• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.175-183
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• 2008

QoS-support technology in networks is based on measuring QoS metrics which reflect a magnitude of stability and performance. The one-way delay measurement of the QoS metrics especially requires a guarantee of clock synchronization between end-to-end hosts. However, the hosts in networks have a relative or absolute difference in clock time by reason of clock offsets. flock skews and clock adjustments. In this paper, we present a theorem, methods and simulation results of one-way delay and clock offset estimations between end-to-end hosts. The proposed theorem is a relationship between one-way delay, one-way delay variation and round-trip time And we show that the estimation error is mathematically smaller than a quarter of round-trip time.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.16-24
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• 2007

Wireless mesh network extends the limited coverage of conventional wireless service from one-hop access point to wider area. It is recognized as an important issue to provide seamless handoff in the wide coverage of wireless mesh network. A long handoff delay may cause high packet loss and disconnection of service, degrading the network performance. The handoff delay is mainly introduced from the channel scanning process obtaining information to make handoff decision and the unnecessary handoffs due to inaccurate handoff decision. In this paper, we propose the handoff algorithm based on one-way trip time (OTT) to expedite the handoff procedure. As compared to the handoff algorithm based on the receiving signal power, the proposed algorithm takes advantage of OTT to obtain the necessary handoff information in a relatively shorter time and reduce the unnecessary handoffs. The performance of proposed algorithm is evaluated through the simulations. It is verified that the proposed handoff algorithm can effectively enhance the handoff accuracy, and therefore reduce the handoff delay and unnecessary handoffs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6B
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• pp.553-562
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• 2003

Supporting QoS (Quality of Service) for the multimedia applications becomes an important issue as the demand of multimedia applications increases. Thus, it is necessary for the application layer to have an efficient congestion control algorithm, which can support the multimedia applications' QoS requirements. In this paper, we propose a new application layer congestion control algorithm, called RRC-OTT (Receiver-based Rate Control with One-way Trip Time). RRC-OTT algorithm differs from the previously proposed algorithms in that the receiver takes the responsibility of the network congestion control. Thus, RRC-OTT algorithm can not only precisely estimate the network congestion using OTT (one-way Trip Time), but reduce the work load from the sender (e.g., the web server). Our simulation study shows that RRC-OTT algorithm can maintain the comparable link utilization to the previously proposed algorithms and keep the packet jitter low, which thus can help enhance the quality of multimedia applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7B
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• pp.481-488
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• 2005

As the demand on the multimedia application increases, the congestion control algorithm for the multimedia applications becomes an important research issue. The ultimate goal of congestion control is to adapt the trans-mission rate at the sender to the mont of network resource available on the forward path. In general, the congestion control algorithms use the round trip time(RTT) to estimate the network congestion on the forward path. however, since the RTT includes the delay on both forward and backward paths, it is possible for the algorithms using the RTT to make a wrong decision such as deciding the congestion on the forward path due to the congestion built on the backward path. In this paper, we enhance the performance of RRC-OTT(Receiver-based rate control with one-way Trip Time) algorithm, which uses the one-way trip time(OTT) to estimate the network congestion. By separating the estimation mechanism on the forward path from the backward path, the performance of RRC-OTT algorithm is hardly affected by the congestion built on the backward path.

• Journal of KIISE:Information Networking
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• v.32 no.3
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• pp.359-369
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• 2005

Delay estimation is a difficult Problem in computer networks. Accurate one-way delay estimation is crucial because it serves a very important role in network performance and thus application design. RTT(Round Trip Time) is often used as an approximation of the delay, but because it is a sum of the forward and reverse delays, the actual one-way delay cannot be estimated accurately from RTT. To estimate one-way delay accurately, this paper proposes a new scheme that analytically derives one-way delay, forward and reverse delay respectively. We show that the performance of TCP can improve dramatically in asymmetric networks using our scheme. A key contribution of this paper is that our one-way deiay estimation is much more accurate than RTT estimation so that TCP can quickly find the network capacity in the slow start phase. Since RTT is the sum of the forward and reverse delays, our scheme can be applied to any protocol that is based on RTT.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7C
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• pp.608-615
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• 2007

Generally time of arrival (TOA) information via two way communications can be derived by accurate round trip time (RTT) between two devices. However, response time demanded in RTT measurement is long, a serious TOA error is caused by each different clock drift between two devices. In order to solve this problem, we propose the TOA and time difference of arrival (TDOA) estimation scheme with mitigating clock drift effect. To verify the performance of proposed method, we compared the proposed scheme with one way based TDOA acquisition method introduced by IEEE 802.15.4a Task Group and then we could conclude that the proposed method has better performance over other methods.

