David H. Su

A differentiated optical services model for WDM networks

This article addresses the issues of scalable end-to-end QoS in metropolitan DWDM networks serving as transit networks for IP access networks. DWDM offering a few wavelengths has been deployed in the past in backbone networks to upgrade point-to-point transmission where sharing is based on coarse granularity. This type of DWDM backbone network, offering a few light-paths, provides no support for QoS services traversing the network. As DWDM networks with larger numbers of wavelengths penetrate the data-centric metro environment, specific IP service requirements such as priority restoration, scalability, dynamic provisioning of capacity and routes, and support for coarse-grain QoS capabilities will have to be addressed in the optical domain in order to achieve end-to-end QoS over a DWDM network. We propose a QoS service model in the optical domain called differentiated optical services (DoS) based on a set of optical parameters that captures the quality and reliability of the optical lightpath.

Quantum key distribution with 1.25 Gbps clock synchronization

Clock recovery techniques at 1.25 Gbps enable continuous quantum key distribution at demonstrated sifted-key rates up to 1.0 Mbps. This rate is two orders of magnitude faster than has been reported previously

A review of contention resolution algorithms for IEEE 802.14 networks

Bidirectional cable TV networks using hybrid fiber coaxial (HFC) systems are good examples of broadcast environments where a contention resolution algorithm is needed in order to allocate the multiaccess medium (in this case the upstream link) among the various nodes. Recent activities of the IEEE 802.14 working group aimed at defining the physical and medium access control (MAC) layer protocols for HFC cable networks have focused on the study and evaluation of several contention resolution solutions for inclusion in the MAC protocol specifications. In this article several contention resolution algorithms considered by the IEEE 802.14 group are reviewed. Different implementations for several well known contention resolution algorithms such as tree-based and p-persistence are presented. Their performance is evaluated in the HFC context with respect to upstream channel allocation, roundtrip delay, various traffic types, and number of stations in the network. Simulation results for configurations and scenarios of interest are also presented.

Experimental study of high speed polarization-coding quantum key distribution with sifted-key rates over Mbit/s

We present a quantitative study of various limitations on quantum cryptographic systems operating with sifted-key rates over Mbit/s. The dead time of silicon APDs not only limits the sifted-key rate but also causes correlation between the neighboring key bits. In addition to the well-known count-rate dependent timing jitter in avalanche photo-diode (APD), the faint laser sources, the vertical cavity surface emission lasers (VCSELs) in our system, also induce a significant amount of data-dependent timing jitter. Both the dead time and the data-dependent timing jitter are major limiting factors in designing QKD systems with sifted-key rates beyond Mbit/s.

High-speed quantum key distribution system supports one-time pad encryption of real-time video

NIST has developed a high-speed quantum key distribution (QKD) test bed incorporating both free-space and fiber systems. These systems demonstrate a major increase in the attainable rate of QKD systems: over two orders of magnitude faster than other systems. NISTs approach to high-speed QKD is based on a synchronous model with hardware support. Practical one-time pad encryption requires high key generation rates since one bit of key is needed for each bit of data to be encrypted. A one-time pad encrypted surveillance video application was developed and serves as a demonstration of the speed, robustness and sustainability of the NIST QKD systems. We discuss our infrastructure, both hardware and software, its operation and performance along with our migration to quantum networks.

A comparison of MAC protocols for hybrid fiber/coax networks: IEEE 802.14 vs. MCNS

Both the IEEE and MCNS medium access control (MAC) interface specifications for hybrid fiber/coax networks share a common goal to provide a standard interface to the same anticipated services (such as cable telephony, Internet and on-line access for Web browsing, chat rooms, interactive games, local area network emulation for work-at-home applications and desktop conferencing). However the solutions offered by the two groups have little in common at the MAC layer. IEEE 802.14 chose ATM transfer as its default solution while MCNS uses a scheme that favors the delivery of variable length IP packets. Our goal in this study is to conduct a comparative performance evaluation of both IEEE 802.14 and MCNS MAC specifications. We focus on the efficiency of the two solutions in terms of contention access, ATM vs IP transfer, and adequate quality of service provision.

A priority scheme for the IEEE 802.14 MAC protocol for hybrid fiber-coax networks

In order to support quality-of-service (QoS) for real-time data communications such as voice, video and interactive services, multiaccess networks must provide an effective priority mechanism. The context of this work is the IEEE 802.14 standard for hybrid fiber coaxial (HFC) networks which has a shared upstream channel for transmissions from stations to the headend. This work presents a multilevel priority collision resolution scheme, which separates and resolves collisions between stations in a priority order, thereby, achieving the capability for preemptive priorities. We present a set of simulation scenarios which show the robustness and efficiency of the scheme, such as its ability to isolate higher priority traffic from lower priorities and to provide quick access to high-priority requests. In March 1998, a framework for handling priorities in the collision resolution process, which adopts a semantics similar to the semantics of our scheme, was included in the 802.14 standard.

Differentiated services over cable networks

The current medium access control interface specifications of the Multimedia Cable Network System (MCNS) project describe a best effort access service over cable networks. We show that even though these specifications are mainly intended to support IP traffic, there is a significant benefit in the stratification of the cable service offerings. We present a priority system to extend the MCNS MAC protocol so that differentiated services can be supported on hybrid fiber coaxial networks with different levels of performance.

A VoD Application Implemented in Java

This article describes an implementation of a Video-on-Demand (VoD) system for the VoD interoperability test laboratory of the National Institute of Standards and Technology. It describes how Java can be used to implement the client side of a DAVIC based client-server system, which consists of a video server and a Set-Top Unit (STU) client. The communication between the video server and the STU is based on the Digital Storage Media Command and Control (DSM-CC) protocols. The VoD application is defined as a set of Java classes. These classes implement the graphical interfaces for user navigation and control. While this system is compliant with DAVIC specifications, it also permits an elegant integration of DAVIC services to the Internet environment.

A framework for managing faults and attacks in all-optical transport networks

Fault and attack survivability in all-optical transport networks (AOTNs) require new approaches because of unique transmission characteristics. Specifically, fiber nonlinearities and network transparency to transmitted signal types may make the network vulnerable to unorthodox attacks. Furthermore, unlike in electronic networks that regenerate signals at every node, attack detection and isolation schemes may not have access to the overhead bits used to transport supervisory information between regenerators or switching sites to perform their functions. This paper presents a discussion on attack scenarios and proposes a conceptual framework for modeling faults and attacks in AOTNs.