2.2 Comparison of SDN and traditional network architectures

Software-Defined Networking (SDN) flips traditional networking on its head. It separates the brains from the brawn, putting network smarts in a central controller while switches focus on moving packets. This setup makes networks more flexible and easier to manage.

SDN's secret sauce is flow-based forwarding and programmability. Instead of treating each packet separately, it groups traffic into flows. This approach, combined with open APIs, lets you change how the network behaves on the fly to meet changing needs.

Control and Data Plane

Centralized Control and Separation

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• Control plane centralization moves network intelligence to a central controller
• Centralized controller manages network-wide policies and configurations
• Data plane separation isolates packet forwarding functions from control logic
• Separation enables independent scaling of control and forwarding resources
• Programmable interfaces allow dynamic modification of network behavior
• Software-defined networking (SDN) controllers use APIs to program network devices

Flow-Based Forwarding and Network Programmability

• Flow-based forwarding treats traffic as flows rather than individual packets
• Flows defined by matching criteria (source/destination IP, port numbers, protocols)
• SDN controllers install flow rules on network devices
• Flow rules determine how to handle matching packets (forward, drop, modify)
• Programmable interfaces enable real-time network reconfiguration
• Network functions can be dynamically adjusted based on application requirements
• Enables more flexible and efficient resource allocation compared to traditional networks

Network Abstraction and Virtualization

Network Abstraction Layers

• Network abstraction simplifies complex network topologies and functions
• Presents a logical view of the network to applications and services
• Abstracts physical infrastructure details from higher-level network operations
• Enables easier management and configuration of large-scale networks
• Southbound APIs facilitate communication between SDN controller and network devices
• OpenFlow protocol serves as a common southbound API for programming switches
• Northbound APIs expose network capabilities to applications and orchestration systems
• REST APIs often used as northbound interfaces for application integration

Network Virtualization Techniques

• Network virtualization creates multiple logical networks on shared physical infrastructure
• Allows isolation of network resources for different tenants or applications
• Supports creation of virtual switches, routers, and other network functions
• Network overlays (VXLAN, NVGRE) enable extending Layer 2 networks across Layer 3 boundaries
• Virtual network functions (VNFs) replace dedicated hardware appliances with software-based services
• Network function virtualization (NFV) deploys VNFs on commodity hardware
• Enables rapid provisioning and scaling of network services

Management and Standards

Open Standards and Interoperability

• Open standards promote interoperability between different vendors' equipment
• OpenFlow protocol standardizes communication between SDN controllers and switches
• Open Networking Foundation (ONF) develops SDN standards and promotes adoption
• OpenDaylight provides an open-source SDN controller platform
• P4 language enables programming of data plane behavior in network devices
• Open vSwitch offers a programmable virtual switch for SDN environments

Policy-Based Network Management

• Policy-based management allows high-level definition of network behavior
• Policies translate business requirements into network configurations
• SDN controllers enforce policies across the network infrastructure
• Intent-based networking uses natural language to define desired network outcomes
• Network automation tools (Ansible, Puppet) facilitate policy deployment at scale
• Closed-loop automation enables self-healing and self-optimizing networks
• Analytics and telemetry data inform policy decisions and network optimization