180 Park Ave - Building 103
Florham Park, NJ
Subject matter expert in IP traffic analysis
Alexandre Gerber is a Principal Member of Technical Staff in the Network and Traffic Analysis Research Department at AT&T Labs Research in Florham Park, NJ. His research focuses on Internet routing, network management, network data mining, and IP traffic measurements across environments ranging from Enterprise VPNs to consumer wireless and wireline broadband Internet access.
He has written more than 25 research articles, has more than 25 patents - issued or pending - and has received in 2005 the AT&T Leaders Council award. Some of his work was covered by the popular press: National Geographic Magazine, the New York Times, TIME magazine, the Wall Street Journal or Newsweek. Some of his research on using communications and digital footprints to better understand Society is highlighted here.
He has also presented, as an invited speaker at OFC 2011, a tutorial on traffic types and traffic growth on Internet Backbones that is available here.
His recent work on wireless application performance and cross-layer interaction is summarized here.
He graduated in Telecommunications Engineering from Eurecom Institue and TELECOM Bretagne and joined AT&T in 2001. He has an MBA in Management and Business Strategy from Rutgers Business School.
Traffic Types and Growth in Backbone Networks (SLIDES)
Alexandre Gerber, Robert Doverspike
in Proc. of OFC/NFOEC, INVITED PAPER,
2011.
[PDF]
[BIB]
{We review the growth of the different sources of data traffic on backbones, highlight the importance and nature of IP services today, and discuss the implications on content distribution and efficient use of backbone capacity.}
Traffic Types and Growth in Backbone Networks
Robert Doverspike, Alexandre Gerber
in Proc. of OFC/NFOEC, INVITED PAPER,
2011.
[PDF]
[BIB]
Optical Society of America Copyright
The definitive version was published in OFC 2011 , 2011-03-06
{We review the growth of the different sources of data traffic on backbones, highlight the importance and nature of IP services today, and discuss the implications on content distribution and efficient use of backbone capacity.}
To Cache or not to Cache: The 3G case
Jeffrey Erman, Alexandre Gerber, Mohammad Hajiaghayi, Dan Pei, Subhabrata Sen, Oliver Spatscheck
IEEE Internet Computing,
2011.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in IEEE Internet Computing, 2011. , 2011-01-01
{Cellular networks have witnessed tremendous traffic growth
recently, fueled by the rapid proliferation of smartphones,
laptops with mobile data cards, and new technologies improving
the performance of these networks. However, unlike
the wired world, there exists a rather limited understanding
of the application mixes and the characteristics of this traffic.
Recent studies have shown that in the wired broadband
world, HTTP traffic accounts for the vast majority of the application
traffic and that forward caching of HTTP objects
results in substantial savings in network resources. What
about cellular networks? The answer is a function of the
traffic characteristics, network architecture, as well as the
various cost points associated with delivering traffic in these
networks. In this paper, we examine the characteristics of
HTTP traffic generated by millions of users across one of
the world�s largest 3G cellular networks, and explore the potential
of forward caching. We provide a simple cost model
that third parties can easily use to determine the cost-benefit
tradeoffs for their own cellular network settings. This is the
first large scale caching analysis in cellular networks.}
The Connected States of America: Quantifying Social Radii of Influence
Francesco Calabrese, Dominik Dahlem, Alexandre Gerber, Deirdre Paul, Xiaoji Chen, James Rowland, Christopher Rath, Carlo Ratti
in Proc. of IEEE International Conference on Social Computing (SocialCom),
2011.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in in Proc. of IEEE International Conference on Social Computing (SocialCom). , 2011-10-09
{Human dynamics are inextricably intertwined with
the social, geographical and economic environment. The continuous
flux of people communicating as well as migrating,
commuting, and traveling inevitably spans acquaintances across
geographic space that is far from random and exhibits regular
patterns. For instance, it has been shown that the probability of
being acquainted with someone is closely related to the inverse
distance between them. In this paper we investigate aggregated
mobile phone call detail records from a large US cellular operator
and map them into space to characterize the social radius of
influence at two different scales: communication and mobility.
We discover that scaling properties with respect to population
agglomeration are similar to those discovered for other indicators
of cities. We also discover spatial community structures that
are divorced from administrative boundaries, and use them to
quantify the different social radii of influence discovered from
the data.}
Profiling Resource Usage for Mobile Applications: A Cross-layer Approach
Feng Qian, Zhaoguang Wang, Alexandre Gerber, Z. Morley Mao, Subhabrata Sen, Oliver Spatscheck
in Proc. of ACM MobiSys,
2011.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2011. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proc of ACM MobiSys , 2011-06-27.
{Despite the popularity of mobile applications, their performance
and energy bottlenecks remain hidden due to a lack of visibility into
the resource-constrained mobile execution environment with po-
tentially complex interaction with the application behavior. We de-
sign and implement ARO, the mobile Application ResourceOptimizer,
the first tool that efficiently and accurately exposes the cross-layer
interaction among various layers including radio resource chan-
nel state, transport layer, application layer, and the user interac-
tion layer to enable the discovery of inefficient resource usage for
smartphone applications. To realize this, ARO provides three key
novel analyses: (i) accurate inference of lower-layer radio resource
control states, (ii) quantification of the resource impact of applica-
tion traffic patterns, and (iii) detection of energy and radio resource
bottlenecks by jointly analyzing cross-layer information. We have
implemented ARO and demonstrated its benefit on several essential
categories of popular Android applications to detect radio resource
and energy inefficiencies, such as unacceptably high (46%) energy
overhead of periodic audience measurements and inefficient con-
tent prefetching behavior.}
Making Sense of Customer Tickets in Cellular Networks
Yu Jin, Nicholas Duffield, Alexandre Gerber, Patrick Haffner, Wen Hsu, Guy Jacobson, Shobha Venkataraman, Zhi-Li Zhang, Subhabrata Sen
in Proc. IEEE INFOCOM Mini-Conference,
2011.
