• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1147-1150
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• 2006

Stream Control Transmission Protocol (SCTP) uses the 32-bit checksum in the common header, by which a corrupted SCTP packet will be regarded as a lost packet and then discarded. This may result in degradation of SCTP's throughput performance over wireless networks. This paper proposes a new chunk checksum scheme for SCTP, in which each data chunk contains its own checksum field and SACK chunk carry corresponding Transmission Sequence Number (TSN) with timestamp for every corruption event. The proposed chunk checksum scheme is introduced with the following three purposes: 1) to distinguish the chunk corruptions from the chunk losses; 2) to avoid the unnecessary halving of the congestion window (cwnd) in the case of chunk corruption; 3) to avoid the unwanted timeouts which can be induced in conventional SCTP in the case that the retransmitted data chunks are corrupted again in wireless networks. Simulation results show that the proposed chunk checksum scheme could improve the SCTP throughput in the wireless environments with a high bit error rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.736-743
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• 2005

NAT-PT is one of the IPv6 transition mechanisms, as defined in RFC2766, allowing IPv6-only devices to communicate with IPv4-only devices and vice versa. In NAT-PT, sender fail to verify TCP/UDP checksum and authentication data due to IP translation in the NAT-PT server The NAT-PT, therefore, has a limit to applying the IPsec that provides the end-to-end security such as confidentiality, authentication, and integrity. This paper proposes a scheme to apply the IPsec using IP HTI in NAT-PT environment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.1
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• pp.75-83
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• 2008

In this paper, we propose an efficient algorithm that assigns single temporary IPv4 address and port number to improve efficiency of IPv4 address that is allocated in DSTM service. And, we have analyzed the elementary functions for DSTM and have designed the functional modules. Also, we have implemented the DTI interface for encapsulation and decapsulation of IPv6 packets. The performance analysis and comparison are investigated whether the appropriate interworking service is possible or not. Our observation results show that the performance of IPv4 over IPv6 tunneling is suitable to DSTM service due to the reduction of delay by eliminating checksum calculations in the header of IPv6 tunneling.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.217-219
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• 2002

TCP has been designed and tuned as a reliable transfer protocol far wired links. However, it incurs end-to-end performance degradation in wireless environments where packet loss is very high. TCP HACK(Header Checksum Option) is a novel mechanism proposed to improve original TCP in lossy link. It presents an extension to TCP that enables TCP to distinguish packet corruption from congestion in losssy environments. TCP HACK performs well when the sender receives the special ACKs correctly, hut if the ACKs are also lost much, the efficient of TCP HACK will net be prominent. In this paper we present an extension to TCP HACK, which can perform well even when the ACKs are much corrupted.

• Journal of the Korea Society of Computer and Information
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• v.14 no.10
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• pp.101-110
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• 2009

The 6LoWPAN(IPv6 Low-power Wireless Personal Area Network) performs IPv6 header compression, TCP/UDP/IGMP header compression, packet fragmentation and re-assemble to transmit IPv6 packet over IEEE 802,15.4 MAC/PHY. However, from the point of view of security. It has the existing security threats issued by IP packet fragmenting and reassembling, and new security threats issued by 6LoWPAN packet fragmenting and reassembling would be introduced additionally. If fragmented packets are retransmitted by replay attacks frequently, sensor nodes will be confronted with the communication disruption. This paper analysis security threats introduced by 6LoWPAN fragmenting and reassembling, and proposes a re-transmission mechanism that could minimize re-transmission to be issued by replay attacks. Re-transmission procedure and fragmented packet structure based on the 6LoWPAN standard(RFC4944) are designed. We estimate also re-transmission delay of the proposed mechanism. The mechanism utilizes timestamp, nonce, and checksum to protect replay attacks. It could minimize reassemble buffer overflow, waste of computing resource, node rebooting etc., by removing packet fragmentation and reassemble unnecessary.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.532-534
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• 2000

IPv4(Internet Protocol version 4)의 차세대 버전인 IPv6는 기존 IPv4의 문제점인 주소부족 및 새로운 부가기능 등의 필요성 때문에 IETF(Internet Engineering Task Force)에서 IPv4를 대체하기 위해 개발한 프로토콜이다. 하지만 IPv4를 어느 한순간에 IPv6로 대체하는 것은 불가능하기 때문에 기존 IPv4와의 호환 및 연동을 위한 터널링 및 기타 여러 가지 transition mechanism들이 고려되고 있다. 이러한 mechanism들 중에서 최근 표준으로 발표된 NAT-PT(Network Address Translation $\square$ Protocol Translation)는 DNS-ALG (Domain Name System $\square$ Application Level Gateway)라는 개념을 도입하여 IPv4와 IPv6간의 양방향 주소변환 및 프로토콜 변환기능을 수행한다. 각각의 기능에서 주소 변환은 주소크기와 형식이 다른 IPv4와 Pv6간의 서로 상대 노드를 엑세스할 수 있도록 하고 프로토콜 변환은 다른 버전의 프로토콜을 사용하는 노드들이 상대노드가 보낸 패킷의 헤더정보를 이해할 수 있도록 한다. 그리고 이러한 기본적인 변환 외에 헤더정보의 정확한 전달을 위해서는 기존의 path MTU(Maximum Transgfer Unit) discovery 그리고 pseudo header checksum 등도 고려되어야 한다.

• The KIPS Transactions:PartC
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• v.12C no.7 s.103
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• pp.1039-1046
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• 2005

TCP SACK is the unique mechanism to reflect the situation of sink's sequence space, some TCP variants and proposals can perform in conjunction with SACK mechanism for achieving optimal performance. By definition of RFC 2018, however, each contiguous block of data queued at the data receiver is defined in the SACK option by two 32-bit unsigned integers in network byte order. Since TCP Options field has a 40-byte maximum length, when error bursts now, we note that the available option space may not be sufficient to report all blocks present in the receiver's queue and lead to unnecessarily force the TCP sender to retransmit Packets that have actually been received by TCP sink. For overcoming this restriction, in this thesis, a new solution named 'one-byte offset based SACK mechanism' is designed to further improve the performance or TCP SACK and prevent those unwanted retransmissions. The results or both theory analysis and simulation also show that his proposed scheme operates simply and more effectively than the other existing schemes by means of the least bytes and most robust mechanism to the high packet error rates often seen in networks environment.