We describe the architecture, design, and implementation of a novel just-in-time (JIT) signaling protocol for optical burst switching (OBS) in wavelength division multiplexed (WDM) optical networks. The JIT-OBS paradigm is designed for ultra-low-latency unidirectional transport of data-bursts across an optical network. It combines the desirable features of circuit-switching and packet-switching. It features out-of-band control signal processing that eliminates buffering of data-burst at intermediate nodes, while minimizing the setup time, and maximizing the cross-connect bandwidth efficiency. We motivate and describe the architecture of JIT signaling, and analyze its basic performance. We present the detailed signaling message design and discuss the rationale and considerations that went into this design. We describe and examine various scenarios that illustrate the operations of the JIT signaling protocol (JIT-SP) in connection establishment and teardown. Finally, we describe and summarize the JIT signaling software prototype in the Washington, DC Testbed network implemented under the MONET project.

Just-in-time signaling for WDM optical burst switching networks

Over the past 25 years, networks have evolved from being relatively static with fairly homogeneous traffic to being more configurable and carrying a heterogeneous array of services. As the applications are ultimately the driver of network evolution, the paper begins with a brief history of circuit, packet, and wave services, along with the development of the corresponding transport layers. The discussion then moves to the evolution of network-node architecture, with an emphasis on the optical-electrical-optical and optical-bypass paradigms. Scalability and cost-effectiveness in meeting network demands are two key factors in the discussion. The evolution of networking equipment, along with the development of the optical control plane, has facilitated a configurable optical layer. The enabling technologies, along with their ramifications, are discussed. Finally, the paper speculates on how capacity might evolve in the future, to handle the undoubtedly new services that are on the horizon.

http://www.monarchna.com/OpticalNetworking25Years-JLT-AnnivIssue-w.pdf

Optical Networking: Past, Present, and Future

Unintentional failures affect links and nodes in communication networks. Recovery mechanisms are the key tool for achieving the dependability required by the services using the network. However, high dependability in communication networks comes at a high cost in terms of the capacity needed by these mechanisms.The traffic from all services and users is carried by the same backbone network. Since the users and services have different requirements, and users have different willingness to pay for a high quality of service, it is desirable to have methods that enable provision of different levels of dependability in the same network, i.e. dependability differentiation. The thesis addresses dependability differentiation in connection-oriented backbone communication networks. Two methods to provide connections meeting differentiated guarantees on the asymptotic availability are proposed.The first of these uses a novel flexible arrangement for dedicated protection denoted a protection pattern. The protection pattern is used in a proposed distributed connection management system. The system is compared with alternative proposals based on centralized management and shows good performance. The second proposal uses shared protection, which may potentially use less resources in terms of bandwidth, but has higher complexity than dedicated protection. The proposed system is based on rules to control the sharing to enable provision of guarantees. Simulation results show that the proposed method performs significantly better than an alternative strategy based on dedicated protection.A different approach to availability-guaranteed services is to offer guarantees on the interval availability which is a measure commonly used Service Level Agreements (SLAs). The thesis contains a proposal of using adaptive management to increase compliance with interval availability guarantees. Different adaptive management policies are proposed and compared to alternative static provisioning policies in a case study. The thesis also addresses the problem of measuring dependability by simulation. To reduce the simulation effort needed to obtain precise estimates of dependability attributes, a rare-event simulation technique has been applied to the well-known Network Simulator 2 (NS2). The results show that the technique is applicable to this types of simulation scenario, but the gain is modest. The thesis also contains a broad literature survey of dependability differentiation research. This is the first survey of the topic. Hence, it is in itself a significant contribution. A classification scheme for how to approach differentiation is proposed and a critical evaluation of the state of art is given.This thesis contributes to fill in some of the ``gaps'' identified, but there are still significant challenges ahead before differentiation may be deployed in operational networks.

