Ashwin Gumaste

Hierarchical routing in multi-domain optical networks

Given the increasing adoption of DWDM networking technology, there is now a growing need to address distributed inter-domain lightpath provisioning issues. Although inter-domain provisioning has been well studied for packet/cell-switching networks, the wavelength dimension presents many additional challenges. To address this challenge, a detailed hierarchical routing GMPLS-based framework for provisioning all-optical and opto-electronic multi-domain DWDM networks is presented. The scheme adapts various topology abstraction schemes to improve routing scalability and lower inter-domain blocking probabilities. Related inter-domain lightpath RWA and signaling schemes are also tabled. Performance analysis results are also presented to demonstrate the effectiveness of the proposed mechanisms along with directions for future research work.

On the state and guiding principles of broadband in India

India, home to 1.2 billion people with a GDP growth of 9 percent, has been experiencing flat to modest growth of broadband services in the past decade despite the fact that the country continues to add 8-10 million cellular connections per month. In this article, we examine the reasons that affect the high cost of broadband in India and the steps required to reduce the cost. We also argue that the usage-based pricing model, which is used widely for billing retail customers, is hampering the growth of local content and services. In contrast, a flat-rate pricing model would spur demand for broadband services and enable content providers to target the local and emerging market. We study the Indian telecommunication scenario from a pricing and technology perspective to understand what the driving forces are for business to prosper. We then discuss the Indian landscape from a metro/access/core networks perspective. The technology choices and the methods of deployment are considered followed by an analysis of the service-centric model adopted by providers.

Integrated Fiber-Wireless (FiWi) Access Networks Supporting Inter-ONU Communications

Integrated fiber-wireless (FiWi) access networks provide a powerful platform to improve the throughput of peer-to-peer communication by enabling traffic to be sent from the source wireless client to an ingress optical network unit (ONU), then to the egress ONU close to the destination wireless client, and finally delivered to the destination wireless client. Such wireless-optical-wireless communication mode introduced by FiWi access networks can reduce the interference in wireless subnetwork, thus improving network throughput. With the support for direct inter-ONU communication in the optical subnetwork, throughput of peer-to-peer communication in a FiWi access network can be further improved. In this paper, we propose a novel hybrid wavelength division multiplexed/time division multiplexed passive optical network (WDM/TDM PON) architecture supporting direct inter-ONU communication, a corresponding decentralized dynamic bandwidth allocation (DBA) protocol for inter-ONU communication and an algorithm to dynamically select egress ONU. The complexity of the proposed architecture is analyzed and compared with other alternatives, and the efficiency of the proposed system is validated by the simulations.

Optimizing light-trail assignment to WDM networks for dynamic IP centric traffic

The rapid growth of IP centric communication in worldwide networks and the parallel mass deployment of fiber based WDM networks have propelled IP over WDM being considered as an eventual solution for bandwidth on demand to customers. Contemporary optical networks are, however, based on lightpath communication and a lightpath represents end-to-end optical circuits from source to destination. Light-trails are a generalization of lightpaths, such that multiple nodes along a trail can participate in time differentiated communication over the same established trail. Managing and setting up of light-trails in order to cater to IP centric traffic is a key to the success of IP centric communication at the optical layer. A light-trail represents an open optical path that allows multiple users to communicate without the need for switch reconfiguration at any user node, the light-trail itself being static. IP communication on the other hand represents a bursty traffic flow often characterized by spurts or bursts of data. The goal of this paper is to show how to create efficient light-trails based virtual topology for a given network traffic flow. We first describe a tree-shaped variant of light-trail, called the clustered light-trail (CLT) and then present optimization techniques for satisfying the given IP centric communication requirements, using the light-trails framework that is very flexible, despite being basically a static mechanism.

Mesh implementation of light-trails: a solution to IP centric communication

Light-trails communication (Chlamtac and Gumaste, 2003) proposes a solution for implementing a conceptual framework for IP centric communication in the optical domain which is a combination of node architecture and protocol for realizing efficient optical communications from IP bursts to dynamic lightpaths. In this paper we introduce a Light-trails solution that is applicable to mesh networks. Contrary to existing proposals for IP type communication in the optical domain light-trail node architecture also presents the first practically implementable solution to enable optical transport with mature technology, nonstringent optical switching requirements, and potentially presents a cost effective alternative to electronics in supporting IP networks.

