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The Real-time Transport Protocol (RTP) is a media transport protocol. RTP is primarily designed to satisfy of the needs for multimedia transmission [1]. The Secure Real-time Transport Protocol (SRTP) provides confidentiality, message authentication, and replay protection for RTP traffic. However, there are risks of weak message authentication in SRTP Protocol [2]. With a weak Message authentication code it is easy for attacker to modify the SRTP packets. The main purpose of this paper is to propose an alternative scheme to provide a stronger authentication and integrity. The proposed scheme is implemented using Microsoft open source project for conference. The implementation is tested using StsGui NIST Statistical suite and Cryptool software [3] for security and Wireshark [4] for performance. The test results show that the proposed modification enhances the security with minor effect on the quality of service (QoS).

Session Initiation Protocol (SIP) is vulnerable to a wide variety of Denial of Service (DoS) attacks, flooding is the most common, effective and the easiest to generate one. In this paper we present an evaluation study to four well-known anomaly detection algorithms, namely: Adaptive Threshold, Cumulative sum (CUSUM), Non Parametric Cumulative Sum (NP-CUSUM), and Hellinger Distance (HD). The evaluation is assisted using simulated traffic dataset. We show that these algorithms suffer from two main problems, the first is called attack masking and the second is adaptation with attack. In the attack masking, attacker sends preamble followed by the attack. The preamble changes the tuned parameters of the detection algorithm, these changes mask the attack and keep it undetected. Attacker in the second problem deviates the detection algorithm parameters gradually, in such a way the attack is considered as normal traffic. The paper also shows that NP-CUSUM and HD algorithms, which utilize the protocol behavior to detect intrusion, suffer from third problem, and they are very simple to con. Attacker simply follows the same protocol behavior, and its related traffic is considered as normal, and cannot be detected.

In this paper the ATM Header Error Correction (HEC) mechanism was analyzed and ATM Quality of Service (QoS) parameters were calculated assuming bursty satellite channel. The use of Reed Solomon (RS) codes as an outer code to improve the QoS of ATM transmission over satellite channels was examined. The various tradeoffs which have to be made when using RS codes, such as the selection of appropriate code rates while maintaining sufficient throughput and minimal processing delay are thoroughly studied. These tradeoffs are to be used as the basis for an adaptive scheme which adapts the correction capability as well as the grouping of ATM cells into RS codewords. A Forward Error Correction (FEC) scheme is proposed which interacts with the ATM layer to alleviate the problem of excessive misinsertion of ATM cells, the performance of the proposed scheme is evaluated via simulation and is shown to significantly reduce the misinsertion rate.