Apr 22, 2023 www.com.dtu.dk 1

Optical burst and packet switching

(the long term goal of optical networking !/?)

Lars Dittmann, NET•COM•DTU,

Technical University of Denmarkld@com.dtu.dk

Apr 22, 2023 www.com.dtu.dk 2

Two areas addressed in this talk:

• Optical network in general (short and long term)

• Optical switching (the E-Photon/ONE perspective)

Apr 22, 2023 www.com.dtu.dk 3

Optical networking – what is that?

• Optical networking and optical transmission is often confused !!

• Generic SDH/SONET is often called “first generation optical networks” – but optics is in no respect involved in any networking function i.e. only static point-to-point connection (but first time optical transmission was standardised).

• Optical networks contains elements where the optical signal (in the optical domain) can be routed/switched in several directions.

- and due to that, is optical network typically analogue networks and as such very simple.

Apr 22, 2023 www.com.dtu.dk 4

Transport network rather than optical networks

• Current evolution of transport network (short term 0-5 years)– Next generation SDH/SONET (VCAT/LCAS – flexible

and dynamic bandwidth, circuit switched capacity below a wavelength)

– PBT – proprietary Ethernet extension to MAC-in-MAC (driven by NORTEL and BT) – Circuit oriented packet switching

– T-MPLS – standardised extension to Ethernet (driven by ALCATEL/LUCENT) – circuit oriented packet switching.

– Ethernet based – extended with routing functions and resource reservation.

– No transport network – just pure transmission (driven by Cisco and Juniper)

Apr 22, 2023 www.com.dtu.dk 5

Trends in optical networking

• Today the optical network technology is (slowly) evolving (in many domains) and is getting more mature for use in operational network.

• WDM enabled the used of wavelength routed network– With or without wavelength conversion (studies indicates that

wavelength converters are mainly an advantage when traffic is highly dynamic)

• The Internet and migration towards packet mode handling of services pushed for time-domain operation in all layer – including the optical layer.

• IP over DWDM – slim layered structure with optics taking over all functionalities below the IP layer (high bandwidth, efficient bandwidth management and QoS, network resilience etc.)

Apr 22, 2023 www.com.dtu.dk 6

Trends in optical networking

• Long terms wavelength assignment• Fast wavelength assignment (wavelength

switching)• Burst switching (or very fast wavelength

switching) • Packet (or cell) switching (fixed or variable

packets)• Overall trend: more time domain dynamics

driven by changes in application demands and better optimization and utilization of bandwidth resources)

Apr 22, 2023 www.com.dtu.dk 7

Key problems in optical networking

• Technological problems are many – a number of things proven in lab or in small scale, but hard to move into reliable operational networks. Including the optical flip/flop and 3R that is first step to make optical networking digital)

• Administrative problems (in addition of getting access to the signal) is also hugely addressed – specially for wavelength routed networks, but also for OBS and OPS networks.

• However – optical networking only make sense in relation to a transport networks as an optical packet router is not a one-to-one replacement for an IP router.

Apr 22, 2023 www.com.dtu.dk 8

Trends in network administration (network resources)

• Classic split in network control (realtime operation) and network management (off-line).

• Network control being automated and based on algorithms and local knowledge

• Network management based on manual interaction and global knowledge.

• Trend: Stronger integration of control and management – dynamic operation in all layers

Service/application layers

Transport network layers

Control

Management

IntegratedControl/Management

Apr 22, 2023 www.com.dtu.dk 9

Trends in network administration (network resources)

Integrated system vs. segmented systems.

Higher layerService/application oriented

(Packet/cell switched)

Lower layerPhysical media oriented

(Circuit switched ??)

Integrated loop

Higherloop

Lowerloop

MPLS e.g.

ASON/ASTNe.g. GMPLS

Apr 22, 2023 www.com.dtu.dk 10

OBS&GMPLS

Source: Anna Vasileva Manolova COM-DTU, ” Contention Resolution in OBS Networks with GMPLS Control”

Integration of GMPLS and OBS function – hybrid control plane

PROPOSAL for OBS and GMPLS integration

Apr 22, 2023 www.com.dtu.dk 11

Comments

• Despite it is said that the optical technology provides unlimited resources – most trends in different areas of optical networking is focusing on resource optimization._____________________________________

• Both OBS and OPS aim at better resource granularity and higher utilization compared to pure WDM networks.

• Control systems aim a having a direct related modification of resource assignment in lower layers (potentially having more stable routing table in application layers)_____________________________________

• Why do we care about resource optimization in the optical layer, when cables usually contains tens or hundreds of fibers that with cheap CWDM easily provides a small (and typical) number of wavelength per fiber. (For the access we aim at ulimited bandwidth.)

