software defined network and network functions virtualization

SOFTWARE DEFINED NETWORK AND NETWORK FUNCTIONS VIRTUALIZATIONAn Inevitable Evolution for Communication Networks

VIKRAM NAIRDirector, Technology

VINOD KUMAR GUPTASenior Technical Leader, Technology

1Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks

This paper starts with describing SDN and NFV technologies and

their relationship. Then it discusses the accelerators driving

adoption and challenges impinging the adoption of the technology.

The paper then captures the applicability of SDN and NFV

technology for mobile networks, for example, the segments or

sub-systems where SDN and NFV can be introduced by service

providers. It also provides a few use cases that can be realized

through the technology introduction and the benefits that such

solutions can yield. The paper also highlights key considerations

for rolling out SDN and NFV technology. Finally, the paper

summarizes the essentials requirements for testing SDN and NFV

technology for successful deployment.

Trends and InsightsSDN and NFV will bring fundamental shift in CSP’s approach to

build network infrastructure. The network transformation is

expected to happen in a phased manner, which will not only help

mature the technology introduction methods and processes

but also de-risk disruption of network services.

Today, networks are built in silos wherein independent infrastructure

is deployed for mobile, fixed, and enterprise markets with minimal

or no infrastructure reuse or sharing. Realizing the benefits from

virtualization, Communications Service Providers (CSPs) are

IntroductionTraditional communications network equipment was built over

proprietary software platforms tied onto proprietary hardware

that evolved slowly, being in a walled garden. This approach

forced service providers to deal with issues such as longer time-

to-market and end of life equipment.

Decoupling underlying hardware from software, through

standardized interfaces, and deploying software solution over

COTS (Commercial off the shelf) hardware has been a successful

shift witnessed in past years. This enables operators in buying

hardware and software platform from a variety of different vendors

with no inter-dependence of hardware and software on each

other. For example a soft-switch (that is used for VoIP call setup)

is a software implementation decoupled from media gateway

used to switch voice traffic. As the standardization of this solution

is at infancy, today’s communications network industry has yet

to fully embrace this hardware and software decoupling in the

coming years.

Software defined networks (SDN) and network function

virtualization (NFV) is a new development that builds on a premise

to decouple hardware and software solutions, and further host

software functions over a virtualized platform to achieve cost

efficiencies with limitless flexibility for network configuration

and operation.

SOFTWARE DEFINED NETWORK AND NETWORK FUNCTIONS VIRTUALIZATIONAn inevitable evolution for communication networks


stepping up the efforts to analyze the impact of virtualization

on networks and O/BSS. It is expected that initial targets for

virtualization will be the software components with minimal or

no dependency on underlying hardware.

In the next 2-3 year it is expected that first step towards

virtualization will find its place in the networks wherein selective

independent network components will get virtualized. For instance,

in LTE networks, network components that are software only

implementation with no specific hardware dependencies such as

MME, IMS, PCRF, HSS will be the first target. OSS transformation

will happen simultaneously to manage virtual assets. This phased

transformation will require OSS to support both legacy as well as

virtual assets with an external management system to manage

the virtualization platform infrastructure.

In the next five years, it is expected that majority of network

components will get virtualized enabling CSPs to sell Network as

a Service (NaaS). Additional network components which earlier

were not targeted for virtualization because of their dependency

on hardware platforms will see de-coupling of such components

into control & data plane functions, with control plan functions

being pushed onto virtualization platforms. For instance, in LTE

networks, such network components will be deep packet

inspection (DPI), serving gateway (SGW) and packet data network

gateway (PGW). This phase will have OSS transformation to not

only manage the virtual assets but also the virtualization platform

infrastructure in a holistic manner.

What are SDN and NFV

SOFTWARE DEFINED NETWORKS (SDN)

In traditional networking paradigm, a data packet arriving at

conventional equipment (switch / router) is treated with a set of

rules. These rules decide how the inbound data packet are treated

and marked such as forward, duplicate, drop, (de-) tunnel, network

address translation (NAT) or quality of service (QoS). Such

equipment is not only expensive but also is a challenge to manage

as the equipment are distributed across the network and may

require synchronization of configuration.

“SDN is a new approach to networking in which network control

is decoupled from the data forwarding function and is directly

programmable. The result is an extremely dynamic, manageable,

cost-effective, and adaptable architecture that gives administrators

unprecedented programmability, automation, and control, through

abstraction of the underlying infrastructure. Implementing SDN

via an open standard enables extraordinary agility while reducing

service deployment and operational costs, and frees network

administrators to integrate best-of-breed technology as it is

developed – Open Networking Foundation [1]”

Decoupled control and data planes help you build a centralized

control plane that manages large number of data plane equipment,

which is spread across network.

