| BU/NSF Workshop on Internet Measurement, Instrumentation and Characterization
Boston University,
Boston,
Massachusetts,
USA
|
| BU/NSF Workshop on Internet Measurement, Instrumentation and Characterization
Boston University,
Boston,
Massachusetts,
USA
|
As a research community, an important next step involves an comprehensive look at the challenges that lie ahead in this area. This includes an an evaluation of both the current unsolved challenges and the upcoming challenges the Internet will present us with in the near future, and a discussion of the promising new techniques that innovators in the field are currently developing. To this end, the Web and InterNetworking Research Group at Boston University (WING@BU), with support from the National Science Foundation, (grant #9985484) organized a one-day workshop which was held at Boston University on Monday, August 30, 1999 (immediately preceding ACM SIGCOMM '99).
We were extremely pleased to find that there was greater than expected interest in the IMIC workshop as soon as it was announced. We put up a Web page with information about the workshop and sent out announcements via e-mail only six weeks before the conference. Eighty people pre-registered for the conference, including thirty-three students. The NSF support that allowed us to waive registration fees for students clearly had an impact in driving student registrations; almost all students specifically requested the waiver. Excluding the students, the remaining people who pre-registered were almost evenly split between industry and academia, demonstrating the wide appeal of the workshop subject.
Attendance at IMIC was superlative and exceeded all expectations of the organizers. The following are some statistics.
The IMIC workshop has attracted over 135 participants (excluding organizers and speakers). Those participants were split almost evenly between academia (73 participant) and industry (62 participant). More than two-thirds of IMIC participants (82 participants) were not local (i.e. not from the Greater Boston Area).
The organization of this workshop on the day before the start of SIGCOM'99 had a positive effect on outreach since over 100 of the participants indicated that they had plans to be at SIGCOMM'99; the rest indicated that they treveled exclusively to attend the IMIC workshop.
Participation of graduate students was particularly encouraging. Of the participants from academia 61 identified themselves as graduate students and 22 of these were females and 12 identified themselves as belonging to an under-represented group. The free registration at IMIC for all student participants was possible thanks to NSF funding as well as to Boston University's matching funds.
Session I: Instrumentation and Measurement
Chair: Paul Barford
There were three presentations in this session which generally dealt with wide area, Internet measurements. Issues involving measurements of Internet topology and performance were discussed in some detail as well as the applications for the measurement data. The session was made up of the following presentations:
Sugih Jamin discussed methods for determining where in the Internet to place measurement systems which are focused on collecting distance metrics (hop count, round-trip time, etc.). The data gathered by these systems is used to generate IDMaps which could be used by clients to, for example, determine which which web server mirror site is the closest. Dr. Jamin presented a set of heuristic placement methods based on network topology features and then analyzed their effectiveness in simulation. The results showed that information from IDMaps can significantly improve the accuracy of the nearest mirror selection over random selection. Results were also presented on how the number of measurement systems used can affect the accuracy of mirror selection.
Matt Zekauskas described the Surveyor IP Measurement project and
discussed a variety of lessons learned and results from that project. The
Surveyor project is based on a measurement infrastructure (consisting of 56
systems) that is distributed throughout the global Internet. This
infrastructure is used to make highly synchronized measurements of route,
packet delay and packet loss characteristics between all of its systems.
The daily summary results of the continuous measurements made by Surveyor
are available on-line. Some of the results from Surveyor show routing to
often be asymmetric, queuing along symmetric paths is often asymmetric and
significant variability in both packet delay and loss along certain paths.
Impact:
The presentations in this session highlighted the fact that Internet measurements can provide valuable insight to network researchers. It is clear that Internet topology, while complex and not well understood, can be systematically discovered without direct information from ISP's. It is also clear that carefully placed measurement systems can provide end users with information which can enhance their performance, and that paths between systems can show very different characteristics over time. The presentations also showed that there are many challenges to making effective measurements in the Internet. These difficulties principally arise from the Internet's immense size, continued growth and complexity. Finally, the session outlined a number of significant opportunities for future, measurement-based research. These include development of a repository of topological data, careful deployment and management of measurement systems which can be used by a variety of applications and the need for new analysis techniques for measurement data.
Session II: Modeling and Characterization
Chair: Mark Crovella
The three presentations in this session dealt with modeling and characterization problems in the Internet. The session included the following presentations:
Don Towsley the described his recent work in internet tomography -- the process of inferring network-internal state from measurements taken only at the edges. Despite the seeming inscrutability of the Internet when viewed from the vantage point of end systems, his results show that considerable information can be obtained by comparing observations made at different points along the edge of the network. In particular, multicast protocols induce correlation among packet streams, and these correlations can be observed at the edge, suggesting elegant estimation methods with remarkably accurate results.
Finally, Jim Pitkow closed the session with a summary of his
recent work in characterizing user "surfing" behavior in the Internet
(i.e., the sequences of Web requests made by individudal users).
His approach models a user's link-following as a random walk with a
decreasing utility function; these models predict long-tailed
distributions in the lengths of sequences of URL requests.
