• Journal of Communications and Networks
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• v.16 no.6
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• pp.656-666
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• 2014

In delay tolerant networks (DTNs), delay is inevitable; thus, making better use of buffer space to maximize the packet delivery rate is more important than delay reduction. In DTNs, epidemic routing is a well-known routing protocol. However, epidemic routing is very sensitive to buffer size. Once the buffer size in nodes is insufficient, the performance of epidemic routing will be drastically reduced. In this paper, we propose a buffer scheme to optimize the performance of epidemic routing on the basis of the Lagrangian and dual problem models. By using the proposed optimal buffer scheme, the packet delivery rate in epidemic routing is considerably improved. Our simulation results show that epidemic routing with the proposed optimal buffer scheme outperforms the original epidemic routing in terms of packet delivery rate and average end-to-end delay. It is worth noting that the improved epidemic routing needs much less buffer size compared to that of the original epidemic routing for ensuring the same packet delivery rate. In particular, even though the buffer size is very small (e.g., 50), the packet delivery rate in epidemic routing with the proposed optimal buffer scheme is still 95.8%, which can satisfy general communication demand.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.667-680
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• 2008

In this work, we present the results of our empirical study on 802.11 wireless LAN network traffic. We collect the packet trace from existing campus wireless LAN infra-structure. We analyzed four different data sets: aggregate traffic, upstream traffic, downstream traffic, tcp only packet trace from aggregate traffic. We analyze the time series aspect of underlying traffic (byte count process and packet count process), marginal distribution of time series, and packet size distribution. We found that in all four data sets there exist long-range dependent property in byte count and packet count process. Inter-arrival distribution is well fitted with Pareto distribution. Upstream traffic, i.e. from the user to Internet, exhibits significant difference in its packet size distribution from the rests. Average packet size of upstream traffic is 151.7 byte while average packet size of the rest of the data sets are all greater than 260 bytes. Packets with full data payloads constitutes 3% and 10% in upstream traffic and the downstream traffic, respectively. Despite the significant difference in packet size distribution, all four data sets have similar Hurst values. The Hurst alone does not properly explain the stochastic characteristics of the underlying traffic. We model the underlying traffic using fractional-ARIMA (FARIMA) and fractional Gaussian Noise (FGN). While the fractional Gaussian Noise based method is computationally more efficient, FARIMA exhibits superior performance in accurately modeling the underlying traffic.

• Journal of Information Technology Services
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• v.7 no.2
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• pp.137-148
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• 2008

This paper measures and compares the traffic of a series of Massively Multi-player On-line Role Playing Game (MMORPG). The purpose of this analysis is to characterize the MMORPG traffic and compare the traffic characteristics of those games caused by the game structure difference between 2D and 3D environment. The target game is 'Lineage I' and 'Lineage II' which represent world's largest MMORPGs in terms of the number of concurrent users. We collect about 280 giga bytes and 1 tera bytes of packet headers, respectively. We compare packet size, packet inter-arrival time and bandwidth usage of these two games. The MMORPG traffic consists of two kinds of packets: client-generated upstream packets and server-generated downstream packets. We observe that the upstream packet size of payload has grown from 9 bytes to 19 bytes, while the average payload size of downstream packets has grown from 37 bytes to 318 bytes. This asymmetry of growing rate is caused by 3D game structure. Packet inter-arrival time becomes shorter from average 2 milliseconds to 58 microseconds. Bandwidth consumption per client has grown from 4 kbps to 20 kbps. We find that there is a linear relationship between the number of users and the bandwidth usage in both case.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3B
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• pp.213-224
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• 2009

Most of existing routing methods in wireless sensor networks to counter the local eavesdropping-based packet-tracing deal with a single asset and suffer from the packet-delivery latency as they prefer to take a separate path of many hops for each packet being sent. Recently, the author proposed a routing method, GSLP-w(GPSR-based Source-Location Privacy with crew size w), that enhances location privacy of the packet-originating node(i.e., active source) in the presence of multiple assets, yet taking a path of not too long. In this paper, we present a refined routing(i.e., next-hop selection) procedure of it and empirically study privacy strength and delivery latency with varying the crew size w(i.e., the number of packets being sent per path). It turns out that GSLP-w offers the best privacy strength when the number of packets being sent per path is randomly chosen from the range [$1,h_{s-b}/4$] and that further improvements on the privacy are achieved by increasing the random walk length TTLrw or the probability prw that goes into random walk(where, $h_{s-b}$ is the number of hops of the shortest path between packet-originating node s and sink b).

• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.65-72
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• 2004

A basic access method using for IEEE 802.11a wireless LANs is the DCF method that is based on the CSMA/CA. But, Since IEEE 802.11 MAC layer uses original backoff algorithm (Exponential backoff method), when collision occurs, the size of contention windows increases the double size. Hence, packet transmission delay time increases and efficiency is decreased by original backoff scheme. In this paper, we have analyzed TCP packet transmission time of IEEE 802.11 MAC DCF protocol for wireless LANs using a proposed enhanced backoff algorithm. From the results, in OFDM/quadrature phase shift keying channel (QPSK), we can achieve that the transmission time in wireless channel decreases as the TCP packet size increases and based on the data collected, we can infer the correlation between TCP packet size and total message transmission time, allowing for an inference of the optimal packet size in the TCP layer.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.590-593
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• 2005

In this paper, it is analyzed a transmission time of ACL Packet in bluetooth wireless link. In order for segment to improve the transfer capability in bluetooth system, it is fragmented in TCP total messages that are coming down from upper layer and then the packets are sent one at time in baseband. And it is studied that transmission time for bluetooth wireless link according to DM1, DM3 or DM5 packet type in bluetooth piconet environment. From the results, we were able to obtain ACL packet transmission time, optimal TCP packet size and DM packet size.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.767-772
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• 2005

The Internet is a packet switched network which offers best-effort service, but current IP network provide enhanced services such Quality of Services, Virtual Private Network (VPN) services, Distribute Firewall and IP Security Gateways. All such services need packet classification for determining the flow. The problem is performing scalable packet classification at wire speeds even as rule databases increase in size. Therefore, this research offer packet classification algorithm that increase classifier performance when working with enlarge rules database by rearrange rule structure into Bitmap Intersection Lookup (BIL) tables. It will use packet's header field for looking up BIL tables and take the result with intersection operation by logical AND. This approach will use simple algorithm and rule structure, it make classifier have high search speed and fast updates.

• IE interfaces
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• v.4 no.1
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• pp.63-69
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• 1991

In this paper, the Go-Back-N ARQ protocol with decoding in communication network is considered. The time delay and throughput are respectively analyzed as a function of window size and decoding time out. Packets arrive continuously at the decoder, and are stored in a buffer if the decoder is busy upon its arrival. The decoder devotes no more than a time-out period of predetermined length to the decoding of any single packet. If packet decoding is completed within that period, the packet leaves the system. Otherwise, it is retransimitted and its decoding starts anew. The time delay and throughput are obtained using recursive formula and difference equation. An appropriate time out and window size that satisfies the grade of service can be determined.

• ETRI Journal
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• v.35 no.4
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• pp.726-729
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• 2013

For secure multimedia communications, existing encryption techniques use an online session key for the key exchange, for which key size is limited to less than 10 digits to accommodate the latency condition caused by user devices only being able to handle low computational loads. This condition results in poor security of recorded encrypted data. In this letter, we propose a packet key scheme that encrypts real-time packets using a different key per packet for multimedia applications. Therefore, a key of a relatively small size can provide after-transmission confidentiality to data of a real-time session.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.327-330
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• 2002

In this paper, we have analyzed transmission time for WAP over CDMA using turbo code scheme. In order for SAR to improve the transfer capability, the transmission of messages have been simulated using a fragmentation that begins with the total package and incremental fragmentation for each layer using the WTP to define tile resultant packet size and the level of fragmentation for each proceeding layer. This turbo code scheme decreases transmission lime of RLP baseband packets. From the results, we arc able to obtain packet transmission time and optimal WTP packet size for WAP over CDMA in a Rician fading channel.