Certain data-communication protocols hog the spotlight, but all of them have a lot in common. Computer Networking: A Top-Down Approach Featuring the Internet explains the engineering problems that are inherent in communicating digital information from point to point. The top-down approach mentioned in the subtitle means that the book starts at the top of the protocol stack--at the application layer--and works its way down through the other layers, until it reaches bare wire. The authors, for the most part, shun the well-known seven-layer Open Systems Interconnection (OSI) protocol stack in favor of their own five-layer (application, transport, network, link, and physical) model. It's an effective approach that helps clear away some of the hand waving traditionally associated with the more obtuse layers in the OSI model. The approach is definitely theoretical--don't look here for instructions on configuring Windows 2000 or a Cisco router--but it's relevant to reality, and should help anyone who needs to understand networking as a programmer, system architect, or even administration guru.The treatment of the network layer, at which routing takes place, is typical of the overall style. In discussing routing, authors James Kurose and Keith Ross explain (by way of lots of clear, definition-packed text) what routing protocols need to do: find the best route to a destination. Then they present the mathematics that determine the best path, show some code that implements those algorithms, and illustrate the logic by using excellent conceptual diagrams. Real-life implementations of the algorithms--including Internet Protocol (both IPv4 and IPv6) and several popular IP routing protocols--help you to make the transition from pure theory to networking technologies. --David WallTopics covered: The theory behind data networks, with thorough discussion of the problems that are posed at each level (the application layer gets plenty of attention). For each layer, there's academic coverage of networking problems and solutions, followed by discussion of real technologies. Special sections deal with network security and transmission of digital multimedia.

Computer Networking: A Top-Down Approach

In this chapter, you will see how the simplex method simplifies when it is applied to a class of optimization problems that are known as “network flow models.” You will also see that if a network flow model has “integer-valued data,” the simplex method finds an optimal solution that is integer-valued.

Flows in Networks

At some point in the future, how far out we do not exactly know, wireless access to the Internet will outstrip all other forms of access bringing the freedom of mobility to the way we access the we...

ACM SIGCOMM computer communication review

BGP severely constrains how networks can deliver traffic over the Internet. Today's networks can only forward traffic based on the destination IP prefix, by selecting among routes offered by their immediate neighbors. We believe Software Defined Networking (SDN) could revolutionize wide-area traffic delivery, by offering direct control over packet-processing rules that match on multiple header fields and perform a variety of actions. Internet exchange points (IXPs) are a compelling place to start, given their central role in interconnecting many networks and their growing importance in bringing popular content closer to end users. To realize a Software Defined IXP (an "SDX"), we must create compelling applications, such as "application-specific peering"---where two networks peer only for (say) streaming video traffic. We also need new programming abstractions that allow participating networks to create and run these applications and a runtime that both behaves correctly when interacting with BGP and ensures that applications do not interfere with each other. Finally, we must ensure that the system scales, both in rule-table size and computational overhead. In this paper, we tackle these challenges and demonstrate the flexibility and scalability of our solutions through controlled and in-the-wild experiments. Our experiments demonstrate that our SDX implementation can implement representative policies for hundreds of participants who advertise full routing tables while achieving sub-second convergence in response to configuration changes and routing updates.

/pdf/sdx-a-software-defined-internet-exchange-19h12ars8p.pdf

SDX: a software defined internet exchange

Quality of Service (QoS) in Software Defined Networking (SDN)

The largest IXPs carry on a daily basis traffic volumes in the petabyte range, similar to what some of the largest global ISPs reportedly handle. This little-known fact is due to a few hundreds of member ASes exchanging traffic with one another over the IXP's infrastructure. This paper reports on a first-of-its-kind and in-depth analysis of one of the largest IXPs worldwide based on nine months' worth of sFlow records collected at that IXP in 2011.A main finding of our study is that the number of actual peering links at this single IXP exceeds the number of total AS links of the peer-peer type in the entire Internet known as of 2010! To explain such a surprisingly rich peering fabric, we examine in detail this IXP's ecosystem and highlight the diversity of networks that are members at this IXP and connect there with other member ASes for reasons that are similarly diverse, but can be partially inferred from their business types and observed traffic patterns. In the process, we investigate this IXP's traffic matrix and illustrate what its temporal and structural properties can tell us about the member ASes that generated the traffic in the first place. While our results suggest that these large IXPs can be viewed as a microcosm of the Internet ecosystem itself, they also argue for a re-assessment of the mental picture that our community has about this ecosystem.