[PDF]
[BIB]
{Abstract�Effective management of large-scale cellular data
networks is critical to meet customer demands and expectations.
Customer calls for technical support provides direct indication as
to the issues and problems customers encounter. In this paper we
study the customer tickets � free-text recordings and classifications
by customer support agents � collected at a large cellular network
provider, with two inter-related goals: i) to characterize and
understand the major factors which lead to customers to call
and seek support; and ii) to utilize such customer tickets to
help identify potential network problems. For this purpose, we
develop a novel statistical approach to model customer call rates
which account for customer-side factors (e.g., user tenure and
handset types) as well as geo-locations. We show that most calls
are due to customer-side factors and can be well captured by the
model. Furthermore, we also demonstrate that location-specific
deviations from the model provide a good indicator of potential
network-side issues. The latter is corroborated with the detailed
analysis of customer tickets and other independent data sources
(non-ticket customer feedback and network performance data).}
Demo: Mobile Application Resource Optimizer (ARO)
Feng Qian, Zhaoguang Wang, Alexandre Gerber, Z. Morley Mao, Subhabrata Sen, Oliver Spatscheck
in Proc. of ACM MobiSys,
2011.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2011. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proc. of ACM MobiSys , 2011-06-27.
{Despite the popularity of mobile applications, their performance
and energy bottlenecks remain hidden due to a lack of visibility into
the resource-constrained mobile execution environment with potentially
complex interaction with the application behavior. We design
and implement ARO, mobile Application Resource Optimizer,
the first tool that efficiently and accurately exposes the cross-layer
interaction to enable the discovery of inefficient resource usage.}
Cellular Data Network Infrastructure Characterization and Implication on Mobile Content Placement
Alexandre Gerber, Qiang Xu, Junxian Huang, Zhaoguang Wang, Feng Qian, Z. Morley Mao
In Proc. of ACM Sigmetrics,
2011.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2011. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM SIGMetrics , 2011-06-05
{Despite the tremendous growth in the cellular data network usage due to the popularity of smartphones, so far there is rather limited understanding of the network infrastructure of various cellular carriers. Understanding the infrastructure characteristics such as the network topology, routing design, address allocation, and DNS service configuration is essential for predicting, diagnosing, and improving cellular network services, as well as for delivering content to the growing population of mobile wireless users. In this work, we propose a novel approach for discovering cellular infrastructure by intelligently combining several data sources, i.e., server logs from a popular location search application, measurement results collected from smartphone users, DNS request logs from a DNS authoritative server, and publicly available routing updates. We perform the first comprehensive analysis to characterize the cellular data network infrastructure of four major cellular carriers within the U.S. in our study. We conclude among other previously little known results that the current routing of cellular data traffic is quite restricted, as it must traverse a rather limited number (4�6) of infrastructure locations, which is in sharp contrast to wireline Internet traffic. We demonstrate how such findings have direct implications on important decisions such as mobile content placement and server selection. We observe that although the local DNS server is a coarsgrained approximation on the user�s network location, for some
carriers, choosing content servers based on the local DNS server is accurate enough due to the restricted routing in cellular networks.}
AccuLoc: Practical Localization of Performance Measurements in 3G Networks
Qiang Xu, Alexandre Gerber, Z. Morley Mao, Jeffrey Pang
in Proc. of ACM MobiSys,
2011.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2011. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Mobisys Conference , 2011-06-27.
{Operators of 3G data networks need to distinguish the performance
of each geographic area in their 3G networks to
detect and resolve localized network problems. This is because
the quality of the �last mile� radio link between 3G
base stations and end-user devices is a crucial factor in the
end-to-end performance that each user experiences. It is relatively
straightforward to measure the performance of all IP
traffic in the 3G network from a small number of vantage
points in the core network. However, the location information
available about each mobile device (e.g., the cell sector
that it is in) is often too stale to be accurate because
of user mobility. Moreover, it is impractical to collect fine grained
location information about all mobile devices on an
on-going basis in large 3G networks. Thus, it is not practical
to accurately assign IP performance measurements to
fine-grained geographic regions of the 3G network using off the-
shelf components. Fortunately, previous studies have observed
that human mobility patterns are very predictable. In
this paper, we exploit this predictability to develop a novel
clustering algorithm that accurately assigns IP performance
measurements to fine-grained geographic regions. At the
GGSNs, we can either localize a subscriber into only 4 cell
sectors with the accuracy of 70% over 5 consecutive days
based on a one-day snapshot of fine-grained 3GPP events,
or increase the accuracy 20% through lightweight handover
statistics hourly collected. We present results from a prototype
in a real 3G network that shows our clustering provides
more accurate performance localization results than existing
approaches. Our results also shed light on the mobility patterns
of 3G devices.}
TOP: Tail Optimization Protocol for Cellular Radio Resource Allocation
Alexandre Gerber, Oliver Spatscheck, Subhabrata Sen, Feng Qian (University Michigan), Zhaoguang Wang (University Michigan), Z. Morley Mao (University Michigan)
ICNP, 18th IEEE International Conference on Network Protocols,
2010.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published inICNP, 18th IEEE International Conference on Network Protocols, 2010 , 2010-10-05
{In 3G cellular networks, the release of radio resources
is controlled by inactivity timers. However, the timeout
value itself, also known as the tail time, can last up to 15 seconds
due to the necessity of trading off resource utilization efficiency
for low management overhead and good stability, thus wasting
considerable amount of radio resources and battery energy at
user handsets. In this paper, we propose Tail Optimization Protocol
(TOP), which enables cooperation between the phone and
the radio access network to eliminate the tail whenever possible.
