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# Topics for the Seminar on Internet Routing, WS 2016/17

Topics for the seminar on Internet Routing (WS 2016/17).
Themen für das Seminar über Internet Routing (WS 2016/17).

## From .academy to .zone: An Analysis of the New TLD Land Rush

The com, net, and org TLDs contain roughly 150 million regis- tered domains, and domain registrants often have a difficult time finding a desirable and available name. In 2013, ICANN began delegation of a new wave of TLDs into the Domain Name Sys- tem with the goal of improving meaningful name choice for regis- trants. The new rollout resulted in over 500 new TLDs in the first 18 months, nearly tripling the number of TLDs. Previous rollouts of small numbers of new TLDs have resulted in a burst of defensive registrations as companies aggressively defend their trademarks to avoid consumer confusion. This paper analyzes the types of do- main registrations in the new TLDs to determine registrant behav- ior in the brave new world of naming abundance. We also exam- ine the cost structures and monetization models for the new TLDs to identify which registries are profitable. We gather DNS, Web, and WHOIS data for each new domain, and combine this with cost structure data from ICANN, the registries, and domain registrars to estimate the total cost of the new TLD program. We find that only 15% of domains in the new TLDs show characteristics consistent with primary registrations, while the rest are promotional, specu- lative, or defensive in nature; indeed, 16% of domains with NS records do not even resolve yet, and 32% are parked. Our financial analysis suggests only half of the registries have earned enough to cover their application fees, and 10% of current registries likely never will solely from registration revenue.

## Large-scale Measurements of Wireless Network Behavior

Meraki is a cloud-based network management system which provides centralized configuration, monitoring, and network troubleshooting tools across hundreds of thousands of sites worldwide. As part of its architecture, the Meraki system has built a database of time-series measurements of wireless link, client, and application behavior for monitoring and debugging purposes. This paper studies an anonymized subset of measurements, containing data from approximately ten thousand radio access points, tens of thousands of links, and 5.6 million clients from one-week periods in January 2014 and January 2015 to provide a deeper understanding of real-world network behavior. This paper observes the following phenomena: wireless network usage continues to grow quickly, driven most by growth in the number of devices connecting to each network. Intermediate link delivery rates are common indoors across a wide range of deployment environments. Typical access points share spectrum with dozens of nearby networks, but the presence of a network on a channel does not predict channel utilization. Most access points see 2.4 GHz channel utilization of 20% or more, with the top decile seeing greater than 50%, and the majority of the channel use contains decodable 802.11 headers.

## Detecting Malicious Activity with DNS Backscatter

Network-wide activity is when one computer (the originator) touches many others (the targets). Motives for activity may be benign (mailing lists, CDNs, and research scanning), malicious (spammers and scanners for security vulnerabilities), or perhaps indeterminate (ad trackers). Knowledge of malicious activity may help anticipate attacks, and understanding benign activity may set a baseline or characterize growth. This paper identifies DNS backscatter as a new source of information about network-wide activity. Backscatter is the reverse DNS queries caused when targets or middleboxes automatically look up the domain name of the originator. Queries are visible to the authoritative DNS servers that handle reverse DNS. While the fraction of backscatter they see depends on the server's location in the DNS hierarchy, we show that activity that touches many targets appear even in sampled observations. We use information about the queriers to classify originator activity using machine-learning. Our algorithm has reasonable precision (70-80%) as shown by data from three different organizations operating DNS servers at the root or country-level. Using this technique we examine nine months of activity from one authority to identify trends in scanning, identifying bursts corresponding to Heartbleed and broad and continuous scanning of ssh.

## Examining How the Great Firewall Discovers Hidden Circumvention Servers

Recently, the operators of the national censorship infrastructure of China began to employ "active probing" to detect and block the use of privacy tools. This probing works by passively monitoring the network for suspicious traffic, then actively probing the corresponding servers, and blocking any that are determined to run circumvention servers such as Tor.

