Juhoon Kim

Short biography

I am a research scientist at Telekom Innovation Laboratories (An-Institute of TU Berlin) in Germany. Within the company, my main responsibilities include the development of network monitoring functions and the analysis of large amounts of network data. Apart from being involved in the company’s internal projects, I am also working on two EU-funded projects (FP7 UNIFY and 5G-PPP 5GEx) which focus on new networking paradigms such as Software-defined Networking (SDN), Network Function Virtualiztion (NFV), and Next Generation Mobile Network (NGMN/5G). More precisely, together with more than 16 project partners in Europe, I design the overarching architecture of the network system and develop virtualized network functions for the architecture.

Previously, I received Ph.D. and M.Sc. degrees in Computer Science from TU Berlin under supervision of Prof. Anja Feldmann (FG-INET) and co-supervision of Prof. Luigi Iannone. During my Ph.D. studies, my research interest was centered around developing and evaluating future Internet protocols and architectures such as IPv6, Locator/ID Separation Protocol (LISP), and Multi-source/Multi-interface data transmission.

Research interests

Future Internet, e.g., Network Function Virtualization (NFV), Locator/ID Separation Protocol (LISP)
Internet traffic analysis
Internet content delivery
Simulation and performance evaluation of future Internet protocols and architectures

Currently involved projects

FP7 UNIFY
UNIFY envisions full network and service virtualization to enable rich and flexible services and operational efficiency. Therefore, the UNIFY consortium will research, develop and evaluate means to orchestrate, verify and observe end-to-end service delivery from home and enterprise networks through aggregation and core networks to data centres. Telecom providers struggle with low service flexibility, increasing complexity and related costs. Although cloud computing and networking have been two active fields of research, there is currently little integration between the vast networking assets and data centres of telecom providers. A unified production environment will create unprecedented opportunities for innovation, an improved quality of experience for users, and technological leadership for European industry and academia. A faster and more flexible network will reduce operating costs and open up new business possibilities.
5G-PPP 5GEx
The goal of the 5G Exchange (5GEx) project is to enable cross-domain orchestration of services over multiple administrations or over multi-domain single administrations. This will allow end-to-end network and service elements to mix in multi-vendor, heterogeneous technology and resource environments. Market fragmentation has resulted in a multitude of network operators each focused on different countries and regions. This makes it difficult to create infrastructure services spanning multiple countries, such as virtual connectivity or compute resources, as no single operator has a footprint everywhere.

Publications

Internet Traffic Analysis

Watching the IPv6 Takeoff from an IXP's Viewpoint
```
@article{JKIM14-WTIT,
  author    = {Juhoon Kim and Nadi Sarrar and Anja Feldmann},
  title     = {Watching the IPv6 Takeoff from an IXP's Viewpoint},
  volume    = {abs/1402.3982},
  year      = {2014},
  url       = {http://arxiv.org/abs/1402.3982},
}
```
Watching the IPv6 Takeoff from an IXP's Viewpoint

The different level of interest in deploying the new Internet address space across network operators has kept IPv6 tardy in its deployment. However, since the last block of IPv4 addresses has been assigned, Internet communities took the concern of the address space scarcity seriously and started to move forward actively. After the successful IPv6 test on 8 June, 2011 (World IPv6 Day [1]), network operators and service/content providers were brought together for preparing the next step of the IPv6 global deployment (World IPv6 Launch on 6 June, 2012 [2]). The main purpose of the event was to permanently enable their IPv6 connectivity. In this paper, based on the Internet traffic collected from a large European Internet Exchange Point (IXP), we present the status of IPv6 traffic mainly focusing on the periods of the two global IPv6 events. Our results show that IPv6 traffic is responsible for a small fraction such as 0.5 % of the total traffic in the peak period. Nevertheless, we are positively impressed by the facts that the increase of IPv6 traffic/prefixes shows a steep increase and that the application mix of IPv6 traffic starts to imitate the one of IPv4-dominated Internet.

