Software-Defined Networking

Technical Forum – Nov. 2013

AgendaLimitations of traditional networkingDefinition of SDNSDN componentsSDN benefitsEnabling network virtualizationEasier orchestration with SDNDefining service paths with SDN

Problems with traditional networkingPackets are processed by each node forwarding logic

independently of other nodes

In large IP networks it is difficult to provide a deterministic path end to end (exception: MPLS-TE w/ FRR)

Tight coupling of control plane and data planeControl plane: protocols/processes which assist the node to

make forwarding decisionsData plane: protocols/processes which make forwarding

decisions

Orchestration is difficult

Traditional network orchestrationTo put it into perspective…..

In most networks routers and switches are individually managed using SSH or telnet In multivendor environments unifying the orchestration

component is impossibleEach vendor has a different interfaces

Different interface naming conventions Different supported routing protocols Different supported L2 protocols (TRILL, shortest path

bridging, STP, RSTP, MSTP, static RBridge, ……)

Result: Pretty much impossible to know every protocol on every OS from every vendor!

Lack of end to end path control in traditional networkingIn IP, only the destination IP address is evaluated against

the forwarding table

One improvement is policy-based routing which can evaluate multiple criteria (port numbers, source IP address, ingress interface, etc)Difficult to scale

Same problem with Ethernet

By definition, Frame Relay provides better deterministic path control

What is SDN?SDN (Software Defined Networking) is really

just three things:Removing the control plane from nodes;Implementing the control plane logic on a

centralised controlled, and;Providing an interface between the controller

(the control plane) and each node (the data plane)

SDN components

So what does this get us?Network virtualization

Easier orchestration

Centralized policy

Enables application to define SLAs of the network rather than the network force SLAs on the applications

Faster deployment of networks

(can be) cheap!

Network virtualizationNetwork virtualization is the idea of bolting

the network on top of the hardware

Means the physical network does not define the logical network

With a homogeneous set of physical servers, a complete SDN solution can be made very easily

Network virtualizationStep 1: Buy a bunch of x86 servers running

some flavour of Linux

Network virtualizationStep 2: Install openvswitch (an open source

multilayer virtual switch) on all servers

Network virtualizationInstall an SDN controller on one or two nodes

Network virtualizationNow, the virtual network can defined ontop of the

physical hardware; i.e. we have an SDN

OpenDaylight holds all the policies about how traffic should flow through the network

OpenFlow is the control plane protocol which pushes the policy to the nodes

OpenVSwitch is the data plane protocol which implements the policy on the servers

Network virtualization

Easier orchestrationOpenFlow provides a mechanism to program TCAMs, route

caches, etc

If a network vendor supports OpenFlow (preferably OFv1.2 or better), this means they have exposed an API which allows an SDN controller to create forwarding logic on their equipment using the OpenFlow protocol

To create a service path through an entire network can all be done through the SDN controller rather than individually typing in the commands on each node

No need to know absolutely every command for every vendor we support!

Forwarding flexibilityTypical IP forwarding is destination based onlyOpenFlow can forward traffic based on:

Source/Destination MAC addressesEtherTypeVLAN ID802.1Q CoSSource/Destination IP addressesSource/Destination port numbresProtocolIngress interfaceIP QoS

Forwarding flexibilityNot only can it match on these things, it can

take the following actions on matched traffic:Set a VLAN ID / set a new VLAN IDSet 802.1p bitsStrip VLAN headerModify either/both MAC addressesModify either/both IP addressesModify IP QoS bitsModify either/both TCP/UDP portsSend the data through a specific service path

Smarter networkingOpenDaylight supports REST which can allow

applications to tell the controller that they will need to start sending traffic and have certain requirements:BandwidthLatencyNumber of hopsEtc..

The SDN controller defines the service path through the network based on the current network climate and program the nodes using OpenFlow to start forwarding traffic down this path with priority

Think SDN is nothing more than a dream?