The nine papers in this special issue focus on network infrastructure configuration and some of the problems encountered in the areas of specification, diagnosis, repair, synthesis, and anonymization.

IP over reconfigurable optical network architectures have been extensively discussed within the research literature over the past few years. However, although reconfigurable optical networks have been deployed and signaling protocols between IP routers and optical networks have been standardized, large IP backbones are typically deployed using the reconfigurable optical networks. One of the most important criteria in determining whether an IP backbone should be carried over a reconfigurable optical network is economic viability - which necessitates a detailed, accurate economic study of IP backbone over reconfigurable optical network architectures. In this paper, we analyze and explore four IP over optical network architectures for a typical large ISP backbone. In contrast with other published claims, our results suggest that an IP over opaque reconfigurable optical network architecture is not economically attractive with current equipment and IP backbone network design requirements. However, for ISPs also carrying large volumes of transport network private line services, our proposed integrated IP over re-configurable optical network architecture may provide an attractive alternative for providing rapid, cost effective failure recovery.

Congestion control in ring based packet networks is challenging due to the fact that every node in the network runs both a rate adaptation algorithm, analogous to an endpoint algorithm in other network architectures, and a rate allocation algorithm, analogous to switch-based algorithms in other network architectures. This work describes a congestion control algorithm for IEEE 802.17 resilient packet rings called the enhanced conservative mode algorithm that aims to avoid congestion and achieve a fair rate allocation for fairness eligible traffic in the case of a single bottleneck. We first present analysis to show that existing approaches for RPR congestion control (aggressive and conservative mode) have deficiencies. We present simulation results showing that the proposed enhanced conservative mode congestion control algorithm is a significant improvement. In conjunction with other mechanisms specified in the IEEE 802.17 MAC, the proposed algorithm achieves high utilization on the ring with minimal starvation and oscillations, allows sources to fast start, and provides quality of service for multiple classes of service that require rate, delay and jitter guarantees.

Today's metro networks have evolved from the need to support traditional voice and private line services and were optimized to support time division multiplexing (TDM) services. However, the growth of private line services is dominated by the access (also called "backhaul") to packet switches that provides frame relay, ATM, IP and Ethernet services. This paper provides a coherent architectural vision for metro access networks, which the author calls the packet-aware transport network (PATN). The PATN is designed to support the packet and TDM transport within metro areas in a scalable manner, and interfaces the inter-city packet and TDM transport backbone networks. Since the PATN supports the IETF pseudo-wire encapsulation (PWE) schemes for all packet access traffic, it is synergistic with the move towards a converged MPLS-based multi-service packet backbone network.

Multiple addresses within an OSPF area can be aggregated and advertised together to other areas. This process is known as address aggregation and is used to reduce router computational overheads and memory requirements and to reduce the network bandwidth consumed by OSPF messages. The downside of address aggregation is that it leads to information loss and consequently sub-optimal (non-shortest path) routing of data packets. The resulting difference (path selection error) between the length of the actual forwarding path and the shortest path varies between different sources and destinations. This paper proves that the path selection error from any source to any destination can be bounded using only parameters describing the destination area. Based on this, the paper presents an efficient algorithm that generates the minimum number of aggregates subject to a maximum allowed path selection error. A major operational benefit of our algorithm is that network administrators can select aggregates for an area based solely on the topology of the area without worrying about remaining areas of the OSPF network. The other benefit is that the algorithm enables trade-offs between the number of aggregates and the bound on the path selection error. The paper also evaluates the algorithm's performance on random topologies. Our results show that in some cases, the algorithm is capable of reducing the number of aggregates by as much as 50% with only a relatively small introduction of maximum path selection error.

In MPLS/GMPLS networks, a range of restoration schemes will be required to support different tradeoffs between service interruption time and network resource utilization. In light of these tradeoffs, path-based end-to-end shared mesh restoration provides a very attractive solution. However, efficient use of bandwidth for shared mesh restoration strongly relies on the procedure for selecting restoration paths. We propose an efficient restoration path selection algorithm for restorable connections over shared bandwidth in a fully distributed MPLS/GMPLS architecture. We also describe how to extend MPLS/GMPLS signaling protocols to collect the necessary information efficiently. To evaluate the algorithm's performance, we compare it via simulation with two other well-known algorithms on a typical intercity backbone network. The key figure of merit for restoration bandwidth efficiency is restoration overbuild, i.e., the extra bandwidth required to meet the network restoration objective as a percentage of the bandwidth of the network with no restoration. Our simulation results show that our algorithm uses significantly less restoration overbuild (63%-68%) compared with the other two algorithms (83%-90%).