Watching the IPv6 Takeoff from an IXP's Viewpoint Juhoon Kim, Nadi Sarrar, Anja Feldmann, 2014
Tigers vs Lions: Towards Characterizing Solitary and Group User Behavior in MMORPG
```
@article{JKIM13-TVLT,
  author    = {Juhoon Kim and Nikolaos Chatzis and Matthias Siebke and Anja Feldmann},
  title     = {Tigers vs Lions: Towards Characterizing Solitary and Group User Behavior in {MMORPG}},
  volume    = {abs/1302.0707},
  year      = {2013},
  url       = {http://arxiv.org/abs/1302.0707},
}
```
Tigers vs Lions: Towards Characterizing Solitary and Group User Behavior in MMORPG

The development of Internet technologies enables software developers to build virtual worlds such as Massively Multi-Player Online Role-Playing Games (MMORPGs). The population of such games shows super-linear growing tendency. It is estimated that the number of Internet users subscribed in MMORPGs is more than 22 million worldwide [1]. However, only little is known about the characteristics of traffic generated by such games as well as the behavior of their subscribers. In this paper, we characterize the traffic behavior of World of Warcraft, the most subscribed MMORPG in the world, by analyzing Internet traffic data sets collected from a European tier-1 ISP in two different time periods. We find that World of Warcraft is an influential application regarding the time spent by users (1.76 and 4.17 Hours/day on average in our measurement), while its traffic share is comparatively low (< 1 %). In this respect, we look at the World of Warcraft subscriber's gaming behavior by categorizing them into two different types of users (solitary users and group users) and compare these two groups in relation to the playing behavior (duration as the metric) and the in-game behavior (distance as the metric).

Tigers vs Lions: Towards Characterizing Solitary and Group User Behavior in MMORPG Juhoon Kim, Nikolaos Chatzis, Matthias Siebke, Anja Feldmann, Technische Universitaet Berlin, 2013
Today's Usenet Usage: Characterizing NNTP traffic
```
@inproceedings{JKIM10-TUUC,
  title     = {Today's Usenet Usage: Characterizing NNTP traffic},
  author    = {Kim, Juhoon and Schneider, Fabian and Ager, Bernhard and Feldmann, Anja},
  booktitle = {Proceedings of INFOCOM IEEE Conference on Computer Communications Workshops},
  year      = {2010},
  doi       = {http://dx.doi.org/10.1109/INFCOMW.2010.5466665},
}
```
Today's Usenet Usage: Characterizing NNTP traffic

The finding by Maier et al that Network News Transport Protocol (NNTP) traffic is responsible for up to 5% of residential network traffic inspires us to revisit today's Usenet usage. For this purpose we have developed an NNTP analyzer for the Bro network intrusion detection system. We find that NNTP is intensively used by a small fraction of the residential broadband lines that we study and that almost all traffic is to NNTP servers that require subscription for a monthly fee. The accessed content resembles what one might expect from file-sharing systems---archives and multimedia files. Accordingly, it appears that NNTP is used by some as a high performance alternative to traditional P2P file-sharing options such as eDonkey or BitTorrent.

Today's Usenet Usage: Characterizing NNTP traffic Juhoon Kim, Fabian Schneider, Bernhard Ager, Anja Feldmann, Proceedings of the 13th IEEE Global Internet Symposium, 2010
Revisiting Cacheability in Times of User Generated Content
```
@inproceedings{JKIM10-RCIT,
  title     = {Revisiting Cacheability in Times of User Generated Content},
  author    = {Ager, Bernhard and Schneider, Fabian and Kim, Juhoon and Feldmann, Anja},
  booktitle = {Proceedings of INFOCOM IEEE Conference on Computer Communications Workshops},
  year      = {2010},
  doi       = {http://dx.doi.org/10.1109/INFCOMW.2010.5466667},
}
```
Revisiting Cacheability in Times of User Generated Content

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.