The control plane comprises SDN controller that interfaces with

data plane switches and enforce packet treatment rules on data

plane switches. Standardization attempt are underway in defining

control protocol (OpenFlow) between SDN controller and switches.

SDN primarily targets layer 2 and layer 3 infrastructure

components. The SDN controller, in addition, exposes north bound

interface using which many additional services can be built or

extended through service chaining and orchestration. Examples

of such services are discussed in detailed in subsequent section

on use cases.

The following diagram shows the high level network architecture

for Software defined networks.

Network virtualization - expected roadmap

Architectural Diagram for SDN

Now Next 2-3 Years Next 5+ Years

NetworkSilos

ComponentVirtualization

NetworkVirtualization

SDN Services

SDN Controller

Open Flow

Orchestration Layer

vSwitch

Switch

Switch Switch Switch

Resilience ServiceChaining

Tra�cManagement


The decoupling will also result into CAPEX optimization by virtue

of commoditized de-coupled data plane equipment. For instance,

by introducing SDN into networks, CAPEX requirements for

backhaul networks globally will reduce by more than $4 billion

by 2017 as per a recent research report [3].

Early benefits of SDN will be greater internal efficiency, reduced

operations costs and higher reliability of the network due to

greater automation and less room for human error.

Ultimate goal is that end customers will be able to interface

their service provider’s network and integrate services on an

automated, software-controlled basis.

NETWORK FUNCTION VIRTUALIZATION (NFV)

Virtualization started with having discrete applications hosted

on cloud platform. Driven by the benefits realized through cloud

hosting such as scalability, resilience, reduced OPEX, usage of

the virtualization technology for communication networks is a

logical evolution.

Cloud appeals because of its potential to lower down risks,

costs, and time-to-market, while increasing agility and flexibility

to experiment with new offerings. Top-line and bottom-line benefits

play into decisions regarding adoption of cloud.

“Network Functions Virtualization aims to transform the way that

network operators architect networks by evolving standard IT

virtualization technology to consolidate many network equipment

types onto industry standard high volume servers, switches and

storage, which could be located in datacenters, network nodes

and in the end user premises. It involves the implementation of

network functions in software that can run on a range of industry

standard server hardware, and that can be moved to, or instantiated

in, various locations in the network as required, without the need

for installation of new equipment – ETSI [2].”

Early implementations of NFV would target moving those

applications on cloud infrastructure that is hardware independent.

OSS, BSS and certain VAS applications are example of such

applications that are part of mobile networks.

Subsequent to that, attempt will be to decouple the control and

data plane implementations of other infrastructure elements

to enable migration of control plane software onto cloud and

deploy commoditized data plane equipment in network.

Consider as an example a LTE network as shown in a high level

network architecture diagram below. Each network element

excluding the eNodeB radio node is typically deployed on a

separate hardware unit in data centers. Out of these network

elements some are software implementation of control plane

protocol and procedures and others require additional

specialized hardware function for traffic handling.

LTE Network Architectural Diagram

Proposed LTE Network Architectural Diagram with NFV (some NEs)

eNodeBUE

Internet

HSS

PCRF

PGW

MME

SGW

eNodeBUE

Internet

PGWSGW

HSSPCRFMME

For instance Mobility Management Entity (MME) network element

falls under the category of network elements that implement

control plane protocol and procedures for managing end-to-end

data service. Other network elements that will fall under same

category are HSS and PCRF implementing control plane protocol

and procedures for subscription and policy control respectively.

Such network elements can be moved onto centralized cloud

platform as shown in the diagram below.

The concept can be further extended for other category of

network elements that implement control plane protocol and

procedures along with traffic handling i.e. Serving Gateway (SGW)

and Packet Data Network Gateway (PGW). These categories of

nodes can be split into two entities the control plane and data

plane functions. The result will be SGW-Ctrl and SGW-Data for

SGW node and PGW-Ctrl and PGW-Data for PGW node. The split

will enable moving the control plane functions i.e. SGW-Ctrl and

PGW-Ctrl onto centralized cloud platform and data plane nodes

i.e. SGW-Data and PGW-Data network switch be deployed during

network rollouts to meet traffic handling requirements.


The pyramid above represents the standard OSI reference model

[5], which is also a generic representation of any network

component. SDN and NFV combined will target virtualization of

layer 4 till layer 7 and also layer 3 partially. From standardization

perspective, ONF [1] is focusing on splitting layer 3 into control

plane and data plane wherein layer 3 control plane can be

deployed in a virtualized environment. ETSI [2] on the other hand

is focusing on virtualization of layer 4 till layer 7.

