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Best Practices for Advertisement of Multiple Paths in BGP
Get PDFBGP Add-Paths: Add-Paths is a BGP enhancement that allows a BGP router to advertise multiple distinct paths for the same prefix/NLRI. This provides a number of potential benefits, including reduced routing churn, faster convergence and better load balancing. Add-paths is currently being standardized within the IDR Working Group of the Routing area of the IETF. draft-ietf-idr-add-paths-guidelines-04 [6], co-authored by Pierre Francois in collaboration with AT&T, Alcatel-Lucent, and Cisco Systems, is a working group item of IDR aimed at providing network operators the tools needed to address their specific applications and to manage the scalability impact of Add-Paths. A router implementing Add-Paths may learn many paths for a prefix and must decide which of these to advertise to peers. This document analyses different algorithms for making this selection and provides recommendations based on the target application. The new version of this document updates previous versions of the draft published in 2011. This document is still facing changes stemming from the operator community, and its ultimate publication target is 2013-2014.Add-Paths is a BGP enhancement that allows a BGP router to advertise multiple distinct paths for the same prefix/NLRI. This provides a number of potential benefits, including reduced routing churn, faster convergence and better loadsharing. This document provides recommendations to implementers of Add-Paths so that network operators have the tools needed to address their specific applications and to manage the scalability impact of Add-Paths. A router implementing Add-Paths may learn many paths for a prefix and must decide which of these to advertise to peers. This document analyses different algorithms for making this selection and provides recommendations based on the target application.Internet Engineering Task Force (IETF)pu
Peer-to-Peer Television for the IP Multimedia Subsystem
Get PDFPREMIO EXTRAORDINARIO DE DOCTORADO UNIVERSIDAD CARLOS III DE MADRID - Curso 2011/2012. PhD Thesis defended on July 18th, 2012, in Madrid, Spain. The prize was awarded on November 27th, 2012.Peer-to-peer (P2P) video streaming has generated a significant amount of interest in both the research community and the industry, which find it a cost-effective solution to the user scalability problem. However, despite the success of Internet-based applications, the adoption has been limited for commercial services, such as Internet Protocol Television (IPTV). With the advent of the next-generation-networks (NGN) based on the IP Multimedia Subsystem (IMS), advocating for an open and inter-operable architecture, P2P emerges as a possible alternative in situations where the traditional mechanisms are not possible or economically feasible. This work proposes a P2P IPTV architecture for an IMS-based NGN, called P2PTV, which
allows one or more service providers to use a common P2P infrastructure for streaming the TV channels to their subscribers. Instead of using servers, we rely on the uploading capabilities of the user equipments, like set-top boxes, located at the customers’ premise. We comply with the
existing IMS and IPTV standards from the 3rd Generation Partnership Project (3GPP) and the Telecommunications and Internet converged Services and Protocols for Advanced Networking(TISPAN) bodies, where a centralized P2PTV application server (AS) manages the customer access to the service and the peer participation. Because watching TV is a complex and demanding user activity, we face two significant challenges. The first is to accommodate the mandatory IMS signaling, which reserves in the network the necessary QoS resources during every channel change, establishing a multimedia session between communicating peers. The second is represented by the streaming interruptions, or churn, when the uploading peer turns off or changes its current TV channel. To tackle these problems, we propose two enhancements. A fast signaling method, which uses inactive uploading sessions with reserved but unused QoS, to improve the tuning delay for new
channel users. At every moment, the AS uses a feedback based algorithm to compute the number of necessary sessions that accommodates well the demand, while preventing the over-reservation of resources. We approach with special care mobility situations, where a proactive transfer of the
multimedia session context using the IEEE 802.21 standard offers the best alternative to current methods. The second enhancement addresses the peer churn during channel changes. With every TV channel divided into a number of streams, we enable peers to download and upload streams
different from their current channel, increasing the stability of their participation. Unlike similar work, we benefit from our estimation of the user demand and propose a decentralized method for via balanced assignment of peer bandwidth. We evaluate the performance of the P2PTV through modeling and large-scale computer simulations. A simpler experimental setting, with pure P2P streaming, indicates the improvements over the delay and peer churn. In complex scenarios, such as those with resource-poor peers having a limited upload capacity, we envision P2P as a complementary solution to traditional approaches like IP multicast. Reserving P2P for unpopular TV channels exploits the peer capacity and prevents the necessity of a large number of sparsely used multicast trees. Future work may
refine the AS algorithms, address different experimental scenarios, and extend the lessons learned
to non-IMS networks.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
BASICS, Scheduling Base Stations to Mitigate Interferences in Cellular Networks
Get PDFThe continuously increasing demand for higher data rates results in increasing network density, so that inter-cell interference is becoming the most serious obstacle towards spectral efficiency. Considering that radio resources are limited and expensive, new techniques are required for the next generation of cellular networks, to enable a more efficient way to allocate and use radio resources. In this framework, we target the design of a frequency reuse 1 scheme, which exploits the coordination between base stations as a tool to mitigate intercell interference. While common approaches proposed in the literature focus on the optimal user scheduling, we tackle the problem from a different angle. In particular, we formulate a base station scheduling problem to decide whether a base station is allowed to transmit to any of its users in a given sub-frame, without causing excessive interference to any of the users of other scheduled base stations. To this aim, we show that finding the optimal base station scheduling is NP-hard, and formulate the BASICS (BAse Station Inter-Cell Scheduling) algorithm, a novel heuristic to approximate the optimal solution at low complexity cost. By means of numerical and packet-level simulations, we prove the effectiveness and reliability of the proposed solution as compared to the state of the art of inter-cell interference
mitigation schemes.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
Reliable Internet-based Master-Worker Computing in the Presence of Malicious Workers
Get PDFWe consider a Master-Worker distributed system where a master processor assigns, over the Internet, tasks to a collection of n workers, which are untrusted and might act maliciously. In addition, a worker may not reply to the master, or its reply may not reach the master, due to unavailabilities or failures of the worker or the network. Each task returns a value, and the goal is for the master to accept only correct values with high probability. Furthermore, we assume that the service provided by the workers is not free; for each task that a worker is assigned, the master is charged with a work-unit. Therefore, considering a single task assigned to several workers, our objective is to have the master processor to accept the correct value of the task with high probability, with the smallest possible amount of work (number of workers the master assigns the task). We probabilistically bound the number of faulty processors by assuming a known probability p < 1/2 of any processor to be faulty.