Revisiting Cacheability in Times of User Generated Content Bernhard Ager, Fabian Schneider, Juhoon Kim, Anja Feldmann, Proceedings of the 13th IEEE Global Internet Symposium, 2010

Locator/ID Separation Protocol (LISP)

Caching Locator/ID mappings: An experimental scalability analysis and its implications
```
@article{JKIM13-CLIM,
  author = {Juhoon Kim and Luigi Iannone and Anja Feldmann},
  title  = {Caching Locator/ID Mappings: An Experimental Scalability Analysis and its Implications},
  journal= {Computer Networks},
  volume = {57},
  number = {4},
  pages  = {897--909},
  year   = {2013},
  url    = {http://dx.doi.org/10.1016/j.comnet.2012.11.007},
  doi    = {10.1016/j.comnet.2012.11.007},
}
```
Caching Locator/ID mappings: An experimental scalability analysis and its implications

Victim of its own success, the current Internet is facing scalability issues that lead the research community to explore alternative architectures. In particular, the Locator/ID Split paradigm, based on the idea of separating the identity from the location of end-systems, is gaining momentum and seems to be the most promising candidate for the future Internet architecture. A critical component of any Locator/ID Split approach, from a performance and resources consumption perspective, as well as from a security point of view, is the cache. The cache is meant to temporarily store mappings, i.e., the bindings between identifiers and locations, in order to provide routers with the knowledge of where to forward packets.

Taking as reference protocol LISP (Locator/ID Separation Protocol), the most successful proposal currently under discussion at the IETF, this paper presents a thorough analysis of such a component, including the implications of policies to increase the level of security, based on real packet-level traces. Our results prove that even a timeout as short as 60 s provides a high hit ratio and that the impact of using security policies is small. Furthermore, a thorough analysis of the scalability of such a component is provided along with the analysis of which class of applications contributes the major fraction of cache-misses.

Caching Locator/ID mappings: An experimental scalability analysis and its implications Juhoon Kim, Luigi Iannone, Anja Feldmann, Elsevier Computer Networks Journal, 2013
A Local Approach to Fast Failure Recovery of LISP Ingress Tunnel Routers
```
@inproceedings{JKIM12-ALAT,
  author    = {Damien Saucez and Juhoon Kim and Luigi Iannone and Olivier Bonaventure and Clarence Filsfils},
  title     = {A Local Approach to Fast Failure Recovery of {LISP} Ingress Tunnel Routers},
  booktitle = {{NETWORKING} 2012 - 11th International {IFIP} {TC} 6 Networking Conference, Prague, Czech Republic, May 21-25, 2012, Proceedings, Part {I}},
  pages     = {397--408},
  year      = {2012},
  doi       = {10.1007/978-3-642-30045-5_30},
}
```
A Local Approach to Fast Failure Recovery of LISP Ingress Tunnel Routers

LISP (Locator/ID Separation Protocol) has been proposed as a future Internet architecture in order to solve the scalability issues the current architecture is facing. LISP tunnels packets between border routers, which are the locators of the non-globally routable identifiers associated to end-hosts. In this context, the encapsulating routers, which are called Ingress Tunnel Routers (ITR) and learn dynamically identifier-to-locators mappings needed for the encapsulation, can cause severe and long lasting traffic disruption upon failure. In this paper, thanks to real traffic traces, we first explore the impact of ITR failures on ongoing traffic. Our measurements confirm that the failure of an ITR can have severe impact on traffic. We then propose and evaluate an ITR synchronization mechanism to locally protect ITRs, achieving disruptionless traffic redirection. We finally explore how to minimize the number of ITRs to synchronize in large networks.

A Local Approach to Fast Failure Recovery of LISP Ingress Tunnel Routers Damien Saucez, Juhoon Kim, Luigi Iannone, Olivier Bonaventure, Clarence Filsfils, In Proceedings of the 11th IFIP International Conference on Networking. Springer, 2012
A Deep Dive into the LISP Cache and What ISPs Should Know about It
```
@inproceedings{JKIM11-ADDI,
  author    = {Juhoon Kim and Luigi Iannone and Anja Feldmann},
  title     = {A Deep Dive into the {LISP} Cache and What ISPs Should Know about it},
  booktitle = {{NETWORKING} 2011 - 10th International {IFIP} {TC} 6 Networking Conference, Valencia, Spain, May 9-13, 2011, Proceedings, Part {I}},
  pages     = {367--378},
  year      = {2011},
  doi       = {10.1007/978-3-642-20757-0_29},
}
```
A Deep Dive into the LISP Cache and What ISPs Should Know about It

