158 research outputs found
Research Letter The Measurement Paradox in Valiant Network Design
Valiant network design was proposed, at least in part, to counter the difficulties in measuring network traffic matrices. However, in this paper we show that in a Valiant network design, the traffic matrix is in fact easy to measure, leading to a subtle paradox in the design strategy
Queuing delays in randomized load balanced networks
Valiant’s concept of Randomized Load Balancing
(RLB), also promoted under the name ‘two-phase routing’,
has previously been shown to provide a cost-effective way of
implementing overlay networks that are robust to dynamically
changing demand patterns. RLB is accomplished in two steps; in
the first step, traffic is randomly distributed across the network,
and in the second step traffic is routed to the final destination.
One of the benefits of RLB is that packets experience only a
single stage of routing, thus reducing queueing delays associated
with multi-hop architectures. In this paper, we study the queuing
performance of RLB, both through analytical methods and
packet-level simulations using ns2 on three representative carrier
networks. We show that purely random traffic splitting in the
randomization step of RLB leads to higher queuing delays than
pseudo-random splitting using, e.g., a round-robin schedule.
Furthermore, we show that, for pseudo-random scheduling,
queuing delays depend significantly on the degree of uniformity
of the offered demand patterns, with uniform demand matrices
representing a provably worst-case scenario. These results are
independent of whether RLB employs priority mechanisms
between traffic from step one over step two. A comparison with
multi-hop shortest-path routing reveals that RLB eliminates the
occurrence of demand-specific hot spots in the network
Shortest Path versus Multi-Hub Routing in Networks with Uncertain Demand
We study a class of robust network design problems motivated by the need to
scale core networks to meet increasingly dynamic capacity demands. Past work
has focused on designing the network to support all hose matrices (all matrices
not exceeding marginal bounds at the nodes). This model may be too conservative
if additional information on traffic patterns is available. Another extreme is
the fixed demand model, where one designs the network to support peak
point-to-point demands. We introduce a capped hose model to explore a broader
range of traffic matrices which includes the above two as special cases. It is
known that optimal designs for the hose model are always determined by
single-hub routing, and for the fixed- demand model are based on shortest-path
routing. We shed light on the wider space of capped hose matrices in order to
see which traffic models are more shortest path-like as opposed to hub-like. To
address the space in between, we use hierarchical multi-hub routing templates,
a generalization of hub and tree routing. In particular, we show that by adding
peak capacities into the hose model, the single-hub tree-routing template is no
longer cost-effective. This initiates the study of a class of robust network
design (RND) problems restricted to these templates. Our empirical analysis is
based on a heuristic for this new hierarchical RND problem. We also propose
that it is possible to define a routing indicator that accounts for the
strengths of the marginals and peak demands and use this information to choose
the appropriate routing template. We benchmark our approach against other
well-known routing templates, using representative carrier networks and a
variety of different capped hose traffic demands, parameterized by the relative
importance of their marginals as opposed to their point-to-point peak demands
Load Balancing for the Agile All-Photonic Network
The Agile All-Photonic Network (AAPN) uses Time Division Multiplexing (TDM) to better utilize the bandwidth of Wavelength Division Multiplexing (WDM) systems. It uses agile all-photonic switches as advances in the photonic switching technology made the design of all-photonic devices with switching latency in the sub-microseconds feasible. The network has a simplified overlaid star architecture that can be deployed in a Metropolitan Area Network (MAN) or a Wide Area Network (WAN) environment. This overlaid architecture, as opposed to general mesh architecture, scales network capacity to multiples of Tera bits per second, simplif�ies routing, increases reliability, eliminates wavelength conversion, and the need for accurate traffic engineering.
The objective of this thesis is to propose and analyze
dif�ferent load balancing methods for the deployment of the AAPN network in a WAN environment. The analysis should provide interested Internet Service Providers (ISPs) with a comprehensive study of load balancing methods for using the AAPN network as their backbone network. The methods balance the load at the ow level to reduce packet reordering.
The methods are stateless and can compute routes quickly based on the packet flow identi�er. This is an important issue when deploying AAPN as an Internet backbone
network where the number of flows is large and storing
ow state in lookup tables can limit the network performance.
