Dean Lorenz - Academia.edu (original) (raw)

Papers by Dean Lorenz

ACM SIGCOMM Computer Communication Review

Cloud computing is transforming networking landscape over the last few years. The first order of ... more Cloud computing is transforming networking landscape over the last few years. The first order of business for major cloud providers today is to attract as many organizations as possible to their own clouds. To that end cloud providers offer a new generation of managed network solutions to connect the premises of the enterprises to their clouds. To serve their customers better and to innovate fast, major cloud providers are currently on the route to building their own "private Internets", which are idiosyncratic. On the other hand, customers that do not want to stay locked by vendors and who want flexibility in using best-for-the-task services spanning multiple clouds and, possibly, their own premises, seek for solutions that will provide smart overlay connectivity across clouds. The result of these developments is a multiplication of closed idiosyncratic solutions rather than an open standardized ecosystem. In this editorial note we argue for desirability of such an ecosys...

ArXiv, 2020

Fifth Generation (5G) networks are envisioned to be fully autonomous in accordance to the ETSI-de... more Fifth Generation (5G) networks are envisioned to be fully autonomous in accordance to the ETSI-defined Zero touch network and Service Management (ZSM) concept. To this end, purpose-specific Machine Learning (ML) models can be used to manage and control physical as well as virtual network resources in a way that is fully compliant to slice Service Level Agreements (SLAs), while also boosting the revenue of the underlying physical network operator(s). This is because specially designed and trained ML models can be both proactive and very effective against slice management issues that can induce significant SLA penalties or runtime costs. However, reaching that point is very challenging. 5G networks will be highly dynamic and complex, offering a large scale of heterogeneous, sophisticated and resource-demanding 5G services as network slices. This raises a need for a well-defined, generic and step-wise roadmap to designing, building and deploying efficient ML models as collaborative com...

In this short paper we give a very simple fully polynomial approximation scheme for the restricte... more In this short paper we give a very simple fully polynomial approximation scheme for the restricted shortest path problem. The complexity of this ffl-approximation scheme is O(jEjn(loglog n + 1=ffl)), which improves Hassin's original result [Has92] by a factor of n. Furthermore, this complexity bound is valid for any graph, regardless of the cost values. This generalizes Hassin's results which apply only to acyclic graphs. Our algorithm is based on Hassin's original result [Has92] with two improvements. First we modify Hassin's result and achieve time complexity of O(jEjn(log log(UB=LB) + 1=ffl)), where UB and LB are upper and lower bounds for the problem. This modified version can be applied to general graphs with any cost values. Then we combine it with our second contribution, which shows how to find an upper and a lower bound such that UB=LB n, to obtain the claimed result. 1

In this paper we study problems related to supporting unicast and multicast connections with Qual... more In this paper we study problems related to supporting unicast and multicast connections with Quality of Service (QoS) requirements. We investigate the problem of optimal routing and resource allocation in the context of performance dependent costs. In this context, each network element can offer several QoS guarantees, each associated with a different cost. This is a natural extension to the commonly used bi-criteria model, where each link is associated with a single delay and a single cost. This framework is simple yet strong enough to model many practical interesting networking problems. An important problems in this framework is finding a good path for a connection that minimizes the cost while retaining the end-to-end delay requirement. Once such a path (or a tree, in the multicast case) is found, one needs to partition the end-to-end QoS requirements among the links of the path (tree). We consider the case of general integer cost functions (where delays and cost are integers). ...

In the traditional IP scheme, both the packet forwarding and the routing protocols are source inv... more In the traditional IP scheme, both the packet forwarding and the routing protocols are source invariant, i.e., their decisions depend on the destination IP address and not on the source address. Recent protocols, such as MPLS, as well as traditional circuit based protocols like PNNI allow routing decisions to depend on both the source and destination addresses. In fact, much of the theoretical work on routing assumes per-flow forwarding and routing, i.e., the forwarding decision is based on both the source and destination addresses.

Abstract—We consider the problem of routing connections with quality of service (QoS) requirement... more Abstract—We consider the problem of routing connections with quality of service (QoS) requirements across networks when the information available for making routing decisions is inaccurate. Such uncertainty about the actual state of a network component arises naturally in a number of different environments. The goal of the route selection process is then to identify a path that is most likely to satisfy the QoS requirements. For end-to-end delay guarantees, this problem is intractable. However, we show that by decomposing the end-to-end constraint into local delay constraints, efficient and tractable solutions can be established. Moreover, we argue that such decomposition better reflects the interoperability between the routing and reservation phases. We first consider the simpler problem of decomposing the end-to-end constraint into local constraints for a given path. We show that, for general distributions, this problem is also intractable. Nonetheless, by defining a certain class...

