Lesson 7: SDN Part 1 Flashcards
What spurred the development of SDN?
- Diversity of Equipment - each piece of equipment within computer networks causes complexity due to software that adheres to different protocols for each equipment.
- Proprietary Technology - equipment typically has closed and proprietary software which means that configuration interfaces vary between them making centralized management difficult.
How do SDNs divide networks to ease management and speed up innovation?
SDNs divide networks into two planes: Control Plane and Data Plane.
What are the three phases in the history of SDNs?
- Phase 1: Active Networks (mid 1990s to early 2000s)
- Phase 2: Control & Data Plane Separation (~2001 to 2007)
- Phase 3: OpenFlow API and Network Operating Systems (~2007 to 2010)
Summarize the first phase of SDN history (Active Networks - mid 1990s to early 2000s), high level overview.
Driven by the idea of more dynamic, customizable environments, making the network infrastructure more programmable and flexible.
Summarize the technology pushes for the first phase of SDN history (Active Networks - mid 1990s to early 2000s).
- Reduction in computation cost allowing more processing within the network
- Advancement in programming languages
- Advancement in rapid code compilation and formal methods
- Funding from agencies such as DARPA
What two types of programming models were in the first phase of SDN history (Active Networks - mid 1990s to early 2000s) and how do they differ?
Capsule Model - carried in-band in data packets.
Programmable Router/Switch Model - established by out-of-band mechanisms.
These models differ based on where the code to execute at the nodes was carried.
Summarize the use case pulls for the first phase of SDN history (Active Networks - mid 1990s to early 2000s).
- Network Service Providers frustration concerning the long development time and deployment time of new network services.
- Researchers interest in having a network that would support large-scale experimentation.
- Third party interests to add value by implementing control at a more individualistic nature. This meant dynamically meeting the needs of specific applications or network conditions.
- Unified control over middleboxes; envisioned unified control that could replace individually managing these boxes.
Summarize the major contributions for the first phase of SDN history (Active Networks - mid 1990s to early 2000s).
- Programmable functions in the network to lower barrier to innovation (specifically programmability within the data plane).
- Network virtualization and the ability to demultiplex to software programs based on packet headers (provided a framework that described a platform that would support experimentation with different programming models lending to network virtualization).
- The vision of a unified architecture for middle box orchestration.
What was the biggest downfall of first phase of SDN history (Active Networks - mid 1990s to early 2000s)?
Too ambitious - required end users to write Java code (too far removed from the reality at that time, hence not trusted to be safe).
Users more concerned about performance and security, which Active Networks not focused on.
Summarize the second phase of SDN history (Control & Data Plane Separation - ~2001 to 2007), high level overview.
Driven by the desire for better network-management functions such as control over paths to deliver traffic (traffic engineering), push to decouple the control and data planes.
Summarize the technology pushes for the second phase of SDN history (Control & Data Plane Separation - ~2001 to 2007) and what two innovations did these inspire?
- Higher link speeds in backbone networks led vendors to implement packet forwarding directly in the hardware, thus separating it from the control-plane software.
- ISPs found it hard to meet the increasing demands for greater reliability and new services (such as virtual private networks), and struggled to manage the increased size and scope of their networks.
- Servers had substantially more memory and processing resources than those deployed one/two years prior, which allowed single servers to store all routing states and compute all routing decisions for a large ISP network and enabled simple backup replication strategies allowing for controller reliability to be ensured.
- Open source routing software lowered the barrier to creating prototype implementations of centralized routing controllers.
Innovations:
1. Open interface between control and data planes
2. Logically centralized control of the network.
How was the second phase of SDN history (Control & Data Plane Separation - ~2001 to 2007) different from the first phase of SDN history (Active Networks - mid 1990s to early 2000s)?
- Second phase focused on spurring innovation by/for network administrators rather than end users and researchers.
- Second phase emphasized programmability in the control domain rather than the data domain.
- Worked towards network-wide visibility and control rather than device-level configurations.
Summarize the use case pulls for the second phase of SDN history (Control & Data Plane Separation - ~2001 to 2007).
- Selecting between network paths based on the current traffic load.
- Minimizing disruptions during planned routing changes.
- Redirection/dropping suspected attack traffic.
- Offering value-added services for virtual private network customers.
- Allowing customer networks more control over traffic flow.
Summarize the major contributions for the second phase of SDN history (Control & Data Plane Separation - ~2001 to 2007).
- The concept of logically centralized control using an open interface to the data plane.
- The concept of distributed state management.
Summarize the third phase of SDN history (OpenFlow API and Network Operating Systems - ~2007 to 2010), high level overview.
Born from the interest/idea of network experimentation at scale; able to balance the vision of fully programmable networks and the practicality of ensuring real world deployment. Built on the existing hardware and enabled more functions than earlier route controllers, this limited flexibility but allowed for immediate deployment.
