John P. Rula

Content delivery and the natural evolution of DNS: remote dns trends, performance issues and alternative solutions

Content Delivery Networks (CDNs) rely on the Domain Name System (DNS) for replica server selection. DNS-based server selection builds on the assumption that, in the absence of information about the clients actual network location, the location of a clients DNS resolver provides a good approximation. The recent growth of remote DNS services breaks this assumption and can negatively impact clients web performance. In this paper, we assess the end-to-end impact of using remote DNS services on CDN performance and present the first evaluation of an industry-proposed solution to the problem. We find that remote DNSusage can indeed significantly impact clients web performance and that the proposed solution, if available, can effectively address the problem for most clients. Considering the performance cost of remote DNS usage and the limited adoption base of the industry-proposed solution, we present and evaluate an alternative approach, Direct Resolution, to readily obtain comparable performance improvements without requiring CDN or DNS participation.

Crowdsourcing ISP characterization to the network edge

Evaluating and characterizing Internet Service Providers (ISPs) is critical to subscribers shopping for alternative ISPs, companies providing reliable Internet services, and governments surveying the coverage of broadband services to its citizens. Ideally, ISP characterization should be done at scale, continuously, and from end users. While there has been significant progress toward this end, current approaches exhibit apparently unavoidable tradeoffs between coverage, continuous monitoring and capturing user-perceived performance. In this paper, we argue that network-intensive applications running on end systems avoid these tradeoffs, thereby offering an ideal platform for ISP characterization. Based on data collected from 500,000 peer-to-peer BitTorrent users across 3,150 networks, together with the reported results from the U.K. Ofcom/SamKnows studies, we show the feasibility of this approach to characterize the service that subscribers can expect from a particular ISP. We discuss remaining research challenges and design requirements for a solution that enables efficient and accurate ISP characterization at an Internet scale.

Crowd (soft) control: moving beyond the opportunistic

A number of novel wireless networked services, ranging from participatory sensing to social networking, leverage the increasing capabilities of mobile devices and the movements of the individuals carrying them. For many of these systems, their effectiveness fundamentally depends on coverage and the particular mobility patterns of the participants. Given the strong spatial and temporal regularity of human mobility, the needed coverage can typically only be attained through a large participant base. In this paper we explore an alternative approach to attain coverage without scale -- (soft) controlling the movement of participants. We present Crowd Soft Control (CSC), an approach to exert limited control over the temporal and spatial movements of mobile users by leveraging the built-in incentives of location-based gaming and social applications. By pairing network services with these location-based apps, CSC allows researchers to use an applications incentives (e.g. game objectives) to control the movement of participating users, increasing the effectiveness and efficiency of the associated network service. After outlining the case for Crowd Soft Control, we present an initial prototype of our ideas and discuss potential benefits and costs in the context of two case studies.

Behind the Curtain: Cellular DNS and Content Replica Selection

DNS plays a critical role in the performance of smartdevices within cellular networks. Besides name resolution, DNS is commonly relied upon for directing users to nearby content caches for better performance. In light of this, it is surprising how little is known about the structure of cellular DNS and its effectiveness as a client localization method. In this paper we take a close look at cellular network DNS and uncover several features of cellular DNS, such as cellular network opaqueness and client to resolver inconsistency, that make it unsuitable for client localization in modern cellular networks. We study these issues in two leading mobile network markets - US and South Korea - using a collection of over 340 volunteer devices to probe the DNS infrastructure of each clients cellular provider. We show the extent of the problem with regards to replica selection and compare its localization performance against public DNS alternatives. As a testament to cellular DNSs poor localization, we find surprisingly that public DNS can render equal or better replica performance over 75% of the time.

In and Out of Cuba: Characterizing Cuba's Connectivity

The goal of our work is to characterize the current state of Cubas access to the wider Internet. This work is motivated by recent improvements in connectivity to the island and the growing commercial interest following the ease of restrictions on travel and trade with the US. In this paper, we profile Cubas networks, their connections to the rest of the world, and the routes of international traffic going to and from the island. Despite the addition of the ALBA-1 submarine cable, we find that round trip times to websites hosted off the island remain very high; pings to popular websites frequently took over 300 ms. We also find a high degree of path asymmetry in traffic to/from Cuba. Specifically, in our analysis we find that traffic going out of Cuba typically travels through the ALBA-1 cable, but, surprisingly, traffic on the reverse path often traverses high-latency satellite links, adding over 200 ms to round trip times. Last, we analyze queries to public DNS servers and SSL certificate requests to characterize the availability of network services in Cuba.

When IPs Fly: A Case for Redefining Airline Communication

The global airline industry conducted over 33 million flights in 2014 alone, carrying over 3.3 billion passengers. Surprisingly, the traffic management system handling this flight volume communicates over either VHF audio transmissions or plane transponders, exhibiting several seconds of latency and single bits per second of throughput. There is a general consensus that for the airline industry to serve the growing demand will require of significant improvements to the air traffic management system; we believe that many of these improvements can leverage the past two decades of mobile networking research. In this paper, we make the case that moving to a common IP-based data channel to support flight communication can radically change the airline industry. While there remain many challenges to achieve this vision, we believe that such a shift can greatly improve the rate of innovation, overall efficiency of global air traffic management, enhance aircraft safety and create new applications that leverage the capability of an advanced data channel. Through preliminary measurements on existing in-flight Internet communication systems, we show that existing in-flight connectivity achieves order of magnitude higher throughput and lower latency than current systems, and operates as a highly reliable and available data link. This position paper takes a first look at the opportunity for IP-based flight communication, and identifies several promising research areas in this space.