The load balancing methods, deployed at the edge nodes, require reliable signaling with the bandwidth schedulers at the core nodes. To provide a reliable channel between the edge and core nodes, the Control Messages Delivery Protocol (CMDP) is proposed as part of this thesis work. The protocol is designed to work in environments where propagation delays are long and/or the error rates are high. It is used to deliver a burst of short messages in sequence and with no errors. Combined with the reliable
routing protocol proposed previously for the AAPN network, they form the control plane for the network.
To extend the applicability of the load balancing methods to topologies beyond AAPN overlaid star topology, the Valiant Load Balancing (VLB) method is used to build an overlaid star topology on top of the physical network. The VLB method provides guaranteed performance for highly variable tra�c matrices within the hose traffic model constraints. In addition to the guaranteed performance, deploying the VLB method in the AAPN network, eliminates signaling and replaces the dynamic core schedulers with static scheduler that can accommodate all tra�c matrices within the hose tra�c model boundaries
Load balancing vs. distributed rate limiting: an unifying framework for cloud control
With the expansion of cloud-based services, the question as to how to control usage of such large distributed systems has become increasingly important. Load balancing (LB), and recently proposed distributed rate limiting (DRL) have been used independently to reduce costs and to fairly allocate distributed resources. In this paper we propose a new mechanism for cloud control that unifies the use of LB and DRL: LB is used to minimize the associated costs and DRL makes sure that the resource allocation is fair. From an analytical standpoint, modelling the dynamics of DRL in dynamic workloads (resulting from LB cost-minimization scheme) is a challenging problem. Our theoretical analysis yields a condition that ensures convergence to the desired working regime. Analytical results are then validated empirically through several illustrative simulations. The closed- form nature of our result also allows simple design rules which, together with extremely low computational and communication overhead, makes the presented algorithm practical and easy to deploy
Framework and Algorithms for Operator-Managed Content Caching
We propose a complete framework targeting operator-driven content caching that can be equally applied to both ISP-operated Content Delivery Networks (CDNs) and future Information-Centric Networks (ICNs). In contrast to previous proposals in this area, our solution leverages operators’ control on cache placement and content routing, managing to considerably reduce network operating costs by minimizing the amount of transit traffic and balancing load among available network resources. In addition, our solution provides two key advantages over previous proposals. First, it allows for a simple computation of the optimal cache placement. Second, it provides knobs for operators to fine-tune performance. We validate our design through both analytical modeling and trace-driven simulations and show that our proposed solution achieves on average twice as many cache hits in comparison to previously proposed techniques, without increasing delivery latency. In addition, we show that the proposed framework achieves 19-33% better load balancing across links and caching nodes, being also robust to traffic spikes
Simple and stable dynamic traffic engineering for provider scale ethernet
Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia InformáticaThe high speeds and decreasing costs of Ethernet solutions has motivated providers’ interest in using Ethernet as the link layer technology in their backbone and aggregation networks.
Provider scale Ethernet offers further advantages, providing not only an easy to manage solution for multicast traffic, but also transparent interconnection between clients’ LANs. These Ethernet deployments face altogether different design issues, requiring support for a significantly
higher number of hosts. This support relies on hierarquization, separating address and
virtual network spaces of customers and providers.
In addition, large scale Ethernet solutions need to grant forwarding optimality. This can be achieved using traffic engineering approaches. Traffic engineering defines the set of engineering methods and techniques used to optimize the flow of network traffic. Static traffic engineering
approaches enjoy widespread use in provider networks, but their performance is greatly penalized by sudden load variations. On the other hand, dynamic traffic engineering is tailored to adapt to load changes. However, providers are skeptical to adopt dynamic approaches as these induce problems such as routing instability, and as a result, network performance decreases.
This dissertation presents a Simple and Stable Dynamic Traffic Engineering framework
(SSD-TE), which addresses these concerns in a provider scale Ethernet scenario. The validation results show that SSD-TE achieves better or equal performance to static traffic engineering approaches, whilst remaining both stable and responsive to load variations
- …