Intuitively, applications can often accurately predict a long idle
time. Therefore the phone can notify the cellular network on such
an imminent tail, allowing the latter to immediately release radio
resources. To realize TOP, we utilize a recent proposal of 3GPP
specification called fast dormancy, a mechanism for a handset to
notify the cellular network for immediate radio resource release.
TOP thus requires no change to the cellular infrastructure
and only minimal changes to smartphone applications. Our
experimental results based on real traces show that with a
reasonable prediction accuracy, TOP saves the overall radio
energy (up to 17%) and radio resources (up to 14%) by reducing
tail times by up to 60%. For applications such as multimedia
streaming, TOP can achieve even more significant savings of
radio energy (up to 60%) and radio resources (up to 50%).}
Speed Testing without Speed Tests: Estimating Achievable Download Speed from Passive Measurements
Jeffrey Pang, Shobha Venkataraman, Oliver Spatscheck, Alexandre Gerber
in Proc. of ACM Internet Measurement Conference (IMC),
2010.
[PDF]
[BIB]
1 Copyright
(c) ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution.
The definitive version was published in ACM Internet Measurement Conference , 2010-11-01.
{How fast is the network? The speed at which real users can download content at different locations and at different times is an important metric for service providers. Knowledge of this speed helps determine where to provision more capacity and helps detect network problems. However, most network-level estimates of these speeds today are obtained using active �speed tests� that place substantial load on the network and are not necessarily representative of actual user experiences due to limited vantage points. These problems are exacerbated in wireless networks where the physical locations of users play an important role in performance. To redress these problems, this paper presents a new technique to estimate achievable download speed using only flow records collected passively. Estimating achievable speed passively is non-trivial because the measured throughput of real flows is often not comparable to the achievable steady-state TCP rate. This can be because, for example, flows are small and never exit TCP slow start or are rate-limited by the content-provider. Our technique addresses these issues by constructing a Throughput Index, a list of flow types that accurately estimate achievable speed. We show that our technique estimates achievable throughput more accurately than other techniques in a large 3G wireless network.}
Network DVR: A Programmable Framework for Application-Aware Trace Collection
Chia-Wei Chang, Alexandre Gerber, University of California Bill Lin, Subhabrata Sen, Oliver Spatscheck
in Proc. Passive and Active Measurement Conference (PAM),
2010.
[PDF]
[BIB]
Springer Copyright
The definitive version was published in PAM/2010 (Springer, LNCS). , 2010-04-09
{Network traces are essential for a wide range of network applications,
including traffic analysis, network measurement, performance monitoring, and
security analysis. Existing capture tools do not have sufficient built-in intelligence
to understand these application requirements. Consequently, they are forced to
collect all packet traces that might be useful at the finest granularity to meet a
certain level of accuracy requirement. It is up to the network applications to process
the per-flow traffic statistics and extract meaningful information. But for a
number of applications, it is much more efficient to record packet sequences for
flows that match some application-specific signatures, specified using for example
regular expressions. A basic approach is to begin memory-copy (recording)
when the first character of a regular expression is matched. However, often times,
a matching eventually fails, thus consuming unnecessary memory resources during
the interim. In this paper, we present a programmable application-aware triggered
trace collection system called Network DVR that performs precisely the
function of packet content recording based on user-specified trigger signatures.
This in turn significantly reduces the number of memory copies that the system
has to consume for valid trace collection, which has been shown previously as
a key indicator of system performance [8]. We evaluated our Network DVR implementation
on a practical application using 10 real datasets that were gathered
from a large enterprise Internet gateway. In comparison to the basic approach in
which the memory-copy starts immediately upon the first character match without
triggered-recording, Network DVR was able to reduce the amount of memorycopies
by a factor of over 500x on average across the 10 datasets and over 800x
in the best case.}
NEVERMIND, the Problem Is Already Fixed: Proactively Detecting and Troubleshooting Customer DSL Problems
Yu Jin, Nicholas Duffield, Alexandre Gerber, Patrick Haffner, Subhabrata Sen, Zhi-Li Zhang
in Proc. of ACM CoNext,
2010.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM CoNext 2010 , 2010-11-30.
