This document provides an introduction to Open vSwitch (OVS), including what a virtual switch is, examples of virtual network topologies using OVS, the main components of OVS, and how to use OVS to build network topologies. It discusses features of OVS like visibility into inter-VM communication and support for tunnels. It also demonstrates OVS configurations for virtual machine to virtual machine communication using GRE tunnels and a demo topology with OVS bridges communicating over a GRE tunnel.

1. The Basic Introduction of
Open vSwitch
Te-Yen(Danny) Liu
Date : 2014/01/08

2. Page 2
Agenda
 What is Virtual Switch?
 Virtual Network Topology using OVS
 What is Open vSwitch and Features?
 The Main Components
 Using OVS to build Network Topology
 Advanced Examples
 Demo

3. Page 3
What is Virtual Switch?
 In virtual network, virtual switch acts like an advanced edge
switch for VMs.
Physical Switch
Hypervisor
Virtual Switch
VM VM VM
Virtual
Network
(L2)vNIC
VIF
NIC as vSwitch’s
uplink port
Data Flow

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Virtual Network Topology (1/2)
 An example of Virtual Network Topology in OpenStack

5. Page 5
Virtual Network Topology (2/2)
 Another example of Virtual Network Topology in OpenStack
 They use Open vSwitch as the solution to deal with the complication in virtual
newtork and multi-tenancy

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What is Open vSwitch?
 A software-based solution
 Resolve the problems of network separation and traffic
visibility, so the cloud users can be assigned VMs with
elastic and secure network configurations
 Flexible Controller in User-Space
 Fast Datapath in Kernel
 An implementation of Open Flow
Controlle
r

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Open vSwitch Design
 Decision about how to process packet made in
userspace
 First packet of new flow goes to ovs-vswitchd,
following packets hit cached entry in kernel

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Features
 Visibility into inter-VM communication via NetFlow, sFlow(R), IPFIX, SPAN, RSPAN, and
GRE-tunneled mirrors
 LACP (IEEE 802.1AX-2008)
 Standard 802.1Q VLAN model with trunking
 BFD and 802.1ag link monitoring
 STP (IEEE 802.1D-1998)
 Fine-grained QoS control
 Support for HFSC qdisc
 Per VM interface traffic policing
 NIC bonding with source-MAC load balancing, active backup, and L4 hashing
 OpenFlow protocol support (including many extensions for virtualization)
 IPv6 support
 Multiple tunneling protocols (GRE, VXLAN, IPsec, GRE and VXLAN over IPsec)
 Remote configuration protocol with C and Python bindings
 Kernel and user-space forwarding engine options
 Multi-table forwarding pipeline with flow-caching engine
 Forwarding layer abstraction to ease porting to new software and hardware platforms
The newest version is 2.0

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sFlow with OpenvSwitch

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The Main Components

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ovsdb-server
 Database that holds switch level configuration
 Custom database with nice properties:
 Log-based
 Speaks OVSDB management protocol(JSON-RPC)
to manager and ovs-vswitchd

12. Page 12
Example: Setup QoS
 There are two ways to do that:
 Interface Rate Limiting ( on Interface )
 For instance:
– sudo ovs-vsctl set Interface eth1 ingress_policing_rate=10000
– sudo ovs-vsctl set Interface eth1 ingress_policing_burst=1000
 Port QoS Policy ( on Port )
 For instance:
– sudo ovs-vsctl set port eth1 qos=@newqos
– -- --id=@newqos create qos type=linux-htb
– other-config:max-rate=200000000 queues=0=@q0,1=@q1
– -- --id=@q0 create queue
– other-config:min-rate=100000000
– other-config:max-rate=100000000
– -- --id=@q1 create queue
– other-config:min-rate=50000000
– other-config:max-rate=50000000
 Qos can have more than 1 queue

13. Page 13
The example of QoS in OVS Database
 It is a GUI tool to see the tables in the ovsdb-server
 This case is about checking QoS setting

14. Page 14
ovs-vswitchd
 Core component in the system:
 Communicates with outside world using OpenFlow
 Communicates with ovsdbserver using management
protocol (OVSDB)
 Communicates with kernel module over netlink
 Communicates with the system through netdev abstract
interface
 Supports multiple independent datapaths (bridges)
 Implements mirroring, bonding, and VLANs through
modifications of the same flow table exposed
through OpenFlow

