NFV is a revolutionary approach offering greater flexibility and scalability in the deployment of virtual network functions. It provides significant advantages over the current vendor-locking infrastructure using physical network functions. The NFV architecture has three building blocks a) Infrastructure b) Virtual Network Functions c) Orchestrator

1. Data Path acceleration
techniques in a NFV world
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Mohanraj Venkatachalam, Purnendu Ghosh

2. Abstract
NFV is a revolutionary approach offering greater flexibility and scalability in the deployment of
virtual network functions. It provides significant advantages over the current vendor-locking
infrastructure using physical network functions. The NFV architecturehas three buildingblocks
a) Infrastructure b)VirtualNetwork Functions c)Orchestrator.
Telcoshave stringentSLA towards latency,throughput, packets-per-sec,
bits-per-seconds to meet both QOE, QOS and guaranteed bandwidth per user subscription.
Therefore, an NFV system has to match the data path capabilitiesat parwith actual Physical
Network Functions. Alot ofresearch is ongoinginthe development ofdata path acceleration
techniques for a virtualized infrastructure by using hypervisors (e.g.:Xen, KVM, VMware,
Hyper-V) inthe following possible ways: (a) Device Emulation(b)
Para-Virtualization (c) PCIPass-through.
Let us walkthroughwith some of the standard HW andSW techniques availableto achievea
comparable performance of VNF (Virtual Network Function) runningin a virtualized environ-
ment as compared to PNF (Physical Network Function) used in legacy network architecture.
The criticalaspect inall ofthese approachesis to:
•Increase packetthroughput fromphysical NICto virtual NICs
•Reduce the number of copiesdonebefore it is processed bythe application
residing in theVM
•Reduce the numberof CPU interruptsbefore a packetis delivered to a VM
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3. VMDq (Virtual Machine DeviceQueues)
These are specializednetwork controllers capableof sorting data packets into multiple queues.
Adistinct queue->vNIC->CPU_Core mappingensures independent parallel I/Ostreams for
each VMworkload.
This solution offloads the overhead of data packet sorting from hypervisor switch to network
siliconand improves the network I/Othroughput over 100 as compared with a traditional
solution. AVMDq solution consists (this is Intel specific) improvements to Hypervisor Switch
(e.g.:VMware ESX). This arrangement ensures that Rxinterruptsare directlyaddressed to CPU
coreofthe VM thereby reducing the number ofcopiesrequired
However, with VMDq there is a performance penalty due to the number of interrupts for VM
directed data-planetraffic. AnSR-IOV based solution brings considerable improvement inthis
aspect as described in thenext section.
SR-IOV
SR-IOV or Single-Root IO Virtualization is a specificationwhich allows a single PCIe device
configured as multiple virtual devicesandthey appearas independent network functions to
the VMs runningin a hypervisor. These devices consist of VFs (named as Virtual Functions)
acting as light-weightPCIe unitsthat are capableofbeingconfigured for data traffic move-
ment. There are also PFs (Physical Functions) which contain full PCIe functions and can be
used to configure SR-IOV enableddevices.
Figure 1:Single Root I/OVirtualizationand Sharing(SR-IOV)
Seen as PCI Express *
Device Ethernet Controllerin
OS “Virtual Function Driver”
Seen as PCI Express *
Device Ethernet Controllerin
OS“ Physical FunctionDriver”
Hardware resources
areavailableforSR-IOV
defined VirtualFunctions
utilizing a HardwareVEB
VMVM
Operati
ngSyste
m
VirtualSwitch
VM
Intel’VT-d
PCIExpress
PFDriver
PF Driver
Name Name
Space Space
Hardware Virtual Ethernet Bridge(VEB)
Intel”Ethernet
withSR-IOV
unctionF
Virtual
1 unctionF
Virtual
2 unctionF
Virtual
n
Physical
Function
LAN
Traffic
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in-a-NFV-world.pdf
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