Understanding the variability of Internet traffic in backbone networks is essential to better plan and manage existing networks, as well as to design next generation networks. However, most traffic analyses that might be used to approach this problem are based on detailed packet or flow level measurements, which are usually not available throughout a large network. As a result there is a poor understanding of backbone traffic variability, and its impact on network operations (e.g. on capacity planning or traffic engineering).This paper introduces a metric for measuring backbone traffic variability that is grounded on simple but powerful traffic theory. What sets this metric apart, however, is that we present a method for making practical measurements of the metric using widely available SNMP traffic measurements. Furthermore, we use a novel method to overcome the major limitation of SNMP measurements -- that they only provide link statistics. The method, based on a "gravity model", derives an approximate traffic matrix from the SNMP data. In addition to simulations, we use more than 1 year's worth of SNMP data from an operational IP network of about 1000 nodes to test our methods. We also delve into the degree and sources of variability in real backbone traffic, providing insight into the true nature of traffic variability.

In MPLS/GMPLS networks, a range of restoration schemes are required to support different tradeoffs between service interruption time and network resource utilization. In light of these tradeoffs, path-based, end-to-end shared restoration provides a very attractive solution. However, efficient use of capacity for shared restoration strongly relies on the selection procedure of restoration paths. We propose an efficient path-selection algorithm for restoration of connections over shared bandwidth in a fully distributed GMPLS architecture. We also describe how to extend GMPLS signaling protocols to collect the necessary information efficiently. To evaluate the algorithm's performance, we compare it via simulation with two other well-known algorithm on a typical intercity backbone network. The key figure-of-merit for restoration capacity efficiency is restoration overbuild, i.e., the extra capacity required to meet the network restoration objective as a percentage of the capacity of the network with no restoration. Our simulation results show that our algorithm uses significantly less restoration overbuild (63-68%) compared to the other two algorithms (83-90%).

An increasing number of communication services are moving to an IP-based infrastructure. Packet telephony is probably the first important real-time service that must be supported well over an IP network. The use of IP presents a tremendous opportunity for service providers to exploit endpoint intelligence to offer creative new services going far beyond the current telephony service model. However, to support telephony, signaling protocols are needed that allow the service provider to offer network-layer service differentiation and, at the same time, to control access to both the enhanced network-layer quality of service as well as other services. This paper describes the distributed open signaling architecture (DOSA), which incorporates protocols that meet these needs. A key contribution of our work is a recognition of the need for coordination between call signaling, which controls access to telephony-specific services, and resource management, which controls access to network-layer resources.

As communications networks grow in both speed and scale, there is a need to switch packets at higher speeds. One approach is to use fast switches that operate at the datalink layer (layer 2) to build a high-performance "cloud" for interconnecting network layer routers. The use of ATM for the layer 2 network provides a number of advantages when the network is shared among multiple services and when additional capabilities that are supported well at layer 2, such as fine-grained per-flow QoS, are needed. This paper describes a robust and efficient solution to the problem of supporting IP over a large non-broadcast multiple-access (NBMA) network, such as ATM. The solution, known as SUBMARINE, calculates loop-free shortcut routes across the NBMA network. SUBMARINE builds on existing IP routing protocols, is designed to scale to multiple areas within a single autonomous system, and makes minimal changes to the IP forwarding process.

