An Architecture for Global Distributed SIP Network Using IPv4 Anycast

Tato diplomová práce se zabývá metodami pro výběr nejbližší RTP proxy k VoIP klientům s použitím IP anycastu. RTP proxy servery jsou umístěny v síti Internetu a přeposílají RTP data pro VoIP klienty za síťovými překladači adres(NAT). Bez zeměpisně rozmístěných RTP proxy serverů a metod pro nalezení nejbližšího RTP proxy serveru by došlo ke zbytečnému poklesu kvality přenosu médialních dat a velkému zpoždení. Tento dokument navrhuje 4 metody a jejich porovnání s podrobnějšími rozbory metod s využitím DNS resolvování a přímo SIP protokolu. Tento dokument také obsahuje měření chování IP anycastu v porovnání mezi metrikami směrování a metrikami časovými. Nakonec dokumentu je také uvedena implemetace na SIP Express Router platformě.This thesis is about using IP anycast-based methods for locating RTP proxy servers close to VoIP clients. The RTP proxy servers are hosts on the public Internet that relay RTP media between VoIP clients in a way that accomplishes traversal over Network Address Translators (NATs). Without geographically-dispersed RTP proxy servers and methods to find one in client's proximity, voice latency may be unbearably long and dramatically reduce perceived voice quality. This document proposes four methods their comparison with further design of DNS-based and SIP-based methods. It includes IP anycast measurements that provides an overview of IP anycast behaviour in terms of routing metrics and latency metrics. It also includes implementation on SIP Express Router platform.

An Economic Analysis of Domain Name Policy

One of the most important features of the architecture of the Internet is the Domain Name System (DNS), which is administered by the Internet Corporation for Assigned Names and Numbers (ICANN). Logically, the DNS is organized into Top Level Domains (such as .com), Second Level Domains (such as amazon.com), and third, fourth, and higher level domains (such as www.amazon.com). The physically infrastructure of the DNS consists of name servers, including the Root Server System which provides the information that directs name queries for each Top Level Domain to the appropriate server. ICANN is responsible for the allocation of the root and the creation or reallocation of Top Level Domains. The Root Server System and associated name space are scarce resources in the economic sense. The root servers have a finite capacity and expansion of the system is costly. The name space is scarce, because each string (or set of characters) can only be allocated to one Registry (or operator of a Top Level Domain). In addition, name service is not a public good in the economic sense, because it is possible to exclude strings from the DNS and because the allocation of a string to one firm results in the inability of other firms to use that name string. From the economic perspective, therefore, the question arises: what is the most efficient method for allocating the root resource? There are only five basic options available for allocation of the root. (1) a static root, equivalent to a decision to waste the currently unallocated capacity; (2) public interest hearings (or beauty contests); (3) lotteries; (4) a queuing mechanism; or (5) an auction. The fundamental economic question about the Domain Name System is which of these provides the most efficient mechanism for allocating the root resource? This resource allocation problem is analogous to problems raised in the telecommunications sector, where the Federal Communications Commission has a long history of attempting to allocate broadcast spectrum and the telephone number space. This experience reveals that a case-by-case allocation on the basis of ad hoc judgments about the public interest is doomed to failure, and that auctions (as opposed to lotteries or queues) provide the best mechanism for insuring that such public-trust resources find their highest and best use. Based on the telecommunications experience, the best method for ICANN to allocate new Top Level Domains would be to conduct an auction. Many auction designs are possible. One proposal is to auction a fixed number of new Top Level Domain slots each year. This proposal would both expand the root resource at a reasonable pace and insure that the slots went to their highest and best use. Public interest Top Level Domains could be allocated by another mechanism such as a lottery and their costs to ICANN could be subsidized by the proceeds of the auction

Stateful Anycast for DDoS Mitigation

MEng thesisDistributed denial-of-service (DDoS) attacks can easily cripple victim hosts or networks, yet effective defenses remain elusive. Normal anycast can be used to force the diffusion of attack traffic over a group of several hosts to increase the difficulty of saturating resources at or near any one of the hosts. However, because a packet sent to the anycast group may be delivered to any member, anycast does not support protocols that require a group member to maintain state (such as TCP). This makes anycast impractical for most applications of interest.This document describes the design of Stateful Anycast, a conceptual anycast-like network service based on IP anycast. Stateful Anycast is designed to support stateful sessions without losing anycasts ability to defend against DDoS attacks. Stateful Anycast employs a set of anycasted proxies to direct packets to the proper stateholder. These proxies provide DDoS protection by dropping a sessions packets upon group member request. Stateful Anycast is incrementally deployable and can scale to support many groups

Untangling the Web: A Guide To Internet Research

[Excerpt] Untangling the Web for 2007 is the twelfth edition of a book that started as a small handout. After more than a decade of researching, reading about, using, and trying to understand the Internet, I have come to accept that it is indeed a Sisyphean task. Sometimes I feel that all I can do is to push the rock up to the top of that virtual hill, then stand back and watch as it rolls down again. The Internet—in all its glory of information and misinformation—is for all practical purposes limitless, which of course means we can never know it all, see it all, understand it all, or even imagine all it is and will be. The more we know about the Internet, the more acute is our awareness of what we do not know. The Internet emphasizes the depth of our ignorance because our knowledge can only be finite, while our ignorance must necessarily be infinite. My hope is that Untangling the Web will add to our knowledge of the Internet and the world while recognizing that the rock will always roll back down the hill at the end of the day