9 Software Defined Networks

Question 1

Why is configuration hard?

Answer 1

1. Defining correctness is hard
2. Interactions between protocols -> unpredicatability
3. Operators make mistakes

Question 2

What do SDNs provide

Answer 2

Network wide views (Topology and Traffic)
Network level objectives (Load balance, Security)
Direct control

Question 3

High level sdn

Answer 3

Remove routing from routers and perform routing computation at the logically centralized controller

Question 4

SDN Advantages

Answer 4

Coordination
Evolve
Reasoning is easier
All of these stem from a separate control plane which allow us to apply CS techniques we couldn’t before

Question 5

Control plane

Answer 5

software program written in a high level language

Logic that controls forwarding behavior

Question 6

Data plane

Answer 6

programmable hardware controlled by control plane

forwarding traffic according to control plane logic

Question 7

SDN applications

Answer 7

data centers
backbone networks
enterprise networks
interent exchange points
home networks

Question 8

Routing protocols that compute path belong in the _____

Answer 8

control plane

Question 9

Forwarding table entries belong in the _____

Answer 9

data plane

Question 10

Why do we separate the data and control planes?

Answer 10

Independent evolution (separate hardware and software)
Control from high level program

Question 11

SDN Benefits for: Data centers

Answer 11

VM Migration

Question 12

SDN Benefits for: Routing

Answer 12

more control over decision logic

Question 13

SDN Benefits for: Enterprise networks

Answer 13

security

Question 14

SDN Benefits for: Research

Answer 14

coexist with production

Question 15

Data center SDNS

Answer 15

Problem: Provisioning/migration in response to load
Solution: Program switch state from a central DB

Question 16

Backbone Security and SDNs

Answer 16

Attacker sending traffic to victim, so controller sees this and responds with something like a null route that “blocks” traffic from attacker

Question 17

Challenges of SDN

Answer 17

Scalability - hundreds to thousands of switches
Consistency - Ensure different replicas see same view
Security/Robustness - failure/ compromised, system must still work

Question 18

Different SDN Controllers

Answer 18

NOX
Ryu
Floodlight
Pyretic
Frenetic
Procera
Routeflow
Trema

Question 19

NOX Overview

Answer 19

open source
stable
widely used

Question 20

Classic nox

Answer 20

c++/python

Question 21

new nox

Answer 21

c++ only, fast

Question 22

Nox architecture

Answer 22

Components: Switches, Network attached servers
Abstraction: Switch control (open flow is default)
Control: Flow granularity

Question 23

Nox flow

Answer 23

10-tuple: statistics, things to do to packets that match this flow definition

Question 24

Nox flow actions

Answer 24

forward
drop
send to controller

Question 25

Nox controller programmatic interface

Answer 25

based on events (packet receive, switch join/leave)
keeps track of network view (underlying network topology)
speaks control protocol to switches in network that allows it to update state in switches

Question 26

Nox characteristics

Answer 26

c++
openflow 1.0
model: event based

Question 27

NOX benefits/downfalls

Answer 27

Good Performance
Requires you to be familiar with low level of openflow
Requires c++ development

Question 28

Pox

Answer 28

easy to use, read, write

performance sucks though

Question 29

Ryu characteristics

Answer 29

Python
open flow 1.0, 1.2, 1.3
OpenStack

Question 30

Ryu downside

Answer 30

performance sucks

Question 31

floodlight characteristics

Answer 31

java
openflow 1.0
fork from beacon

Question 32

floodlight advantages

Answer 32

documentation
REST compatability
performance

Question 33

floodlight disadvantage

Answer 33

hard to learn

Question 34

Pox algorithm for switch

Answer 34

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