We draw upon multiple forms of measurements, some spanning years, to illuminate the nature of this probing. We identify the different types of probing, develop fingerprinting techniques to infer the physical structure of the system, localize the sensors that trigger probing---showing that they differ from the "Great Firewall" infrastructure---and assess probing's efficacy in blocking different versions of Tor. We conclude with a discussion of the implications for designing circumvention servers that resist such probing mechanisms.

## Jupiter Rising: A Decade of Clos Topologies and Centralized Control in Google’s Datacenter Network

We present our approach for overcoming the cost, operational complexity, and limited scale endemic to datacenter networks a decade ago. Three themes unify the five generations of datacenter networks detailed in this paper. First, multi-stage Clos topologies built from commodity switch silicon can support cost-effective deployment of building-scale networks. Second, much of the general, but complex, decentralized network routing and management protocols supporting arbitrary deployment scenarios were overkill for single-operator, pre-planned datacenter networks. We built a centralized control mechanism based on a global configuration pushed to all datacenter switches. Third, modular hardware design coupled with simple, robust software allowed our design to also support inter-cluster and wide-area networks. Our datacenter networks run at dozens of sites across the planet, scaling in capacity by 100x over ten years to more than 1Pbps of bisection bandwidth.

## Inside the Social Network’s (Datacenter) Network

Large cloud service providers have invested in increasingly larger datacenters to house the computing infrastructure required to support their services. Accordingly, researchers and industry practitioners alike have focused a great deal of effort designing network fabrics to efficiently interconnect and manage the traffic within these datacenters in performant yet efficient fashions. Unfortunately, datacenter operators are generally reticent to share the actual requirements of their applications, making it challenging to evaluate the practicality of any particular design.

Moreover, the limited large-scale workload information available in the literature has, for better or worse, heretofore largely been provided by a single datacenter operator whose use cases may not be widespread. In this work, we report upon the network traffic observed in some of Facebook's datacenters. While Facebook operates a number of traditional datacenter services like Hadoop, its core Web service and supporting cache infrastructure exhibit a number of behaviors that contrast with those reported in the literature. We report on the contrasting locality, stability, and predictability of network traffic in Facebook's datacenters, and comment on their implications for network architecture, traffic engineering, and switch design.

## BlindBox: Deep Packet Inspection over Encrypted Traffic

Many network middleboxes perform deep packet inspection (DPI), a set of useful tasks which examine packet payloads. These tasks include intrusion detection (IDS), exfiltration detection, and parental filtering. However, a long-standing issue is that once packets are sent over HTTPS, middleboxes can no longer accomplish their tasks because the payloads are encrypted. Hence, one is faced with the choice of only one of two desirable properties: the functionality of middleboxes and the privacy of encryption. We propose BlindBox, the first system that simultaneously provides {\em both} of these properties. The approach of BlindBox is to perform the deep-packet inspection {\em directly on the encrypted traffic. BlindBox realizes this approach through a new protocol and new encryption schemes.

We demonstrate that BlindBox enables applications such as IDS, exfiltration detection and parental filtering, and supports real rulesets from both open-source and industrial DPI systems. We implemented BlindBox and showed that it is practical for settings with long-lived HTTPS connections. Moreover, its core encryption scheme is 3-6 orders of magnitude faster than existing relevant cryptographic schemes.

## Don’t Mind the Gap: Bridging Network-wide Objectives and Device-level Confgurations

We develop Propane, a language and compiler to help network operators with a challenging, error-prone task -- bridging the gap between network-wide routing objectives and low-level configurations of devices that run complex, distributed protocols. The language allows operators to specify their objectives naturally, using high-level constraints on both the shape and relative preference of traffic paths. The compiler automatically translates these specifications to router-level BGP configurations, using an effective intermediate representation that compactly encodes the flow of routing information along policy-compliant paths. It guarantees that the compiled configurations correctly implement the specified policy under all possible combinations of failures. We show that Propane can effectively express the policies of datacenter and backbone networks of a large cloud provider; and despite its strong guarantees, our compiler scales to networks with hundreds or thousands of routers.

