Abstract-YouTube has become the most successful Internet website providing a new generation of short video sharing service since its establishment in early 2005. YouTube has a great impact on Internet traffic nowadays, yet itself is suffering from a severe problem of scalability. Therefore, understanding the characteristics of YouTube and similar sites is essential to network traffic engineering and to their sustainable development.To this end, we have crawled the YouTube site for four months, collecting more than 3 million YouTube videos' data. In this paper, we present a systematic and in-depth measurement study on the statistics of YouTube videos. We have found that YouTube videos have noticeably different statistics compared to traditional streaming videos, ranging from length and access pattern, to their growth trend and active life span. We investigate the social networking in YouTube videos, as this is a key driving force toward its success. In particular, we find that the links to related videos generated by uploaders' choices have clear small-world characteristics. This indicates that the videos have strong correlations with each other, and creates opportunities for developing novel techniques to enhance the service quality.

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We have measured the Raman spectra of heavily carbon doped (pϾ10 19 cm Ϫ3) GaSb and GaAsSb. A local vibrational mode ͑LVM͒ due to carbon residing on group-V lattice sites was observed at 540 cm Ϫ1 for GaSb and 568 cm Ϫ1 for GaAs 0.44 Sb 0.56. A gap mode at 164 cm Ϫ1 was observed for GaSb. The frequency of the LVM as well as the gap mode is in quantitative agreement with recent theoretical predictions.

Abstract-The Internet has become a cost-effective vehicle for software development and release, particular in the free software community. Given the free nature of this software, there are often a number of users motivated by altruism to help out with the distribution, so as to promote the healthy development of this voluntary society. It is thus naturally expected that a peer-topeer distribution can be implemented, which will scale well with large user bases, and can easily explore the network resources made available by the volunteers.Unfortunately, this application scenario has many unique characteristics, which make a straightforward adoption of existing peer-to-peer systems for file sharing (such as BitTorrent) suboptimal. In particular, a software release often consists of a large number of packages, which are difficult to distribute individually, but the archive is too large to be distributed in its entirety. The packages are also being constantly updated by the loosely-managed developers, and the interest in a particular version of a package can be very limited depending on the computer platforms and operating systems used.In this paper, we propose a novel peer-to-peer assisted distribution system design that addresses the above challenges. It enhances the existing distribution systems by providing compatible and yet more efficient downloading and updating services for software packages. Our design leads to apt-p2p, a practical implementation that extends the popular apt distributor. apt-p2p has been used in conjunction with Debian-based distribution of Linux software packages and is also available in the latest release of Ubuntu. We have addressed the key design issues in apt-p2p, including indexing table customization, response time reduction, and multi-value extension. They together ensure that the altruistic users' resources are effectively utilized and thus significantly reduces the currently large bandwidth requirements of hosting the software, as confirmed by our existing real user statistics gathered over the Internet.

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