Quality of Service Abstractions for Software-defined Networks

ABSTRACT Software-defined networking (SDN) provides a means of configuring the packet-forwarding behavior of a network from a logically-centralized controller. Expressive, high-level languages have emerged for expressing data-plane configurations, and new tools allow for verifying packet reachability properties in real time. But SDN largely ignores quality of service (QoS) primitives, such as queues, queuing disciplines, and rate limiters, leaving configuration of these elements to be performed out of band in an ad-hoc manner. Not only does this make QoS elements difficult to configure, it also leads to a "try it and see" approach to analysis and verification of QoS properties. We propose a new language for configuring SDNs with quality of service primitives. Our language comes equipped with a well-defined semantics drawn from the network calculus, which we believe will yield an equational theory for reasoning about network quality of service as well as decision procedures for verifying QoS properties

Decentralized Task-aware Scheduling for Data Center Networks.

ABSTRACT Many data center applications perform rich and complex tasks (e.g., executing a search query or generating a user's news-feed). From a network perspective, these tasks typically comprise multiple flows, which traverse different parts of the network at potentially different times. Most network resource allocation schemes, however, treat all these flows in isolation -rather than as part of a task -and therefore only optimize flow-level metrics. In this paper, we show that task-aware network scheduling, which groups flows of a task and schedules them together, can reduce both the average as well as tail completion time for typical data center applications. To achieve these benefits in practice, we design and implement Baraat, a decentralized task-aware scheduling system. Baraat schedules tasks in a FIFO order but avoids head-of-line blocking by dynamically changing the level of multiplexing in the network. Through experiments with Memcached on a small testbed and large-scale simulations, we show that Baraat outperforms state-of-the-art decentralized schemes (e.g., pFabric) as well as centralized schedulers (e.g., Orchestra) for a wide range of workloads (e.g., search, analytics, etc)

Ultrafast optical circuit switching for data centers using integrated soliton microcombs

Networks inside current data centers comprise a hierarchy of power-hungry electronic packet switches interconnected via optical fibers and transceivers. As the scaling of such electrically-switched networks approaches a plateau, a power-efficient solution is to implement a flat network with optical circuit switching (OCS), without electronic switches and a reduced number of transceivers due to direct links among servers. One of the promising ways of implementing OCS is by using tunable lasers and arrayed waveguide grating routers. Such an OCS-network can offer high bandwidth and low network latency, and the possibility of photonic integration results in an energy-efficient, compact, and scalable photonic data center network. To support dynamic data center workloads efficiently, it is critical to switch between wavelengths in sub nanoseconds (ns). Here we demonstrate ultrafast photonic circuit switching based on a microcomb. Using a photonic integrated Si3N4 microcomb in conjunction with semiconductor optical amplifiers (SOAs), sub ns (< 500 ps) switching of more than 20 carriers is achieved. Moreover, the 25-Gbps non-return to zero (NRZ) and 50-Gbps four-level pulse amplitude modulation (PAM-4) burst mode transmission systems are shown. Further, on-chip Indium phosphide (InP) based SOAs and arrayed waveguide grating (AWG) are used to show sub-ns switching along with 25-Gbps NRZ burst mode transmission providing a path toward a more scalable and energy-efficient wavelength-switched network for future data centers.Comment: 11 pages, 6 figure

Complexity Oblivious Network Management

Networks are hard to manage and in spite of all the so called holistic management packages, things are getting worse. We argue that this is an outcome of two fundamental flaws in the existing architecture: the management plane depends on the data plane and the complexity of the ever-evolving data plane encumbers the management plane. Consequently, addressing these flaws can make the network amenable to management. In this paper, we present Complexity Oblivious Network Management (CONMan), a network architecture in which the management plane does not depend on the data plane and all data plane protocols expose a generic management interface. This restricts the operational complexity of protocols to their implementation and allows the management plane to achieve high level policies in a structured fashion. Our preliminary experience with building the CONMan interface of a couple of protocols and using them for real world management tasks indicates the architecture's potential to alleviate the management troubles of the Internet

Understanding IP Anycast

In this paper we present the first detailed analysis of IP anycast as used in the anycasting of the root-servers. The main results of our study are: The anycasting of an IP prefix does not have any unfavorable interactions with the routing system. Hence, IP anycast offers very good affinity2 - this alleviates concerns regarding running connection oriented services on top of anycast. IP Anycast, by itself, does not offer proximity in terms of metrics such as latency. IP Anycast's backwards compatibility derives from the fact that it is transparent to existing routing protocols, but this transparency also implies that in many cases inter-domain routing, which was designed with unicast path-selection in mind, chooses anycast locations which are not close to the source. We also present deployment schemes 1the problems include scalability by the number of anycast groups, difficulty of deployment etc.; these have restricted the use of IP anycast to critical infrastructure services 2tendency of subsequent packets of a connection to be delivered to the same target that might allow anycast to achieve good latency based proximit

