Lecture 7 Software Defined Network - Control Plane

Programing Levels

• Level 1: South-Bound Interface
  • Program switches directly through OpenFlow
• Level 2: SDN Controller
  • Program with general-purpose language like C, Java, Python
• Level 3: Network Programming Languages
  • Program with domain-specific languages for networks
  • A Domain-Specific Language (DSL) is a programming language that offers, through appropriate notations and abstractions, expressive power focused on, and usually restricted to, a particular problem domain

Level 1: South-Bound Interface

Task:

make PC1 and PC2 reachable on layer 2

Use ovs-ofctl

Level 2: Controller

Modes

• Reactive vs. Proactive
• Centralized vs. Distributed

Reactive Control vs. Proactive

Reactive

• First packet of flow triggers controller to insert flow entries
• Efficient use of flow table
• Every flow incurs an additional flow setup time
• If control connection lost, switch has limited utility

Proactive

• Controller pre-populates flow table in switch (预处理)
• Requires aggregated rules
• Zero additional flow setup time
• Loss of control connection does not disrupt traffic

Centralized vs. Distributed Control

分布式系统的意义是将“压力”分担给多个controller，以防某一个controller出问题导致系统整体出问题

分布式系统并不意味着“隔离”，事实上，每个“区域级”的Controller包含“所有区域整体”的信息，因此不会存在“区域”之间的壁垒

NOX / POX Architecture

Topology Discovery

How to know the correct "path (topo)"? => use LLDP

def: Link Layer Discovery Protocol (LLDP)

A vendor neutral link layer protocol in the Internet Protocol Suite used by network devices for advertising(公布) their identity, capabilities and neighbors on an IEEE 802 LAN.

Learning Switch

Floodlight

• An open, free, OpenFlow controller in Java
• Slowly supporting OpenFlow v1.3

ONOS: Open Network Operating System

Architecture

Scale - Out

• An instance is responsible for maintaining a part of network graph.
• Control capacity can grow with network size or application need

Intent Framework

Translates intents into device instructions

• Compiler: produce more specific Intents given the environment
• Installer: transform Intents into device commands

OpenDaylight (ODL)

• Open-source project hosted by the Linux Foundation
  • Language: Java
  • License: Eclipse Public License 1.0
• Releases are named with chemical elements
  • Stable release: Chlorine (17) October 2022

Ryu

• Implemented with Python
• Open source, Apache 2.0 license
• Support various protocols for managing network devices, such as OpenFlow, Netconf, OF-config, etc.
  • For OpenFlow, Ryu supports fully 1.0, 1.2, 1.3, 1.4, 1.5 and Nicira Extensions

Network Programming Languages

Frenetic

• High-level language
  • On top of NOX
  • Query (询问式) language
  • Composition of forwarding policies
• Program snippet: simple repeater
  • When a switch joins the network, install two forwarding rules.
• Query language for traffic monitoring
  • Provide a declarative SQL-like query language for classifying and aggregating network traffic
• Program snippet（代码片段）: summarize the total volume of traffic arriving on physical port 2, grouped by destination host, every 60 seconds.

Other

• Pyretic
• Merlin
• ......