15. Page 15
OVS Kernel Module: openvswitch_mod.ko
 Handles switching and tunneling
 Exact-match cache of flows
 Designed to be fast and simple
 Packet comes in, if found, associated actions
executed and counters updated. Otherwise, sent to
userspace
 Does no flow expiration
 Knows nothing of OpenFlow
 Implements tunnels

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Using OVS to build Network Topology
 Physical Machine to Physical Machine
>ovs-vsctl add-br br0
>ovs-vsctl add-port br0
eth0
>ovs-vsctl add-port br0
eth1

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Using OVS to build Network Topology
 Virtual Machine to Virtual Machine
 Hypervisor is KVM
>ovs-vsctl add-br br0
>cat /etc/ovs-ifup
#!/bin/sh
switch= 'br0'
/sbin/ifconfig $1 0.0.0.0 up
ovs-vsctl add-port ${switch} $1
>cat /etc/ovs-ifup
#!/bin/sh
switch= 'br0'
/sbin/ifconfig $1 0.0.0.0 down
ovs-vsctl del-port ${switch} $1
>kvm -m 512 -net nic,macaddr=00:11:22:33:44:55-net
tap,script= /etc/ovs-ifup ,downscript= /etc/ovs-ifdown-
drive
file = /path/to/disk-image ,boot=on
>kvm -m 512 -net nic,macaddr=11:22:33:44:55:66-net
tap,script= /etc/ovs-ifup ,downscript= /etc/ovs-ifdown-
drive
file = /path/to/disk-image ,boot=on

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Using OVS to build Network Topology
 The profile of the virtual network
 Internal port is connected to IP Stack
 VMs connect with outside network via vport ( tap virtual
interface )

19. Page 19
Using OVS to build Network Topology
 Virtual Machine to Virtual Machine with GRE Tunnel
GRE Tunnel
GRE Tunnel

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Using OVS to build Network Topology
sudo ifconfig eth1 0
sudo ovs-vsctl add-br br1
sudo ovs-vsctl add-br br2
sudo ovs-vsctl add-port br1 eth0
sudo ifconfig br1 192.168.1.155 netmask 255.255.255.0
sudo ifconfig br2 10.1.1.1 netmask 255.255.255.0
sudo ovs-vsctl add-port br2 gre0 -- set interface gre0 type=gre options:remote_ip=192.168.1.152
sudo ifconfig eth1 0
sudo ovs-vsctl add-br br1
sudo ovs-vsctl add-br br2
sudo ovs-vsctl add-port br1 eth0
sudo ifconfig br1 192.168.1.152 netmask 255.255.255.0
sudo ifconfig br2 10.1.1.2 netmask 255.255.255.0
sudo ovs-vsctl add-port br2 gre0 -- set interface gre0 type=gre options:remote_ip=192.168.1.155
sudo vi /etc/ovs-ifup
#!/bin/sh
switch='br2'
/sbin/ifconfig $1 0.0.0.0 up
ovs-vsctl add-port ${switch} $1
sudo vi /etc/ovs-ifdown
#!/bin/sh
switch=’br2’
/sbin/ifconfig $1 0.0.0.0 down
ovs-vsctl del-port ${switch} $1
sudo chmod +x /etc/ovs-ifup /etc/ovs-ifdown
sudo kvm -m 512 -net nic,macaddr=11:22:33:44:55:66 -net tap,script=/etc/ovs-ifup,downscript=/etc/ovs-ifdown -cdrom
/home/brent/images/ubuntu-12.04-desktop-i386.iso &

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Using OVS to build Network Topology
 Bridge to Bridge
 They need a patch port to communicate with each other
ovs-vsctl add-br br0
ovs-vsctl add-br br1
ovs-vsctl add-port br0 patch-to-br1
ovs-vsctl set interface patch-to-br1type=patch
ovs-vsctl set interface patch-to-br1 options:peer=patch-
to-br0
ovs-vsctl add-port br1 patch-to-br0
ovs-vsctl set nterface patch-to-br0type=patch
ovs-vsctl set interface patch-to-br0 options:peer=patch-
to-br1

22. Page 22
Demo Topology
 The host: OVS1 and OVS2 communicate with each other by GRE Tunnel
 The host: KVM will provision a VM guest and communicates with OVS1
and OVS2