What this means is that NFV functions (actually telecom function

apps) can sit on top of SDN and leverage (use SDN as a service)

cost effective SDN routing/switching/transport and enable

unprecedented efficiencies in terms of resource utilization,

configuration, customer interface/support.

The venn diagram below shows that SDN and NFV are mutually

exclusive technologies but maximum benefits of SDN and NFV

can be achieved when these are coupled together with open

innovative apps on the top. Use cases and accelerators describe

benefits in detail, which are covered in subsequent sections.

To summarize, role of SDN and NFV when combined in an

implementation can be understood as - decoupling control

plane and data plane is what SDN recommends and moving the

decoupled control plane (or the entire network equipment

software functionality wherever possible) to a virtualized platform

is what NFV recommends.

Though, this split is not defined completely as part of

specifications, however this is another example of implementing

NFV. Additional virtualization use cases would also emerge for

Radio side such as Cloud RAN which are discussed under

subsequent sections.

Additional network element (Open Flow Switch) shown in the

diagram above is introduced as part of section on SDN.

SDN and NFV RelationSDN and NFV emerged as independent concepts and are

self-sufficient for the purpose they were built for. The two

technologies are complementary to each other and do not

compete against each other. Combined implementation of SDN

and NFV will maximize the benefits that are mentioned in

subsequent sections.

The scope of virtualization can be understood with the

following diagram.

Proposed LTE Network Architectural Diagram with NFV and SDN

Venn diagram – interaction of SDN, NFV, Open Innovation

Scope of Virtualization

eNodeB OpenFlowSwitch

UE

Internet

HSSPCRFMME

SGW-CtrlPGW-Ctrl

SGWData

PGWData

AppLayer

PresentationLayer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Vir

tual

izat

ion

Sco

pe

Creates networkabstractions to

enable faster innovation

Creates competitivesupply of innovativeapplications bythird parties

Open Innovation Software-DefinedNetwork

NetoworkFunctions

Virtualization

Reducescapex, opex,

space and powerconsumption


IMPROVED TIME-TO-MARKET

Time to market will be drastically reduced in a SDN/NFV enabled

network. Most of the solutions will be hardware independent

and would use the same infrastructure, thus saving testing and

integration time. Some of the services would become available

by simply adding an app at controller software in a virtualized

environment.

EASE OF OPERATIONS

Key benefit in operations will be homogeneity of the network

and efficient management and flow control of mobile IPs.

Centralization and less number of equipment will ease out

configuration management, implementation, and also reduces

risk of miss-configuration. There would be no need to login to

individual equipment for configuration, hence will save time

and resources.

Virtualization will give a readymade platform for migration of

network elements and services to cloud. Scalability and multi-

tenancy capabilities on virtualized platforms will enable easy

rollouts, upgrades and operations.

OPENNESS

SDN will provide an excellent platform for app development work,

which will help in building advanced networks. Dependency

from OEM to come up with innovative solution will be reduced

that provides openness to the technology. Readymade apps from

freelancers and domain experts will reduce cost and time for

carriers.

TECHNOLOGY MANAGEMENT

Managing multiple technologies, domains, vendors, skills processes

and policies are always complicated and challenging. SDN and

NFV will bring a common platform for technologies, vendors,

and skills required to manage. Some of the direct benefits from

technology management perspective are:

> Improved automation

> Common policy management and enforcement

> Increased availability, reliability, scalability, multi tenancy

and security

> Easy deployment and up-gradation of new technology, features

> Common skills set for resources to manage network

Adoption ChallengesSDN and NFV technology is evolving not only from technology

standardization standpoint but also in terms of broad set of use

cases that it can address to realize the benefits claimed.

Accelerators Driving Adoptions Numerous benefits across CAPEX & OPEX reduction ease of

operation, flexibility and scalability is what will and is driving

adoption of SDN & NFV technology. Few such benefits that can

be realized through the technology adoption are:-

CAPEX AND OPEX REDUCTION

Service providers will be able to reduce their CAPEX and OPEX

spend through SDN and NFV technology adoption. While CAPEX

benefits will be realized by virtue of control plane functionality

consolidation on cloud and commoditization of data switches,

the OPEX benefits will be realized by virtue of reduction in power

usage, space requirements and number of operational staff

required for operation and maintenance

Service providers can further reduce customer onboarding and

support spend by deploying commoditized data switch equipment

at enterprise customer premises as opposed to fully functional

switch, and manage those switch through control plane in service

provider’s cloud environment. Thus reducing customer on-boarding

and support spend.

“It is estimated that a CSP can have up to 50% direct CAPEX

saving by adopting SDN in backhaul [3]. Some vendors are

claiming 90% saving in CAPEX when purpose built hardware is

replaced with high performance server and routers [6].”

