a perspective on photonic multi -protocol label switching · a perspective on photonic multi...

AdvancedNetworkArchitectureResearch

A Perspective on Photonic Multi-Protocol

Label Sw itching

Masayuki MurataCybermedia Center, Osaka Universitye-mail: [email protected]:/ / www-ana.ics.es.osaka-u.ac.jp/


Contents1. MPλS (MPLS based on WDM

Lightpaths) Implementation Issues and Challenging

Problems2. OC-MPLS (MPLS based on Optical

Code) Optical Implementations and Challenging

Issues3. Perspectives on MPλS and OC-MPLS

Advantages and Disadvantages

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Mapping from Generic MPLS to Lambda MPLS (or GMPLS)

Ingress LSR;Maps from IP address to lambda

X

X

X

LSR (Label Switching Router);Optical crossconnect directly connecting input wavelength to output wavelength

LSP (Label-Switched Path);Wavelength path (Lightpath)

LDP (Label Distribution Protocol);Dimensioning by wavelength and routing assignment algorithm

Wavelength Demux Wavelength Mux

Optical Crossconnect

λ1λ1

λ1

λ1

λ2λ2

λ2

λ2

λ2

λ1

λ1

OpticalSwitch

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Four K inds of Architecture1. WDM link network

Connects adjacent routers by WDM (multiple wavelengths increase the bandwidth)

2. WDM path network Cut-through techniques for

IP packets on established path provided by the underlying networks

Photonic Internet Architecture

Router

Optical Crossconnect

RouterX

X

X

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3. WDM Path Network Lambda switching by

MPLS technology(MPλS or GMPLS)

4. WDM Packet-switched Network E.g., burst switching

by routing and wavelength assignment (RWA) on demand basis

Photonic Internet Architecture (Cont’d)

X

X

X

Optical Cross-Connect

Router

X

X

X

burst

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Logical Topology by Wavelength Routing

Physical Topology Logical TopologyIP Router

Ingress LSRλ2

λ2

λ1

λ2

λ1N2

N4N1

N3

Core LSR

λ-MPLS

λ1

λ1

N5

IP Router

Ingress LSRλ2

λ2

λ1

λ2

λ1

N2

N4N1

N3

Core LSR

λ-MPLS

λ1

λ1

N5

λ2

Wavelength Demux Wavelength Mux

Optical Cross-Connectλ2

λ1

λ1

λ1

λ1

λ2

λ2

λ2

λ1

λ1

λ2

λ2

N2

N3

N4

N2

N3

N4Optical Switch

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Logical View Provided to IP

Redundant Network w ith Large Degrees

Smaller number of hop-counts between end-nodes

Decrease load for packet forwarding at the router

Relief bottleneck at the router

IP Router

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Challenging Problems of MPλS

Logical Topology Design IssuesPast researches assume the traffic matrix is givenObjective is maximization of wavelength utilization

or minimization of the required # of wavelengthsOptimization problem is then solved by LP or

heuristics Bottleneck at Ingress Nodes

Bottleneck is shifted to the Ingress Nodes requiring electronic processing

Survivability IP and WDM Functional Partitioning or Integration

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Incremental Capacity Dimensioning Approach

Initial Phase Design Logical topology

with given traffic demand Incremental Phase

primary lightpath is incrementally setup

reconfigure backup lightpaths

Readjustment Phase All of the lightpath

(including primary lightpath) is reconfigured

Readjustment Phase

Incremental Phase

Initial Phase

Reconfigurebackup lightpaths

Reconfigure both primary and backup

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Traffic Load Distribution by WDM Ring

Distribute the traffic load by WDM ring at the Ingress node

λ1

Ingress LSR

λ-MPLS λ3λ1

λ2

WDM Ring

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Effects of Introducing WDM Ring

Packet Processing Rate Required at Router Required Number of Wavelengths

10+E2

10+E3

10+E4

10+E5

0 5 10 15 20

Requ

ired

Proc

essin

g Ca

pabi

lity

(Mpp

s)

The Number of Local Nodes LN

Logical Degree = 8128512

1024

1

10

100

1000

0 5 10 15 20

Requ

ired

# o

f Wav

elen

gths

The Number of Local Nodes LN

8

Logical Degree = 1024512128

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Do We Need More “Intelligent” WDM Network? WDM network itself has network control capabilities

Routing function IP also has it!

