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Natcracker: Nat combinations matter
KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS. (SCS)
Nile University, Egypt.
KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS. (SCS)ORCID iD: 0000-0002-6718-0144
2009 (English)In: Proceedings - International Conference on Computer Communications and Networks, ICCCN, San Francisco, CA, 2009Conference paper, Published paper (Other academic)
Abstract [en]

In this paper, we report our experience in working with Network Address Translators (NATs). Traditionally, there were only 4 types of NATs. For each type, the (im)possibility of traversal is well-known. Recently, the NAT community has provided a deeper dissection of NAT behaviors resulting into at least 27 types and documented the (im)possibility of traversal for some types. There are, however, two fundamental issues that were not previously tackled by the community. First, given the more elaborate set of behaviors, it is incorrect to reason about traversing a single NAT, instead combinations must be considered and we have not found any study that comprehensively states, for every possible combination, whether direct connectivity with no relay is feasible. Such a statement is the first outcome of the paper. Second, there is a serious need for some kind of formalism to reason about NATs which is a second outcome of this paper. The results were obtained using our own scheme which is an augmentation of currently-known traversal methods. The scheme is validated by reasoning using our formalism, simulation and implementation in a real P2P network. ©2009 IEEE.

Place, publisher, year, edition, pages
San Francisco, CA, 2009.
Keyword [en]
Network address translators, P2P network, Computer simulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Computer Engineering
Identifiers
URN: urn:nbn:se:kth:diva-32889DOI: 10.1109/ICCCN.2009.5235278Scopus ID: 2-s2.0-70449103450OAI: oai:DiVA.org:kth-32889DiVA: diva2:412761
Note
QC 20110426Available from: 2011-04-26 Created: 2011-04-26 Last updated: 2013-11-22Bibliographically approved
In thesis
1. Design and Implementation of Centrally-Coordinated Peer-to-Peer Live-streaming
Open this publication in new window or tab >>Design and Implementation of Centrally-Coordinated Peer-to-Peer Live-streaming
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, we explore the use of a centrally-coordinated peer-to-peer overlay as a possible solution to the live streaming problem. Our contribution lies in showing that such approach is indeed feasible given that a number of key challenges are met.

The motivation behind exploring an alternative design is that, although a number of approaches have been investigated in the past, e.g. mesh-pull and tree-push, hybrids and best-of-both-worlds mesh-push, no consensus has been reached on the best solution for the problem of peer-to-peer live streaming, despite current deployments and reported successes.

In the proposed system, we model sender/receiver peer assignments as an optimization problem. Optimized peer selection based on multiple utility factors, such as bandwidth availability, delays and connectivity compatibility, make it possible to achieve large source bandwidth savings and provide high quality of user experience. Clear benefits of our approach are observed when Network Address Translation constraints are present on the network.

We have addressed key scalability issues of our platform by parallelizing the heuristic which is the core of our optimization engine and by implementing the resulting algorithm on commodity Graphic Processing Units (GPUs). The outcome is a Linear Sum Assignment Problem (LSAP) solver for time-constrained systems which produces near-optimal results and can be used for any instance of LSAP, i.e. not only in our system.

 

As part of this work, we also present our experience in working with Network Address Translators (NATs) traversal in peer-to-peer systems. Our contribution in this context is threefold. First, we provide a semi-formal model of state of the art NAT behaviors. Second, we use our model to show which NAT combinations can be theoretically traversed and which not. Last, for each of the combinations, we state which traversal technique should be used. Our findings are confirmed by experimental results on a real network.

Finally, we address the problem of reproducibility in testing, debugging and evaluation of our peer-to-peer application. We achieve this by providing a software framework which can be transparently integrated with any already-existing software and which is able to handle concurrency, system time and network events in a reproducible manner.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. viii, 78 p.
Series
Trita-ICT-ECS AVH, ISSN 1653-6363 ; 2011:03
Keyword
peer-to-peer, live-streaming, nat traversal
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Computer Engineering
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-32387 (URN)978-91-7415-957-8 (ISBN)
Presentation
2011-05-05, Sal D, Forum 105, Kista, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20110426Available from: 2011-04-26 Created: 2011-04-13 Last updated: 2011-04-26Bibliographically approved
2. A System, Tools and Algorithms for Adaptive HTTP-live Streaming on Peer-to-peer Overlays
Open this publication in new window or tab >>A System, Tools and Algorithms for Adaptive HTTP-live Streaming on Peer-to-peer Overlays
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In recent years, adaptive HTTP streaming protocols have become the de facto standard in the industry for the distribution of live and video-on-demand content over the Internet. In this thesis, we solve the problem of distributing adaptive HTTP live video streams to a large number of viewers using peer-to-peer (P2P) overlays. We do so by assuming that our solution must deliver a level of quality of user experience which is the same as a CDN while trying to minimize the load on the content provider’s infrastructure. Besides that, in the design of our solution, we take into consideration the realities of the HTTP streaming protocols, such as the pull-based approach and adaptive bitrate switching.

The result of this work is a system which we call SmoothCache that provides CDN-quality adaptive HTTP live streaming utilizing P2P algorithms. Our experiments on a real network of thousands of consumer machines show that, besides meeting the the CDN-quality constraints, SmoothCache is able to consistently deliver up to 96% savings towards the source of the stream in a single bitrate scenario and 94% in a multi-bitrate scenario. In addition, we have conducted a number of pilot deployments in the setting of large enterprises with the same system, albeit tailored to private networks. Results with thousands of real viewers show that our platform provides an average offloading of bottlenecks in the private network of 91.5%.

These achievements were made possible by advancements in multiple research areas that are also presented in this thesis. Each one of the contributions is novel with respect to the state of the art and can be applied outside of the context of our application. However, in our system they serve the purposes described below.

We built a component-based event-driven framework to facilitate the development of our live streaming application. The framework allows for running the same code both in simulation and in real deployment. In order to obtain scalability of simulations and accuracy, we designed a novel flow-based bandwidth emulation model.

In order to deploy our application on real networks, we have developed a network library which has the novel feature of providing on-the-fly prioritization of transfers. The library is layered over the UDP protocol and supports NAT Traversal techniques. As part of this thesis, we have also improved on the state of the art of NAT Traversal techniques resulting in higher probability of direct connectivity between peers on the Internet.

Because of the presence of NATs on the Internet, discovery of new peers and collection of statistics on the overlay through peer sampling is problematic. Therefore, we created a peer sampling service which is NAT-aware and provides one order of magnitude fresher samples than existing peer sampling protocols.

Finally, we designed SmoothCache as a peer-assisted live streaming system based on a distributed caching abstraction. In SmoothCache, peers retrieve video fragments from the P2P overlay as quickly as possible or fall back to the source of the stream to keep the timeliness of the delivery. In order to produce savings, the caching system strives to fill up the local cache of the peers ahead of playback by prefetching content. Fragments are efficiently distributed by a self-organizing overlay network that takes into account many factors such as upload bandwidth capacity, connectivity constraints, performance history and the currently being watched bitrate.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xix, 41 p.
Series
TRITA-ICT-ECS AVH, ISSN 1653-6363 ; 13:18
Keyword
peer-to-peer, distributed caching, nat traversal, congestion control, adaptive HTTP streaming, live streaming
National Category
Computer Science
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-134351 (URN)978-91-7501-915-4 (ISBN)
Public defence
2013-12-12, Sal D, Forum, KTH-ICT, Isafjordsgatan 39, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20131122

Available from: 2013-11-22 Created: 2013-11-21 Last updated: 2016-01-21Bibliographically approved

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Haridi, Seif

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