Software Defining Network Flashcards
Examples of Network management tasks
balancing traffic load
achieving security goals
satisfying business relationships
Examples of Network Configuration Errors
- Persistent oscillations can occur when routers can’t agree on a route to a destination.
- Loops
- Partitions occur when the network is split into two or more segments that are not connected.
- Black holes (router will just drop the packet)
The main goal of SDN
Change device-level configuration - centralize the network configuration to a logically centralized controller.
Three things that SDN provide operators
- Provides operators with network-wide views of both topology and traffic
- the ability to satisfy network-level objectives, such as load balancing and security
- allows an operator to write a control program that directly affects the data plane.
Two functions of today’s routers
Data Plane: forward traffic
Control Plane: compute routing tables (state) to make decisions for data plane
Defining features of SDN
- Control plane (software program written in high-level language) runs in a logically centralized controller
- Provide network view - control all of the routers in the network
Advantages of SDN
- easier debug and reason
- easier coordination of behavior across network devices
- easier evolution of network behavior
Reasons for separating data and control plane
- Independent evolution of data plane (network hardware) & control plane (software control)
- Easier debug and reason
- Separate vendor hardware from the control logic
How does control/data separation make managing data center easier?
- Monitor/control of routers from a central point
2. Migrating VMs without renumbering host address
Challenges of SDN
Scalability: hundreds to thousands of switches
Consistency: ensure different replicas see the same view
Security/robustness: cope with failers
Ways to cope with scalability challenges
- eliminate redundant data structures
- only perform control-plane operations for a limited number of operations
- cache forwarding decisions in switches
- run multiple controllers