The ability to host multi-version for applications and multi-tenancy

will further drive down costs for service providers.

NEW REVENUE STREAMS

Mainstream adoption of SDN and NFV technology will not only

help drive down costs but also help create new revenue streams

that to an extent will compensate for declining ARPUs.

Dynamic programmability of network control elements coupled

with open standard interfaces will enable rapid introduction

of new revenue generating, value added services in network

environment.

For instance, a service that allows an enterprise subscriber to

purchase additional bandwidth through an on-line portal. Such

request from a subscriber gets orchestrated in a manner that

the policies to grant additional bandwidth towards subscriber

CPE/device get provisioned automatically at the network layer

and at edge router. This dynamic programing of the network

will reduce time to provision the policies in the network, if done

manually from operations standpoint, resulting into quick upsell

of existing data services.

Example of such services/use cases is discussed in subsequent

sections.


However, there are challenges to be addressed before SDN and

NFV technology get into mainstream adoption. Subsequent

section mentions such challenges.

STANDARDIZATION

As the technology is in its nascent stage standardization of SDN

controller APIs is not compete yet. For successful adoption of

SDN and NFV technologies there is a need to have standardized

APIs for traffic flow management, interconnect policies, and

authentication and authorization with other network elements

on priority.

For instance, in the case of policy management, PCRF and SDN

controller integration is required. While PCRF is a service/

application level policy enforcement entity also used in LTE

network, SDN controller is a L2/L3 level policy enforcement entity

for data network. Integration of these two entities is depicted in

the diagram below.

As shown in the diagram above, interface between PCRF and

PCEF (policy control enforcement function), labeled Gx, has

been standardized by 3GPP. However, there is not much focus

on standardization of APIs between SDN controller and PCRF,

which implies no coordination between policy decisions across

network elements.

This is a big challenge for successful deployment of SDN / NFV

and application development community.

IMPLEMENTATION

Migration would be a real challenge and needs a proper planning

in terms of selecting network islands and prioritizing their upgrade

keeping in mind minimum interruption to services, co-existence

with legacy networks, rollback plans and QoS maintenance.

Special considerations are required for integration of SDN

controllers as the technology is evolving and security aspects

are not mature enough.

TESTING AND DEBUGGING

In a virtualized environment, network elements would be present

in distributed fashion i.e. network elements providing same

service can be placed at different physical location. So there is

a need for specialized testing tools, which can collect data, analyze

and report exact faults points. In a virtualized network it is difficult

to ensure that traffic is properly routed. Dynamic behavior of

traffic flow according to configuration and network load would

add complications for testing. A rigorous testing is needed

keeping in mind APIs, and multiple vendors for general purpose

server and user experience.

SECURITY

As SDN / NFV are not matured technologies there are many

associated security challenges. For instance, service provider

would target 3rd party application providers to tap new business

opportunities, which risks networks against security threats. To

mitigate such security threats, a high level of security in terms

of authentication and authorization is required for 3rd party

applications that use network assets. Moreover, all controls would

be concentrated at SDN controller and any intrusion at SDN

controllers could impact the whole network.

MAINTENANCE

Operators have already invested heavily in existing network

infrastructure. Legacy infrastructure will co-exist for years to

come. The migration to SDN/NFV will be gradual with specific

nodes and functions being introduced as legacy equipment

become depreciated or obsolete and based on SDN/NFV available

feature set, resilience (carrier grade) and other operational

attributes. Centralized control plane at SDN controller makes

availability of controller an important aspect.

Due to the above facts, fault Management (hardware / software

failure) is going to be a big challenge, as it would not be easy to

troubleshoot a problem in virtualized network with simple tools.

PERFORMANCE

Telecom networks are designed with the consideration to have

minimum latency in the network to provide high throughput and

low connection time. Maintaining a low latency is a main challenge.

SDN and NFV will add more complications as single controller

has to communicate with multiple nodes and maintaining its

huge database will impact the performance. Controller-to-controller

interface is not yet standardized which otherwise improve

performance by load sharing.

Interface between SDN controller and PCRF

Gx ?

OpenFlow

PCRF

PCEF PCEF

Gx

SDN Controller

Switch


demand, service providers would need more hardware, space

and resources. EPC virtualization is an approach that service

providers can leverage to optimally address the capacity and

management requirements. Refer to section “Network Function

Virtualization” above for details.

Implementation of EPC virtualization is possible in many ways.

For instance, one virtualized logical node can have multiple

virtual machines (VMs) working as different network elements

as shown in the following diagrams.

