Yun Mao

IDES: An Internet Distance Estimation Service for Large Networks

The responsiveness of networked applications is limited by communications delays, making network distance an important parameter in optimizing the choice of communications peers. Since accurate global snapshots are difficult and expensive to gather and maintain, it is desirable to use sampling techniques in the Internet to predict unknown network distances from a set of partially observed measurements. This paper makes three contributions. First, we present a model for representing and predicting distances in large-scale networks by matrix factorization which can model suboptimal and asymmetric routing policies, an improvement on previous approaches. Second, we describe two algorithms-singular value decomposition and non-negative matrix factorization-for representing a matrix of network distances as the product of two smaller matrices. Third, based on our model and algorithms, we have designed and implemented a scalable system-Internet Distance Estimation Service (IDES)-that predicts large numbers of network distances from limited samples of Internet measurements. Extensive simulations on real-world data sets show that IDES leads to more accurate, efficient and robust predictions of latencies in large-scale networks than existing approaches

Declarative automated cloud resource orchestration

As cloud computing becomes widely deployed, one of the challenges faced involves the ability to orchestrate a highly complex set of subsystems (compute, storage, network resources) that span large geographic areas serving diverse clients. To ease this process, we present COPE (Cloud Orchestration Policy Engine), a distributed platform that allows cloud providers to perform declarative automated cloud resource orchestration. In COPE, cloud providers specify system-wide constraints and goals using COPElog, a declarative policy language geared towards specifying distributed constraint optimizations. COPE takes policy specifications and cloud system states as input and then optimizes compute, storage and network resource allocations within the cloud such that provider operational objectives and customer SLAs can be better met. We describe our proposed integration with a cloud orchestration platform, and present initial evaluation results that demonstrate the viability of COPE using production traces from a large hosting company in the US. We further discuss an orchestration scenario that involves geographically distributed data centers, and conclude with an ongoing status of our work.

DHARMA: distributed home agent for robust mobile access

Mobile wireless devices have intermittent connectivity, sometimes intentional. This is a problem for conventional Mobile IP, beyond its well-known routing inefficiencies and deployment issues. DHARMA selects a location-optimized instance from a distributed set of home agents to minimize routing overheads; set management and optimization are done using the PlanetLab overlay network. DHARMAs session support overcomes both transitions between home agent instances and intermittent connectivity. Cross-layer information sharing between the session layer and the overlay network are used to exploit multiple wireless links when available. The DHARMA prototype supports intermittently connected legacy TCP applications in a variety of scenarios and is largely portable across host operating systems. Experiments with DHARMA deployed on more than 200 PlanetLab nodes demonstrate routing performance consistently better than that for best-case Mobile IP.

Declarative configuration management for complex and dynamic networks

Network management and operations are complicated, tedious, and error-prone, requiring signifcant human involvement and domain knowledge. As the complexity involved inevitably grows due to larger scale networks and more complex protocol features, human operators are increasingly short-handed, despite the best effort from existing support systems to make it otherwise. This paper presents coolaid, a system under which the domain knowledge of device vendors and service providers is formally captured by a declarative language. Through effcient and powerful rule-based reasoning on top of a database-like abstraction over a network of devices, coolaid enables new management primitives to perform network-wide reasoning, prevent misconfguration, and automate network confguration, while requiring minimum operator effort. We describe the design and prototype implementation of coolaid, and demonstrate its effectiveness and scalability through various realistic network management tasks.

S4: small state and small stretch compact routing protocol for large static wireless networks

Routing protocols for large wireless networks must address the challenges of reliable packet delivery at increasingly large scales and with highly limited resources. Attempts to reduce routing state can result in undesirable worst-case routing performance, as measured by stretch, which is the ratio of the hop count of the selected path to that of the optimal path. We present a new routing protocol, Small State and Small Stretch (S4), which jointly minimizes the state and stretch. S4 uses a combination of beacon distance-vector-based global routing state and scoped distance-vector-based local routing state to achieve a worst-case stretch of 3 using O(√(N)) routing state per node in an N-node network. Its average routing stretch is close to 1. S4 further incorporates local failure recovery to achieve resilience to dynamic topology changes. We use multiple simulation environments to assess performance claims at scale and use experiments in a 42-node wireless sensor network testbed to evaluate performance under realistic RF and failure dynamics. The results show that S4 achieves scalability, efficiency, and resilience in a wide range of scenarios.

