Named Data Networking (NDN) is one of five projects funded by the U.S. National Science Foundation under its Future Internet Architecture Program. NDN has its roots in an earlier project, Content-Centric Networking (CCN), which Van Jacobson first publicly presented in 2006. The NDN project investigates Jacobson's proposed evolution from today's host-centric network architecture (IP) to a data-centric network architecture (NDN). This conceptually simple shift has far-reaching implications for how we design, develop, deploy, and use networks and applications. We describe the motivation and vision of this new architecture, and its basic components and operations. We also provide a snapshot of its current design, development status, and research challenges. More information about the project, including prototype implementations, publications, and annual reports, is available on named-data.net.

Prior measurement studies of the Internet have explored traffic and topology, but have largely ignored edge hosts. While the number of Internet hosts is very large, and many are hidden behind firewalls or in private address space, there is much to be learned from examining the population of visible hosts, those with public unicast addresses that respond to messages. In this paper we introduce two new approaches to explore the visible Internet. Applying statistical population sampling, we use censuses to walk the entire Internet address space, and surveys to probe frequently a fraction of that space. We then use these tools to evaluate address usage, where we find that only 3.6% of allocated addresses are actually occupied by visible hosts, and that occupancy is unevenly distributed, with a quarter of responsive /24 address blocks (subnets) less than 5% full, and only 9% of blocks more than half full. We show about 34 million addresses are very stable and visible to our probes (about 16% of responsive addresses), and we project from this up to 60 million stable Internet-accessible computers. The remainder of allocated addresses are used intermittently, with a median occupancy of 81 minutes. Finally, we show that many firewalls are visible, measuring significant diversity in the distribution of firewalled block size. To our knowledge, we are the first to take a census of edge hosts in the visible Internet since 1982, to evaluate the accuracy of active probing for address census and survey, and to quantify these aspects of the Internet.

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Retransmission based error control for large scale multicast applications is dificult because of implosion and exposure. Existing schemes (SRM, RMTe TMTe LBRRM) have good solutions to implosion, but only approximate solutions to exposure. We present a scheme that achieves finer grain fault recovery by exploiting new forwarding services that allow us to create a dynamic hierarchy of receivers. We extend the IP Multicast service model so that routers provide a more refined form of multicasting (which may be useful to other applications), that enables local recovery. The new services are simple to implement and do not require routers to examine or store application packets; hence, they do not violate layering. Besides providing better implosion control and less exposure than other schemes, our scheme integrates well with the current IP model, has small recovery latencies (it requires no back-off delays), and completely isolates group members from topology. Our scheme can be used with a variety of multicast routing protocols, including DVMRP and PIM. We have implemented our scheme in NetBSD Unix, using about 250 lines of new C-code. The implementation requires two new IP options, 4 additional bytes in each routing entry and a slight modiJication to IGMP reports. The forwarding overhead incurred by the new services is actually lower than forwarding normal multicast trafic.