## Inter-Technology Backscatter: Towards Internet Connectivity for Implanted Devices

We introduce inter-technology backscatter, a novel approach that transforms wireless transmissions from one technology to another, on the air. Specifically, we show for the first time that Bluetooth transmissions can be used to create Wi-Fi and ZigBee-compatible signals using backscatter communication. Since Bluetooth, Wi-Fi and ZigBee radios are widely available, this approach enables a backscatter design that works using only commodity devices.

We build prototype backscatter hardware using an FPGA and experiment with various Wi-Fi, Bluetooth and ZigBee devices. Our experiments show we can create 2--11~Mbps Wi-Fi standards-compliant signals by backscattering Bluetooth transmissions. To show the generality of our approach, we also demonstrate generation of standards-complaint ZigBee signals by backscattering Bluetooth transmissions. Finally, we build proof-of-concepts for previously infeasible applications including the first contact lens form-factor antenna prototype and an implantable neural recording interface that communicate directly with commodity devices such as smartphones and watches, thus enabling the vision of Internet connected implanted devices.

## End-User Mapping: Next Generation Request Routing for Content Delivery

Content Delivery Networks (CDNs) deliver much of the world's web, video, and application content on the Internet today. A key component of a CDN is the mapping system that uses the DNS protocol to route each client's request to a proximal'' server that serves the requested content. While traditional mapping systems identify a client using the IP of its name server, we describe our experience in building and rolling-out a novel system called end-user mapping that identifies the client directly by using a prefix of the client's IP address. Using measurements from Akamai's production network during the roll-out, we show that end-user mapping provides significant performance benefits for clients who use public resolvers, including an eight-fold decrease in mapping distance, a two-fold decrease in RTT and content download time, and a 30% improvement in the time-to-first byte. We also quantify the scaling challenges in implementing end-user mapping such as the 8-fold increase in DNS queries. Finally, we show that a CDN with a larger number of deployment locations is likely to benefit more from end-user mapping than a CDN with a smaller number of deployments.

## A Distributed and Robust SDN Control Plane for Transactional Network Updates

Software-defined networking (SDN) is a novel paradigm that outsources the control of programmable network switches to a set of software controllers. The most fundamental task of these controllers is the correct implementation of the network policy, i.e., the intended network behavior. In essence, such a policy specifies the rules by which packets must be forwarded across the network.

This paper studies a distributed SDN control plane that enables concurrent and robust policy implementation. We introduce a formal model describing the interaction between the data plane and a distributed control plane (consisting of a collection of fault- prone controllers). Then we formulate the problem of consistent composition of concurrent network policy updates (termed the CPC Problem). To anticipate scenarios in which some conflicting policy updates must be rejected, we enable the composition via a natural transactional interface with all-or-nothing semantics.

We show that the ability of an f-resilient distributed control plane to process concurrent policy updates depends on the tag complexity, i.e., the number of policy labels (a.k.a. tags) available to the controllers, and describe a CPC protocol with optimal tag complexity f + 2.

## InterTubes: A Study of the US Long-haul Fiber-optic Infrastructure

The complexity and enormous costs of installing new long-haul fiber-optic infrastructure has led to a significant amount of infrastructure sharing in previously installed conduits. In this paper, we study the characteristics and implications of infrastructure sharing by analyzing the long-haul fiber-optic network in the US. We start by using fiber maps provided by tier-1 ISPs and major cable providers to construct a map of the long-haul US fiber-optic infrastructure. We also rely on previously under-utilized data sources in the form of public records from federal, state, and municipal agencies to improve the fidelity of our map. We quantify the resulting map's connectivity characteristics and confirm a clear correspondence between long-haul fiber-optic, roadway, and railway infrastructures. Next, we examine the prevalence of high-risk links by mapping end-to-end paths resulting from large-scale traceroute campaigns onto our fiber-optic infrastructure map. We show how both risk and latency (i.e., propagation delay) can be reduced by deploying new links along previously unused transportation corridors and rights-of-way. In particular, focusing on a subset of high-risk links is sufficient to improve the overall robustness of the network to failures. Finally, we discuss the implications of our findings on issues related to performance, net neutrality, and policy decision-making.

