Vishy Poosala

Constraint-based design of optical transmission systems

The last decade has witnessed wide-scale deployment of optical networks to support the growing data traffic. This success can be traced back to advances in optical transmission systems such as dense wavelength-division multiplexing, Raman amplification, etc., which allow a single fiber to carry several wavelengths very far, while sharing expensive equipment. However, these cutting-edge technologies require careful placement of amplifiers and other network elements to ensure error-free propagation of the signal and to minimize costs. In practice, it is common to use a set of constraints to ensure valid configurations for deployment. It is nontrivial to identify the optimal configuration under all but the simplest constraints. In this paper, we consider a set of constraints with varying flexibilities and present algorithms for efficiently computing the cost-optimal configuration under them. We also present experimental and theoretical results to evaluate the various constraints and algorithms.

Load-balanced architecture for dynamic traffic

We present a novel and practical scheme for carrying dynamic data traffic over circuits at lower costs than existing architectures. We demonstrate its effectiveness in handling burstiness as well as long-term variations in traffic patterns.

Delay distributed VCAT for efficient data-optical transport

We introduce a novel scheme that flexibly distributes the differential delays in virtual concatenation (VCAT) paths in SONET/SDH networks. We show that this increases the utilization of the network in carrying dynamic traffic and reduces the total buffer requirements.

Routing and design in K-shared networks

Fast shared restoration is critical to the success of WDM mesh networking. A restricted form of sharing called K-sharing was recently proposed, which allows rapid, signaling-free restoration. However, the routing and design algorithms used for traditional shared restoration do not work for this scheme. Also, K-sharing can potentially increase capacity requirements in the network because it limits sharing. In this paper, we present novel routing and design algorithms for K-shared networks. We also show that a practical version of the routing problem is NP-hard and present heuristics to solve it. We also summarize experimental results demonstrating that the additional capacity requirements imposed by K-sharing are in fact minimal in practice.

Designing operational WDM networks

Network design tools are routinely used in practice to design optical networks that can carry a given set of traffic demands at the least cost The criteria used to route demands during design are often different from those used while routing in the operational network. As a result, the routes computed may be different during design and operations, leading to over- or under- utilization of portions of the network and even failure to route some demands. In this paper, we propose a general solution for this problem, which handles any combination of routing criteria. It works by enhancing the designed network with minimal additional capacity such that it can carry the demands during operations. We also provide experimental results evaluating the performance of this technique and the operational effectiveness of various design algorithms.

WaveTunnel — Accurately designing deployable optical networks

Network design tools are routinely used to design optical networks that can carry a set of demands at the least cost. While there are several planning tools in existence, they lack either algorithm quality, or usability, or operational effectiveness of the designed networks. We have developed WaveTunnel, a customer-facing planning tool for designing wave division multiplexed (WDM) networks that addresses these issues. It includes detailed equipment modeling that leads to accurate cost models and novel algorithms for validating the designed network against the routing algorithms used for network provisioning, and selecting add-drop multiplexers versus cross connects. It offers simulation capabilities and works in conjunction with an operational network. The software is easily extensible to new networking technologies and design algorithms, due to the use of Extensible Markup Language (XML) and component models. This document presents an overview of the tool and describes in detail the techniques used to realize accurate network designs.

Guest editorial: new converged telecommunications applications for the end user

The very first and most universal telecommunication application is voice, or, in other words, the telephone. Let us start this article by highlighting an important milestone in the industry. In mid-July 2010 (the time of this writing) it was announced (by the GSMA Association) that global mobile connections surpass 5 billion (18 months after the 4 billion connection milestone, with predictions for 6 billion in the first half of 2012), meaning 74 percent penetration. Is that not impressive? Think of other technologies like TV, or other sectors like banks, automotive? that do not have those universality rates. It is astonishing that in a few years (almost) every citizen of the world will use (mobile) telecommunications services. This success story is not only a privilege but certainly a responsibility for the advance of the world society. Innovation in telecommunications services for all these billions of users is certainly a rewarding challenge.

Balancing the accuracy and practicality of location tracking in heterogeneous mobile networks

Location tracking has several applications in mobile (cellular or ad hoc) networks, such as location-based routing algorithms and consumer services. It is often difficult to compute the location of a node precisely because of the infrastructure costs and the errors inherent in most tracking techniques. Furthermore, this accuracy differs amongst nodes based on the scattered availability of equipment such as GPS. We focus on heterogeneous mobile networks, wherein some nodes know their locations more precisely than others and there is a short-range peer-to-peer communication channel such as Bluetooth or 802.11. We consider a generalized notion of location, called vicinity, which is the set of potential locations for a node. We formulate a hierarchy of distance constraints that can be applied in a network and devise efficient distributed techniques for computing the most optimal (smallest) vicinities under various constraint classes. In particular, our algorithms use both proximity and non-proximity relationships between the nodes. We present simulation results establishing the effectiveness of using these different types of constraints.

FASTeR: shared restoration without signalling

We present a novel technique for rapid restoration in optical/electrical mesh networks that does not incur signaling or cross-connect setup latencies. We show that it easily meets the 50 ms requirement in most scenarios.

FASTeR: Sub-50 ms shared restoration in mesh networks

Shared restoration is key to realizing the bandwidth savings offered by mesh networking. In order to be viable, restoration has to be effected fast, typically within 50 ms after failure. However, traditional schemes involve signaling and cross-connect (XC) setups that are too slow to be effective. In this paper, we describe a novel restoration scheme called FASTeR that dramatically reduces restoration times by eliminating these slow operations in either all-optical or electrical networks. The scheme involves a novel Select-Multicast feature of the XCs, and our experimental results show that a small multicasting degree is sufficient to achieve the savings gained under traditional shared restoration. Finally, we show that the generalized multiprotocol label switching (GMPLS) standard can be extended to support FASTeR.