CS 6250 CORRECT EXAMS ANSWERS AND
QUESTIONS SET A+
✔✔How did higher link speeds in backbone networks encourage control and data plane
separation? - ✔✔packet forwarding implemented in hardware, separate from control
plane (7)
✔✔What 2 innovations led to the control and data plane separation? - ✔✔1. open
interface between control and data plane
2. logically centralized control of network(7)
✔✔Was the network centrally controlled logically, physically, or both under control and
data plane separation? - ✔✔LOGICALLY centrally controlled(7)
✔✔What are 3 ways control plane and data plane separation differed form active
networks? - ✔✔1. Spurred innovation for network ADMINS instead of users
2. emphasized programmability in CONTROL domain instead of data domain
3. worked towards NETWORK-WIDE visibility and control rather than device level
configurations(7)
✔✔Was visibility and control at network level or device level for active networks?
Control/data plane separation? - ✔✔Device level
Network level
(7)
✔✔Was programmability in control domain or data domain for active networks?
Control/data plane separation? - ✔✔Data domain
control domain
(7)
,✔✔Was innovation for network admins or users for active networks? Control/data plane
separation? - ✔✔Users
Admins
(7)
✔✔What are 5 use cases for control plane/data plane? - ✔✔1. path selection based on
network traffic load
2. minimized disruptions during planned routing changes
3. redirecting or dropping suspected attack traffic
4. allow customer networks more control over network flow
5. offer value added services for virtual private network customers
(7)
✔✔Were control plane and data plane separation efforts focused on managing routing
WITHIN ONE ISP? - ✔✔No
some wanted to enable flexible route control across many ASes
(7)
✔✔What 2 concepts resulted from control and data plane separation? - ✔✔1.
LOGICALLY centralized control w/ open interface to data plane
2. DISTRiBUTED state management
(7)
✔✔Was control plane/data plane separation logically distributed? - ✔✔No logically
CENTRALIZED (7)
✔✔Was control plane/data plane state management distributed or centralized? -
✔✔Distributed (7)
✔✔Why was OpenFlow built on existing hardware? What was the weakness of this? -
✔✔Enabled immediate deployment
Less flexibility
,(7)
✔✔How does an openflow switch work? - ✔✔Switch has TABLE OF PACKET
HANDLING RULES
each rule has a pattern, list of actions, set of counters, and priority
when packet is received, the switch:
- determines highest priority matching rule
- performs action
- increments counter
(7)
✔✔What happens when an openflow switch receives a packet? - ✔✔- determines
highest priority matching rule
- performs action
- increments counter
(7)
✔✔Which SDN tech was adopted in the industry: active networks, control/data plane
separation, Openflow? - ✔✔Openflow (7)
✔✔What are 3 tech developments that encouraged openflow? - ✔✔1. programmers
could control some forwarding behavior (b/c of switch chipset vendors)
2. companies could build switches without designing their own DATA PLANE
3. early versions of openflow were built on tech that switches ALREADY SUPPORTED
- just a firm upgrade
(7)
✔✔Were early versions of openflow built from the ground up? - ✔✔No, built on tech that
switches already supported (7)
✔✔Was it difficult to integrate openflow? Why? - ✔✔No, built on already supported tech
(7)
✔✔What were 3 use cases for openflow? - ✔✔1. large scale experiments on network
2. managing traffic at large scales in data-center networks
, 3. investing in programmers to write control programs, and less in proprietary switches
that couldn't support new features
(7)
✔✔Did openflow prevent small players from being competitve? Why - ✔✔No, became
more competitive b/c they could just focus on writing control programs instead of
proprietary switches
(7)
✔✔What are 3 key effects of openflow? - ✔✔1. GENERALIZATION of network devices
and functions
2. Vision of NETWORK OPERATING SYSTEM
3. DISTRIBUTE STATE MANAGEMENT techniques
(7)
✔✔What does the control plane do? - ✔✔Logic that controls forwarding behavior of
routers such as ROUTING PROTOCOLS and NETWORK MIDDLEBOX configurations
DICTATES forwarding behavior
(7)
✔✔What does the data plane do? - ✔✔PERFORMS actual forwarding as dictated by
control plane
IP FORWARDING and LAYER 2 SWITCHING
(7)
✔✔What are 2 reasons to separate control and data plane? - ✔✔1. independent
evolution and development of both planes
- ex. routing algorithms can improve WITHOUT AFFECTING EXISTING ROUTERS
2. Control from HIGH LEVEL software program
- SDN uses software to COMPUTE forwarding tables
- software to CONTROL router's behavior
- DEBUGGING IS EASIER
(7)
✔✔What are 4 areas the separation of control/data plane helps? - ✔✔1. Data centers
- network management is easier
2. routing
- SDN makes it easier to update state
- more control over path selection
QUESTIONS SET A+
✔✔How did higher link speeds in backbone networks encourage control and data plane
separation? - ✔✔packet forwarding implemented in hardware, separate from control
plane (7)
✔✔What 2 innovations led to the control and data plane separation? - ✔✔1. open
interface between control and data plane
2. logically centralized control of network(7)
✔✔Was the network centrally controlled logically, physically, or both under control and
data plane separation? - ✔✔LOGICALLY centrally controlled(7)
✔✔What are 3 ways control plane and data plane separation differed form active
networks? - ✔✔1. Spurred innovation for network ADMINS instead of users
2. emphasized programmability in CONTROL domain instead of data domain
3. worked towards NETWORK-WIDE visibility and control rather than device level
configurations(7)
✔✔Was visibility and control at network level or device level for active networks?