Our work demonstrates that it is possible to obtain, with provable analytical guarantees, high probability of correct acceptance with low work. In particular, we first show lower bounds on the minimum amount of (expected) work required, so that any algorithm accepts the correct value with probability of success 1 - ε, where ε ≪ 1 (e.g., 1/n). Then we develop and analyze two algorithms, each using a different decision strategy, and show that both algorithms obtain the same probability of success 1 - ε, and in doing so, they require similar upper bounds on the (expected) work. Furthermore, under certain conditions, these upper bounds are asymptotically optimal with respect to our lower bounds.TRUEpu
Assigned BGP extended communities
Get PDFBGP Extended Communities:
Within the IDR working group, an IETF working group document ("Assigned BGP extended communities", draft-ietf-idr-reserved-extended-communities-03, and -04 [3]) co-authored with Bruno Decraene, Senior Researcher at France Telecom - Orange, is progressing in its standardization process. This draft is putting a registry into place for "well-known" BGP extended communities. Its goal is to ease the standardization of BGP features relying on BGP extended communities by providing a pool for ISPs and Router Vendors to pick values dedicated to specific BGP features. These documents update a previous version, published in 2011.This document defines an IANA registry in order to assign non-transitive extended communities from. These are similar to the existing well-known BGP communities defined in
RFC 1997 but provide a control over inter-AS community advertisement as, per RFC 4360,they are not transitive across Autonomous System boundaries.
For that purpose, this document defines the use of the reserved Autonomous System number 0.65535 in the non-transitive generic four-octet AS specific extended community type.Internet Engineering Task Force (IETF)pu
Rate allocation for layered multicast streaming with inter-layer network coding
Get PDFMulti-layer video streaming allows to provide different
video qualities to a group of multicast receivers with
heterogeneous receive rates. The number of layers received determines the quality of the decoded video stream. For such layered multicast streaming, network coding provides higher capacity than multicast routing. Network coding can be performed within a layer (intra-layer) or across layers (inter-layer), and in general inter-layer coding outperforms intra-layer coding. An optimal solution to a network coded layered multicast problem may require decoding of the network code at interior nodes to extract
information to be forwarded. However, decoding consumes
resources and introduces delay, which is particularly undesirable
at interior nodes (the routers) of the network. In this paper, we
thus focus on the inter-layer network coding problem without
decoding at interior nodes. We propose a heuristic algorithm
for rate allocation and code assignment based on the Edmonds-
Karp maximum flow algorithm and perform simulations that
show that our algorithm may even outperform other heuristics
that do require decoding at interior nodes.TRUEpu
Explicitly Accommodating Origin Preference for Inter-Domain Traffic Engineering
Get PDFISBN: 978-1-4503-0857-1Inter-domain traffic engineering is an important aspect of network operation both technically and economically. Traffic engineering the outbound direction is less problematic as routers under the control of the network operator are responsible for the way traffic leaves the network. The inbound direction is considerably harder as the way traffic enters a network is based on routing decisions in other networks. There are very few mechanisms available today that facilitate inter-domain inbound traffic engineering, such as prefix deaggregation, AS path prepending and systems based on BGP communities. These mechanisms have severe drawbacks such as an increase of the size of global routing table or providing only coarse-grained control. In this paper we propose and evaluate an alternative mechanism that does not increase the size of the global routing table, is easy to configure through a simple numeric value and provides a finer-grained control compared to existing mechanisms that also do not add additional prefixes to the global routing table.TRUEpu
Fair Allocation of Delays in the Real-Time Control of an Autonomous Traffic Signal
No full textpaper 12-1688, session 535TRUEpu