The rapid advancement of smartphones has instigated tremendous data applications for cell phones. Supporting simultaneous voice and data services in a cellular network is not only desirable but also becoming indispensable. However, if the voice and data are serviced through the same antenna (like the 3G UMTS network), a voice call with data sessions requires better radio connection than a voice-only call. In this paper, we systematically study the coordination between the voice and data transmissions in UMTS networks. From analyzing a large carrier's UMTS network recording data, we first identify the most relevant network measurements/features indicating a potential call drop, then propose a drop-call predictor based on AdaBoost. Moreover, we develop an intelligent call management strategy to voluntarily block data sessions when the voice is predicted to be dropped. Our analysis utilizing real service provider's data sets shows that our proposed scheme can not only predict drop calls with a very high accuracy but also achieve the highest user satisfaction compared to the other existing call management strategies.

While dense wavelength division multiplexing equipment has been deployed in networks of major telecommunications carriers for over a decade, the capabilities of its networking and associated network control and management have not caught up to those of digital cross-connect systems and packet-switched counterparts in higher layer networks. We shed light on this situation by examining the current structure of the optical layer, its relationship to other network technology layers, and current network management and control implementations. We provide additional insight by explaining how a combination of business and technical perspectives has driven evolution of the optical layer. We conclude by exploring activities to close this gap in the future.

Cloud service providers use replication across geographically distributed data centers to improve end-to-end performance as well as to offer high reliability under failures. Content replication often involves the transfer of huge data sets over the wide area network and demands high backbone transport capacity. In this paper, we discuss how a Globally Reconfigurable Intelligent Photonic Network (GRIPhoN) between data centers could improve operational flexibility for cloud service providers. The proposed GRIPhoN architecture is an extension of earlier work [34] and can provide a bandwidth-on-demand service ranging from low data rates (e.g., 1 Gbps) to high data rates (e.g., 10-40 Gbps). The inter-data center communication network which is currently statically provisioned could be dynamically configured based on demand. Today's backbone optical networks can take several weeks to provision a customer's private line connection. GRIPhoN would enable cloud operators to dynamically set up and tear down their connections (sub-wavelength or wavelength rates) within a few minutes. GRIPhoN also offers cost-effective restoration capabilities at wavelength rates and automated bridge-and-roll of private line connections to minimize the impact of planned maintenance activities.

Today's networks typically handle traffic engineering (e.g., tuning the routing-protocol parameters to optimize the flow of traffic) and failure recovery (e.g., pre-installed backup paths) independently. In this paper, we propose a unified way to balance load efficiently under a wide range of failure scenarios. Our architecture supports flexible splitting of traffic over multiple precomputed paths, with efficient path-level failure detection and automatic load balancing over the remaining paths. We propose two candidate solutions that differ in how the routers rebalance the load after a failure, leading to a trade-off between router complexity and load-balancing performance. We present and solve the optimization problems that compute the configuration state for each router. Our experiments with traffic measurements and topology data (including shared risks in the underlying transport network) from a large ISP identify a "sweet spot" that achieves near-optimal load balancing under a variety of failure scenarios, with a relatively small amount of state in the routers. We believe that our solution for joint traffic engineering and failure recovery will appeal to Internet Service Providers as well as the operators of data-center networks.

Traditional backbone optical networks can take months to provision a wavelength connection. Future optical networking aims at reducing the provisioning time to a few minutes. In conjunction, new services that allow the customers to dynamically set up and take down their connections is emerging. In this paper, we introduce the problem of optimizing network resources on a reconfigurable optical backbone network that provides such dynamic optical services. The problem grows exponentially in network scale and customer's demands, thus solving the entire problem for a realistic network is impractical. We address this problem by developing a heuristic optimization procedure, combined with problem-size reduction techniques. We show that good results can be achieved using small amounts of computing power and that our solutions are within 11% of a lower bound.