Control/data plane separation? - ✔✔Device level
Network level
(7)
✔✔Was programmability in control domain or data domain for active networks?
Control/data plane separation? - ✔✔Data domain
control domain
(7)
,✔✔Was innovation for network admins or users for active networks? Control/data plane
separation? - ✔✔Users
Admins
(7)
✔✔What are 5 use cases for control plane/data plane? - ✔✔1. path selection based on
network traffic load
2. minimized disruptions during planned routing changes
3. redirecting or dropping suspected attack traffic
4. allow customer networks more control over network flow
5. offer value added services for virtual private network customers
(7)
✔✔Were control plane and data plane separation efforts focused on managing routing
WITHIN ONE ISP? - ✔✔No
some wanted to enable flexible route control across many ASes
(7)
✔✔What 2 concepts resulted from control and data plane separation? - ✔✔1.
LOGICALLY centralized control w/ open interface to data plane
2. DISTRiBUTED state management
(7)
✔✔Was control plane/data plane separation logically distributed? - ✔✔No logically
CENTRALIZED (7)
✔✔Was control plane/data plane state management distributed or centralized? -
✔✔Distributed (7)
✔✔Why was OpenFlow built on existing hardware? What was the weakness of this? -
✔✔Enabled immediate deployment
Less flexibility
,(7)
✔✔How does an openflow switch work? - ✔✔Switch has TABLE OF PACKET
HANDLING RULES
each rule has a pattern, list of actions, set of counters, and priority
when packet is received, the switch:
- determines highest priority matching rule
- performs action
- increments counter
(7)
✔✔What happens when an openflow switch receives a packet? - ✔✔- determines
highest priority matching rule
- performs action
- increments counter
(7)
✔✔Which SDN tech was adopted in the industry: active networks, control/data plane
separation, Openflow? - ✔✔Openflow (7)
✔✔What are 3 tech developments that encouraged openflow? - ✔✔1. programmers
could control some forwarding behavior (b/c of switch chipset vendors)
2. companies could build switches without designing their own DATA PLANE
3. early versions of openflow were built on tech that switches ALREADY SUPPORTED
- just a firm upgrade
(7)
✔✔Were early versions of openflow built from the ground up? - ✔✔No, built on tech that
switches already supported (7)
✔✔Was it difficult to integrate openflow? Why? - ✔✔No, built on already supported tech
(7)
✔✔What were 3 use cases for openflow? - ✔✔1. large scale experiments on network
2. managing traffic at large scales in data-center networks
, 3. investing in programmers to write control programs, and less in proprietary switches
that couldn't support new features
(7)
✔✔Did openflow prevent small players from being competitve? Why - ✔✔No, became
more competitive b/c they could just focus on writing control programs instead of
proprietary switches
(7)
✔✔What are 3 key effects of openflow? - ✔✔1. GENERALIZATION of network devices
and functions
2. Vision of NETWORK OPERATING SYSTEM
3. DISTRIBUTE STATE MANAGEMENT techniques
(7)
✔✔What does the control plane do? - ✔✔Logic that controls forwarding behavior of
routers such as ROUTING PROTOCOLS and NETWORK MIDDLEBOX configurations
DICTATES forwarding behavior
(7)
✔✔What does the data plane do? - ✔✔PERFORMS actual forwarding as dictated by
control plane
IP FORWARDING and LAYER 2 SWITCHING
(7)
✔✔What are 2 reasons to separate control and data plane? - ✔✔1. independent
evolution and development of both planes
- ex. routing algorithms can improve WITHOUT AFFECTING EXISTING ROUTERS
2. Control from HIGH LEVEL software program
- SDN uses software to COMPUTE forwarding tables
- software to CONTROL router's behavior
- DEBUGGING IS EASIER
(7)
✔✔What are 4 areas the separation of control/data plane helps? - ✔✔1. Data centers
- network management is easier
2. routing
- SDN makes it easier to update state
- more control over path selection