## R2C2: A Network Stack for Rack-scale Computers

Rack-scale computers, comprising a large number of micro-servers connected by a direct-connect topology, are expected to replace servers as the building block in data centers. We focus on the problem of routing and congestion control across the rack's network, and find that high path diversity in rack topologies, in combination with workload diversity across it, means that traditional solutions are inadequate. We introduce R2C2, a network stack for rack-scale computers that provides flexible and efficient routing and congestion control. R2C2 leverages the fact that the scale of rack topologies allows for low-overhead broadcasting to ensure that all nodes in the rack are aware of all network flows. We thus achieve rate-based congestion control without any probing; each node independently determines the sending rate for its flows while respecting the provider's allocation policies. For routing, nodes dynamically choose the routing protocol for each flow in order to maximize overall utility. Through a prototype deployed across a rack emulation platform and a packet-level simulator, we show that R2C2 achieves very low queuing and high throughput for diverse and bursty workloads, and that routing flexibility can provide significant throughput gains.

## Enabling End-host Network Functions

Many network functions executed in modern datacenters, e.g., load balancing, application-level QoS, and congestion control, exhibit three common properties at the data-plane: they need to access and modify state, to perform computations, and to access application semantics  this is critical since many network functions are best expressed in terms of application-level messages. In this paper, we argue that the end hosts are a natural enforcement point for these functions and we present Eden, an architecture for implementing network functions at datacenter end hosts with minimal network support. Eden comprises three components, a centralized controller, an enclave at each end host, and Eden-compliant applications called stages. To implement network functions, the controller configures stages to classify their data into messages and the enclaves to apply action functions based on a packet's class. Our Eden prototype includes enclaves implemented both in the OS kernel and on programmable NICs. Through case studies, we show how application-level classification and the ability to run actual programs on the data-path allows Eden to efficiently support a broad range of network functions at the network's edge.

## Condor: Better Topologies Through Declarative Design

The design space for large, multipath datacenter networks is large and complex, and no one design fits all purposes. Network architects must trade off many criteria to design cost-effective, reliable, and maintainable networks, and typically cannot explore much of the design space. We present Condor, our approach to enabling a rapid, efficient design cycle. Condor allows architects to express their requirements as constraints via a Topology Description Language (TDL), rather than having to directly specify network structures. Condor then uses constraint-based synthesis to rapidly generate candidate topologies, which can be analyzed against multiple criteria. We show that TDL supports concise descriptions of topologies such as fat-trees, BCube, and DCell; that we can generate known and novel variants of fat-trees with simple changes to a TDL file; and that we can synthesize large topologies in tens of seconds. We also show that Condor supports the daunting task of designing multi-phase network expansions that can be carried out on live networks.

## Poptrie: A Compressed Trie with Population Count for Fast and Scalable Software IP Routing Table Lookup

Internet of Things leads to routing table explosion. An inexpensive approach for IP routing table lookup is required against ever growing size of the Internet. We contribute by a fast and scalable software routing lookup algorithm based on a multiway trie, called Poptrie. Named after our approach to traversing the tree, it leverages the population count instruction on bit-vector indices for the descendant nodes to compress the data structure within the CPU cache. Poptrie outperforms the state-of-the-art technologies, Tree BitMap, DXR and SAIL, in all of the evaluations using random and real destination queries on 35 routing tables, including the real global tier-1 ISP's full-route routing table. Poptrie peaks between 174 and over 240 Million lookups per second (Mlps) with a single core and tables with 500800k routes, consistently 4578% faster than all competing algorithms in all the tests we ran. We provide the comprehensive performance evaluation, remarkably with the CPU cycle analysis. This paper shows the suitability of Poptrie in the future Internet including IPv6, where a larger route table is expected with longer prefixes.