Metropolitan (metro) carriers are deploying next-generation metro Ethernet networks. This deployment will eventually replace traditional private-line services provided by legacy Time Division Multiplexing (TDM) technologies (such as Digital Cross-Connect Systems and SONET rings) with metro Ethernet services. A critical near-term need is the enabling of rich wireless data applications and, thus, begins a massive upgrade of backhaul links from cellular base stations to their Mobile Telephone Switching Offices (MTSOs), where the various voice and data applications will be provided. These base stations are evolving to 3G/4G technology and require metro Ethernet transport and at significantly higher backhaul technology than the prevalent TDM DS1s (1.5 Mb/s). In this paper, we describe a methodology to enable the rapid introduction of metro Ethernet networks, which includes architecture planning, switch location selection, link placement and sizing, as well as customization for cellular network reliability. Our approach uses a combination of many optimization algorithms and has been integrated into a pragmatic tool used by AT&T network planners. Case studies in very large US metro areas have shown that the tool gives cost-ffective solutions consistent with planner expectations and intuition.

Recent deployment of IP based multimedia distribution, especially broadcast TV distribution has increased the importance of simple and fast restoration during IP network failures for service providers. In this paper, we propose and evaluate a simple but efficient method for fast rerouting of IP multicast traffic during link failures in managed IPTV networks. More specifically, we devise an algorithm for tuning IP link weights so that the multicast routing path and the unicast routing path between any two routers are failure disjoint, allowing us to use unicast IP encapsulation for undelivered multicast packets during link failures. We demonstrate that, our method can be realized with minor modification to the current multicast routing protocol (PIM-SM). We run our prototype implementation in Emulab which shows our method yields to good performance.

In a network with Reconfigurable Optical Add/drop Multiplexers (ROADMs), transient effects from network failures trigger sudden power changes to channels, even on spans (ROADM-to-ROADM links) upstream/downstream from the failure. Some ROADMs rely on restrictive wavelength assignment rules, calledfield-of-use(FOU), to insure surviving channels meet performance objectives.Dropdepth(DD) (ratio of surviving channels) andspanoverlapcount(SOC) (length of spans of overlapping lightpaths) are two parameters defined for FOU guidelines. For a given DD, FOU guidelines specify a corresponding maximum SOC for each wavelength. Generally, a wavelength can support a longer span overlap count under a smaller drop depth restriction. However, the measured drop-depth changes as wavelengths are assigned. We propose methods to optimize transient-constrained wavelength assignment in commercial ROADM networks. Our solutions have been shown to provide 40% more channels than with typical FOU guidelines.

Broadcast TV distribution over an IP network requires stringent QoS constraints, such as low latency and loss. The main challenge to achieving these QoS objectives is how to design the network to respond to network failures. Streaming content in IPTV is typically delivered to the distribution points on the IP backbone using IP multicast, and in the case being considered, with protocol independent multicast source specific mode (PIM-SSM). A proven failure restoration technique at the IP layer is link-restoration using MPLS or layer-2 fast reroute (FRR). Link-based FRR creates a pseudo-wire or tunnel in parallel to the IP adjacencies (links) along the forwarding path used by the PIM tree. For each such tunnel both a primary and backup path are defined. The backup path is Layer-1-disjoint from the physical link and when the link fails, the pseudo-wire can be rapidly restored. Thus, single link failures are transparent to the interior gateway protocol (IGP). Although one may choose the back-up pathpsilas IGP link weights to avoid traffic overlap during any single link failure, multiple failures may still cause traffic overlap with FRR. We present a cross-layer restoration approach that combines both FRR-based restoration for single link failure and ldquohitlessrdquo (i.e., without loss) PIM tree reconfiguration algorithms to prevent traffic overlap when multiple failures occur.