Congestion control function TCP also has it! TCP over ATM (ABR service class) is difficult to work well

Parameter tuning of control parameters in ABR is not easy Connection establishment

IP is connectionlessMultimedia application does not require 10Gbps channel

Multi-layered Functionalities? Important is reliability

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Functional Partitioning between IP and WDM?

Reliability functionalities offered by two layers IP Layer: Routing WDM Layer: Path Protection and Restoration

WDM should provide its high-reliability mechanism to IP Protection mechanism

link protection dedicated-path protection shared-path protection

Network dimensioning is important to properly acquire the required capacity of IP paths (traffic glooming) Reconfiguration mechanism of logical topology by wavelength

routing

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WDM Protection

Immediately sw itch to backup path on failure of nodes/ links In the order of 10ms

1:1 Protection vs. Many:1 Protection

Protection technique suitable to IP over WDM network? IP has its own protection mechanism (i.e., routing) while it is slow We want an effective usage of wavelengths Many:1 protection is reasonable

1:1 Protection

Primary Path

Backup Path

Many:1 Protection

Primary Path

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Routing

Cross-Connect, Switch and Router

Photonic sw itch w ithin MPLS requires packet forwarding based on “label” queue management based on “label” packet switching and buffering

payload header

Cross-Connect

Photonic Packet Switch supported by GMPLS

Photonic IP Router

Buffering

QueueManagement

Forwarding

Switching

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Label Swapping in MPLS

Ingress LSR

In Label Out Label

10 4Label Swapping

In Label Out Label

4 133.1.12.4

Label SwappingIn Label Out Label

133.1.12.14

10

Label Swapping Core LSR

Egress LSR

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Optical Code based MPLS

Photonic label based on optical codes

Output fiber N

λ-DEMUX

λ-DEMUX

λ-DEMUX

Input fiber 1

Input fiber N

Output fiber 1

λ1, λ2, ..., λK

λ1

λ1, λ2, ..., λK

λK

MUX

MUX

MUX

MUX

MUX

MUX

MUX

MUX

OC-MPLSR#1

λ1

OC-MPLSR#N

λK

Photonic labelprocessor

Optical switch

Photonic labelswapper

Inputpackets

Outputpackets

t

1 bit time0 π 0 π

OC-based photonic label

Optical buffer

OC-based Switching NodeOC –based Switch

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Photonic Label Processing

Optical code by BPSK Photonic label processing in optical domain

photonic label is tapped from packet header optically dupilcated by optical amplification power-splitted as many copies as the count of label entries in the table optical correlations between the copies and the label entries is performed in

parallel

Input Replicas Address entries Output

Duplication Correlationx

.

.

.

.

.

.

t

t

t

t

t

t

t

#1

# 104

x104

t

t

t

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Implementations of Optical Buffers by Delay Lines

Inputpacket

Outputpacket

DL1 DL2

2x2 switch(a) Multi-stage switched delay line buffer

EDFA:Erbium doped fiber amplifier

PC: Polarization controller

PC

EDFA

(b) Re-circulating loop buffer

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Photonic Packet Switch for Asynchronously Arriving Variable Packets

Buffer Scheduling Delayed Line Buffer

Variable-Length Packets Counter for Buffer State; bij for output line j on wavelength

i For each arrival of packet with length x

For each delay unit D

For asynchronous arriving Introduce packet sequencer

/i j i jb b x D鴿・・・・・

ｬ+

1i j i jb bｬ-

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Structure of OC-based Photonic Packet SwitchWithout Wavelength Conversion