Since each VM works in isolation and is independent of other

VMs, they don’t impact on performance of one another. These

VMs can be configured dynamically (links, network topology

etc.) as per required capacity and traffic pattern.

EPC virtualization will help operators reduce CAPEX and OPEX

and also enable dynamic optimization for rapidly changing

needs. Other advantages are stated in the section “Accelerators

Driving Adoption”.

SDN/NFV Applicability for Mobile NetworksSDN and NFV can be implemented in various segments and

sub-systems of mobile networks using industry standard COTS

hardware. Refer to the diagram SDN and NFV applicability in

Mobile Networks below for few examples of segments/sub-

systems, which are elaborated subsequently.

EPC VIRTUALIZATION

With the advent of technologies like LTE and LTE-A, data traffic

is increasing exponentially on timescale and this demand is

expected to explode in the future. To meet the increasing

SDN & NFV applicability in Mobile Networks

Mobile Backhaul

Provisioning

Cloud RAN

EPC Virtualization

CPE Virtualization

SoftwareDefinedNetworks

NetworkFunctionVirtualization

WAN Accelerator

O/BSS

Server Load Balancer

Security Functions

MME MME MME

Server

OPTION 1: Several VMs of same software component can be installed on same virtualized infrastructure. No need for dedicated HW.


The above architecture will optimize the requirement for baseband

processing capacity as it gets shared across radio heads.

“Base Station hotel” has been around for some time with

centralized baseband processing and remote radio heads fed with

fiber (up to 10-15km) but NFV provides opportunity to run

baseband on inexpensive hardware.

CPE VIRTUALIZATION

Customer premise equipment (CPE) comprises two logical

functions – service control function and data switch function.

CPE virtualization will enable service provider to host CPE service

function within its own cloud environment and deploy standard

L2/L3 switch at customer premises.

The CPE Virtualization diagram shows architecture where CPE

switch is replaced by a server which is running virtualized router

and service code.

The previous approach will not only save hardware cost and

transportation cost of signaling, but also operational cost as the

CPE service logic will reside in service provider cloud environment,

which can be easily managed from remote location. This implies

an efficient way to deploy, upgrade and configure CPEs.

CLOUD RAN

An operator’s CAPEX, OPEX expenditure on RAN is much more

as compared to core. Cloud RAN will have several benefits right

from direct cost reduction (less civil structures, less hardware,

less energy consumption) to enhanced capacity and dynamic

and uniform utilization of resources.

Today, cloud RAN architecture is evolving. Possible architecture

would have a pole mounted radio head connected through fiber

and RF signals transferred to baseband processers located in

cloud. An illustrative diagram is shown below.

EPC Virtualization

CPE Virtualization

MME SGW-Ctrl PGW-Ctrl

Server

OPTION 2: Several VMs can have di�erent software components running on virtualized infrastructure.

Cloud RAN

RRH

Fiber

UE

RRHUE

PHYMACO&M

Baseband Processors

L2/L3 CPE router withservices functionsrunning in SP Datacenter

SP NGN

IP Edge

Centralized DC

Orchestration

CPE Services

SP GW

Internet


This approach will enable implementation of many use cases as

described in subsequent section.

Service providers can benefit from implementing SDN and NFV

in many other areas such as O/BSS, security functions (Firewalls,

IDS/IPS, SSL, VPNs etc), server load balancers, WAN acceleration

and provisioning systems.

Use CasesAs discussed in previous section, SDN & NFV can be introduced

in many segments/sub-systems of mobile networks. This section

presents few end-to-end use cases that can be realized by

introducing SDN & NFV.

DYNAMIC BANDWIDTH MANAGEMENT

There is an increasing demand for bandwidth hungry services

such as HD video on demand, online gaming, cloud based apps

etc. To deliver these services with desired QoE there is a need

for better bandwidth management.

By virtue of SDN, subscriber will be able to define his/her

bandwidth need, allocate and make changes in required bandwidth

dynamically. Bandwidth management can also be orchestrated

by application or end user without involvement of service provider

personal. A framework for dynamic bandwidth management is

shown below in this section.

MOBILE BACKHAUL

Mobile backhaul comprises a complex mesh and chained

topologies designed for network resilience, traffic carrying capacity

while delivering desired QoS. Introduction of SDN in mobile

backhaul will enable managing backhaul capacity through

optimal resource utilization and dynamic traffic management.

In addition, it will also allow for co-existence of multiple technologies

on the same mobile backhaul infrastructure.

An illustrative diagram is shown below, wherein, a SDN controller,

optionally running on a virtualized platform, makes decision on

traffic forwarding and pushes the forwarding rules onto the

switches deployed.