LiTPiC -- Light-trails and Photonic Integrated Circuits: Issues of Network Design and Performance

A recent advance in high-speed networks is the concept of Photonic Integrated Circuits (PICs) on an Indium Phosphide substrate, allowing miniaturization and integration of multiple OE and EO modules in a chip. PICs have the potential to do away with the opto-electronic bandwidth mismatch as well as result in severe cost reduction, hence questioning the need for all-optical networking. In this paper we analyze the impact of this digital optical networking concept by combining PIC technology with an all-optical solution - light-trails, resulting in a new solution called LiTPiC (Light-Trail Photonic Integrated Circuit). LiTPiCs offer the best of both digital and all-optical worlds. By enabling selective (and on-demand) regeneration of the signal, we are able to enhance the reach of all-optical light-trails. In addition, we are able to partition light-trail buses into multiple geographically disjoint sub-buses called PIC-Trails, thus for the first time introducing wavelength reuse within a light-trail. The LiTPiC concept gives PICs a new direction - that of being a technology enabler for next generation services using ROADM (Reconfigurable Optical Add-Drop Multiplexer) architecture and a complementary solution to the light-trail technology.In order to be part of a peer-to-peer (P2P) file sharing network a host must be fully powered-on all of the time. In addition to providing a user interface, a P2P host handles query messages and serves requested files. In this paper, we describe the development of a prototype Gnutella-like P2P power management proxy sub-system that handles query messages. This can allow desktop PCs acting as P2P hosts to enter a low-power sleep state for most of the time and be woken-up by the proxy only when needed to serve files. TCP connections with neighbors are maintained by the host when it is awake and by the proxy when the host is sleeping. Experiments show that a low-cost Freescale ColdFire processor can effectively proxy for a P2P host. This suggests that a controller for a Gnutella P2P proxy could be co-located on an Ethernet NIC at low cost. This could lead to significant energy savings by allowing P2P hosts to power manage into a low-power sleep state when not in active use.

Multipath de-fragmentation: Achieving better spectral efficiency in elastic optical path networks

In elastic optical networks, the spectrum consecutive and continuous constraints may cause the so-called spectrum fragmentation issue, degrading spectrum utilization, which is especially critical under dynamic traffic scenarios. In this paper, we propose a novel multipath de-fragmentation method which aggregates spectrum fragments instead of reconfiguring existing spectrum paths. We propose an optimization model based on Integer Linear Programming (ILP) and heuristic algorithms and discuss the practical feasibility of the proposed method. We show that multipath routing is an effective de-fragmentation method, as it improves spectral efficiency and reduces blocking under dynamic traffic conditions. We also show that the differential delay issue does not present an obstacle to the application of multipath de-fragmentation in elastic optical networks.

Proliferation of the optical transport network: a use case based study

The ITU-T G.709 standard is perhaps the most underrated and yet widely used of all telecommunication standards, especially pertaining to the transport layer. In this article we focus on OTN as a delivery platform for emerging services. We will understand why OTN was originally proposed and how it can be a critical enabler for emerging services. To this end, we build use cases of OTN especially for Ethernet transport, mobile backhaul, IP router interconnection, sub-wavelength support, and support of overlaid services, especially across multiple domains. The use cases will bring to the fore key advantages of OTN and how this technology solution is ideal for emerging applications. We also discuss future movements in this technology and how these can affect the transport network.

Dual auction (and recourse) opportunistic protocol for light-trail network design

A light-trail is a generalization of a lightpath such that multiple nodes can take part in communication along the path. Light-trail based networks lead to dynamic provisioning and optical multicasting while deploying a pragmatic low-cost platform. Dynamic connections can be setup and torn down over semi-permanent light-trails facilitating bandwidth-on-demand and optical multicasting. We introduce a protocol that enables efficient dynamic provisioning and fairness within light-trails. The protocol is based on a modification of the auction algorithm. We apply this protocol to bandwidth allocation within a light-trail as well as to the task of growth and reduction of the virtual topology of light-trails. The article presents an analysis of this protocol and its functioning. We extensively simulate this protocol. A new performance metric for light-trail networks called the opportunistic ratio (OR) is defined. The OR also enables computation of fairness in light-trail networks

Evolution of packet-optical integration in backbone and metropolitan high-speed networks: a standards perspective

Network operators are currently in the midst of a situation in which there is doubling of bandwidth requirement every two years, although the growth in revenue is nearly flat. In this situation providers must plan their networks to optimize for future growth and take into consideration flat-to-declining operating margins. The OPEX benefits of keeping the data in the lower layers of the network stack can be leveraged to plan future networks. We focus on the impact of evolving standards in the lower layers of the telecommunications stack through the contributions of the IEEE, ITU, and IETF. Specifically, we focus on the WDM, carrier Ethernet, OTN, MPLS, and MPLS-TP set of transport standards. These standards have evolved and are being adapted to meet the requirements of next generation networks and currently being considered in the standard bodies. We show through a simulation study that by adopting the packet-optical integrated standard families, providers would benefit because of CAPEX reduction and thereby enhance margins - benefiting the e-community through better services.