Computer Networks -CS6250 Exam 3 Questions and
Answers
What is CIDR? Classless internet Domain Routing - ✔✔Assigns IP addresses using
arbitrary-length prefixes. Decreases the router table size but then brings us a problem of
longest-matching-prefix lookup
Why do we need packet classification? - ✔✔Finer packet handling (TCP flags,
source addresses, etc)
3 variants of packet classification - ✔✔1. firewalls: routers implement firewalls at the
entry and exit points of the network to filter traffic
2. resource reservation protocols: reserve bandwidth between source and a destination
3. routing based of traffic type: routing based of specific traffic helps avoid delays for
time-sensitive applications
3 Simple solutions to packet classification and what are they? - ✔✔1. Linear search:
Firewall implementations perform a linear search of the rules database and keep track of the
best-match rule
2. Caching: Another approach is cache results. two problems, miss rate.
3. Passing Labels: MPLS, a label-switched path is setup bt 2 sites. Before traffic leaves site A, a
router maps the web traffic into an MPLS header. Thus redoing packet classification is not
needed.
What spurred the development of SDN? - ✔✔1. Diversity of equipment: Too many
different tools make network management complex
2. Proprietary Technologies
What are the three phases in history of SDN? - ✔✔1. Active Networks
2. Control and data plane separation
, 3. OpenFlow API and network operating systems
Active Networks summary - ✔✔resulted in
1. programmable functions in the network to lower the barrier to innovation
2. Network virtualization, and the ability to demultiplex to software programs based on packet
headers
3. the vision of a unified architecture for middlebox orchestration
Control and data plane separation summary - ✔✔Open interface between control and
data planes
Logically centralized control of the network
openflow API summary - ✔✔generalizing network devices and functions
the vision of a networked operating system
distrubted state management techniques
Answers
What is CIDR? Classless internet Domain Routing - ✔✔Assigns IP addresses using
arbitrary-length prefixes. Decreases the router table size but then brings us a problem of
longest-matching-prefix lookup
Why do we need packet classification? - ✔✔Finer packet handling (TCP flags,
source addresses, etc)
3 variants of packet classification - ✔✔1. firewalls: routers implement firewalls at the
entry and exit points of the network to filter traffic
2. resource reservation protocols: reserve bandwidth between source and a destination
3. routing based of traffic type: routing based of specific traffic helps avoid delays for
time-sensitive applications
3 Simple solutions to packet classification and what are they? - ✔✔1. Linear search:
Firewall implementations perform a linear search of the rules database and keep track of the
best-match rule
2. Caching: Another approach is cache results. two problems, miss rate.
3. Passing Labels: MPLS, a label-switched path is setup bt 2 sites. Before traffic leaves site A, a
router maps the web traffic into an MPLS header. Thus redoing packet classification is not
needed.
What spurred the development of SDN? - ✔✔1. Diversity of equipment: Too many
different tools make network management complex
2. Proprietary Technologies
What are the three phases in history of SDN? - ✔✔1. Active Networks
2. Control and data plane separation
, 3. OpenFlow API and network operating systems
Active Networks summary - ✔✔resulted in
1. programmable functions in the network to lower the barrier to innovation
2. Network virtualization, and the ability to demultiplex to software programs based on packet
headers
3. the vision of a unified architecture for middlebox orchestration
Control and data plane separation summary - ✔✔Open interface between control and
data planes
Logically centralized control of the network
openflow API summary - ✔✔generalizing network devices and functions
the vision of a networked operating system
distrubted state management techniques