Harnessing Tunnels For Dirty-Slate Network Solutions

The tremendous success of the Internet has been both a boon and bane for networking research. On one hand, Internet growth has led to a plethora of problems and has prompted work towards next-generation network architectures. While very important, the success of the Internet has also meant that such cleanslate proposals are difficult to deploy. Thus, it is imperative that we find practically deployable dirty-slate solutions. In this thesis, we explore the possibility of tackling network problems in the existing framework through the use of tunnels. Tunneling involves encapsulating protocols in each other and we argue that this can serve as an enabler to the use of existing protocols in novel ways. We have found that, in many cases, such an approach can be used to address the root cause of a problem afflicting the network without necessitating protocol changes. Further, the increasing adoption of tunnels in mainstream networks augurs well for the deployability of such tunnels-based solutions. In this thesis, we focus on two important network problems and present tunnel-driven, dirty-slate solutions to address them. The first problem is routing scalability and includes the growing size of the Internet routing table. We note that routing table size is problematic since every router is required to maintain the entire table. Consequently, we propose ViAggre (Virtual Aggregation), a scalability technique that uses tunnels to ensure that individual routers only maintain a fraction of the global routing table. ViAggre is a "configurationonly" approach to shrinking the routing table on routers -- it does not require any changes to router software and routing protocols and can be deployed independently and autonomously by any ISP. We present the design, evaluation, implementation and deployment of ViAggre to show that it can offer substantial reduction in routing table size with negligible overhead. The second part of the thesis delves into IP Anycast. The route-to-closestserver abstraction offered by IP Anycast makes it an attractive primitive for service discovery. Further, the growth of P2P, overlay and multimedia applications presents new uses for IP Anycast. Unfortunately, IP Anycast suffers from serious limitations -- it is difficult to deploy, scales poorly and lacks important features like load balancing. As a result, its use has been limited to a few critical infrastructure services like DNS root servers. Further, despite such deployments, the performance of IP Anycast and its interaction with IP routing practices is not well understood. While these are valid concerns, we also believe that IP Anycast has compelling advantages. Motivated by these, we first conduct a detailed study of IP Anycast that equips us with the knowledge of how to maximize its potential. Building upon this, we present PIAS (Proxy IP Anycast Service), an anycast architecture that uses tunnels and proxies to decouple the anycast service from Internet routing. This allows PIAS to overcome IP Anycast's limitations while largely maintaining its strengths. We present simulations, measurement results, implementation and wide-area deployment details and describe how PIAS supports two important P2P and overlay applications

A Measurement-based Deployment Proposal for IP Anycast ABSTRACT

Despite its growing use in critical infrastructure services, the performance of IP(v4) Anycast and its interaction with IP routing practices is not well understood. In this paper, we present the results of a detailed measurement study of IP Anycast. Our study uses a two-pronged approach. First, using a variant of known latency estimation techniques, we measure the performance of current commercially operational IP Anycast deployments from a large number (&gt;20,000) of vantage points. Second, we deploy our own small-scale anycast service that allows us to perform controlled tests under different deployment and failure scenarios. To the best of our knowledge, our study represents the first large-scale evaluation of existing anycast services and the first evaluation of the behavior of IP Anycast under failure. We find that: (1) IP Anycast, if deployed in an ad-hoc manner, does not offer good latency-based proximity, (2) IP Anycast, if deployed in an ad-hoc manner, does not provide fast failover to clients, (3) IP Anycast typically offers good affinity to all clients with the exception of those that explicitly load balance traffic across multiple providers, (4) IP Anycast, by itself, is not effective in balancing client load across multiple sites. We thus propose and evaluate practical means by which anycast deployments can achieve good proximity, fast failover and control over the distribution of client load. Overall, our results suggest that an IP Anycast service, if deployed carefully, can offer good proximity, load balance, and failover behavior

ABSTRACT CONMan: Taking the Complexity out of Network Management

Network management is difficult, costly, and error prone, and this is becoming more so as network complexity increases. We argue that this is an outcome of two fundamental flaws in the existing architecture: the management plane depends on the data plane, and network device management interfaces are varied, complex, and constantly evolving. In this paper, we present Complexity Oblivious Network Management (CONMan), a network architecture in which the management plane does not depend on the data plane and all data plane protocols expose a simple generic management interface. This restricts the operational complexity of protocols to their implementation and allows the management plane to achieve high level policies in a structured fashion