Overview

In the last few years, a few emerging technologies and concepts have disrupted how network equipment is designed, and how networks are built and operated: hardware commoditization and disaggregation of software from hardware and of software itself, extensive use of open source (Linux), Software Defined Networking (SDN), Network Functions Virtualization (NFV) and DevOps.

Operators need to deploy new services in order to grow their revenue, and time to market, thus rapid network deployment, is crucial. Rapid deployment is significantly helped by automation and programmability. In this environment, CLI is no longer the norm: since it cannot be easily as a programmatic interface, the CLI is not suitable for automation. Network engineers have adapted to an industry where the only constant is change, by combining Development and Operations into DevOps: a practice that aims to unify software development and operations. DevOps combines programming and network administration, and allows rapid prototyping and network build, generally using the Python programming language.

OpenSwitch (OPX) – a network operating system (NOS) - was one the early adopters of these concepts and technologies. Architected using OpenSwitch (OPX) – an open source network operating system (NOS) and ecosystem - is an early adopter of emerging concepts and technologies (hardware and software disaggregation, use of open source, SDN, NFV and DevOps) which disrupt how networks and networking equipment are built and operated. Designed using a standard Debian Linux distribution with an unmodified Linux kernel, OpenSwitch provides a programmable high-level abstraction of network components, such a as switching ASICs (Network Processors) and optical transceivers. Architected as a scalable, cloud-ready, agile solution, the open source OpenSwitch software implements a flexible infrastructure to enable both network operators and vendors to rapidly on-board open source Networking OS applications. OpenSwitch provides a YANG based programmatic interface, that can be accessed using Python, thus providing an ideal DevOps environmentan environment well-suited for DevOps.

OpenSwitch Features

OpenSwitch (or OPX) provides an abstraction of hardware network devices in a Linux OS environment, and . It has been designed from its inception in order to support the newest technologies and concepts in the networking industry:

• Software In OPX, software is disaggregated from hardware, and software components are disaggregated software components.as well.

  • OpenSwitch can be deployed on diverse networking hardware  – only the low-level software layers SAI (Switch Abstraction Interface) and System Device Interface (SDI) are hardware specific and may need to be adapted.  A minimum requirement is for hardware to be build around a standard ASIC, with Layer 2 switching, Layer 3 routing, ACL and QoS functionality.

• Makes extensive use of Uses standard open source software, such as the for instance:
  • ONIE installer
  and an unmodified Linux kernel based on the Debian distribution.
  • Linux Debian distribution with an unmodified Linux kernel 
  • Switch Abstraction Interface (SAI) defined in Open Compute Project for interfacing with the networking ASIC.
• Integrates Linux native APIs with networking ASIC functionality. In OpenSwitch, networking features are also accessible using the Linux standard API’s (“netlink”). Thus standard open source network packages (such as FRR) can be installed and supported in binary format.
• OPX supports containers and NFV. The Docker container environment (Docker CE), or any other Linux container environment,  can be installed on any OpenSwitch device - in this environment, users can deploy their own containerized virtualized network functions (VNF).
• Supports programmability, automation and DevOps:
  • A robust and flexible programmatic
  API
  • interface – namely the Control Plane Services (CPS). The API is defined using YANG models and is accessible through Python (and C/C++). 
  • The
  YANG models are converted into a CPS binary encoding.Use of the open source Switch Abstraction Interface (SAI) defined in Open Compute Project for interfacing with the switching ASIC.
  • availability of a programmatic interface (CPS API/YANG models) allows integration with external orchestrators and SDN controllers
• Provides a rich set of networking features including full access to the networking ASIC ACL and QoS functionality using CPS API/YANG models.Integrates Linux native APIs to ASIC functionality - networking features are also accessible the Linux standard API’s (“netlink”). Thus standard open source network packages (such as FRR) can be installed and supported in binary format.

OpenSwitch provides support for:

• L2 protocols: LLDP, LACP (link aggregation interfaces), 802.1q (VLAN interfaces), STP and bridge interfaces
• L3 protocols (e.g. BGP),
• QoS,
• ACL
• ACL and QoS network functions (through CPS / YANG API's)
• Instrumentation: sFlow, telemetry

...

• Orchestration and management

Programmability and

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Automation 

OpenSwitch supports a rich ecosystem for automated deployment, for instance:

• Ansible – various modules are already defined for OPXOpenSwitch
• Zero-touch provisioning (ZTP) allows provisioning of new OpenSwitch ONIE-enabled devices a network automatically, without manual intervention
• Puppet

North-Bound Programmatic Interfaces

The OpenSwitch CPS

...

programmatic interface is defined using YANG models, and in combination with Python, provides support for programming the network

...

functionality, automation and DevOps. While the CPS API is the native OpenSwitch API, a REST API can be added as well, by mapping REST requests to CPS.

In addition, a set of OpenSwitch specific commands are available and can be invoked from a Linux shell (e.g. display the current software version, hardware inventory etc.).

Container Support

Since OpenSwitch is developed using a standard Debian distribution, the Docker container environment (Docker CE), or any other Linux container environment,  can be installed on any OpenSwitch device.   

OpenSwitch Architecture

The figure below illustrates the main areas of the OpenSwitch architecture:

• OPX Base
• OPX Applications

OPX Base

The key components of OPX Base are:

...

• Manages the high level abstraction of the switching ASIC
• NAS manages the middleware middle-ware that associates physical ports to Linux interfaces, and adapts Linux native API calls (e.g. netlink) to the switching ASIC

...

• Object centric framework
• Mediates between application software components and the platform
• Provides a pub/sub model and set/get/delete/create
• Provides a the framework for defining YANG modeled API APIs - with Python and C/C++ bindings. In OPX, YANG models are used with an efficient CPS binary encoding.

SAI – Switch Abstraction Interface

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A variety of open source or vendor specific applications are supported and have been tested with Open Switchand can be deployed with OpenSwitch:

• FRR - BGP
• AAA: TACACS+, RADIUS
• Telemetry: Broadview, Packet Trakker 
• Inocybe OpenDaylight integration
• NetSNMP
• Puppet
• Chef

It should be noted that these applications are not pre-installed with OpenSwitch. In a "disaggregated" model, users select applications to install them based on the requirements of a given network deployment.

In general, since OpenSwitch is based on Linux Debian distribution with an unmodified kernel, any Debian binary application can be installed and executed on OpenSwitch devices.

Hardware Simulation

OPX software supports hardware virtualization (or simulation). Software simulation of basic hardware functionality is also provided (simulated simulation specific SAI and SDI components), and the higher layer software functionality can be developed and tested on generic PC/server hardware. OPX hardware simulation can be executed in under Virtual Box, or GNS3 / QEmu etc.