The feature of his model is in agreement with empirical studies showing
long tails in the lengths of user click-sequences.
Impact:
This session showed that sophisticated models for Internet characteristics are starting to emerge. Like Session I, this session showed that considerable information about the internal state of the Internet can be obtained without cooperation from service providers. In addition, the session showed that the models used for characterizing Internet properties are substantially different from those commonly encountered in performance evaluation; in particular, the long-tailed properties of the models proposed for user behavior and network traffic represent radical departures from traditional Markovian models.
Session III: End-to-End Protocols and Services
Chair: John Byers
There were three presentations in this session which generally dealt with wide area, Internet measurements. Issues involving measurements of Internet topology and performance were discussed in some detail as well as the applications for the measurement data. The session was made up of the following presentations:
Venkata Padmanabhan argued for coordination across concurrent data streams sharing both a common endpoint and common network resources. For example, in the context of multiple TCP streams emanating from a commmon source, coordinating congestion control enables faster shared learning of network resources and more predictable performance across streams. Dr. Padmanabhan demonstrated a strong correlation in queuing delay along connections which shared a single common congested Intranet link, but also pointed to the fact that this correlation can be weakened in the presence of multiple congested links. He then went on to describe a router tagging mechanism which used a form of explicit congestion notification (ECN) to mark packets sharing a congested link. On a related point, Padmanabhan argued that not all packets are created equal (such as TCP SYN packets), and recommended shielding those packets against loss.
Vaduvur Bharghavan discussed the challenges associated with supporting
heterogeneous packet flows (HPF) at the transport layer. One emerging example
of an HPF that Dr. Bharghavan cited was in the context of multimedia applications,
in which video, audio and text may have different QoS policies regarding reliability,
priority, sequencing and deadlines. The theme for the architecture he defined
allows applications to specify the QoS policies they desire, while the transport
layer implements the policies on a per-frame basis. Rather than segregate these
subflows under separate administrative control, Bharghavan motivated a unified,
integrated transport architecture which determines what and when to send across
the entire HPF. As examples of how one might achieve this, he provided details
of a selective reliability option, a goodput control mechanism and some preliminary
performance results.
Impact:
The presentations in this session highlighted the rich array of problems that can be addressed by enabling emerging applications to better manage their use of network resources from an end-to-end perspective. One theme of this session was that these policies should be implemented as middleware services or as enhanced transport-level mechanisms which applications can leverage from without specific application-level customization. Dr. Ammar's talk motivated a new form of hierarchical directory service kept up to date with scalable point-to-point measurements; Dr. Padmanabhan's talk motivated the problem of shared bottleneck detection which coincided with the initiation of several other studies which seek to identify bottlenecks using purely end-to-end methods; Dr. Bharghavan's talk motivated end-to-end methods of improving the quality-of-service of flows he termed Heterogeneous Packet Flows, treating them not as a collection of heterogeneous objects, but by treating them as an ensemble of objects which can be coordinated. Talks from this session have already been cited extensively in the literature as they all study new problems of fundamental importance emphasizing the end-to-end methods that form a cornerstone of the current Internet architecture.
Session IV: Network Support for Next Generation Applications
Chair: Ibrahim Matta
This session consisted of the following three presentations, which were concerned with network services needed to effectively support next-generation applications.
Bala Rajagopalan discussed practical issues in the development and deployment of constraint-based (QoS/policy) unicast and multicast routing mechanisms. Bala described the role of these mechanisms in the overall QoS framework of the Next-Generation Internet, and the current developments in the Internet protocol areas that facilitate the deployment of these mechanisms. Bala discussed the provision of VPNs and diff-serv SLAs using LSPs. For diff-serv, he pointed to the difficulties involved due to the lack of knowledge of the traffic demand matrix, which has to be estimated/measured. Bala raised several practical issues, including scalability and multicast. He presented a flexible methodology for constraint-based routing (CBR) based on distributed overlays, where the underlying IGP is used by CBR entities to communicate.
John Zinky discussed the need for a network resource status
service. This service would allow a distributed application to know
the expected network performance BEFORE it starts
using the resources, so that it can choose among several alternatives or
know when to switch to a new alternative. John described how applications
could use the service within the BBN Quality Objects (QuO) framework, which
adds QoS control and measurement into CORBA. John also discussed options
on how to implement such a network resource status service, and experience
with several proto-type implementations, including CMU Remos.
Impact:
This session raised a number of challenging open questions that the community needs to address. First, the network, even diff-serv, needs some form of admission control to support controlled degradation in quality for multimedia. In addition, users need economic incentives to adapt. Second, constraint-based routing has to address the practical issues of scalability, flexible deployment and measurement/estimation of traffic demands. Finally, it was felt that applications are in need for a wide-area network resource status service (a QoS layer) that measures and predicts QoS.
Panel: IMIC Challenges, Opportunities & Initiatives
Coordinator: Azer Bestavros
There were five panelists invited to the panel. Four of the panelists were chosen as representatives of the four sessions of the workshop. The Fifth panelist was chosen as a representative of funding agencies (namely NSF). The panelists were:
Created on: 2000.06.01