1. The impact of SDN on the technological development and usage of future optical networks
PhD candidate: Shuna Yang
Department of Telematics, NTNU, Norway
Supervisor: Associate Professor Norvald Stol

2. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Common open interface
Conclusions

3. Introduction Future optical network Applications Big data Cloud
A wide range of services with variable service demands.
Development direction (more transparent data plane)
Higher transmission capacity
Unlimited bandwidth growth of applications
Longer optical reach
Optical signal quality decreases as transmission distance increases
Higher switching capacity
Optical switching elements
Development direction (more intelligent control plane)
More dynamic (current static network)
applications with unpredictable traffic patterns
More flexibility
Improve resource utilization (traffic grooming..)
Simpler control and management
Large, multi-domain networks
Today, the hot words like big data, cloud, advanced LTE is bonded up with our daily life. Large amounts of new applications is coming into our network.some has ... Some has... In one word, we can say,
The future optical network has two main direction.
Long-term requirement: high capacity intelligent optical network.

4. Introduction Intelligent optical networks: ASON-PCE-SDON
ASON (Automatic switched optical network)
(objective) fast connection set up/delete
(mechanism) distributed signalling/ distributed routing
(protocol) GMPLS
Provides automatic switching and connection management functions
Main property: Distributed control model
Path setup initiated by the head-end of path
The head-end computes the path based on local information
The path is set up via distributed signaling (RSVP)
The network retains autonomous actions (e.g. restoration)
Not suitable for large, multi-domain networks.

5. Introduction Intelligent optical networks: ASON-PCE-SDON
PCE (Path computation element)
(objective) constraint-based path computation
(mechanism) distributed signalling/centralized routing
(protocol) PCEP
Solves the problem of path computation in large, multi-domain networks.
Main property: Central path compute model
Path setup initiated by the head-end of path
The head-end asks for a path from centralized path computation (PCE)
The path is set up via distributed signaling (RSVP)
The network retains autonomous actions (e.g. restoration)
Partly suitable for large, multi-domain networks.

6. Introduction Intelligent optical networks: ASON-PCE-SDON
SDON (Software defined optical network)
Main property: Centralized model
Path setup initiated by SDN controller
SDN controller computes the path based on global information
SDN controller sets up the path by provisioning each node separately
Most (all) network control funcitions are centrallized
(objective) Transfering the network into a progammable resource
(mechanism) centralized signaling/ centralized routing
(protocol) OpenFlow
Realize the broader control functions in large, multi-layer optical networks
Main advantages:
Programmable optical layer: flexible hardware selections
more efficient and reliable automatic unified control
optimize the utilization of network resources
shorter time to implement new technologies and products

7. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Common open interface
Conclusions

8. Introduction What is SDN
The international Optical Fiber Conference lists «SDN» as one of the most important hot topics.

9. Introduction What is SDN
SDN definition: a control framework that supports programmability of network functions and protocols by decoupling the data plane and control plane, which are currently integrated vertically in most network equipments.
Framework-three layers:
Application layer: consists of network services, applications and orchestration tools to interact with control layer.
Control layer: consists of a centralized control plane to provide centralized global view to entire network; uses OpenFlow protocol to communicate with lower layer.
Infrastructure layer: physical network devices, implementing OpenFlow protocol to implement traffic forwarding rules.
Main features:
Separation of the control plane from the data plane.
A centralized controller and view of the network
Open interfaces between the devices in the data and control plane.
Programmability of the network by external applications

10. Introduction What is SDN
OpenFlow: a standards based protocol allowing for a centralized control plane in a seperate device (the controller), It seperates the programming of routers and switches from underlying hardware.
OpenFlow switch:
Flow table: several flow entries (match rules, counters, actions).
Secure channel: exchanging message between switch and controller.
OpenFlow controller:
Add, update, or delete flow entries from the switch’s flow tables
While SDN is a architecture, OpenFlow is a protocol that enables deployment & implementation of it.

11. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Common open interface
Conclusions

12. Introduction SDN-SDON
So far, the SDN and OpenFlow technologies are mainly applicable on packet-switched IP network, and cannot be applied directly on the circuit-switched transport networks.
Optical transport network vs. packet-switched network:
Large capacity: single fiber transmission capacity has exceeded 100 Tb/s.
Low power consumption: optical circuit switch vs electronic packet switch; optical signal operations-combining, filtering (completely passive)
High scalability: large switching granularity of optical circuit switch.
Future direction: SDN + Optical transport network = SDON
SDN (+ Optical transport network):
High capacity.
High scalability.
Low power consumption
Optical network (+SDN):
More intelligent: more flexibility on hardware selection, shorter time to implement new services, more efficient and reliable automatic control, optimized network resource utilization.