{Traditional DSL troubleshooting solutions are reactive, relying
mainly on customers to report problems, and tend to
be labor-intensive, time consuming, prone to incorrect resolutions
and overall can contribute to increased customer
dissatisfaction. In this paper, we propose a proactive approach
to facilitate troubleshooting customer edge problems
and reducing customer tickets. Our system consists of: i) a
ticket predictor which predicts future customer tickets; and
ii) a trouble locator which helps technicians accelerate the
troubleshooting process during field dispatches. Both components
infer future tickets and trouble locations based on
existing sparse line measurements, and the inference models
are constructed automatically using supervised machine
learning techniques. We propose several novel techniques to
address the operational constraints in DSL networks and to
enhance the accuracy of NEVERMIND. Extensive evaluations
using an entire years worth of customer ticket and measurement
data from a large network show that our method
can predict thousands of future customer tickets per week
with high accuracy and reduce significantly reduce the time
and effort for diagnosing these tickets. This is beneficial as it
has the effect of both reducing the number of customer care
calls and improving customer satisfaction.}
FlowRoute: Inferring Forwarding Table Updates Using Passive Flow-level Measurements
Lee Breslau, Cheng Ee, Alexandre Gerber, Subhabrata Sen, Amogh Dhamdhere, Nicholas Duffield, Carsten Lund
in Proc. of ACM Internet Measurement Conference (IMC),
2010.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Internet Measurement Conference , 2010-11-01.
{The reconvergence of routing protocols in response to changes
in network topology can impact application performance.
While improvements in protocol specification and implementation have significantly reduced reconvergence times,
increasingly performance-sensitive applications continue to
raise the bar for these protocols. As such, monitoring the
performance of routing protocols remains a critical activity
for network operators. We design FlowRoute, a tool based
on passive data plane measurements that we use in conjunction with control plane monitors for offline debugging and
analysis of forwarding table dynamics. We discuss practical
constraints that affect FlowRoute, and show how they can
be addressed in real deployment scenarios. As an application of FlowRoute, we study forwarding table updates by
backbone routers at a tier-1 ISP. We detect interesting behavior such as delayed forwarding table updates and routing
loops due to buggy routers � confirmed by network opera-
tors � that are not detectable using traditional control plane
monitors.}
Characterizing Radio Resource Allocation for 3G Networks
Oliver Spatscheck, Subhabrata Sen, Alexandre Gerber, Feng Qian, Zhaoguang Wang, Z. Morley Mao
in Proc. of ACM Internet Measurement Conference (IMC),
2010.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Internet Measurement Conference , 2010-11-01.
{3G cellular data networks have recently witnessed explosive
growth. In this work, we focus on UMTS, one of the
most popular 3G mobile communication technologies. Our
work is the first to accurately infer, for any UMTS network,
the state machine (both transitions and timer values)
that guides the radio resource allocation policy through a
light-weight probing scheme. We systematically characterize
the impact of operational state machine settings by analyzing
traces collected from a commercial UMTS network, and
pinpoint the inefficiencies caused by the interplay between
smartphone applications and the state machine behavior.
Besides the basic characterization, we explore the optimal
state machine settings in terms of several critical timer values
evaluated using real network traces.
Our findings suggest that the fundamental limitation of
the current state machine design is the static nature of treating
all traffic according to the same inactivity timer, making
it difficult to balance the tradeoffs among radio resource usage
efficiency, network management overhead, device radio
energy consumption, and performance. To the best of our
knowledge, our work is the first empirical study that employs
real cellular traces to investigate the optimality of the state
machine configurations. Our analysis also demonstrates that
traffic patterns impose significant impact on the radio resource
and energy consumption. In particular, We propose
a simple improvement that reduces YouTube streaming energy
by 80% by leveraging an existing feature called fast
dormancy supported by the 3GPP specifications.}
Towards Estimating the Presence of Visitors from the Aggregate Mobile Phone Network Activity they Generate
Fabien Girardin, Andrea Vaccari, Alexandre Gerber, Assaf Biderman, Carlo Ratti
International Conference on Computers in Urban Planning and Urban Management (CUPUM),
2009.
[PDF]
[BIB]
{This paper illustrates how aggregated mobile phone network activity logs
provide anonymous information that reveals valuable insight into the presence of
tourists visiting a city. Technologies supporting pervasive services like cellular
networks have the potential to generate vast quantities of detailed subscriber data,
raising important privacy concerns. But they also provide to researchers and city
planners an unprecedented opportunity to understand the presence and movement
of physical communities. We demonstrate how aggregated communication records
offer the opportunity to note where people are transmitting and receiving information.
The emergence of these spatial imprints obtained through novel technological means
has a significant potential to support urban studies and particularly the optimization of
tourism strategies, plans and marketing tools. In this study, we examine the use of
locally and non-locally registered mobile phones in the vicinity of the �Waterfalls�
public exhibit in New York City in 2008. We study aggregated statistics (i.e. number
of calls) related to the network sectors covering the exhibit and its proximity. With the
future contribution of traditional survey techniques, such as field counts, to calibrate
these mobile phone network measurements, we aim to develop techniques to
estimate the aggregate movements and location of visitors through time and space,
while assuring their privacy.}
The Case for Enterprise-Ready Virtual Private Clouds
Timothy Wood, Alexandre Gerber, Kadangode Ramakrishnan, Prashant Shenoy, Jacobus Van
in Proc. of the USENIX Workshop on Hot Topics in Cloud Computing (HotCloud),
2009.
[PDF]
[BIB]
USENIX Copyright
This is the author's version of the work. It is posted here by permission of Usenix for your personal use. Not for redistribution. The definitive version was published in HotCloud '09. , 2009-06-14, http://www.usenix.org/event/hotcloud09/.