• International Journal of Computer Science & Network Security
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• v.22 no.1
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• pp.276-282
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• 2022

One of the most essential foundations upon which big institutions rely in delivering cloud computing and hosting services, as well as other kinds of multiple digital services, is the security of infrastructures for digital and information services throughout the world. Distributed denial-of-service (DDoS) assaults are one of the most common types of threats to networks and data centers. Denial of service attacks of all types operates on the premise of flooding the target with a massive volume of requests and data until it reaches a size bigger than the target's energy, at which point it collapses or goes out of service. where it takes advantage of a flaw in the Transport Control Protocol's transmitting and receiving (3-way Handshake) (TCP). The current study's major focus is on an architecture that stops DDoS attacks assaults by producing code for DDoS attacks using a cloud controller and calculating Round-Tripe Time (RTT).

• The Research Journal of the Costume Culture
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• v.13 no.4 s.57
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• pp.658-670
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• 2005

Kublai Khan on a Hunting Trip were painted by Liu Guan-dao. This painting gives us very important information for understanding cosume of Yuan dynasty because of realistic description. We studied the name of costume of the king Shizu in this painting by using the way of comparison his costume with another paintings, the records and archaeological finds. This study showed that the costume of the king Shizu is judged to be Jisun, the traditional costume of Mongolian own meaning one colour. The name of each is the Yinshu warm hat, being making into the for of a kind of rodents, the Yinshu Jisun, the Red colour Jisun, being railed on the robe, and the Cloud boots cover. And we found that the decoration on the neck and sleeve tib of the Yinshu Jisun had been made by sable furs, and the decoration on the surface had been made by tails of them, going by the name of Rondes at that time. It also showed that the meaning of one colour of the Jisun is not only just appearing one colour on the one person but also being able to appear two set of one colour.

• Journal of Korean Classical Literature and Education
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• no.15
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• pp.67-88
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• 2008

In spite of a few numbers of Hyangga that is handed down today, Hyangga has diverse and abundant contents. So it is possible to survey Hyangga as a journey literature of the middle age. On this purpose we can inquire into the Hwarangs' group journey, because the Hwarang was one of the main enjoying group of Hyangga. Hwarangs' group journey shows many aspects. They made a journey for the public purpose like a tour of inspection of people's daily life and the fortresses of the country's peripheral areas. Also, they made a journey for personal purposes like enjoying the attractive view of the mountains and rivers or seeking pretty girls outside of the palace. On these journeys, Hwarang made and enjoyed Hyanggas. Among Hyanggas that remains today, Hyeseongga and Cheoyongga have a direct relation to Hwarang's journey. Hyeseongga was made to eliminate the calamities that occurred at the time of the start of a journey. It is expressed in this poem that Hwarang could take a peaceful trip with the condition that the celestial objects shed light on the earth path. As such, the trip becomes a sacred ceremony. Cheoyongga reflects the fact that the foreigner Cheoyong became Hwarang and toured the streets of Seorabeol, the capital of Shilla. The Cheoyong's bitterness of broken love is expressed in this poem. SongSadahamga and MoJukjirangga come under a broad category of Hwarang's journey literature. SongSadahamga is a farewell poem for Hwarang who leaves to fight on the battlefield. It was universal to make a journey for the fighting of a battle in Shilla period, so many Hyanggas would be made under those situations. MoJukjirangga has the content of Hwarang's trip for saving his follower who was taken by another senior. It expresses the intimate relationship between Hwarang and the follower. Though the words of the song have not been remained, Hyeongeumpogok, Daedogok, and Mungungok were created on the way of Hwarang's journey. These seem to be a series poems which have the proper characteristic features of the Hwarang's journey literature. In these poems, the king's open mind and liberal political views are reflected. In short, Hwarang created and enjoyed Hyanggas on the way of their journey, so Hyangga has the features of journey literature in Korean middle ages.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.332-337
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• 2016

The rapid reconstruction of a transfer path is caused by frequent secession of nodes in many applications using overlay multicast. For this, however, many studies have been proposed, but a study of fast path recovery is required. This paper proposes a new method for fast path recovery to improve the path reconstruction time and for stable path maintain caused by the sudden secession of the parent node on overlay multicast. The proposed method uses the virtual transfer path and the candidate parent node for the fast path recovery. All nodes exchange periodically the RTT (Round Trip Time) information between the other nodes of similar position itself and neighboring node. All nodes have a candidate parent node list, and each node stores the exchanged RTT information on the list. Each node constructs the virtual transfer path to reduce the recovery time after deciding a candidate parent node that is one of them by the RTT order. In this way, when the parent node is seceded, all nodes can recover the transfer path quickly using the virtual transfer path. The simulation result showed that the recovery time of the proposed method is an average 30% faster than the known method.