Due to scalability issues that the current Internet is facing, the research community has re-discovered the Locator/ID Split paradigm. As the name suggests, this paradigm is based on the idea of separating the identity from the location of end-systems, in order to increase the scalability of the Internet architecture. One of the most successful proposals, currently under discussion at the IETF, is LISP (Locator/ID Separation Protocol). A critical component of LISP, from a performance and resources consumption perspective, as well as from a security point of view, is the LISP Cache. The LISP Cache is meant to temporarily store mappings, i.e., the bindings between identifiers and locations, in order to provide routers with the knowledge of where to forward packets. This paper presents a thorough analysis of such a component, based on real packet-level traces. Furthermore, the implications of policies to increase the level of security of LISP are also analyzed. Our results prove that even a timeout as short as 60 seconds provides high hit ratio and that the impact of using security policies is small.

A Deep Dive into the LISP Cache and What ISPs Should Know about It Juhoon Kim, Luigi Iannone, Anja Feldmann, In Proceedings of the 10th IFIP International Conference on Networking. Springer, 267-278, 2011
Can TCP and Locator/ID Seperation get along?
```
@misc{JKIM11-CTAL,
  title = {Can TCP and Locator/ID Seperation get along?},
  author = {Kim, Juhoon and Iannone, Luigi and Feldmann, Anja},
  year = {2011},
  location = {Berlin, Germany},
  howpublished = {Poster at CHANGE and Ofelia Summer School},
  url = {http://www.net.t-labs.tu-berlin.de/papers/KIF-CTLISGA-11.pdf},
}
```
Can TCP and Locator/ID Seperation get along?

Aiming at solving the scalability problem that the current Internet is facing, the separation of the IP namespace into two different namespaces (the Locator and the Identifier namespaces) is one of the most promising paradigms. However, the impact of this new paradigm on the Internet traffic is yet to be assessed. In this extended abstract, we present a preliminary analysis of TCP performance in the context of Locator/ID separation.

Can TCP and Locator/ID Seperation get along? Juhoon Kim, Luigi Iannone, Anja Feldmann, CHANGE and Ofelia Summer School, 2011

Multi-source Multipath HTTP (mHTTP)

Multi-source Multipath HTTP (mHTTP): A Proposal
```
@inproceedings{DBLP:conf/sigmetrics/KimCKTF14,
  author    = {Juhoon Kim and Yung{-}Chih Chen and Ramin Khalili and Don Towsley and Anja Feldmann},
  title     = {Multi-source multipath {HTTP} (mHTTP): a proposal},
  booktitle = {{ACM} {SIGMETRICS} / International Conference on Measurement and Modeling of Computer Systems, {SIGMETRICS} '14, Austin, TX, {USA}, 2014},
  pages     = {583--584},
  year      = {2014},
  url       = {http://doi.acm.org/10.1145/2591971.2592029},
  doi       = {10.1145/2591971.2592029},
}
```
Multi-source Multipath HTTP (mHTTP): A Proposal

Today, most devices have multiple network interfaces. Coupled with wide-spread replication of popular content at multiple locations, this provides substantial path diversity in the Internet. We propose Multi-source Multipath HTTP, mHTTP, which takes advantage of all existing types of path diversity in the Internet. mHTTP needs only client-side but not server-side or network modifications as it is a receiver-oriented mechanism. Moreover, the modifications are restricted to the socket interface. Thus, no changes are needed to the applications or to the kernel.