Apr 22, 2023 12

VD-S: Optical Switching SystemsVD-S: Optical Switching Systems

Overview of Research in Optical Switching(VD-S: Virtual Department Switching)

Apr 22, 2023 www.com.dtu.dk 13

Key issues identified by partners as scope of work:

• Optical Packet Switching• Optical Buffering• Wavelength Converter Usage

Reduction• Optical Signal Monitoring• Packet Compression

Techniques• Recovery Switching• Quality of Service in Switches• Physical Impairment Based

Switching• Optical Clock Recovery• Wavelength Conversion by

Nonlinear Effects

• Optical Flip-Flops• Hybrid Optical Switch

Architectures • GMPLS Optical Switch Nodes• Contention Resolution

Schemes• OTDM Time-slot Switching• Multi-wavelength

Regeneration• Optical Cross Connect• 2R Regeneration• OCDM encoders/decoders• Optical Multicast Architecture

Apr 22, 2023 14

Signaling Protocol Extensions forSignaling Protocol Extensions forConverter-saving Wavelength Assignment in GMPLS Converter-saving Wavelength Assignment in GMPLS Optical NetworksOptical Networks

N. AndriolliN. Andriolli11, J. Buron, J. Buron22, S. Ruepp, S. Ruepp22, F. Cugini, F. Cugini33, L. Valcarenghi, L. Valcarenghi11, P. Castoldi, P. Castoldi11

IEEE Workshop on High Performance Switching and RoutingHPSR 2006 – Poznań

1: Scuola Superiore Sant’Anna di Studi Universitari e di Perfezionamento, Pisa, Italy2: Department of Communications, Optics & Materials, DTU, Copenhagen, Denmark3: CNIT, National Laboratory of Photonic Networks, Pisa, Italy

Apr 22, 2023 www.com.dtu.dk 15

Motivations

Converter waste increases: the network cost the blocking probability, with a

limited amount of WC

• Extends connection-oriented, traffic-engineered MPLS approach to multiple switching layers

• Defines specific protocol extensions to simplify operation in WDM optical networks

GMPLS framework strong candidate to control next generation data networks

The wavelength assignment process performed by GMPLS

signaling can be optimized• Use standard and novel

signaling extensions to collect information on the label preference from the nodes along the path

• Design node-local algorithms exploiting these extensions to reach the specific target

Minimize wavelength converterutilization in wavelength-routed

optical networks

Apr 22, 2023 www.com.dtu.dk 16

LSP setup procedure Routing: shortest path on the sub-graph with links having

at least an available wavelength Wavelength assignment: signaling session along the found path

• From destination to source• Carries the wavelength selected by each

upstream node for its previous hop

RESV message:

PATH message:• From source to destination• May carry additional objects,

such as the Label Set

Asource

B

WC

C

WC

Ddest

1

2

3

4

1

RESV

PATH

1

2

4

Label Set =

PATH

1

3

4

RESV

1

RESV

1 3

RESVRESV

3

RESV

2WavelengthConversion

Not designed to avoidunnecessary WC

PATH

1

3

Apr 22, 2023 www.com.dtu.dk 17

Label preference with Suggested Vector• Novel optional object

included in PATH message• Indicates the preference

level for each wavelength within the Label Set

• General purpose: allows to rank wavelengths according to a given preference metric

Asource B C D

dest

1

2

3

4

1

RESV

1

3

4

PATH

1

3

PATH

RESV

1

RESV

1

000

Suggested Vector

010

01

PATH

1

2

4

Label

Set

=

SV computing algorithm Source node: 0 for any label (no

WC) Intermediate nodes: same value

for labels available on the previous hop, otherwise minimum received SV + 1

Label reservation algorithm At destination, reserve the label

with minimum received SV and propagate it as far as possible

If a conversion is needed, reserve the label with minimum received SV

In this scenario SV contains the number of conversions needed to

use the corresponding label

Apr 22, 2023 www.com.dtu.dk 18

Optical flip-flop based on Erbium-Ytterbium doped fibre

Mirco Scaffardi, SSSUP, Pisa

Apr 22, 2023 www.com.dtu.dk 19

Reset pulsesSet pulses

t

t

out

50/50

coupler

t

tSet Pulses (1535 nm)

Reset Pulses (1565 nm)

Er3+/Yb fiber

t CW1541 nm

outt

Read Signal(1541 nm)

1 2

3

circulator

Operating principle absorption stimulated

emission

1,5 m

Fibre transparent

Fibre not transparent

=1541 nm

Pulsewidth: 10 nsRep. Frequency: ~ 900 kHzPulse energy: 18.48 nJ

Pulsewidth: 10 nsRep. Frequency: ~ 900 kHzPulse energy: 19.82 nJ

Apr 22, 2023 www.com.dtu.dk 20

Experimental results

-4,5 -4,3 -4,1 -3,9 -3,7 -3,5 -3,3 -3,1 -2,9 -2,7 -2,5 -4,5 -4,3 -4,1 -3,9 -3,7 -3,5 -3,3 -3,1 -2,9 -2,7 -2,5

-4,5 -4,3 -4,1 -3,9 -3,7 -3,5 -3,3 -3,1 -2,9 -2,7 -2,5

Time (µs)

Time (µs)

Time (µs)

Out

put (

a.u.

)O

utpu

t (a.

u.)

Inpu

t (a.

u.)

PSet =9dBm

PSet =12dBm

Pread=-12dBm

Pread=-4dBm

1102 ns

1102 ns 422 ns

680 ns

Set pulses

Reset pulses

1.25 mV

3.2 mV

•Transition time of 10 ns measured.•Transition time reduced increasing set and reset power and decreasing their width.•High level memorization time up to dozens of µs is possible

Apr 22, 2023 www.com.dtu.dk 21

Thank you for listening!

Questions and comments!