We investigate the problem of optimal resource allocation for end-to-end QoS requirements on unic... more We investigate the problem of optimal resource allocation for end-to-end QoS requirements on unicast paths and multicast trees. Specifically, we consider a framework in which resource allocation is based on local QoS requirements at each network link, and associated with each link is a cost function that increases with the severity of the QoS requirement. Accordingly, the problem that we address is how to partition an end-to-end QoS requirement into local requirements, such that the overall cost is minimized. We establish efficient (polynomial) solutions for both unicast and multicast connections. These results provide the required foundations for the corresponding QoS routing schemes, which identify either paths or trees that lead to minimal overall cost. In addition, we show that our framework provides better tools for coping with other fundamental multicast problems, such as dynamic tree maintenance. Keywords --- QoS, QoS-dependent costs, Multicast, Routing, Broadband ne...

2017 IEEE International Conference on Smart Computing (SMARTCOMP), 2017

With a growing number of infrastructure cloud services becoming available there are many benefits... more With a growing number of infrastructure cloud services becoming available there are many benefits to interconnecting several cloud services. However, seamless cloud interoperability is the complex issue, especially when different cloud platforms are interconnected. One of the major aspects of federating clouds resources is network federation. Federated networks must deal not only with heterogeneous cloud platforms, but also with different virtualization technologies and the added complexity of multi-layer virtualization. In order to allow monitoring and analysis of the complex heterogeneous environment, there is a need to present a user with the full aggregated view of the federated network including cloud interconnect and with the match between different layers and platforms. In this paper we present a framework that uses Skydive tool for network monitoring and analysis in BEACON federated network environment.

Proceedings of the 10th ACM International Systems and Storage Conference, 2017

Operating a cloud-scale service is a huge challenge. There are millions of users worldwide and mi... more Operating a cloud-scale service is a huge challenge. There are millions of users worldwide and millions of requests per seconds. For example, Amazon's Simple Storage Service (S3) in 2013 contained two trillion objects and its logs contained 1.1 million log lines per second, which are approximately 10 PB of log records per year (see [1]). Cloud scale implies thousands of servers and network elements, and hundreds of services from multiple cross-regional data centers. Cloud service operation data is scattered over various types of semi-structured and unstructured logs (e.g., application, error, debug), telemetry and network data, as well as customer service records. It is therefore extremely difficult for the multiple owners and administrators in such systems, coming from different units of the organization, to follow the possible paths and system alternatives in order to detect problems, solve issues and understand the service operation.

Proceedings of the 11th ACM International Systems and Storage Conference, 2018

Network slicing is a fundamental architectural feature of 5G network infrastructure [2], whereby ... more Network slicing is a fundamental architectural feature of 5G network infrastructure [2], whereby independent endto-end logical networks support a wide spectrum of vertical industries on shared resource, despite their diverging requirements. Network slice management is challenging and complicated, taking into account the various intraand interdomain deployment scenarios, divergent use cases with different requirements, stakeholders of different roles and business models, etc. The SliceNet project [1] aims to extend 5G infrastructure with cognitive management, control, and orchestration of cross-domain/cross-layer slices, to maximize the potential of the infrastructure, with emphasis on Quality of Experience (QoE) for vertical industries. SliceNet management takes a “verticals in the whole loop” approach, integrating the vertical perspective into the slice management process. SliceNet investigates three use cases, Smart City, Smart Grid, and eHealth, each with its distinct QoE require...

Proceedings of the 17th International Conference on emerging Networking EXperiments and Technologies

Hash-based stateful load-balancers employ connection tracking to avoid per-connection-consistency... more Hash-based stateful load-balancers employ connection tracking to avoid per-connection-consistency (PCC) violations that lead to broken connections. In this paper, we propose Just Enough Tracking (JET), a new algorithmic framework that significantly reduces the size of the connection tracking tables for hash-based stateful loadbalancers without increasing PCC violations. Under mild assumptions on how backend servers are added, JET adapts consistent hash techniques to identify which connections do not need to be tracked. We provide a model to identify these safe connections and a pluggable framework with appealing theoretical guarantees that supports a variety of consistent hash and connectiontracking modules. We implement JET in two different environments and with four different consistent hash techniques. Using a series of evaluations, we demonstrate that JET requires connection-tracking tables that are an order of magnitude smaller than those required with full connection tracking while preserving PCC and balance properties. In addition, JET often increases the lookup rate due to improved caching.