Multimedia distribution, especially broadcast TV distribution over an IP network requires high bandwidth combined with tight latency and loss constraints, even under failure conditions. Due to the high bandwidth requirements of broadcast TV distribution, use of IP-based multicast to distribute TV content is needed for efficient use of capacity. The protection and restoration mechanisms currently adopted in IP backbones use either IGP re-convergence or some form of fast reroute. The IGP re-convergence mechanism is too slow for real-time multimedia distribution while a drawback of fast reroute is that traffic is re-routed on a link-basis (instead of end-to-end) so there can be traffic overlap during failures. By this we mean traffic passing through the same link along the same direction more than once; this requires more link capacity or it will result in congestion. We propose a routing method that interacts with Fast Reroute and multicast to minimize traffic overlap during failures. We also present an algorithm for link weight setting that avoids traffic overlap due to any single link failure. Performance analysis shows that our methods improve network service availability and significantly reduce the impact of failures.

With more service providers making considerable investments to roll out multimedia services using IP technology, live TV distribution on IP network is expected to grow impressively over next few years. To make efficient use of IP network infrastructure, service providers use multicast to transmit broadcast video content to the receiving nodes while simultaneously using unicast to transport other services on the same network, such as video on demand (VoD), high-speed Internet (HIS) etc. How to engineer different traffic flows on the same network to avoid traffic congestion becomes a major design issue. Although the service traffic flows are from source to receivers, the IP multicast tree is calculated using IGP shortest path from the receivers to the source (backwards from the flow), while the unicast path is calculated from the source to the receivers (same direction as the flow). To minimize congestion, we take advantage of this property and propose an algorithm to tune IGP link weights (such as OSPF) such that the traffic flows for multicast and unicast don't overlap. This proposal provides a natural way for service providers to use the spare capacity on the opposite direction of multicast traffic flow to roll out additional services in the same IP networks without impacting existing multicast services.

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.

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%).

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%).

We develop a telecommunications architecture based on IP routers and compare it empirically to the current TDM hierarchy. The study is based on two premises: first that data traffic will continue to grow much faster than voice traffic and will be mostly IP, and second, that IP routers and networks will soon achieve the scalability and dependability necessary to provide the service quality expected of telecommunications networks. The IP architecture exploits a number of mechanisms to improve network efficiency: mesh restoration requires less spare bandwidth than SONET rings; private line services are carried as virtual leased lines, enabling more fine-grained bandwidth offerings; a voice subnetwork uses OC-48 links rather than DS-1 trunk groups, so it requires less total bandwidth to achieve the same blocking probability; and the multiplying inefficiencies of layer-by-layer routing in the TDM hierarchy are avoided. We find that an all-IP architecture could offer much greater network efficiency and considerable capital savings. We examine how technology must evolve to support such an architecture.

Provides the results of an economic study on the use of SONET digital cross-connect systems (DCS) to provide survivable transmission network architectures in local exchange networks. Three fundamental survivable transmission technologies are considered: (1) a SONET self-healing ring, (2) a SONET point-to-point fiber system with 1:1 automatic protection switching and diverse routing of protection facilities, and (3) a DCS mesh with automatic DCS restoration (rerouting) protection. These three technologies are used in various combinations to form six survivable network alternatives for evaluation. Two local exchange carrier (LEC) networks are used (a 15 node network and a 53 node network) and demand, network connectivity, and unit equipment cost sensitivities are evaluated on these alternatives. In addition, the survivability of each alternative in the event of a major node failure is calculated. The motivation for the study is to determine the viability of DCS-based survivable network architectures and, in particular, the viability of SONET DCS with integrated optical terminations. The study has two objectives: (1) given a specific survivable network technology, under what conditions is it economical to place a broadband DCS (B-DCS) in a central office as opposed add-drop multiplexers (ADM); and (2) which survivable technologies with B-DCS are economical, and under what conditions. The authors conclude that the most cost-effective networks consist of "hybrids" of SONET point-to-point, ring, and mesh technologies, and that the B-DCS is economically viable for interconnection between these technologies.>