23. Page 23
OVS with GRE Tunnel Demo (1/2)
 OVS1 and OVS2 communicate with each other by GRE Tunnel
sudo ovs-vsctl add-br br0
sudo ovs-vsctl add-br br1
sudo ovs-vsctl add-port br0 eth0
sudo ifconfig eth0 0
sudo ifconfig br0 192.168.1.10 netmask 255.255.255.0
sudo route add default gw 192.168.1.1 br0
sudo ifconfig br1 10.1.2.10 netmask 255.255.255.0
sudo ovs-vsctl add-port br1 gre1 -- set interface gre1
type=gre options:remote_ip=192.168.1.11
sudo ovs-vsctl add-br br0
sudo ovs-vsctl add-br br1
sudo ovs-vsctl add-port br0 eth0
sudo ifconfig eth0 0
sudo ifconfig br0 192.168.1.11 netmask 255.255.255.0
sudo route add default gw 192.168.1.1 br0
sudo ifconfig br1 10.1.2.11 netmask 255.255.255.0
sudo ovs-vsctl add-port br1 gre1 -- set interface gre1
type=gre options:remote_ip=192.168.1.10
br0
eth0
br1
IP: 192.168.1.10
Default GW: 192.168.1.1
Remote IP:
192.168.1.11
gre1
IP: 10.1.2.10

24. Page 24
OVS with GRE Tunnel Demo (2/2)
 OVS1 and OVS2 in bare metal mode to communicate with each
other by GRE Tunnel
sudo ovs-vsctl add-br br-int
sudo ifconfig eth0 192.168.1.10 netmask 255.255.255.0
sudo route add default gw 192.168.1.1 eth0
sudo ovs-vsctl add-port br-int mgmt0 -- set interface
mgmt0 type=internal
sudo ifconfig mgmt0 10.1.2.10 netmask 255.255.255.0
sudo ovs-vsctl add-port br-int gre1 -- set interface gre1
type=gre options:remote_ip=192.168.1.11
sudo ovs-vsctl add-br br-int
sudo ifconfig eth0 192.168.1.11 netmask 255.255.255.0
sudo route add default gw 192.168.1.1 eth0
sudo ovs-vsctl add-port br-int mgmt0 -- set interface
mgmt0 type=internal
sudo ifconfig mgmt0 10.1.2.11 netmask 255.255.255.0
sudo ovs-vsctl add-port br-int gre1 -- set interface gre1
type=gre options:remote_ip=192.168.1.10
br0
mgmt0
IP: 192.168.1.10
Default GW: 192.168.1.1
Remote IP:
192.168.1.11
gre1
IP: 10.1.2.10
eth0

25. Page 25
OVS with KVM and guest VM Demo
 The host: KVM will provision a VM guest and communicates with OVS1 and
OVS2
sudo ovs-vsctl add-br br0
sudo ovs-vsctl add-port br0 eth0
sudo ovs-vsctl list port
sudo ifconfig eth0 0
sudo ifconfig br0 192.168.1.20 netmask 255.255.255.0
sudo route add default gw 192.168.1.1 br0
sudo kvm -m 512 -hda /home/liudanny/kvm_lab/linux-core-4.7.7-openvswitch-1.11.0_guagga-
0.99.22.4.img -net nic,macaddr=00:11:22:33:44:55 -net tap,script=/etc/ovs-ifup,downscript=/etc/ovs-
ifdown
sudo kvm -m 512 -hda /home/liudanny/kvm_lab/linux-core-4.7.7-openvswitch-1.11.0_guagga-
0.99.22.4.img -net nic,macaddr=11:22:33:44:55:66 -net tap,script=/etc/ovs-ifup,downscript=/etc/ovs-
ifdown
br0 IP: 192.168.1.20
Default GW: 192.168.1.1
tap0
eth0
VM1
tap1
VM2
IP: 10.1.2.10 IP: 10.1.2.11

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Q&A

27. Page 27
Reference
 http://blog.scottlowe.org/2013/05/07/using-gre-tunnels-with-
open-vswitch/
 http://lamoop.com/post/2013-11-18/40060149263
 http://www.youtube.com/watch?v=rYW7kQRyUvA
 http://networkstatic.net/open-vswitch-gre-tunnel-configuration/
 http://networkstatic.net/configuring-vxlan-and-gre-tunnels-on-
openvswitch/
 http://openvswitch.org/ovs-vswitchd.conf.db.5.pdf
 http://openvswitch.org/