A survey of resilience differentiation frameworks in communication networks

The Shared Risk Link Group (SRLG) concept introduced in [IPO-Frame] is considered as one of the most important criteria concerning the constrained-based path computation of optical channel routes. By applying the SRLG criteria to the constrained-based path computation, one can select a route taking into account physical resource and logical structure disjointness that implies a lower probability of simultaneous lightpath failure. This contribution describes the various physical and logical resource types considered in the SRLG concept. The proposed model focuses on the inference of SRLG information between the network physical layers as well as logical structures such as geographical locations. The main applications of the proposed model are the related Constraint-based Shortest Path First (CSPF) algorithm for optical channel path computation and the reduction of the SRLG information flooded through traffic engineering extensions of the IGP routing protocols (such as OSPF and IS-IS). Notice: This contribution has been created to assist the Optical Internetworking Forum (OIF). This document is offered to the OIF solely as a basis for discussion and is not a binding proposal on the companies listed as resources above. Each company in the source list, and the OIF, reserves the rights to at any time to add, amend, or withdraw statements contained herein.

https://www.cse.wustl.edu/~jain/oif/ftp/oif2001.066.2.pdf

Inference of Shared Risk Link Groups

When using link-state protocols such as OSPF or IS-IS, forwarding loops can occur transiently when the routers adapt their forwarding tables as a response to a topological change. In this paper, we present a mechanism that lets the network converge to its optimal forwarding state without risking any transient loops and the related packet loss. The mechanism is based on an ordering of the updates of the forwarding tables of the routers. Our solution can be used in the case of a planned change in the state of a set of links and in the case of unpredictable changes when combined with a local protection scheme. The supported topology changes are link transitions from up to down, down to up, and updates of link metrics. Finally, we show by simulations that sub-second loop-free convergence is possible on a large Tier-1 ISP network.

/pdf/avoiding-transient-loops-during-the-convergence-of-link-4pp2k4807y.pdf

Avoiding transient loops during the convergence of link-state routing protocols

Optical Network Control is the first expert guide and single-source reference for controlling and managing optical networks. This book fills the gap between optical network engineering and routing/signaling-helping both optical and IP professionals build networks that are more robust, flexible, manageable, and profitable. Coverage includes: Designing networks to deliver a range of on-demand services from mission-critical, time-sensitive protected services to low-cost unprotected services Network control and operations in WDM/DWDM and SONET/SDH environments Control principles and features for evolving mesh-based optical networks and existing ring networks-with practical examples Emerging, proposed, and future optical routing/signaling protocols and standards including GMPLS, ASON and Optical UNI Optical network control planes: design, scenarios, interworking, and interactions with existing network management systems Crucial IETF, ITU-T, OIF, ANSI, Bellcore, and industry information-brought together for the first time

Optical Network Control: Architecture, Protocols, and Standards

Link Bundling in Optical Networks

Routing Information Exchange in Optical Networks

With the advent of optical mesh networks, certain new protection schemes have been defined. This encompasses both local span and end-to-end path protection. But the implementations of these protection schemes have so far been based on proprietary mechanisms developed by each vendor. This has made it virtually impractical to construct a heterogeneous network with interoperable mesh protection schemes. Also, while the notion of a standard IP-centric control plane for optical networks based on Generalized Multi-Protocol Label Switching (GMPLS) has gained wide acceptance, the work in this area has so far focused exclusively on connection provisioning rather than restoration. This paper defines standard, IP-based signaling protocols for restoration in optical mesh networks. These protocols focus on a new local span protection mode and end-to-end shared protection. The main requirements on these protocols are simplicity and speed. The signaling mechanisms described in this paper are complimentary to the GMPLS provisioning mechanisms.

Bala Rajagopalan

Papers

Optical Network Control: Architecture, Protocols, and Standards

Link Bundling in Optical Networks

Routing Information Exchange in Optical Networks

Signaling for fast restoration in heterogeneous optical mesh networks

RSVP Extensions for Signaling Optical Paths