2018 IEEE International Conference on Cloud Engineering (IC2E), 2018

Given a large variety of resources and billing contracts offered by today’s cloud providers, cust... more Given a large variety of resources and billing contracts offered by today’s cloud providers, customers face a nontrivial optimization challenge for their application workloads. A number of works are dealing with either billing contracts selection optimization or resource types selection. We argue that the largest cost savings to elastic workloads result from jointly optimizing heterogeneous resources and billing contracts selection. To this end, we introduce a novel cloud control and management framework and formulate a novel optimization problem called Heterogeneous Resource Reservation (HRR). We evaluate our solution through a thorough simulation study using publicly available cloud workload data as well as internal anonymous customer data. For these data our approach attain dramatic cost savings compared to the current state of the art.

This research is done in the context of the SliceNet project [4] that aims to extend 5G infrastru... more This research is done in the context of the SliceNet project [4] that aims to extend 5G infrastructure with cognitive management of cross-domain, cross-layer network slices [1], with emphasis on Quality of Experience (QoE) for vertical industries. The provisioning of network slices with proper QoE guarantees is seen as one of the key enablers of future 5G-enabled networks. The challenge is to assess the QoE experienced by the vertical application and its users without requiring the applications or the users to measure and report QoE related metrics back to the provider. To address this challenge, we propose a method for deriving application-level QoE from network-level Quality of Service (QoS) measurements, easily accessible by the provider. In particular, we describe a PoC where QoE, perceived by application users, is estimated from low level network monitoring data, by applying cognitive methods. Our main goal is enabling the cloud provider to support the desired E2E QoE-based Ser...

Hybrid switching combines a high-bandwidth optical circuit switch in parallel with a low-bandwidt... more Hybrid switching combines a high-bandwidth optical circuit switch in parallel with a low-bandwidth electronic packet switch. It presents an appealing solution for scaling datacenter architectures. Unfortunately, it does not fit many traffic patterns produced by typical datacenter applications, and in particular the skewed traffic patterns that involve highly intensive one-to-many and many-to-one communications. In this paper, we introduce composite-path switching by allowing for composite circuit/packet paths between the two switches. We show how this enables the datacenter network to deal with skewed traffic patterns, and offer a practical scheduling algorithm that can directly extend any hybrid-switching scheduling algorithm. Through extensive evaluations using modern datacenter workloads, we show how our solution outperforms two recently proposed state-of-the-art scheduling techniques, both in completion time and in circuit utilization.

Abstract—In this paper, we study problems related to supporting unicast and multicast connections... more Abstract—In this paper, we study problems related to supporting unicast and multicast connections with quality of service (QoS) requirements. We investigate the problem of optimal routing and resource allocation in the context of performance dependent costs. In this context, each network element can offer several QoS guarantees, each associated with a different cost. This is a natural extension to the commonly used bi-criteria model, where each link is associated with a single delay and a single cost. This framework is simple yet strong enough to model many practical interesting networking problems. An important problems in this framework is finding a good path for a connection that minimizes the cost while retaining the end-to-end delay requirement. Once such a path (or a tree, in the multicast case) is found, one needs to partition the end-to-end QoS requirements among the links of the path (tree). We consider the case of general integer cost functions (where delays and cost are i...

2019 IEEE International Congress on Big Data (BigDataCongress)

2018 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB)

Network slicing has emerged as a major new networking paradigm for meeting the diverse requiremen... more Network slicing has emerged as a major new networking paradigm for meeting the diverse requirements of various vertical businesses in virtualised and softwarised 5G networks. SliceNet is a project of the EU 5G Infrastructure Public Private Partnership (5G PPP) and focuses on network slicing as a cornerstone technology in 5G networks, and addresses the associated challenges in managing, controlling and orchestrating the new services for users especially vertical sectors, thereby maximising the potential of 5G infrastructures and their services by leveraging advanced software networking and cognitive network management. This paper presents the vision of the SliceNet project, highlighting the gaps in existing work and challenges, the proposed overall architecture, proposed technical approaches, and use cases.

IEEE/ACM Transactions on Networking