13. Introduction How does SDN apply to optical transport networks??
SDN-SDON
How does SDN apply to optical transport networks??
Packet switch!=optical switch
Optical networks!=generic hardware
Transport SDN is much more than OpenFlow and protocol extensions.

14. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Open common interface
Conclusions

15. SDON concepts General architecture of SDON SDON structure (reference):
Three elements:
Physical hardware: transmitter, receiver, switching nodes, amplifiers, etc.
Network controller: different application software, network hypervisor, operating system, debugger and manager.
Common open interface: allows the control application software from different vendors to be applied seamlessly over the same network, allows simultaneous control of multiple networks by the same control and management software
Note: network controller here consists of SDN controller and application controller

16. SDON concepts SDN-SDON: Main function extension Main technologies:
Physical hardware: software-defined optics.
Network controller: network visualization; SDN control function extension
Common open interface: OpenFlow protocol extension with circuit switching
Three elements requirements:
Software defined optics: Physical hardware are software programmable to perform flexible operations
Intelligent controller: utilizes the flexibility of physical hardware to manage the network, perform network optimization and customization.
Common open interface: OpenFlow protocol with extended optical circuit switching capability
SDON structure (reference):

17. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Open common interface
Conclusions

18. SDON technologies Physical hardware technologies for SDON
Key technologies: variable transponder, flexible wavelength grid and dynamic switching node
Variable transponder: Objective: the network operator can dynamically change signal characteristics (e.g. data rate, modulation format, error-correction coding scheme) for different WDM channels according to their instantaneous link conditions and service demands.
Modulation format
method:
1.altering the number of constellation points whilst maintaining the symbol rate to vary the payload data rate between Gbps (commercial 100Gbps DP-QRSK transceiver).
Optical limitation: tradeoff between bandwidth and reach for a specific network span: higher bandwidth capacity over shorter distances or lower bandwidth capacity over very long distances.
DP-QRSK: Dual polarization. Quadrature Phase shift keying.
Symbol rate: header information. Is not equal to Payload rate.

19. SDON technologies Physical hardware technologies for SDON
Variable transponder:
realization schemes:
Digital transmitter (modulation format is changed dynamically by DSP),+DAC to modulate onto the optical signal. (+++: can select appropriate FEC coding scheme without excess overhead. ---: high-speed electronics, high cost and power hungry)
Cascading optical modulators and an E-O-E multilevel drive signal generator. (+++: no DSP and DAC, ---:the available modulation schemes are limited)
Design: the properties of the transponder (bit rate, optical reach, bandwidth requirement) should be adjusted based on the link length and physical properties of the channel.
A model of a software-programmable transponder (transmission parameters can be adjusted based on network demand)
Cross talk, four-wave mixing, etc.

20. SDON technologies Physical hardware technologies for SDON
Key technologies: variable transponder, flexible wavelength grid and dynamic switching node
Flexible wavelength grid:
Main objective: flexibly define the super-channels to accommodate any combination of optical carriers, modulations, and data rates.
ITU-T G :
Variable frequency slots
12.5 Ghz increment slots
Superchannel width with Nx12.5 Ghz
Network design: spectral efficiency vs. network fragmentation
If spectral efficiency is of primary importance : the channel can be small and the modulation scheme tuned accordingly.
If span budget and distance is of primary importance: a wide channel can be defined to accommodate a less bandwidth efficient but longer distance modulation scheme.

21. SDON technologies Physical hardware technologies for SDON
Key technologies: variable transponder, flexible wavelength grid and dynamic switching node
Dynamic ROADMs:
Realization method: using various architecture with (flexible grid ) WSS, Photonic cross connect, or multicasting switch.
Directionless: any transponder can receive signal dropped from any input degree, and can send signal to any output degree.
Colorless:any wavelength can be dropped to or added from each transponder.
Contensionless: any signal from the same wavelngth can be dropped down from multiple inputs simultanenously. And can be added to different outputs simultaneously.
Flexible:individual passband with can be changed dynamically to fit signals from variable transponders.

22. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Open common interface
Conclusions

23. SDON technologies controller technologies for SDON
Extensions: control plane design, OpenFlow extension, and network abstraction&virtualization
Control plane design:
In principle, GMPLS control plane can:
Constraint-based path computation.
Path & equipment constraint
Wavelength constraints
Optical constraints (OSNR, power,…)
Optical layer automation
End to end path provisioning
Optical path restoration
Multi-layer operation
Service activation across layers
Exchange of topology information
Virtual topology concept
Makes optical layer operation as simple as electrical layer.
Is transport SDN just GMPLS repackaged?