{Cloud computing platforms such as Amazon EC2 provide customers
with flexible, on demand resources at low cost. However,
while existing offerings are useful for providing basic
computation and storage resources, they fail to provide the security
and network controls that many customers would like. In
this work we argue that cloud computing has a great potential
to change how enterprises run and manage their IT systems, but
that to achieve this, more comprehensive control over network
resources and security need to be provided for users. Towards
this goal, we propose CloudNet, a cloud platform architecture
which utilizes virtual private networks to securely and seamlessly
link cloud and enterprise sites.}
TCP Revisited: A Fresh Look at TCP in the Wild
Feng Qian, Alexandre Gerber, Z. Morley Mao, Subhabrata Sen, Oliver Spatscheck, Walter Willinger
in Proc. of ACM Internet Measurement Conference (IMC),
2009.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2009. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Internet Measurement Conference, 2009-11-04
{Since the last in-depth studies of measured TCP traffic some 6-
8 years ago, the Internet has experienced significant changes, including
the rapid deployment of backbone links with 1-2 orders
of magnitude more capacity, the emergence of bandwidth-intensive
streaming applications, and the massive penetration of new TCP
variants. These and other changes beg the question whether the
characteristics of measured TCP traffic in today�s Internet reflect
these changes or have largely remained the same. To answer this
question, we collected and analyzed packet traces from a number of
Internet backbone and access links, focused on the �heavy-hitter�
flows responsible for the majority of traffic. Next we analyzed their
within-flow packet dynamics, and observed the following features:
(1) in one of our datasets, up to 15.8% of flows have an initial congestion
window (ICW) size larger than the upper bound specified
by RFC 3390. (2) Among flows that encounter retransmission rates
of more than 10%, 5% of them exhibit irregular retransmission behavior
where the sender does not slow down its sending rate during
retransmissions. (3) TCP flow clocking (i.e., regular spacing between
flights of packets) can be caused by both RTT and non-RTT
factors such as application or link layer, and 60% of flows studied
show no pronounced flow clocking. To arrive at these findings,
we developed novel techniques for analyzing unidirectional TCP
flows, including a technique for inferring ICW size, a method for
detecting irregular retransmissions, and a new approach for accurately
extracting flow clocks.}
Revisiting route caching: the world should be flat
Changhoon Kim, Matthew Caesar, Alexandre Gerber, Jennifer Rexford
in Proc. Passive and Active Measurement Conference (PAM),
2009.
[BIB]
{Internet routers� forwarding tables (FIBs), which must be stored in
expensive fast memory for high-speed packet forwarding, are growing quickly in
size due to increased multihoming, finer-grained traffic engineering, and
deployment of IPv6 and VPNs. To address this problem, several Internet architectures
have been proposed to reduce FIB size by returning to the earlier approach
of route caching: storing only the working set of popular routes in the
FIB. This paper revisits route caching. We build upon previous work by studying
flat, uni-class (/24) prefix caching, with modern traffic traces from more than
60 routers in a tier-1 ISP. We first characterize routers� working sets and then
evaluate route-caching performance under different cache replacement strategies
and cache sizes. Surprisingly, despite the large number of deaggregated /24 subnets,
caching uni-class prefixes can effectively curb the increase of FIB sizes.
Moreover, uni-class prefixes substantially simplify a cache design by eliminating
longest-prefix matching, enabling FIB design with slower memory technologies.
Finally, by comparing our results with previous work, we show that the distribution
of traffic across prefixes is becoming increasingly skewed, making route
caching more appealing.}
Quantifying urban attractiveness from the distribution and density of digital footprints
Fabien Girardin, Andrea Vaccari, Alexandre Gerber, Assaf Biderman, Carlo Ratti
International Journal of Spatial Data Infrastructures Research, Volume 4 (2009) pp. 175-200,
2009.
[PDF]
[BIB]
{In the past, sensors networks in cities have been limited to fixed sensors,
embedded in particular locations, under centralised control. Today, new
applications can leverage wireless devices and use them as sensors to develop
aggregated information. In this paper, we show that the emerging patterns
unveiled through the analysis of large sets of aggregated digital footprints can
provide novel insights into how people experience the city and into some of the
drives behind these emerging patterns. This information has uses for local
authorities, researchers, as well as service providers such as mobile network
operators. To explore this capacity for quantifying urban attractiveness, we
performed a case study using the distribution and density of digital footprints in
the area of the New York City Waterfalls, a public art project of four man-made
waterfalls rising from the New York Harbor. Methods to study the impact of an
event of this nature are traditionally based on the collection of static information
such as surveys and ticket-based people counts, which allow to generate
estimates about visitors� presence in specific areas over time. In contrast, our
contribution makes use of the dynamic data that visitors generate, such as the
amount and distribution of aggregate phone calls and photos taken in different
areas of interest and over time. Our analysis provides novel ways to quantify the
impact of the public art exhibit on the distribution of visitors and the attractiveness
of points of interest in the proximity of the event.}
Quantifying the Extent of IPv6 Deployment
Elliott Karpilovsky, Alexandre Gerber, Dan Pei, Jennifer Rexford, Aman Shaikh
in Proc. Passive and Active Measurement Conference (PAM),
2009.
[BIB]
{Internet routers� forwarding tables (FIBs), which must be stored in
expensive fast memory for high-speed packet forwarding, are growing quickly in
size due to increased multihoming, finer-grained traffic engineering, and deployment
of IPv6 and VPNs. To address this problem, several Internet architectures
have been proposed to reduce FIB size by leveraging route caching: storing only
the working set of popular routes in the FIB. This paper revisits route caching.