DECOR: DEClarative network management and OpeRation

Network management operations are complicated, tedious and error-prone, requiring significant human involvement and expert knowledge. In this paper, we first examine the fundamental components of management operations and argue that the lack of automation is due to a lack of programmability at the right level of abstraction. To address this challenge, we present DECOR, a database-oriented, declarative framework towards automated network management. DECOR models router configuration and any generic network status as relational data in a conceptually centralized database. As such, network management operations can be represented as a series of transactional database queries, which provide the benefit of atomicity, consistency and isolation. The rule-based language in DECOR provides the flexible programmability to specify and enforce network-wide management constraints, and achieve high-level task scheduling. We describe the design rationale and architecture of DECOR and present some preliminary examples applying our approach to common network management tasks.

A declarative perspective on adaptive manet routing

In this paper, we present a declarative perspective on adaptable extensible MANET protocols. Our work builds upon declarative networking, a recent innovation for building extensible network architectures using declarative languages. We make the following contributions. First, we demonstrate that traditional MANET protocols, ranging from proactive, reactive, to epidemic can be expressed in a compact fashion as declarative networks, and we validate experimentally the use of declarative techniques to implement traditional MANETs emulated on a testbed cluster. Second, we show that the declarative framework enables policy-driven adaptation, in which a generic set of declarative rule-based policies are used to make runtime decisions on the choice of MANET protocols. Third, we present some initial ideas on fine-grained protocol composition and adaptation, where a typical MANET protocol can be composed and adapted from simpler components.

Declarative policy-based adaptive mobile ad hoc networking

This paper presents DAWN, a declarative platform that creates highly adaptive policy-based mobile ad hoc network (MANET) protocols. DAWN leverages declarative networking techniques to achieve extensible routing and forwarding using declarative languages. We make the following contributions. First, we demonstrate that traditional MANET protocols can be expressed in a concise fashion as declarative networks and policy-driven adaptation can be specified in the same language to dictate the dynamic selection of different protocols based on various network and traffic conditions. Second, we propose interprotocol forwarding techniques that ensure packets are able to seamlessly traverse across clusters of nodes running different protocols selected based on their respective policies. Third, we have developed a full-fledged implementation of DAWN using the RapidNet declarative networking system. We experimentally validate a variety of policy-based adaptive MANETs in various dynamic settings using a combination of ns-3 simulations and deployment on the ORBIT testbed. Our experimental results demonstrate that hybrid protocols developed using DAWN outperform traditional MANET routing protocols and are able to flexibly and dynamically adapt their routing mechanisms to achieve a good tradeoff between bandwidth utilization and route quality. We further demonstrate DAWNs capabilities to achieve interprotocol forwarding across different protocols.

Unified Declarative Platform for Secure Netwoked Information Systems

We present a unified declarative platform for specifying, implementing, and analyzing secure networked information systems. Our work builds upon techniques from logic-based trust management systems, declarative networking, and data analysis via provenance. We make the following contributions. First, we propose the Secure Network Datalog (SeNDlog) language that unifies Binder, a logic-based language for access control in distributed systems, and Network Datalog, a distributed recursive query language for declarative networks. SeNDlog enables network routing, information systems, and their security policies to be specified and implemented within a common declarative framework. Second, we extend existing distributed recursive query processing techniques to execute SeNDlog programs that incorporate authenticated communication among untrusted nodes. Third, we demonstrate that distributed network provenance can be supported naturally within our declarative framework for network security analysis and diagnostics. Finally, using a local cluster and the PlanetLab testbed, we perform a detailed performance study of a variety of secure networked systems implemented using our platform.

Declarative policy-based adaptive MANET routing

This paper presents the design and implementation of declarative policy-based adaptive MANET routing protocols. Our work builds upon declarative networking, a recent innovation for building extensible network architectures using declarative languages. We make the following contributions. First, we demonstrate that traditional MANET protocols can be expressed in a compact fashion as declarative networks. We validate these declarative protocols via an experimental study on the ORBIT wireless testbed and a cluster-based emulation environment. Second, we demonstrate that policy-driven adaptation can be specified in a generic set of declarative rule-based policies that dictate the dynamic selection of different protocols based on network conditions. Third, we conduct extensive evaluation results of declarative policy-based adaptation of MANET routing on the ORBIT wireless testbed and the cluster-based emulation environment. Our experimental results show that the specified policies enable MANETs to dynamically hybridize a variety of routing protocols to achieve a good tradeoff in bandwidth utilization and route quality.