No abstract

DNS tunnels allow circumventing access and security policies in firewalled networks. Such a security breach can be misused for activities like free web browsing, but also for command & control traffic or cyber espionage, thus motivating the search for effective automated DNS tunnel detection techniques. In this paper we develop such a technique, based on the monitoring and analysis of network flows. Our methodology combines flow information with statistical methods for anomaly detection. The contribution of our paper is twofold. Firstly, based on flow-derived variables that we identified as indicative of DNS tunnelling activities, we identify and evaluate a set of non-parametrical statistical tests that are particularly useful in this context. Secondly, the efficacy of the resulting tests is demonstrated by extensive validation experiments in an operational environment, covering many different usage scenarios.

The IP Multimedia Subsystem (IMS)

The next generation of communication networks is expected to create a heterogeneous network environment encompassing an ever‐increasing number of different access networks and end‐user terminals that will enable the introduction of and provide access to numerous feature‐rich end‐user services. It is essential that end users be able to roam from one access network to another if they are to enjoy a seamless roaming experience, which is especially important for multimedia applications such as voice, audio, and video. This paper describes how to make such a roaming experience possible in multimedia applications based on Session Initiation Protocol (SIP). It also describes several mobility management solutions and compares the suitability of SIP sessions for roaming across General Packet Radio Service (GPRS), Universal Mobile Telecommunications System (UMTS), and wireless local area network (WLAN) networks. The comparison is based on the implementation of a prototype. The advantages and disadvantages of each mobility management solution are discussed, as are the issues encountered during the implementation of the prototype. © 2004 Lucent Technologies Inc.

It is a real challenge for cloud providers to offer cloud resources that are 'virtually unlimited and can be appropriated in any quantity at any time' in a cost-effective way. In this paper, we propose quantitative models that enable cloud providers to make an informed trade-off between cost and quality. Distinguishing between public and private cloud environments we consider infinite and finite source models respectively. In both cases either homogeneous or heterogeneous cloud resource requests are considered. These models can be applied to cloud dimensioning based on request blocking probability, an important SLA parameter. We derive a novel, insightful method that makes it possible to compute resource requirements in private clouds with heterogeneous resource requests. We show the importance of applying finite source models in the context of private clouds. We also use the proposed models to quantify the benefits of cloud federations.