Multi-source Multipath HTTP (mHTTP): A Proposal Juhoon Kim, Yung-Chih Chen, Ramin Khalili, Anja Feldmann, and Don Towsley, ACM SIGMETRICS, 2014
Multi-source Multipath HTTP (mHTTP): A Proposal
```
@article{JKIM13-MSMP,
  author    = {Juhoon Kim and Ramin Khalili and Anja Feldmann and Yung{-}Chih Chen and Don Towsley},
  title     = {Multi-Source Multi-Path {HTTP} (mHTTP): {A} Proposal},
  volume    = {abs/1310.2748},
  year      = {2013},
  url       = {http://arxiv.org/abs/1310.2748},
}
```
Multi-source Multipath HTTP (mHTTP): A Proposal

Today, most devices have multiple network interfaces. Coupled with wide-spread replication of popular content at multiple locations, this provides substantial path diversity in the Internet. We propose Multi-source Multipath HTTP, mHTTP, which takes advantage of all existing types of path diversity in the Internet. mHTTP needs only client-side but not server-side or network modifications as it is a receiver-oriented mechanism. Moreover, the modifications are restricted to the socket interface. Thus, no changes are needed to the applications or to the kernel.

As mHTTP relies on HTTP range requests, it is specific to HTTP which accounts for more than 60% of the Internet traffic. We implement mHTTP and study its performance by conducting measurements over a testbed and in the wild. Our results show that mHTTP indeed takes advantage of all types of path diversity in the Internet, and that it is a viable alternative to Multipath TCP for HTTP traffic. mHTTP decreases download times for large objects up to 50%, whereas it does no harm to small object downloads.

Multi-source Multipath HTTP (mHTTP): A Proposal Juhoon Kim, Ramin Khalili, Anja Feldmann, Yung-Chih Chen, Don Towsley, 2013

Software Defined Networking (SDN) & Network Function Virtualization (NFV)

DevOps for Software-Defined Telecom Infrastructure

The introduction of virtualization technologies, starting from the physical layer and going all the way up to the application plane, is transforming the telecom network infrastructure onto an agile, model-driven production environment for communication services. Carrier-grade network management was optimized for environments built with monolithic physical nodes and involves significant deployment, integration and maintenance efforts from network service providers. The DevOps movement in the data center is a source of inspiration regarding how to simplify and automate management processes for software-defined infrastructure. This first version of this draft identifies three areas that we consider key to applying DevOps principles in a telecom service provider environment, namely for monitoring, verification and troubleshooting processes. Finally, we introduce challenges associated with operationalizing DevOps principles at scale in software-defined telecom networks.

DevOps for Software-Defined Telecom Infrastructure. IETF draft-unify-nfvrg-devops-00, 01, 02 Catalin Meirosu, Antonio Manzalini, Juhoon Kim, Rebecca Steinert, Sachin Sharma, Guido Marchetto, Ioanna Papafili
Service Provider DevOps for Large Scale Modern Network Services
```
@inproceedings{JKIM15-SPDF,
  title     = {Service Provider DevOps for Large Scale Modern Network Services},
  author    = {Kim, Juhoon and Meirosu, Catalin and Papafili, Ioanna and Steinert, Rebecca and Sharma, Sachin and Westphal, Fritz-Joachim and Kind, Mario and Shukla, Aproov and Nemeth, Felician and Manzalini, Antonio},
  booktitle = {10th International Workshop on Business-driven IT Management, part of IM2015, the IEEE International Symposium on Integrated Network Management, Proceedings},
  isbn      = {9783901882760},
  location  = {Ottawa, Canada},
  pages     = {1391--1397},
  year      = {2015},
  doi       = {http://dx.doi.org/10.1109/INFCOMW.2010.5466665},
}
```
Service Provider DevOps for Large Scale Modern Network Services

Network service providers are facing challenges for deploying new services mainly due to the growing complexity of software architecture and development process. Moreover, the recent architectural innovation of network systems such as Network Function Virtualization (NFV), Software-defined Networking (SDN), and Cloud computing increases the development and operation complexity yet again. One of the emerging solutions to this problem is a novel software development concept, namely DevOps, that is widely employed by major Internet software companies. Although the goals of DevOps in data centers are well-suited for the demands of agile service creation, additional requirements specific to the virtualized and software-defined network environment are important to be addressed from the perspective of modern network carriers. In this paper, we thoroughly debate DevOps requirements for developing a modern service creation platform by taking EU FP7 project UNIFY as a reference architecture and suggest the corresponding extensions of UNIFY interfaces that meet the discovered requirements.