## Central Control Over Distributed Routing

Centralizing routing decisions offers tremendous flexibility, but sacrifices the robustness of distributed protocols. In this paper, we present Fibbing, an architecture that achieves both flexibility and robustness through central control over distributed routing. Fibbing introduces fake nodes and links into an underlying link-state routing protocol, so that routers compute their own forwarding tables based on the augmented topology. Fibbing is expressive, and readily supports flexible load balancing, traffic engineering, and backup routes. Based on high-level forwarding requirements, the Fibbing controller computes a compact augmented topology and injects the fake components through standard routing-protocol messages. Fibbing works with any un-modified routers speaking OSPF. Our experiments also show that it can scale to large networks with many forwarding requirements, introduces minimal overhead, and quickly reacts to network and controller failures.

## Beacon-Based Routing Optimization in Data-Gathering Wireless Sensor Networks

In this paper we focus on beacon-based routing optimization of data-gathering wireless sensor networks. Such a network consists of a sink node and a number of scattered sensor nodes which send data packets back to the sink in a multihop fashion. Usually the routing messages, denoted as “beacon”, are initiated by the sink and spread out the whole network by flooding or gossiping. We believe that the mechanism of selecting upstream node as relay has great impact to the packet delivery performance. In this work several beacon rebroadcasting mechanism are inspected and the data packet delivery performance of them are compared by simulations. The simulation result shows that current Zigbee tree-based routing has great flaw in large scale networks. Based on the comparison of the results we propose an optimal link-state beacon-based routing (OLSBR) which shows that parent selection by link state can greatly improve the packet delivery performance.

## Hypercube-Based Multipath Social Feature Routing in Human Contact Networks

Most routing protocols for delay tolerant networks resort to the sufficient state information, including trajectory and contact information, to ensure routing efficiency. However, state information tends to be dynamic and hard to obtain without a global and/or long-term collection process. In this paper, we use the internal social features of each node in the network to perform the routing process. In this way, feature-based routing converts a routing problem in a highly mobile and unstructured contact space to a static and structured feature space. This approach is motivated from several human contact networks, such as the Infocom 2006 trace and MIT reality mining data, where people contact each other more frequently if they have more social features in common. Our approach includes two unique processes: social feature extraction and multipath routing. In social feature extraction, we use entropy to extract the m most informative social features to create a feature space (F-space): (F1, F2,..., Fm), where Fi corresponds to a feature. The routing method then becomes a hypercube-based feature matching process, where the routing process is a step-by-step feature difference resolving process. We offer two special multipath routing schemes: node-disjoint-based routing and delegation-based routing. Extensive simulations on both real and synthetic traces are conducted in comparison with several existing approaches, including spray-and-wait routing, spray-and-focus routing, and social-aware routing based on betweenness centrality and similarity. In addition, the effectiveness of multipath routing is evaluated and compared to that of single-path routing.

## An Empirical Reexamination of Global DNS Behavior

The performance and operational characteristics of the DNS protocol are of deep interest to the research and network operations community. In this paper, we present measurement results from a unique dataset containing more than 26 billion DNS query-response pairs collected from more than 600 globally distributed recursive DNS resolvers. We use this dataset to reaffirm findings in published work and notice some significant differences that could be attributed both to the evolving nature of DNS traffic and to our differing perspective. For example, we find that although characteristics of DNS traffic vary greatly across networks, the resolvers within an organization tend to exhibit similar behavior. We further find that more than 50% of DNS queries issued to root servers do not return successful answers, and that the primary cause of lookup failures at root servers is malformed queries with invalid TLDs. Furthermore, we propose a novel approach that detects malicious domain groups using temporal correlation in DNS queries. Our approach requires no comprehensive labeled training set, which can be difficult to build in practice. Instead, it uses a known malicious domain as anchor, and identifies the set of previously unknown malicious domains that are related to the anchor domain. Experimental results illustrate the viability of this approach, i.e. , we attain a true positive rate of more than 96%, and each malicious anchor domain results in a malware domain group with more than 53 previously unknown malicious domains on average.

