Clicks is a new software architecture for building flexible and configurable routers. A Click router is assembled from packet processing modules called elements. Individual elements implement simple router functions like packet classification, queuing, scheduling, and interfacing with network devices. A router configurable is a directed graph with elements at the vertices; packets flow along the edges of the graph. Several features make individual elements more powerful and complex configurations easier to write, including pull connections, which model packet flow drivn by transmitting hardware devices, and flow-based router context, which helps an element locate other interesting elements. Click configurations are modular and easy to extend. A standards-compliant Click IP router has 16 elements on its forwarding path; some of its elements are also useful in Ethernet switches and IP tunnelling configurations. Extending the IP router to support dropping policies, fairness among flows, or Differentiated Services simply requires adding a couple of element at the right place. On conventional PC hardware, the Click IP router achieves a maximum loss-free forwarding rate of 333,000 64-byte packets per second, demonstrating that Click's modular and flexible architecture is compatible with good performance.

The click modular router

Click is a new software architecture for building flexible and configurable routers. A Click router is assembled from packet processing modules called elements. Individual elements implement simple router functions like packet classification, queueing, scheduling, and interfacing with network devices. Complete configurations are built by connecting elements into a graph; packets flow along the graph's edges. Several features make individual elements more powerful and complex configurations easier to write, including pull processing, which models packet flow driven by transmitting interfaces, and flow-based router context, which helps an element locate other interesting elements.We demonstrate several working configurations, including an IP router and an Ethernet bridge. These configurations are modular---the IP router has 16 elements on the forwarding path---and easy to extend by adding additional elements, which we demonstrate with augmented configurations. On commodity PC hardware running Linux, the Click IP router can forward 64-byte packets at 73,000 packets per second, just 10% slower than Linux alone.

/pdf/the-click-modular-router-1nn6g98t3q.pdf

The Click modular router

http://rboutaba.cs.uwaterloo.ca/Papers/Journals/2010/Mosharaf10.pdf

A survey of network virtualization

Today's data networks are surprisingly fragile and difficult to manage. We argue that the root of these problems lies in the complexity of the control and management planes--the software and protocols coordinating network elements--and particularly the way the decision logic and the distributed-systems issues are inexorably intertwined. We advocate a complete refactoring of the functionality and propose three key principles--network-level objectives, network-wide views, and direct control--that we believe should underlie a new architecture. Following these principles, we identify an extreme design point that we call "4D," after the architecture's four planes: decision, dissemination, discovery, and data. The 4D architecture completely separates an AS's decision logic from pro-tocols that govern the interaction among network elements. The AS-level objectives are specified in the decision plane, and en-forced through direct configuration of the state that drives how the data plane forwards packets. In the 4D architecture, the routers and switches simply forward packets at the behest of the decision plane, and collect measurement data to aid the decision plane in controlling the network. Although 4D would involve substantial changes to today's control and management planes, the format of data packets does not need to change; this eases the deployment path for the 4D architecture, while still enabling substantial innovation in network control and management. We hope that exploring an extreme design point will help focus the attention of the research and industrial communities on this crucially important and intellectually challenging area.

/pdf/a-clean-slate-4d-approach-to-network-control-and-management-2ks1hufhx0.pdf

A clean slate 4D approach to network control and management

Component-based software structuring principles are now commonplace at the application level; but componentization is far less established when it comes to building low-level systems software. Although there have been pioneering efforts in applying componentization to systems-building, these efforts have tended to target specific application domains (e.g., embedded systems, operating systems, communications systems, programmable networking environments, or middleware platforms). They also tend to be targeted at specific deployment environments (e.g., standard personal computer (PC) environments, network processors, or microcontrollers). The disadvantage of this narrow targeting is that it fails to maximize the genericity and abstraction potential of the component approach. In this article, we argue for the benefits and feasibility of a generic yet tailorable approach to component-based systems-building that offers a uniform programming model that is applicable in a wide range of systems-oriented target domains and deployment environments. The component model, called OpenCom, is supported by a reflective runtime architecture that is itself built from components. After describing OpenCom and evaluating its performance and overhead characteristics, we present and evaluate two case studies of systems we have built using OpenCom technology, thus illustrating its benefits and its general applicability.

https://ftaiani.ouvaton.org/ressources/TOCS.pdf

A generic component model for building systems software

This paper argues that there is a need for routers to move from being closed, special-purpose network devices to being open, general-purpose computing/communication systems. The central challenge in making this shift is to simultaneously support increasing complex forwarding logic and high performance, while using commercial hardware components and open operating systems. This paper introduces the hardware and software architecture for such a general-purpose router. The architecture includes two key innovations. First, it better integrates the router's switching capacity and compute cycles. We expect this to result in significantly better scaling properties, and an order of magnitude improvement in performance for packets that require only minimum processing cycles. Second, the architecture supports a hierarchy of forwarding paths, ranging from fast/fixed paths implemented entirely in hardware to slow/programmable paths implemented entirely in software, but also including intermediate paths that exploit the improved integration of cycles and switching.

OS support for general-purpose routers

https://www.cs.princeton.edu/~scott/Papers/vera_cn_02.pdf

VERA: an extensible router architecture

This paper describes an operating system (OS) interface for active routers. This interface allows code loaded into active routers to access the router's memory, communication, and computational resources on behalf of different packet flows. In addition to motivating and describing the interface, the paper also reports our experiences implementing the interface in three different OS environments: Scout, the OSKit, and the esokernel.

/pdf/an-os-interface-for-active-routers-4xe3p5cy1e.pdf

An OS interface for active routers

Motivated by the demand for routers with new capabilities, researchers have been building extensible routers that aid in the design and development of network protocols and services. This paper evaluates and compares three such systems: (1) Princeton's Scout-based Extensible Router, (2) MIT's Click router, and (3) Washington University's Router Plugins. To provide a framework in which these three systems can be studied, the paper also presents a simple model of an extensible router based on four primitive objects: queues, classifiers, forwarders, and schedulers. By composing these primitive objects it is possible to model everything from a standard, best-effort IP router to an application-level proxy. The paper also briefly discusses the role that extensible routers play in the construction of active, programmable, and overlay networks.

A comparative study of extensible routers

This paper describes our effort to build an extensible router in support of active networks. Our work is driven by two goals: (1) supporting the injection of new functionality into a router, and (2) exploiting commercially available hardware. Our approach is a hierarchical architecture, in which packet flows traverse a range of processing/forwarding paths. This paper both presents the architecture, and describes our experiences implementing the architecture across a combination of general-purpose and network processors.

L. Peterson

Papers

OS support for general-purpose routers

VERA: an extensible router architecture

An OS interface for active routers

A comparative study of extensible routers

Extensible routers for active networks