We build upon previous work by studying flat, uni-class (/24) prefix caching, with
modern traffic traces from more than 60 routers in a tier-1 ISP. We first characterize
routers� working sets and then evaluate route-caching performance under
different cache replacement strategies and cache sizes. Surprisingly, despite the
large number of deaggregated /24 subnets, caching uni-class prefixes can effectively
curb the increase of FIB sizes. Moreover, uni-class prefixes substantially
simplify a cache design by eliminating longest-prefix matching, enabling FIB
design with slower memory technologies. Finally, by comparing our results with
previous work, we show that the distribution of traffic across prefixes is becoming
increasingly skewed, making route caching more appealing.}
Network-Aware Forward caching
Jeffrey Erman, Alexandre Gerber, Mohammad Hajiaghayi, Dan Pei, Oliver Spatscheck
in Proc. World Wide Web Conference (WWW),
2009.
[PDF]
[BIB]
IW3C2 Copyright
"Copyright is held by the International World Wide Web Conference Committee (IW3C2)."
{This paper proposes and evaluates a Network Aware Forward
Caching approach for determining the optimal deployment strategy
of forward caches to a network. A key advantage of this approach
is that we can reduce the network costs associated with forward
caching to maximize the benefit obtained from their deployment.
We show in our simulation that a 37% increase to net benefits could
be achieved over the standard method of full cache deployment to
cache all POPs traffic. In addition, we show that this maximal point
occurs when only 68% of the total traffic is cached.
Another contribution of this paper is the analysis we use to motivate
and evaluate this problem. We characterize the Internet traffic
of 100K subscribers of a US residential broadband provider. We
use both layer 4 and layer 7 analysis to investigate the traffic volumes
of the flows as well as study the general characteristics of
the applications used. We show that HTTP is a dominant protocol
and account for 68% of the total downstream traffic and that 34%
of that traffic is multimedia. In addition, we show that multimedia
content using HTTP exhibits a 83% annualized growth rate and
other HTTP traffic has a 53% growth rate versus the 26% over all
annual growth rate of broadband traffic. This shows that HTTP
traffic will become ever more dominant and increase the potential
caching opportunities. Furthermore, we characterize the core
backbone traffic of this broadband provider to measure the distance
traveled by content and traffic. We find that CDN traffic is much
more efficient than P2P content and that there is large skew in the
Air Miles between POP in a typical network. Our findings show
that there are many opportunities in broadband provider networks
to optimize how traffic is delivered and cached.}
Multimedia content growth: From IP networks to Medianets
Alexandre Gerber, Jeffrey Erman, Oliver Spatscheck
IEEE Communications Society Live Webinar: TRANSFORMING NEXT GENERATION IP NETWORKS INTO MEDIANETS,
2009.
[PPT]
[BIB]
{Multimedia Content growth is driving network evolution
Content hybrid delivery solutions will take advantage of information across layer boundaries:
+ Network-aware applications
+ Application-aware networks
The network will have the opportunity to become the information aggregator
+ Scalable solution to the problem of �who to tell� and �who to ask�
Medianets should not forget MediaNetworkManagement! }
Multicast Redux: A First Look at Enterprise Multicast Traffic
Elliott Karpilovsky, Lee Breslau, Alexandre Gerber, Subhabrata Sen
in Proc. of ACM SIGCOMM Workshop: Research on Enterprise Networking (WREN),
2009.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2009. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM SICOMM 2009 , 2009-08-17.
{IP multicast, after spending much of the last 20 years as
the subject of research papers, protocol design efforts and
limited experimental usage, is finally seeing significant deployment in production networks. The efficiency afforded
by one-to-many network layer distribution is well-suited to
such emerging applications as IPTV, file distribution, conferencing, and the dissemination of financial trading information. However, it is important to understand the behavior
of these applications in order to see if network protocols are
appropriately supporting them. In this paper we undertake
a study of enterprise multicast traffic as observed from the
vantage point of a large VPN service provider. We query
multicast usage information from provider edge routers for
our analysis. To our knowledge, this is the first study of production multicast traffic. Our purpose is both to understand
the characteristics of the tra�c (in terms of �ow duration,
throughput, and receiver dynamics) and to gain insight as
to whether the current mechanisms support multicast VPNs
can be improved. Our analysis reveals several classes of multicast traffic for which changes to the underlying protocols
may yield benefits.}
Multi-VPN Optimization for Scalable Routing via Relaying
MohammadHossein Bateni, Alexandre Gerber, Mohammad Hajiaghayi, Subhabrata Sen
in Proc. IEEE INFOCOM Mini-Conference and IEEE/ACM Transactions on Networking,
2009.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in Proc. IEEE INFOCOM Mini-Conference and IEEE/ACM Transactions on Networking, 2009. , 2009-04-19
{Enterprise networks are increasingly adopting
Layer 3 Multiprotocol Label Switching (MPLS) Virtual Private
Network (VPN) technology to connect geographically disparate
locations. The any-to-any direct connectivity model of this technology
involves a very high memory footprint and is causing
associated routing tables in the service provider�s routers to grow
very large. The concept of Relaying was proposed earlier [9]
to separately minimize the routing table memory footprint of
individual VPNs, and involves selecting a small number of hub
routers to maintain complete reachability information for that
VPN, and enabling non-hub spoke routers with reduced routing
tables to achieve any-to-any reachability by routing traffic via a
hub.