## Cell vs. WiFi: On the Performance of Metro Area Mobile Connections

Cellular and 802.11 WiFi are compelling options for mobile Internet connectivity. The goal of our work is to understand the performance afforded by each of these technologies in diverse environments and use conditions. In this paper, we compare and contrast cellular and WiFi performance using crowd-sourced data from Speedtest.net. Our study considers spatio-temporal performance (upload/download throughput and latency) using over 3 million user-initiated tests from iOS and Android apps in 15 different metro areas collected over a 15 week period. Our basic performance comparisons show that (i) WiFi provides better absolute download/upload throughput, and a higher degree of consistency in performance; (ii) WiFi networks generally deliver lower absolute latency, but the consistency in latency is often better with cellular access; (iii) throughput and latency vary widely depending on the particular access type e.g., HSPA, EVDO, LTE, WiFi, etc.) and service provider. More broadly, our results show that performance consistency for cellular and WiFi is much lower than has been reported for wired broadband. Temporal analysis shows that average performance for cell and WiFi varies with time of day, with the best performance for large metro areas coming at non-peak hours. Spatial analysis shows that performance is highly variable across metro areas, but that there are subregions that offer consistently better performance for cell or WiFi. Comparisons between metro areas show that larger areas provide higher throughput and lower latency than smaller metro areas, suggesting where ISPs have focused their deployment efforts. Finally, our analysis reveals diverse performance characteristics resulting from the rollout of new cell access technologies and service differences among local providers.

## Bobtail: Avoiding Long Tails in the Cloud

Highly modular data center applications such as Bing, Facebook, and Amazon’s retail platform are known to be susceptible to long tails in response times. Services such as Amazon’s EC2 have proven attractive platforms for building similar applications. Unfortunately, virtualization used in such platforms exacerbates the long tail problem by factors of two to four. Surprisingly, we find that poor response times in EC2 are a property of nodes rather than the network, and that this property of nodes is both pervasive throughout EC2 and persistent over time. The root cause of this problem is co-scheduling of CPU-bound and latency-sensitive tasks. We leverage these observations in Bobtail, a system that proactively detects and avoids these bad neighboring VMs without significantly penalizing node instantiation. With Bobtail, common communication patterns benefit from reductions of up to 40% in 99.9th percentile response times.

## CONGA: distributed congestion-aware load balancing for datacenters

We present the design, implementation, and evaluation of CONGA, a network-based distributed congestion-aware load balancing mechanism for datacenters. CONGA exploits recent trends including the use of regular Clos topologies and overlays for network virtualization. It splits TCP flows into flowlets, estimates real-time congestion on fabric paths, and allocates flowlets to paths based on feedback from remote switches. This enables CONGA to efficiently balance load and seamlessly handle asymmetry, without requiring any TCP modifications. CONGA has been implemented in custom ASICs as part of a new datacenter fabric. In testbed experiments, CONGA has 5x better flow completion times than ECMP even with a single link failure and achieves 2-8x better throughput than MPTCP in Incast scenarios. Further, the Price of Anarchy for CONGA is provably small in Leaf-Spine topologies; hence CONGA is nearly as effective as a centralized scheduler while being able to react to congestion in microseconds. Our main thesis is that datacenter fabric load balancing is best done in the network, and requires global schemes such as CONGA to handle asymmetry.

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## Internet Routing (Se,WS 16/17)

Seminar

Lecturer: Anja Feldmann

Period:
from 17.10.2016

Location: MAR 4.033