Introduction to the SDN lab · 2020. 12. 15. · TNG group-Politecnico di Torino Introductionto SDN...

Introduction to SDN lab - 1TNG group - Politecnico di Torino

Introduction to the SDN lab

Andrea Bianco, Paolo Giaccone, German Sviridovhttp://www.telematica.polito.it/


Mininet• network emulator

host

switch

SDN controller

host

switch

SDN controller

Mininet


Mininet• network emulator

– host– switch (in our lab: P4 switch)– SDN controller

• linux container/process for each node• command line interface CLI

– global commands for the emulator– local commands for the nodes


Mininet global commands• nodes display nodes

– h1 -> host 1– s1 -> switch 1

• links display links– h1-eth0s1-eth1

• net display a summary of all the nodes and links– h1 h1-eth0:s1-eth1

• dump dump information about all nodes–


Mininet local commands• local commands for the nodes

– if the first string typed a host, switch or controller name, the command is executed on that node

• h1 ifconfig provides the list of the network interfaces attached to h1

• h1 ping h2 sends ICMP packets from h1 to h2• h1 iperf –c 10.0.0.1 uses iperf to test the

bandwidth towards 10.0.0.1 • etc.


Network performance tool• iperf to test the available bandwidth between two

hosts• client server application

– client: generates the traffic (TCP/UDP)– server: receives the traffic (TCP/UDP)

• iperf –c dest_IP run the test as client• iperf –s run the test as server

– by default, each host is already running it in background • many options are available: iperf --help


Lab steps1. preliminary steps to become familiar with

Mininet and its commands2. test topology

– discovery in terms of node graph and IP addresses

– test connectivity3. modify flow tables to provide full connectivity4. experiments with rate limiting

– meters to classify flows based on rates5. experiments with load balancer


Tools and configuration• main folder /lab/forwarding• forwarding.p4 describes the model

implemented in the switch– based on v1model.p4

• Makefile runs the emulator• simple_topology.json describes the

topology (specified in Makefile)• under tables/, sX-commands describes the

actual processing of the packets– routing, rate limiting, load balancing


Lab logistics• you must follow the instructions available

under Materiale/Lab Info– install VirtualBox– download the ISO of the VM for the lab– start the VM

• the installation of the VM must be working by Monday 21th at 12AM– if assistance needed, please send an email to

[email protected], cc:[email protected]

mailto:[email protected]:[email protected]


Lab logistics• the lab will be managed through individual

Breakout Rooms through BBB– mandatory to activate the microphone when you

join the lab– (optional) enable the webcam– be prepared to share your screen when

interacting with the professors


P4 for programming the data plane


P4 as language

• Programming Protocol-independent Packet Processor

• language to describe how the packet are processed within the switch

• allows to program the switch• specifies the data plane and

the interface between the data plane and the control plane

• does not specify the control plane


Switch OS

Run-time APIDriver

“This is how I know toprocess packets”

(i.e. the ASIC datasheetmakes the rules)

Fixed-function ASIC

Status Quo: Bottom-up design

?slides taken from P4 language tutorial https://bit.ly/p4d2-2018-spring


Switch OS

Run-time APIDriver

“This is how I want the network to behave and how to

switch packets…”(the user / controller

makes the rules)P4 Programmable Device

A Better Approach: Top-down design

14

P4

Feedback

slides taken from P4 language tutorial https://bit.ly/p4d2-2018-spring


P4 vs traditional networking

• the data plane functionality is not fixed in advance

• data plane is configured at initialization time• no built-in knowledge of preexisting network

protocols• set of tables defined by a P4 program

P4 switch


P4 vs Openflow• Very different!• Openflow is just a southbound protocol/API

– prefixed matching fields and actions– no internal states within the switches

• P4 is a language to program the data plane– can be used to program a switch to act as an

Openflow switch– protocol independence

• flexibility in defining the protocol parser – stateful SDN


PISA: Protocol-Independent Switch Architecture

17

ProgrammableParser

ProgrammableDeparser

Programmable Match-Action Pipeline

Programmer declares the headers that should be

recognized and their order in the packet

Programmer defines the tables and the exact processing algorithm

Programmer declares how the output packet will look on the wire



P416 Language Elements

Architecture Description

Extern Libraries

Programmable blocks and their interfaces

Support for specialized components

Data Types Bistrings, headers, structures, arrays

Controls Tables, Actions, control flow statements

Parsers

Expressions Basic operations and operators

State machine, bitfield extraction



Example Architectures and Targets

19

TM

TM

TM

V1Model

Anything

SimpleSumeSwitch

Portable Switch Architecture (PSA)



Programming a P4 Target

P4 ArchitectureModel

P4 Compiler

Target-specific configuration

binaryData PlaneTables ExternobjectsLoad

TargetVendor supplied

P4 Program

User supplied

Control Plane

Add/removetable entries

CPU port

Packet-in/outExterncontrol

RU

NTI

ME


Introduction to the SDN lab · 2020. 12. 15. · TNG group-Politecnico di Torino Introductionto SDN...

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