Optical Switching Unit Optical Scheduling Unit Optical Buffering Unit

Scheduler S1W

O1

I1

λ-DEMUX

λ1- λW

λ-M

UX

λ1

λWλ1- λW

λ1λW λ1

b1WλW

λ1

λ1

τ0τ1

τ2

τ0τ1

τ2

b11λ1

Head

er


Optical SW1


Optical SW


Optical SW1


Optical SW

λ1

Head

er

λWλW

λ1

λW

O2

I2

λ-DEMUX

λ1- λW

λ-M

UX

λ1

λWλ1- λW


Optical SW1


Optical SW

Head

er


Optical SW1


Optical SW

λ1

Head

er

λW

λ1

λW

Scheduler S11

SC+Gate

SC+GateSC+GateSC+Gate

λW

OC Encoder

OCEncoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

SC+Gate


λW

OC Encoder

OCEncoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

Scheduler S2W

λ1λW λ1

b1WλW

λ1

λ1

τ0τ1

τ2

τ0τ1

τ2

b11λ1

λW

Scheduler S21

SC+Gate


λW

OC Encoder

OCEncoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

SC+Gate


λW

OC Encoder

OCEncoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

OC Decoder

Tim

eSy

nchr

onize

rTi

me

Sync

hron

izer

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Structure of OC-based Photonic Packet SwitchWith Wavelength ConversionOptical Switching Unit Optical Scheduling Unit Optical Buffering Unit

Scheduler S1

O1

I1

λ-DEMUX

λ1- λW

λ-M

UX

λ1

λWλ1- λW

λ1

λW

SC+Gate

λ1

SC+GateSC+Gate


OC Encoder/Decoder

b1WλW

λ1

λW

SC+Gateλ1

SC+Gate

SC+Gate

SC+Gate

SC+Gate

SC+Gate

OC Encoder/Decoder

τ0τ1

τ2

τ0τ1

τ2

b11λ1

Head

er


Optical SW1


Optical SW


Optical SW1


Optical SW

λ1

Head

er

λWλW

λ1

λW

Scheduler S2

O2

I2

λ-DEMUX

λ1- λW

λ-M

UX

λ1

λWλ1- λW

λ1

λW

SC+Gate

λ1

SC+GateSC+Gate


OC Encoder/Decoder

b2WλW

λ1

λW

SC+Gateλ1

SC+Gate

SC+Gate

SC+Gate

SC+Gate

SC+Gate

OC Encoder/Decoder

τ0τ1

τ2

τ0τ1

τ2

b21λ1


Optical SW1


Optical SW

Head

er


Optical SW1


Optical SW

λ1

Head

er

λWλW

λ1

λW

Tim

e Sy

nchr

onize

rTi

me

Sync

hron

izer

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Performance of Proposed Switch

1E-181E-161E-141E-121E-101E-081E-061E-041E-02

1

5 10 15 20

Pack

et L

oss

Prob

abilit

y

The Number of Wavelengths W

ρ = 0.85

ρ = 0.8ρ = 0.75

ρ = 0.65ρ = 0.7

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Problems of MPλS

The incremental capacity dimensioning is infeasible in the current logical topology design approach Network performance is heavily dependent on the logical

topology design approach Unit of Path Granularity is Wavelength Capacity

too large to accommodate the end-to-end traffic The capacity increase per each wavelength does not alleviate

the problem The increase in the number of wavelengths may help it.

However, it requires the large-scaled of, e.g., 1,000x1,000 optical cross-connect

Flow aggregation at the Core LSR cannot be expected The label exchange within the network poses the wavelength

change at an optical node

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Advantages of OC-MPLS The granularity is “packet”

Allows a flexible network structure Simplified packet switching can offer large capacity in the optical domain An ATM-based MPLS protocol suite can be applied Traffic engineering developed for MPLS is also utilized.

OC-MPLS is capable of merging of packets by introducing optical buffering Attains an ultimate bandwidth efficiency MPλS is unable to realize it due to the coarse granularity.

The length of OC photonic label could be flex ible The longer label could be used as the network layer header of the packet Can be used both to assigned multiple flows from IP prefix to

application-level flow Possible to offer QoS-enabled services Optical codes are not only applicable to the exact match algorithm in the

OC-MPLS but also applicable to the longest prefix match, and hence OC-based destination-based IP routing might be realizable.

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Remaining Problems of Establishing OC-MPLS

The sw itch fabric, constructed w ith photonic space sw itch and photonic buffer, has to be optimized to achieve the desired performance

Statistical multiplex ing would work well by very huge bandw idth provided by OC techniques even if the packet buffer capacity is not large. However, a further research on the traffic engineering approach of MPLS is necessary under the conditions that the bandw idth is very large, but the packet buffer size is small.

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