Dynamic Bandwidth Management

OpenFlow API

Bandwidth Management Application

Higher bandwidthallocation for network

latency sensitive application

FTP Server Online Gaming Servers Online Gaming Client FTP Client

NetworkMonitoring (OF)

BandwidthManagement

SDN Controller

Orchestration Logic

Mobile Backhaul

eNodeBUE

eNodeBUE

Small CellUE

SGW

MME

SDN Controller


The architecture enables implementation of many dynamic

provisioning uses cases eliminating the need to pre-define VLANs,

interconnection of VMs and configuration parameters.

DEEP PACKET INSPECTION

Deep packet inspection (DPI) has been used since a long time to

identify and act on packet streams in the networks. The DPI

solutions today has evolved into software based implementations

that brings much better analytics for inspecting application

level (layer 4+) traffic. The software DPI solutions are easy to

manage, upgrade with new traffic signatures and are easy to

deploy in the networks compared to traditional methods.

DPI software solution, optionally deployed onto virtualized

platform, can be utilized for scenarios such as offloading certain

traffic streams to other technologies, for example Wi-Fi.

APPLICATION AWARE ROUTING

Content delivery networks typically comprise a large distributed

set of content hosting and content delivery servers that are

deployed across multiple data centers. Application aware routing

(AAR) service can be used by service providers to route service

requests to content servers that can best serve the request.

The following diagram shows an architectural implementation

of AAR service. The centralized request server, hosted on a

virtualized platform, is the first hop for all the service requests

from the subscribers. The centralized request router redirects

service request to the content server that can best serve the

request. The centralized request router acts as an application

level (layer 4+) load balancer redirecting requests based on

subscriber geographical location, availability of content in the

content server, service availability, and content server load.

As shown in the diagram, the end-to-end traffic between online

gaming servers and online gaming clients (shown by a solid green

arc) is shaped to meet service QoS requirement. In a real world

scenario such request for dynamic bandwidth allocation for a

gaming service will either be ordered by the end user through a

self-care portal or by the game provider. The bandwidth

management application will orchestrate policies for network

wide deployment and pass it to SDN controller which in turn will

push required configuration in network switches.

This auto provisioning will require no intervention from service

operations teams. This business model wherein the service

provider ties up with OTT players or directly sells on demand

bandwidth services to end users will open up new revenue streams

for a service provider to cope up with declining ARPU.

WAN INTERCONNECT

As an extension to dynamic bandwidth management use case,

WAN interconnect will allow subscribers to design their enterprise

level policies for shortest paths through the service provider

network as per bandwidth requirement which have less latency

or congestion and fewer hops across their networks. This assures

network-wide load balancing beyond node-level load balancing,

and reduces OPEX for service providers.

DYNAMIC PROVISIONING

Traditional network implementations require configuration of

pre-defined VLANs, interconnections etc. without providing

flexibility for dynamic provisioning. Introducing SDN, which implies

a centralized SDN controller, optionally deployed on virtualized

platforms, can be used to configure network switches as per the

orchestration function that runs on a remote application server.

Architectural implementation of AAR

Caching or Streaming Servers



Online user

L7 Monitoring Probes

Control MessagesData Flow

3

1

4

2

Centralized Request Router


overheads due to fewer touch points to provision and operate

as compared to a traditional network.

Key ConsiderationsWhile the benefits of adopting SDN & NFV are multi-fold, which

is evident from both the applicability of technology across mobile

networks and also from the use cases discussed in earlier

sections. However, there are few important factors that need

to be considered in order to successfully implement the SDN

and NFV technologies.

In SDN architecture, the routing rules will be pushed by SDN

controller onto the network switches. Since the network switches

will not inspect the packet flows, there would be need for additional

DPI and security solutions.

Interoperability across network equipment supporting OpenFlow

and also with IT systems would require verification as OpenFlow

implementations are evolving.

Service level policies (which acts on layer 4+ of the traffic) in mobile

networks is decided by PCRF (policy and charging rules function),

whereas policies for SDN networks (which acts on layer 2/3

traffic) is decided by SDN Controller. These two entities, namely

PCRF and SDN controller, are yet to work in tandem, which

means that service level policies at PCRF shall be linked with

L2/L3 traffic policies at SDN controller.

Network security might require network and process audit and

redesign for access privileges, firewalls. For example, a scenario

would be to detect and block applications generating unwanted

traffic.

AAR implementation can be extended further with increased

application awareness, which can be built into the network by

developing SDN controller applications that keep track of

application-level characteristics and use that intelligence to

provision flow into the network switches.

