11 research outputs found
A Multi-perspective Analysis of Carrier-Grade NAT Deployment
As ISPs face IPv4 address scarcity they increasingly turn to network address
translation (NAT) to accommodate the address needs of their customers.
Recently, ISPs have moved beyond employing NATs only directly at individual
customers and instead begun deploying Carrier-Grade NATs (CGNs) to apply
address translation to many independent and disparate endpoints spanning
physical locations, a phenomenon that so far has received little in the way of
empirical assessment. In this work we present a broad and systematic study of
the deployment and behavior of these middleboxes. We develop a methodology to
detect the existence of hosts behind CGNs by extracting non-routable IP
addresses from peer lists we obtain by crawling the BitTorrent DHT. We
complement this approach with improvements to our Netalyzr troubleshooting
service, enabling us to determine a range of indicators of CGN presence as well
as detailed insights into key properties of CGNs. Combining the two data
sources we illustrate the scope of CGN deployment on today's Internet, and
report on characteristics of commonly deployed CGNs and their effect on end
users
Beyond Counting: New Perspectives on the Active IPv4 Address Space
In this study, we report on techniques and analyses that enable us to capture
Internet-wide activity at individual IP address-level granularity by relying on
server logs of a large commercial content delivery network (CDN) that serves
close to 3 trillion HTTP requests on a daily basis. Across the whole of 2015,
these logs recorded client activity involving 1.2 billion unique IPv4
addresses, the highest ever measured, in agreement with recent estimates.
Monthly client IPv4 address counts showed constant growth for years prior, but
since 2014, the IPv4 count has stagnated while IPv6 counts have grown. Thus, it
seems we have entered an era marked by increased complexity, one in which the
sole enumeration of active IPv4 addresses is of little use to characterize
recent growth of the Internet as a whole.
With this observation in mind, we consider new points of view in the study of
global IPv4 address activity. Our analysis shows significant churn in active
IPv4 addresses: the set of active IPv4 addresses varies by as much as 25% over
the course of a year. Second, by looking across the active addresses in a
prefix, we are able to identify and attribute activity patterns to network
restructurings, user behaviors, and, in particular, various address assignment
practices. Third, by combining spatio-temporal measures of address utilization
with measures of traffic volume, and sampling-based estimates of relative host
counts, we present novel perspectives on worldwide IPv4 address activity,
including empirical observation of under-utilization in some areas, and
complete utilization, or exhaustion, in others.Comment: in Proceedings of ACM IMC 201
Packet analysis for network forensics: A comprehensive survey
Packet analysis is a primary traceback technique in network forensics, which, providing that the packet details captured are sufficiently detailed, can play back even the entire network traffic for a particular point in time. This can be used to find traces of nefarious online behavior, data breaches, unauthorized website access, malware infection, and intrusion attempts, and to reconstruct image files, documents, email attachments, etc. sent over the network. This paper is a comprehensive survey of the utilization of packet analysis, including deep packet inspection, in network forensics, and provides a review of AI-powered packet analysis methods with advanced network traffic classification and pattern identification capabilities. Considering that not all network information can be used in court, the types of digital evidence that might be admissible are detailed. The properties of both hardware appliances and packet analyzer software are reviewed from the perspective of their potential use in network forensics
Informing protocol design through crowdsourcing measurements
Mención Internacional en el tÃtulo de doctorMiddleboxes, such as proxies, firewalls and NATs play an important role in the modern Internet
ecosystem. On one hand, they perform advanced functions, e.g. traffic shaping, security or enhancing application
performance. On the other hand, they turn the Internet into a hostile ecosystem for innovation,
as they limit the deviation from deployed protocols. It is therefore essential, when designing a new protocol,
to first understand its interaction with the elements of the path. The emerging area of crowdsourcing
solutions can help to shed light on this issue. Such approach allows us to reach large and different sets of
users and also different types of devices and networks to perform Internet measurements. In this thesis,
we show how to make informed protocol design choices by expanding the traditional crowdsourcing focus
from the human element and using crowdsourcing large scale measurement platforms.