Service Provider DevOps for Large Scale Modern Network Services Juhoon Kim, Catalin Meirosu, Ioanna Papafili, Rebecca Steinert, Sachin Sharma, Fritz-Joachim Westphal, Mario Kind, Aproov Shukla, Felician Nemeth, Antonio Manzalini, 10th International Workshop on Business-driven IT Management, 2015

Theses and Projects

Towards Utilizing Network Diversity for future Internet Protocols
```
@phdthesis{JKIM14-TUND,
  author = {Juhoon Kim},
  title  = {Towards utilizing network diversity for future internet protocols},
  year   = {2014}
  urn    = {urn:nbn:de:kobv:83-opus4-52917},
}
```
Towards Utilizing Network Diversity for future Internet Protocols

In the past few decades, the Internet has evolved from a research network to an important infrastructure used by everyone. This means it has changed in almost all aspects including size, topology, and usage. Indeed, due to the ever-increasing number of users and capabilities of end-devices, various types of network diversity have been created in the Internet. For example, users can connect to the Internet through different service providers in various access speeds using miscellaneous devices equipped with multiple network interfaces via two different address spaces (IPv4 and IPv6). Such diversity can be found almost everywhere in the Internet. However, to what extent this diversity can be used to improve the Internet is largely uncharted. Recently, several scalability issues emerged in the Internet, i. e., those related to the large number of network-enabled devices. The exhaustion of the Internet address space is one, the plethora of the routing information within the core Internet is another one. Moreover, the constantly increasing volume of digital content causes significant mismatch between the demand for the high end-to-end performance and the actual capabilities of the Internet infrastructure. These problems hinder the future evolution of the Internet; hence, they are the topics of this thesis.

First, we conduct an assessment study of IPv6 adoption in today's Internet by analyzing a rich set of Internet traffic data collected from a large Internet eXchange Point (IXP). Although the result shows a sharp increase of IPv6 traffic in recent years, the level of IPv6 deployment is still marginal. Thus, the two Internet protocols have to coexist for a while. Next, to cope with scalability issue caused by the enormous number of routing entries in the core of the Internet, we closely examine the most promising solution for this problem, the Locator/ID Separation Protocol (LISP). In particular, our work focuses on evaluating the performance, security overhead, and resilience of LISP. By analyzing recent Internet traffic, previous studies found that a major portion of Internet traffic is delivered by HTTP (< 60 % [67]) and most of the content providers replicate their content on multiple servers [91]. To this end, we confront the challenge of end-to-end performance by suggesting an easily deployable solution, the Multi-source Multipath HTTP (mHTTP), for improving the HTTP performance based on utilizing various types of network diversity.

Towards Utilizing Network Diversity for future Internet Protocols Juhoon Kim, Ph.D. Thesis, Technische Universitaet Berlin, 2014
Thesis Committee:
Prof. Anja Feldmann, TU-Berlin, Germany
Prof. Don Towsley, UMass, USA
Prof. Luigi Iannone, Telecom ParisTech, France
Dr. Ramin Khalili, Huawei European Research Center in Munich
eDonkey and Kad Traffic Analysis based on Semantic Protocol Identification Juhoon Kim, Master Thesis, Technische Universitaet Berlin, 2010
NNTP Traffic Analysis Juhoon Kim, Master project, Technische Universitaet Berlin, 2009

Internship

08/01/2012 - 09/30/2012: International Carrier Sales & Solutions (ICSS), Deutsche Telekom

Teaching experience

Thesis supervision

Diplom thesis supervision: Matthias Siebke, "Analyse und Untersuchung des World-of-Warcraft-Netzwerkprotokolls"
Master thesis supervision: Karl Fischer
Master thesis supervision: Soumya Ranjan Parida (on going)

Teaching

Software

Multi-source Multipath HTTP
LISP Cache Emulator
Web-based DNS Lookup
Web-based eDonkey Querier (this page is being repaired)

Telekom Innovation Laboratories

Winterfeldtstr. 21, 10781 Berlin

jkim@net.t-labs.tu-berlin.de

+49 30 8353 58158