24. SDON technologies controller technologies for SDON
Reality, GMPLS control plane:
Facilitates LSPs through LSRs, autonomously, but:
In practice is usually single layer implementation, and there is no higher level awareness of the network
Is typically not interoperable across different vendors
SDN (service-oriented):
Multi domain
Multi vendor
Multi layer
Programmable
How to leveage existing GMPLS control plane for SDN?
One possible solution: we can use GMPLS as internal Signal Protocol

25. SDON technologies controller technologies for SDON
Control plane design:
Possible solution 2: Using SDN (OpenFlow) control plane to replace the existing control plane (e.g.GMPLS)
Intradomain table(holds flow identifiers and associated actions for each NE within a particular domain). Interdomain table (enforcing cross technology constraints for bandwidth allocation). Note: domain flow table in controller map the technology abstractions, the flow table in device provide individual network node abstraction

26. SDON technologies controller technologies for SDON
Extensions: control plane design, OpenFlow extension, and network abstraction&virtualization
OpenFlow extension:
Generic flow definition (which can be generalized for different optical transport technologies).
Objective: flow identifiers are made general enough to allow applying the concept of optical flow to both existing and emerging optical transport technologies.

27. SDON technologies controller technologies for SDON
Extensions: control plane design, OpenFlow extension, and network abstraction&virtualization
Challenges in optical networks:
Built as vendor islands; vendor-propriety transport technologies; element and technology complexity.
Abstraction&virtualization is a key concept to pool servers, storage and appliances and share them in a flexible and dynamic way.
Network-as-a-service
Optical network virtualization can happen at different levels
Main aim of SDN: Tuning network into a programmable resource

28. SDON technologies controller technologies for SDON
Optical transport network virtualization (resource virtualization):
Complexity hiding (what happens in optical network, stays in optical networks); constraints modeling (in IT terminology, without optical characteristics).
Three key methods: node scope, link scope , and network scope virtualization.
Node scope virtualization:
Partition individual physical resources to multiple virtual nodes
Represent individual complex nodes as groups of simple nodes
Virtualization can be divided into function virtualization and resource virtualization.

29. SDON technologies controller technologies for SDON
Optical transport network virtualization:
Complexity hiding (what happens in optical network, stays in optical networks); constraints modeling (in IT terminology, without optical characteristics).
Link scope: paths in one network become links in another network
Hide unneeded information (e.g. Inline amplifiers, etc.)
Suitable for complex layer adaptions (for example, path in ODUk network becomes link in ethernet network, thus OTN transport element providing ethernet link)
Network scope: networks become virtual nodes in other networks
Respect administrative, security, regulatory boundaries

30. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Open common interface
Conclusions

31. SDON technologies Common open interface for SDON
OpenFlow extensions: to support optical network (upload the NE capabilities and download configuration information)
A reference SDON architecture of multi-layer multi-technology network
Two main extensions:
flow mapping rule in multi-domain scenario (overcome the cross technology constraints).
OF protocol extension (Switch_Feature message and Cflow_Mod message)

32. SDON technologies Common open interface for SDON
Generic flow definition: be made general enough to allow applying the concept of optical flow to both existing and emerging optical transport technologies.
OpenFlow protocol extension:
Switch_Feature message: supports optical NE capabilities (CF, bandwidth granularity, signal types)
Cflow_Mod message: configuring optical NE, e.g. transponders, switching nodes
Flow mapping rule

33. Outline Introduction SDON concepts SDON technologies Conclusions
Future optical networks (evolution)
What is SDN
SDN-SDON
SDON concepts
General architecture
Main functions
SDON technologies
Physical hardware technologies
Control function extension
Open common interface
Conclusions

34. Conclusions Improvements and Challenges Improvements:
more flexibility on hardware selection,
shorter time to implement new services,
more efficient and reliable automatic control,
optimize network resource utilization,
reduce the CAPEX and OPEX,…
Challenges:
Standard: how to make one open standard protocol in large, multi-technologies, multi-vendor network (OpenFlow, GMPLS, PCEP, etc.)?
Scalability: how to enable the controller to provide a global network view? (latency? Network dimension?)
Security: how can the software-defined network be protected from malicious attack?
Interoperability: how can SDN solutions be integrated into existing networks? (deploy a completely new infrastructure? impossible)

35. Thanks!!! Questions??