A large service provider network typically hosts many thousands
of different VPNs. In this paper, we generalize Relaying
to the multi-VPN environment, and consider new constraints on
resources shared across VPNs, such as router uplink bandwidth
and memory. The hub selection problem involves complex tradeoffs
along multiple dimensions including these shared resources,
and the additional distance traversed by traffic. We formulate the
hub selection as a constraint optimization problem and develop
an algorithm with provable guarantees to solve this NP-complete
problem. Evaluations using traces and configurations from a
large provider and many real-world VPNs indicate that the
resulting Relaying solution substantially reduces the total router
memory requirement by 85% while smoothing out the utilization
on each router and requiring only a small increase in the endto-
end path for the relayed traffic.}
A holistic framework for the study of urban traces and the profiling of urban processes and dynamics
Andrea Vaccari, Liang Liu, Assaf Biderman, Carlo Ratti, Francisco Pereira, Universidade de Coimbra Joao Oliveirinha, Alexandre Gerber
in Proc. IEEE Conference on Intelligent Transportation Systems (ITSC),
2009.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in Proc. IEEE Conference on Intelligent Transportation Systems (ITSC), 2009. . , 2009-10-04
{Pervasive systems produce massive amounts of data
as by-products of their interaction with users. Cell phone calls
can inform us on how many people are present in a given area and
how many are entering or leaving it. Geotagged photos can tell us
where tourists go within the city and how much time they spend
in each place. Descriptions of events, products, and services allow
us to characterize places based on their most popular activities,
products, and services.
In this paper we illustrate a research agenda that aims at
developing a holistic framework for the study of urban traces
and the profiling of urban processes and their dynamics which
will enable us to better understand how cities function and to
develop more efficient urban policies. We also present the results
of a preliminary case study in New York City where we analyzed
the correlation between cell phone network handovers and traffic
volumes and between semantic indexes of public events and
local variations in cell phone activity. The results showed that
there exist causal relationships between these types of data, and
confirmed that there is strong promise in the holistic study of
urban traces.}
Scalable VPN Routing via Relaying
Changhoon Kim, Alexandre Gerber, Carsten Lund, Dan Pei, Subhabrata Sen
in Proc. ACM SIGMETRICS,
2008.
[PDF]
[BIB]
ACM Copyright
(c) ACM, 2008. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM SIGMETRICS 2008 , 2008-06-06.
{Enterprise customers are increasingly adopting MPLS(Multiprotocol Label Switching) VPN (Virtual Private Network) service that offers direct any-to-any reachability among the customer sites via a provider network. Unfortunately this direct reachability model makes the service provider's routing tables grow very large as the number of VPNs and the number of routes per customer increase. As a result, router memory in the provider's network has become a key bottleneck in provisioning new customers. This paper proposes Relaying, a scalable VPN routing architecture that the provider can implement simply by modifying the configuration of routers in the provider network, without requiring changes to the router hardware and software. Relaying substantially reduces the memory footprint of VPNs by choosing a small number of hub routers in each VPN that maintain full reachability information, and by allowing nonhub routers to reach other routers through a hub. Deploying Relaying in practice, however, poses a challenging optimization problem that involves minimizing router memory usage by having as few hubs as possible, while limiting the additional latency due to indirect delivery via a hub. We first investigate the fundamental tension between the two objectives and then develop algorithms to solve the optimization problem by leveraging some unique properties of VPNs, such as sparsity of traffic matrices and spatial locality of customer sites. Extensive evaluations using real traffic matrices, routing configurations, and VPN topologies demonstrates that Relaying is very promising and can reduce routing-table usage by up to 90%, while increasing the additional distances traversed by traffic by only a few hundred miles, and the backbone bandwidth usage by less than 10%. }
Network-Aware Forward caching
Alexandre Gerber, Jeffrey Erman, Mohammad Hajiaghayi, Dan Pei, Oliver Spatscheck
2008.
[PPT]
[BIB]
Multicast Instant Channel Change in IPTV Systems
Kadangode Ramakrishnan, Alexandre Gerber, Oliver Spatscheck, Damodar Banodkar, Shivkumar Kalyanaraman
In Proc. of the Conference on COMmunication System softWAre and middlewaRE (COMSWARE),
2008.
[BIB]
{IPTV delivers television content over an IP infrastructure with the potential to enrich the viewing experience of users by integrating data applications with video delivery. From an engineering perspective, IPTV places both significant steady state and transient demands on network bandwidth. Typical IPTV streaming techniques incur delays to fill the play-out buffer. But, when viewers switch or surf channels, it is important to minimize this user-perceived latency. Traditional Instant Channel Change (ICC) techniques reduce this latency by having a separate unicast assist channel for every user changing channels. Instead, we propose a multicast-based approach using a secondary "channel change stream" in association with the multicast of the regular quality stream for the channel requested. During channel change events, the user does a multicast join to this new stream and experiences smaller display latency. In the background, the play-out buffer of the new full-quality multicast stream is filled. Then, the transition to the new channel is complete. We show that this approach has several performance benefits including lower bandwidth consumption even during flash crowds of channel changes, lower display latency (50% lower), and lower variability of network & server load. The tradeoff is a lower quality video during the play-out buffering period of a few seconds. Our results are based upon both synthetic channel change arrival patterns as well as traces collected from an operational IPTV environment. }
Towards Quantification of IP Network Reliability
Hao Wang, Alexandre Gerber, Albert Greenberg, Jia Wang, Yang Richard Yang
ACM SIGCOMM (Poster),
2007.