We consider specific use cases, namely the case of pervasive encryption in the modern Internet, TCP
Fast Open and ECN++. We consider such use cases to advance the global understanding on whether wide
adoption of encryption is possible in today’s Internet or the adoption of encryption is necessary to guarantee
the proper functioning of HTTP/2. We target ECN and particularly ECN++, given its succession of
deployment problems. We then measured ECN deployment over mobile as well as fixed networks. In the
process, we discovered some bad news for the base ECN protocol—more than half the mobile carriers we
tested wipe the ECN field at the first upstream hop. This thesis also reports the good news that, wherever
ECN gets through, we found no deployment problems for the ECN++ enhancement. The thesis includes
the results of other more in-depth tests to check whether servers that claim to support ECN, actually respond
correctly to explicit congestion feedback, including some surprising congestion behaviour unrelated
to ECN.
This thesis also explores the possible causes that ossify the modern Internet and make difficult the
advancement of the innovation. Network Address Translators (NATs) are a commonplace in the Internet
nowadays. It is fair to say that most of the residential and mobile users are connected to the Internet
through one or more NATs. As any other technology, NAT presents upsides and downsides. Probably the
most acknowledged downside of the NAT technology is that it introduces additional difficulties for some
applications such as peer-to-peer applications, gaming and others to function properly. This is partially
due to the nature of the NAT technology but also due to the diversity of behaviors of the different NAT implementations
deployed in the Internet. Understanding the properties of the currently deployed NAT base
provides useful input for application and protocol developers regarding what to expect when deploying
new application in the Internet. We develop NATwatcher, a tool to test NAT boxes using a crowdsourcingbased
measurement methodology.
We also perform large scale active measurement campaigns to detect CGNs in fixed broadband networks
using NAT Revelio, a tool we have developed and validated. Revelio enables us to actively determine from within residential networks the type of upstream network address translation, namely NAT
at the home gateway (customer-grade NAT) or NAT in the ISP (Carrier Grade NAT). We deploy Revelio
in the FCC Measuring Broadband America testbed operated by SamKnows and also in the RIPE Atlas
testbed.
A part of this thesis focuses on characterizing CGNs in Mobile Network Operators (MNOs). We develop
a measuring tool, called CGNWatcher that executes a number of active tests to fully characterize CGN
deployments in MNOs. The CGNWatcher tool systematically tests more than 30 behavioural requirements
of NATs defined by the Internet Engineering Task Force (IETF) and also multiple CGN behavioural metrics.
We deploy CGNWatcher in MONROE and performed large measurement campaigns to characterize the
real CGN deployments of the MNOs serving the MONROE nodes.
We perform a large measurement campaign using the tools described above, recruiting over 6,000 users,
from 65 different countries and over 280 ISPs. We validate our results with the ISPs at the IP level and,
reported to the ground truth we collected. To the best of our knowledge, this represents the largest active
measurement study of (confirmed) NAT or CGN deployments at the IP level in fixed and mobile networks
to date.
As part of the thesis, we characterize roaming across Europe. The goal of the experiment was to try to
understand if the MNO changes CGN while roaming, for this reason, we run a series of measurements that
enable us to identify the roaming setup, infer the network configuration for the 16 MNOs that we measure
and quantify the end-user performance for the roaming configurations which we detect. We build a unique
roaming measurement platform deployed in six countries across Europe. Using this platform, we measure
different aspects of international roaming in 3G and 4G networks, including mobile network configuration,
performance characteristics, and content discrimination. We find that operators adopt common approaches
to implementing roaming, resulting in additional latency penalties of 60 ms or more, depending on geographical
distance. Considering content accessibility, roaming poses additional constraints that leads to
only minimal deviations when accessing content in the original country. However, geographical restrictions
in the visited country make the picture more complicated and less intuitive.
Results included in this thesis would provide useful input for application, protocol designers, ISPs and
researchers that aim to make their applications and protocols to work across the modern Internet.Programa de Doctorado en IngenierÃa Telemática por la Universidad Carlos III de MadridPresidente: Gonzalo Camarillo González.- Secretario: MarÃa Carmen Guerrero López.- Vocal: Andrés GarcÃa Saavedr