Second Chance: Understanding diversity in broadband access network performance

In recognition of the increasing importance of broadband, several governments have embarked on large-scale efforts to measure broadband services from devices within end-users homes. Participants for these studies were selected based on features that, a priori, were thought to be relevant to service performance such as geographic region, access technology and subscription level. Every new-year deployment since has followed the same model, ensuring that the number of measurement points remains stable despite the natural churn. In this paper, we start to explore the issue of vantage point selection in residential broadband networks by leveraging the publicly available datasets collected as part of the FCC Broadband America study. We present the first analysis of the variation of performance in edge networks and diversity of individual vantage points. We explore the underlying causes of this diversity through a factor analysis of contextual factors within an ISP such as the geographic location of subscribers. The goal of this analysis is to inform additional deployments in ongoing studies, and guide the design and deployment of future investigations into broadband networks.

Mile High WiFi: A First Look At In-Flight Internet Connectivity

In-Flight Communication (IFC), available on a growing number of commercial flights, is often received by consumers with both awe for its mere availability and harsh criticism for its poor performance. Indeed, IFC provides Internet connectivity in some of the most challenging conditions with aircraft traveling at speeds in excess of 500 mph at 30,000 feet above the ground. Yet, while existing services do provide basic Internet \em accessibility, anecdotal reports rank their quality of service as, at best, poor. In this paper, we present the first characterization of deployed IFC systems. Using over 45 flight-hours of measurements, we profile the performance of IFC across the two dominant access technologies -- direct air-to-ground communication (DA2GC) and mobile satellite service (MSS). We show that IFC QoS is in large part determined by the high latencies inherent to DA2GC and MSS, with RTTs averaging 200ms and 750ms, respectively, and that these high latencies directly impact the performance of common applications such as web browsing. While each IFC technology is based on well studied wireless communication technologies, our findings reveal that IFC links experience further degraded link performance than their technological antecedents. We find median loss rates of 7%, and nearly 40% loss at the 90th percentile for MSS, 6.8x larger than recent characterizations of residential satellite networks. We extend our IFC study exploring the potential of the newly released HTTP/2 and QUIC protocols in an emulated IFC environment, finding that QUIC is able to improve page load times by as much as 7.9 times. In addition, we find that HTTP/2»s use of multiplexing multiple requests onto a single TCP connection performs up to 4.8x \em worse than HTTP/1.1 when faced with large numbers of objects. We use network emulation to explore proposed technological improvements to existing IFC systems finding that high link losses, and not bandwidth, account for the largest factor of performance degradation with applications such as web browsing.

Cell spotting: studying the role of cellular networks in the internet

The impressive growth of the mobile Internet has motivated several industry reports retelling the story in terms of number of devices or subscriptions sold per regions, or the increase in mobile traffic, both WiFi and cellular. Yet, despite the abundance of such reports, we still lack an understanding of the impact of cellular networks around the world. We present the first comprehensive analysis of global cellular networks. We describe an approach to accurately identify cellular network IP addresses using the Network Information API, a non-standard Javascript API in several mobile browsers, and show its effectiveness in a range cellular network configurations. We combine this approach with the vantage point of one of the worlds largest CDNs, with servers located in 1,450 networks and clients distributed across across 245 countries, to characterize cellular access around the globe. We find that the majority of cellular networks exist as mixed networks (i.e., networks that share both fixed-line and cellular devices), requiring prefix - not ASN - level identification. We discover over 350 thousand /24 and 23 thousand /48 cellular IPv4 and IPv6 prefixes respectively. By utilizing addresses level traffic from the same CDN, we calculate the fraction of traffic coming from cellular addresses. Overall we find that cellular traffic comprises 16.2% of the CDNs global traffic, and that cellular traffic ranges widely in importance between countries, from capturing nearly 96% of all traffic in Ghana to just 12.1% in France.

eXploring Xfinity - A First Look at Provider-Enabled Community Networks.

Several broadband providers have been offering community WiFi as an additional service for existing customers and paid subscribers. These community networks provide Internet connectivity on the go for mobile devices and a path to offload cellular traffic. Rather than deploying new infrastructure or relying on the resources of an organized community, these provider-enabled community WiFi services leverage the existing hardware and connections of their customers. The past few years have seen a significant growth in their popularity and coverage and some municipalities and institutions have started to considered them as the basis for public Internet access. In this paper, we present the first characterization of one such service – the Xfinity Community WiFi network. Taking the perspectives of the home-router owner and the public hotspot user, we characterize the performance and availability of this service in urban and suburban settings, at different times, between September, 2014 and 2015. Our results highlight the challenges of providing these services in urban environments considering the tensions between coverage and interference, large obstructions and high population densities. Through a series of controlled experiments, we measure the impact to hosting customers, finding that in certain cases, the use of the public hotspot can degrade host network throughput by up-to 67% under high traffic on the public hotspot.