VIRTUALIZATION OF CONTENT DELIVERY NETWORK

As an extension to application aware routing (AAR), content

delivery servers along with the content can also be hosted on

virtualized platforms. Such improvements in network will simplify

removal or changing location of content delivery components.

Virtualization creates an isolation layer across virtual machines,

which will enable hosting of multiple instances of content delivery

from multiple content providers on same virtualized platform,

which will optimize management and maintenance cost..

SERVICE CHAINING

As an extension to application aware routing (AAR), service

providers can further launch composite services by service

chaining the service requests across multiple application servers

in a pre-defined order. An example of service chaining is when

a subscriber request for HD video service, this will first trigger

dynamic bandwidth management service to allocate desired

bandwidth to the subscriber for service consumption. Upon

successful grant of bandwidth, the request is routed to HD video

content delivery server to start HD video streaming.

VIRTUALIZED AGGREGATION NETWORK

Service providers can benefit by centralizing the control for

aggregation network. The centralized control will manage the

switches that are deployed in networks. This reduces operational

AAR implementation with SDN




Network Monitoring Bandwidth Management Request Routing

L7 Monitoring Probes

Control MessagesData Flow

1

2

Provisioning of Flows

SDN Controller

Online user

Route Optimization Configuration Analytics and Reporting


Testing SDN and NFV TechnologyWith advent of new technologies like SDN and NFV, the test

methodologies also require change which spans across know-

how of the technology, and specialized testing and diagnostic

tools to troubleshoot problems in this complex network

environment. Options of putting test tools and test infrastructure

on cloud is a natural evolution for test setup leading to resource

optimization.

Subsequent section gives high level guidelines on scenarios

that should be tested for successfully introducing SDN & NFV

technologies in the network.

OPENFLOW TEST SCENARIOS (FOR SDN)

> Control Channel functional testing to verify signaling protocol

e.g. connection setup, failure, and interruption of a control

channel.

> Conformance testing of protocol messages including

negative scenarios.

> Spanning tree protocol testing to test port state and its

configuration message

> Flow administration and management testing to verify the

requirements for adding, editing, deleting and removing a

flow along with flow table.

> Counter value verification per flow, per port, per queue and

per table.

> Data plane testing to verify supported actions by a switch.

TEST RECOMMENDATIONS BASED ON ETSI REQUIREMENTS FOR NFV

> Interoperability and Integration testing shall verify that

the NFV framework is capable to re-host, optimize, and

load integrate Virtualized network functions (VNF) in a

standardized multivendor environment.

> Performance testing shall verify that the NFV framework

is independent of HW used and framework shall be capable

to collect performance related information.

> Security testing shall verify that the NFV framework protects

network from E2E vulnerabilities (new HW, interfaces, third

party entities) and provide authentication, authorization,

data encryption, data confidentiality and data integrity.

> Scalability testing shall verify that the NFV framework is

capable of scaling VNFs (scale up and scale down) and moving

its components from one computing resource to another.

> Resiliency testing shall verify that Network functions are

capable to recover after failure and the NFV framework is

able to classify Network functions according to resiliency

and facilitate resiliency scheme in both control plane and

user plane.

> O&M testing shall verify that the NFV framework is capable

to provide mechanism for automated O&M (creation, scaling

and healing of VNFs based on pre-defined criteria)

OSS and BSS would require enhancements to support SDN & NFV

deployments. OSS transformation would be the key challenge

that needs a detailed strategy and planning for architectural

impacts and functional impacts.

OSS need to support virtualized infrastructure and orchestrate

virtualized network elements and virtual platform infrastructure.

Additional support to legacy network is needed during transition.

Following are some of the subsystems and processes for OSS

functional domains (service assurance and service fulfillment)

that get impacted.

SERVICE ASSURANCE

> Impacted subsystems - Fault and alarm management systems,

performance and threshold management systems,

configuration systems, security systems, service quality

management systems, health monitoring systems, SLA

management systems, reporting systems

> Impacted Processes - Network and device configuration

process, performance management process, capacity

management process

SERVICE FULFILLMENT

> Impacted subsystems - Resource and service provisioning

systems, network planning and design systems, activation

systems, workforce management, network inventory

modeling and management systems, capacity management

systems, network discovery systems, reconciliation systems,

GIS systems, reporting systems

> Impacted processes - Inventory reservation and allocation

process, Network element discovery process, reconciliation

process, Service address change process, order modification

processes, CPE management, IP address management,

network and virtual infrastructure capacity management

process, service activation process

South bound interface for SDN implementation is defined, which

is OpenFlow. However, the north bound interface is yet to be

defined. Service providers should consider defining this interface

so that it is future proof.