http://conferences.sigcomm.org/sigcomm/2012/paper/sigcomm/p163.pdf

Anatomy of a large european IXP

The Domain Name System (DNS) is a fundamental building block of the Internet. Today, the performance of more and more applications depend not only on the responsiveness of DNS, but also the exact answer returned by the queried DNS resolver, e.g., for Content Distribution Networks (CDN).In this paper, we compare local DNS resolvers against GoogleDNS and OpenDNS for a large set of vantage points. Our end-host measurements inside 50 commercial ISPs reveal that two aspects have a significant impact on responsiveness: (1) the latency to the DNS resolver, (2) the content of the DNS cache when the query is issued. We also observe significant diversity, even at the AS-level, among the answers provided by the studied DNS resolvers. We attribute this diversity to the location-awareness of CDNs as well as to the location of DNS resolvers that breaks the assumption made by CDNs about the vicinity of the end-user and its DNS resolver. Our findings pinpoint limitations within the DNS deployment of some ISPs, as well as the way third-party DNS resolvers bias DNS replies.

/pdf/comparing-dns-resolvers-in-the-wild-56n9vxgqiw.pdf

Comparing DNS resolvers in the wild

Content delivery systems constitute a major portion of today's Internet traffic. While they are a good source of revenue for Internet Service Providers (ISPs), the huge volume of content delivery traffic also poses a significant burden and traffic engineering challenge for the ISP. The difficulty is due to the immense volume of transfers, while the traffic engineering challenge stems from the fact that most content delivery systems themselves utilize a distributed infrastructure. They perform their own traffic flow optimization and realize this using the DNS system. While content delivery systems may, to some extent, consider the user's performance within their optimization criteria, they currently have no incentive to consider any of the ISP's constraints. As a consequence, the ISP has ``lost control'' over a major part of its traffic. To overcome this impairment, we propose a solution where the ISP offers a Provider-aided Distance Information System (PaDIS). PaDIS uses information available only to the ISP to rank any client-host pair based on distance information, such as delay, bandwidth or number of hops.In this paper we show that the applicability of the system is significant. More than 70% of the HTTP traffic of a major European ISP can be accessed via multiple different locations. Moreover, we show that deploying PaDIS is not only beneficial to ISPs, but also to users. Experiments with different content providers show that improvements in download times of up to a factor of four are possible. Furthermore, we describe a high performance implementation of PaDIS and show how it can be deployed within an ISP.

/pdf/improving-content-delivery-using-provider-aided-distance-4d1ubag4db.pdf

Improving content delivery using provider-aided distance information

Inter-domain routing is based on a fully decentralized model, where multiple Autonomous Systems (AS) interact via the BGP protocol. Although BGP is the "glue" of the Internet, it faces a lot of problems regarding its fully distributed nature, policy enforcement capabilities, scalability, security and complexity. Due to the widespread adoption of BGP, only incrementally deployable solutions are feasible. Taking this observation into account, we describe a new, backwards-compatible routing model which is based on outsourcing and logically centralizing the routing control plane. We claim that outsourcing enables enhanced inter-domain routing. As multiple ASes outsource their routing control plane to the same outsourcing service contractor, AS clusters are being gradually formed. A logically centralized multi-AS routing control platform based on Software Defined Networking (SDN) principles is the natural point for taking efficient routing decisions, detecting policy conflicts, troubleshooting routing problems, and evolving BGP. We present the technical and financial incentives which support the feasibility of the model and also propose an implementation scheme to facilitate it.

/pdf/outsourcing-the-routing-control-logic-better-internet-33njh2bs8r.pdf

Outsourcing the routing control logic: better internet routing based on SDN principles

Today's Internet traffic is dominated by users' demand for exchanging content. In particular, multi-media content, i. e., photos, music, and video, as well as software downloads and updates contribute substantially to today's Internet traffic. One option for reducing network costs is to use caches-exploiting the observation that content popularity is consistent with Zipf's law. Yet, Web caching became unprofitable due to the increase in popularity of dynamic Web content. However, since at this point rich content is not very dynamic caching appears to be worthwhile again. We base our analysis on anonymized traces from a large European ISP connecting more than 20,000 residential DSL customers to the Internet, collected in 2009. We focus on the most prominent protocols in this environment - HTTP, BitTorrent (BT), eDonkey, and NNTP - and estimate the potential of caching for traffic reduction. On the one hand, our results show that the potential for caching most client/server-based applications like HTTP and NNTP is small. On the other hand P2P-based applications such as BitTorrent and certain HTTP based applications have high content duplication ratios.

http://www.net.t-labs.tu-berlin.de/teaching/ss10/IM_seminar/pdf/AKSF-RCTUGC-10.pdf

Bernhard Ager

Papers

Anatomy of a large european IXP

Comparing DNS resolvers in the wild

Improving content delivery using provider-aided distance information

Outsourcing the routing control logic: better internet routing based on SDN principles

Revisiting Cacheability in Times of User Generated Content