Packet telephony is of increasing interest in both the telecommunications and Internet communities. The emergence of packet telephony will create new services, and presents an opportunity to rethink how conventional telephony services are implemented. In this paper, we present an architecture for telephony over packet networks (TOPS). TOPS allows users to move between terminals or to use mobile terminals while being reachable by the same name. TOPS users can have multiple terminals and control how calls are routed to them. TOPS allows for terminals with a range of capabilities such as support for video, whiteboard, and other media with a variety of coding formats. TOPS retains the necessary information on terminal capabilities to determine the appropriate type of communication to be established with the remote terminal. The architecture assumes that the underlying network supports the establishment of end-to-end connectivity between terminals, with an appropriate quality of service. The components of TOPS are a directory service, an application layer signaling protocol, and a logical channel abstraction for communication between end-systems. The directory service maps a user's name to a set of terminals where the user may be reached. A user can control the translation operation by specifying profiles that customize how his name is mapped to a set of terminals where he can be reached. Terminal capabilities are also stored in the directory service. The application layer signaling protocol establishes and maintains call state between communicating terminals. The logical channel abstraction provides a shared end-to-end context for a call's constituent media and control streams, while isolating the applications from the details of the network transport mechanisms. In addition to supporting simple point-to-point calls, the architecture supports both centralized and decentralized conferencing. We also introduce a simple encapsulation format for voice.

This paper is a retrospective on the design of Xunet 2, one of the earliest functional wide-area asynchronous transfer mode (ATM) networks. Work on Xunet 2 began in 1989 and the network, consisting of experimental ATM switches, IP routers, and 45 Mb/s transmission lines, has been operational since October 1991. The network serves as a "laboratory without walls" for eight research groups across the United States. While Xunet 2 has only a small number of nodes, it was designed as a prototype of a nationwide ATM network. This paper reviews some of the design decisions and lessons learned in the project and points out the research directions motivated by this work, focusing on the areas of traffic management, ATM switch design, network control, and the implementation of an IP router.

The paper considers the problem of routing a set of permanent virtual circuit requests over a backbone network. Several factors make this routing problem complicated. Routing decisions must be made on-line without any knowledge of future request sets. Furthermore, frequent rerouting to correct inefficiencies that can result from the on-line routing decisions is not possible since rerouting creates a service disruption for the customer. Finally, the forward and reverse bandwidth of a virtual circuit must be routed over the same single path. Using an extensive set of simulations, the paper evaluates several different strategies for on-line permanent virtual circuit routing. The authors find that a strategy based on results in competitive analysis and ideas from combinatorial optimization consistently provides the best performance. The problem of admission control is closely related to the problem of routing. The paper also provides a theoretical lower bound that suggests that non-greedy admission control is a fundamental component of an efficient on-line permanent virtual circuit routing algorithm.

Article Free Access Share on Rednet: a wireless ATM local area network using infrared links Authors: J. H. Condon AT&T Bell Laboratories, Murray Hill NJ AT&T Bell Laboratories, Murray Hill NJView Profile , T. S. Duff AT&T Bell Laboratories, Murray Hill NJ AT&T Bell Laboratories, Murray Hill NJView Profile , M. F. Jukl AT&T BelI Laboratories, Murray Hill NJ AT&T BelI Laboratories, Murray Hill NJView Profile , C. R. Kalmanek AT&T Bell Laboratories, Murray Hill NJ AT&T Bell Laboratories, Murray Hill NJView Profile , B. N. Locanthi AT&T Bell Laboratories, Murray Hill NJ AT&T Bell Laboratories, Murray Hill NJView Profile , J. P. Savicki AT&T Bell Laboratories, Murray Hill NJ AT&T Bell Laboratories, Murray Hill NJView Profile , J. H. Venutolo AT&T Bell Laboratories, Murray Hill NJ AT&T Bell Laboratories, Murray Hill NJView Profile Authors Info & Claims MobiCom '95: Proceedings of the 1st annual international conference on Mobile computing and networkingDecember 1995 Pages 151–159https://doi.org/10.1145/215530.215568Published:01 December 1995Publication History 14citation523DownloadsMetricsTotal Citations14Total Downloads523Last 12 Months31Last 6 weeks3 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Xunet 2 is an experimental wide-area network that serves as a testbed for research on data communications techniques. The authors provide an overview of the architecture of the Xunet 2 testbed. Xunet 2 has three principal components: routers, switches and network management systems. Long-haul transmission between them will initially use DS3 facilities. Performance objectives for the backbone have been set to cover a wide range of transmission speeds. Each router attaches a local area network to the backbone network. The backbone network provides virtual circuit connectivity between the routers. Circuit setup and teardown is done by a control computer associated with each switch, and the network as a whole will be managed by a network management station in the network operations center.>