Early implementations from OEMs might have proprietary

extensions and could impact successful interoperability

NFV will not only bring change in how service is delivered but also

on how the service is monitored. There will be a shift from

measuring hardware downtime to service downtime. Therefore,

resilience shall be built in the service software running on

virtualized platform to instantly start up a new virtual machine

on capacity overrun or an instance crash.

NFV would also mean many virtual machines in multiple locations.

Service operations should be planned for upgrade, patching,

failure recovery across each virtual machine.


How Aricent Can Help?Aricent has helped service providers and equipment manufacturer

across the world with its thought leadership, technology

know-how, and expertise in integration, validation, rollout and

maintenance of new cutting edge technologies.

Aricent’s expertise spans across SDN and NFV technologies,

including OpenFlow, SDN applications and Northbound APIs.

Aricent has proven record for successfully delivering end to end

solutions, delivering telecom testing services (end-to-end testing,

performance testing, functional testing and test automation),

managed lab services and OSS transformation to support

virtualized networks having multi-vendor, multi- technology and

multi-release environment.

Fore-sighting the need for constantly evolving communication

networks, Aricent has developed reusable test assets (test

strategy, test plans, test cases, and processes) to reduce time-

to-market for service providers.

ConclusionNFV and SDN will change the fundamental approach of how

networks will be built in future. Focus will shift from building

networks in silos to component virtualization and then to

network virtualization.

Though lack of standardization and other issues around security,

performance of virtualized appliances / applications currently

impinge mainstream adoption of SDN and NFV, but, it is a matter

of time, when the specification forums will standardize the

technology aspects, some of which are already being addressed

in respective forums.

The use cases and applicability of NFV and SDN as discussed in

this paper will not only bring down CAPEX and OPEX in medium

to long term, but also improve time-to-market for new services,

simplify network operations and management.

> Service continuity testing shall verify that the NFV framework

is able to restore services (recover VMs, provide alternative

solution) as per SLAs.

> Co existence and transition testing shall verify that the NFV

framework co-exists with legacy network and supports

transition phase (interwork with O/BSS, ensure security of

VNF instances during transition)

> Service assurance testing shall verify that Network functions

are remotely accessible, monitored, and can perform diagnosis.

3GPP COMPLIANCE TESTING

For EPC virtualization scenario as described in sections above,

protocols and messages flow across the network will be impacted

because of the architectural changes. Therefore compliance to

3GPP specs is a must to facilitate multi-vendor eco-system.

> Exhaustive conformance testing is highly recommended for

all virtualized telecom equipment.

> KPI, Load, Capacity testing should be performed to raise

overall QoE.

> A new protocol that would get defined between control plane

and user plane of S-GW and P-GW, would require thorough

testing.

NETWORK TESTING

There would be significant changes in the network, when SDN /

NFV are pervasively deployed. It is extremely essential to test all

existing network services and to check there is no harm to the

network in terms of Quality, User Experience with introduction

of new services. Testing recommended for networks is:

> Integration testing to assure smooth roll-outs.

> End-to-end testing of all the services in real or near real network

having multi-vendor / multi technology environment.

> Field trial to assure overall performance of new technology.

> SDN controller security testing.

> No Harm to the network testing will assure that all legacy

services are working fine and not impacted with

introduction of SDN/NFV

VIKRAM NAIR

is Director Technology at Aricent

responsible for E2E Testing, VAS

& M2M practice.

[email protected]

VINOD KUMAR GUPTA

is Senior Technical Leader at

Aricent responsible for E2E

Testing pre-sales.

[email protected]

REFERENCES

(1) Open Networking Foundation https://www.opennetworking.org)

(2) Network Functions Virtualization. An Introduction, Benefits, Enablers, Challenges & Call for Action (http://portal.etsi.org/NFV/NFV_White_Paper.pdf)

(3) SDN: Bridging the Mobile Backhaul Funding Gap (http://www.tellabs.com/solutions/mobilebackhaul/tlab_bridging_backhaul_funding_gap.pdf)

(4) White Paper by Aricent: Application Aware Routing in SDN (http://info2.aricent.com/hs-fs/hub/280086/file-210287459-pdf/Whitepapers/Aricent_Whitepaper_-_Application_Aware_Routing_in_SDN.pdf)

(5) OSI model (http://en.wikipedia.org/wiki/OSI_model)

(6) http://www.nfvzone.com/topics/nfv/articles/353495-brocade-discusses-nfv-based-router.htm

(7) ETSI GS NFV 004 v1.1.1Network function virtualization (NFV), virtualization requirements (http://www.etsi.org/deliver/etsi_gs/NFV/001_099/004/01.01.01_60/gs_NFV004v010101p.pdf)

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company has 20-plus years experience co-creating ambitious products with the leading

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