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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
2Software Defined Network and Network Functions Virtualization - An 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
3Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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.
4Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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
5Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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.
6Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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
7Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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.
8Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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
9Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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
10Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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
Caching or Streaming Servers
Caching or Streaming Servers
Online user
L7 Monitoring Probes
Control MessagesData Flow
3
1
4
2
Centralized Request Router
11Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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
Caching or Streaming Servers
Caching or Streaming Servers
Caching or Streaming Servers
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
12Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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.
13Software Defined Network and Network Functions Virtualization - An Inevitable Evolution for Communication Networks
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.
vikram.nair@aricent.com
VINOD KUMAR GUPTA
is Senior Technical Leader at
Aricent responsible for E2E
Testing pre-sales.
vinod.gupta@aricent.com
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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