Lesson 7: SDN (Part 1) Flashcards
(41 cards)
What are the three phases in the history of SDN?
- Active Networks
- Control and Data Plane Separation
- OpenFlow API and Network Operating Systems
What is the main goal of active networks?
To open up network control by allowing programmable functionality inside the network.
What are the two programming models of active networking?
- Capsule model – code in data packets (in-band)
- Programmable router/switch model – code delivered out-of-band
What were some technology push factors for active networks?
- Cheaper computation
- Safer and portable programming languages (e.g., Java)
- DARPA funding
- Rapid code compilation and formal methods
What were some use pull factors for active networks?
- Delayed deployment of new services
- Demand for application-specific control
- Need for experimentation
- Unified control over middleboxes
What major contributions did active networks make to SDN?
- Programmability in the network
- Network virtualization
- Early vision for unified middlebox architecture
Why did active networking decline?
- Too ambitious
- Required Java coding by users
- Lacked emphasis on performance and security
- Didn’t solve short-term problems
What problem did the control/data plane separation address?
Tight coupling of control and data planes made networks hard to manage and evolve
What were the key innovations of the control/data plane separation phase?
- Open interface between control and data planes
- Logically centralized control
What were some technology push factors during the control/data plane separation phase?
- Hardware-based forwarding
- Complex ISP demands
- Powerful servers
- Open-source routing software
What were some use pull factors during the control/data plane separation phase?
- Traffic-aware path selection
- Minimal disruption during updates
- Attack traffic filtering
- Customer control
- VPN services
How did the control/data plane separation differ from active networking?
It focused on operators, control-plane programmability, and network-wide visibility rather than end-user programmability
What challenges did early SDN efforts face regarding control/data separation?
- Skepticism about controller failure
- Routers having limited network views
What is OpenFlow and when was it developed?
- A protocol enabling control over switches for experimentation and deployment
- Developed around 2007–2010
How does an OpenFlow switch work?
- Matches packets against a table of rules (pattern, actions, counters, priority)
- Executes the highest-priority match
Why was OpenFlow more successful than earlier efforts?
- Built on existing hardware
- Easy adoption (firmware upgrade)
- Aligned with industry capabilities
What were the use pull factors for OpenFlow adoption?
- Large-scale experimentation
- Data center traffic control
- Shift toward software-defined control
- Market entry for smaller vendors
What contributions did OpenFlow make to SDN?
- Generalized network devices
- Vision of a network operating system
- Advanced distributed state management
What is the function of the control plane?
Contains the logic that controls packet forwarding (e.g., routing protocols, middlebox config)
What is the function of the data plane?
Performs actual packet forwarding based on rules from the control plane
Why separate the control plane from the data plane?
- Enables independent development
- Supports high-level software control
- Easier debugging and innovation
How does SDN benefit data centers?
Makes managing large networks with many servers/VMs easier
How does SDN improve routing?
Provides finer control over routing decisions, unlike rigid BGP protocols
How can SDN enhance enterprise network security?
Allows strategic blocking of attacks (e.g., DDoS) using programmable control