[PDF]
[BIB]
Copyright
(c) ACM, 2007. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM SIGCOMM '07 , 2007-09-01.
{}
Reliability as an Interdomain Service
Hao Wang, Yang Richard Yang, Paul H. Liu, Jia Wang, Alexandre Gerber
in Proc. of ACM SIGCOMM,
2007.
[PDF]
[BIB]
Copyright
(c) ACM, 2007. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM SIGCOMM '07 , 2007-08-27.
{Reliability is a critical requirement of the Internet. The availability and resilience of the Internet under failures can have significant global effects. However, in the current Internet routing architecture, achieving the high level of reliability demanded by many mission-critical activities can be costly. In this paper, we first propose a novel solution framework called reliability as an interdomain service (REIN) that can be incrementally deployed in the Internet and substantially improve the redundancy of ISP networks at low cost. We then present robust algorithms to efficiently utilize network redundancy to maximize reliability. We use real ISP topologies and traffic traces to demonstrate the effectiveness of our framework and algorithms. }
P2P, the gorilla in the cable
Alexander Gerber, Matthew Roughan, Subhabrata Sen, Joseph Houle, Han Nguyen
National Cable & Telecommunications Association (NCTA) National Show,
2003.
[PDF]
[BIB]
Copyright
� 2003 AT&T Corp. All rights reserved.
{There is considerable interest in peer-to-peer (P2P) traffic because of its remarkable increase over the last few years. By analyzing flow measurements at the regional aggregation points of several cable operators, we are able to study its properties. P2P has become a large part of broadband traffic and its characteristics are different from older applications, such as the Web. It is a stable balanced traffic: the peak to valley ratio during a day is around two and the IN/OUT traffic balance is close to one. Although P2P protocols are based on a distributed architecture, they don't show strong signs of geographical locality. A cable subscriber is not much more likely to download a file from a close region than from a far region. It is clear that most of the traffic is generated by heavy hitters who abuse P2P (and other) applications, whereas most of the subscribers only use their broadband connections to browse the web, exchange emails or chat. However it is not easy to directly block or limit P2P traffic, because these applications adapt themselves to their environment: the users develop ways of eluding the traffic blocks. The traffic that could historically be identified with five port numbers is now spread over thousands of TCP ports, pushing port based identification to its limits. More complex methods to identify P2P traffic are not a long-term solution, the cable industry should opt for a ?pay for what you use? model like the other utilities. }
Trajectory Engine: A backend for trajectory sampling
Nicholas Duffield, Alexander Gerber, Matthias Grossglauser
In Proc. IEEE Network Operations and Management Symposium (NOMS),
2002.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in Proc. IEEE Network Operations and Management Symposium (NOMS), 2002. , 2002-04-19
{The management of communications networks increasingly requires detailed knowledge of network usage, acquired by direct measurement. We report on the design and implementation of a backend system for Trajectory Sampling, a method for the consistent sampling of packets in transmission across a network domain. This Trajectory Engine collects trajectory samples and stores them after appropriate preprocessing. It provides a querying and visualization tool to aid in traffic engineering and troubleshooting tasks. }
Sampling And Analyzing Packets In A Network,
Tue Dec 14 15:05:20 EST 2010
The preferred embodiments of the present invention can include sampling packets transmitted over a network based on the content of the packets. If a packet is sampled, the sampling unit can add one or more fields to the sampled packet that can include a field for a number of bytes contained in the packet, a packet count, a flow count, a sampling type, and the like. The sampled packets can be analyzed to discern desired information from the packets. The additional fields that are added to the sampled packets can be used during the analysis.
Scalable Multiprotocol Label Switching Based Virtual Private Networks And Methods To Implement The Same,
Tue Sep 14 15:04:40 EDT 2010
Example scalable multi-protocol label switching (MPLS) based virtual private networks (VPNs) and methods to implement the same are disclosed. A disclosed example spoke provider edge (PE) router for an MPLS-based VPN includes a truncated virtual routing and forwarding (VRF) table containing a first value referencing a hub PE router and a second value referencing a first customer edge (CE) router coupled to the VPN via the PE router, and a forwarding module to forward a packet received from the first CE router to the hub PE router when the packet contains an address referencing a second CE router coupled to the VPN via a second spoke PE router.
Method For Computing Multicast Traffic Matrices,
Tue Sep 07 15:04:35 EDT 2010
A system and method for receiving, from one or more ingress routers, a first set of records including data corresponding to network traffic, receiving, from one or more egress routers, a second set of records including data corresponding to network traffic and creating a multicast traffic matrix using at least a portion of the data included in the first and second sets of records.
Method For Controlling Traffic Balance Between Peering Networks,
Tue Jul 27 15:04:15 EDT 2010
A method that measures ratio, relative to a peering network, of traffic burden of incoming traffic to traffic burden of outgoing traffic, where traffic burden takes into account traffic volume and distance that the traffic traverses through the network. A determination is made from this ratio as to whether an imbalance exists with the peering network. With the assistance of a simulation of changes in routing policy and their effects, an existing or impending imbalance is remedied by changing the routing policy relative to particular customers, for example from a "hot potato" routing policy to a "best exit" routing policy.
