Software Defined Networks

Question 1

SDN

Answer 1

Software Defined Network

Question 2

Goals of Configuring Networks

Answer 2

Load Balance, Security, Business Relationships

Question 3

What cn go wrong during configuration

Answer 3

Oscillation, Loops, Partitions, “BlackHoles”

Question 4

Why is configuration hard?

Answer 4

Defining correctness is hard, Interactions between protocols(unpredictability), Operators make mistakes

Question 5

What does SDN provide operators

Answer 5

Network-wide views, Network level objectives, Direct Control

Question 6

Examples of network wide views in SDN

Answer 6

Topology, Traffic

Question 7

Examples of network level objectives

Answer 7

Load balance, Security

Question 8

Examples of Direct Control

Answer 8

Direct Manipulation of data plane

Question 9

What should routers do to make network operations easier

Answer 9

Forward Packets, collect measurement

Question 10

What is SDN equivalent to

Answer 10

“Removing routes from the router”

Question 11

What is the data plane

Answer 11

forward traffic

Question 12

Routers have state called

Answer 12

routing tables

Question 13

job of control plane

Answer 13

compute routing table

Question 14

where does data and control run on conventional networks

Answer 14

on the distributed routers

Question 15

How is the control and data plane handled in SDN

Answer 15

Logically centralized control, Network-wide control

Question 16

SDN timeline

Answer 16

2004 RCP BGP only, 2005 4D (decision, dissmination/discovery, data) 2008, Openflow (cheap switches)

Question 17

Advantages of sdn

Answer 17

Coordination, Evolve, Reasoning

Question 18

What does separation of the control plane allow

Answer 18

Apply CS techniques to network problems

Question 19

Infrastructure control plane

Answer 19

Software program

Question 20

Data plane

Answer 20

programmable hardware

Question 21

SDN Applications

Answer 21

Data Centers, Backbone networks, Enterprise networks, Internet Exchange Points (IXPs), Home networks

Question 22

Examples of control plane operations

Answer 22

Compute a forwarding path that satisfies a high level policy, Compute shortest path routing tree, Authenticate a users device

Question 23

Control Plane functions

Answer 23

Logic that controls forwarding behavior. Examples routing protocols configuration for network middle boxes

Question 24

Data plane

Answer 24

forward traffic according to control plane logic Examples: forwarding switching

Question 25

Why is separating data and control a good idea

Answer 25

Independent evaluation (software and hardware can evolve independently), Control from high level (debug check behavior more easily)

Question 26

Opportunities when separating data and control

Answer 26

Data Centers (VM migration) Routing (more control over decision logic) Enterprise network (security) Research (coexist with production)

Question 27

Data center problem SDN solves

Answer 27

Provisioning/migration in response to load Solution: program switch state from central database

Question 28

How does SDN help Backbone Security

Answer 28

monitor traffic identify attack send to a null route

Question 29

SDN Challenges

Answer 29

Scalability (hundreds to thousands of switches) Consistency (Ensuring different replicas see same view) Security/robustness (failure or compromise)

Question 30

Some different SDN controllers

Answer 30

NOX, RYU, Floodlight, Pyretic, Frenetic, Procera, Routerflow, Trema

Question 31

What are the two flavors in NOX

Answer 31

"classic": c++/python, "new": c++ only

Question 32

NOX Protocol

Answer 32

openflow

Question 33

How is flow defined in NOX

Answer 33

(header: counter, actions) 10-tuple. Actions could be forward, drop, send to controller

Question 34

What is POX

Answer 34

python version of nox. it is slow, not used by industry due to speed

Question 35

RYU (pro vs con)

Answer 35

python, openflow, openstack (poor performance)

Question 36

Floodlight (pro vs con)

Answer 36

Java, good doc, rest app, (hard to learn)

Question 37

Nox (pro vs con)

Answer 37

+ High performance (slow debugging/programming)

Question 38

POX distro learning switch example (high level)

Answer 38

1. Update address/port table 2. If multicast flood 3. If no table entry flood 4. If src=dst drop 5. install flow table entry

Question 39

How is caching handled at switch

Answer 39

1. Packet only reaches controller if no flow table entry at the switch 2. when controller decides on action installs in switch 3. Decision/flow table entry is cached