduling scheme.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.140-143
• /
• 2000

This research presents new type of remote monitoring and control solution of PLC that can be used bi-directional and efficient management of factory automation through internet. This system has client/server architect for information handling between PLC and remote computer where a user can control and monitor target PLC. Actually the authors redirect RS232C connection between PLC and server computer into Internet connection between PLC and remote client computer using supplied PLC tool program So user feel like in front of PLC panel when he operates remote PLC through Internet. Each client/server program is constructed with Java language for security. In this paper the internet-based remote control system was proposed and proved validity by being applied to redirection of PLC control for factory automation.