Recovery Time of Degraded Throughput in Best-Effort CWDM Networks with ROADMs

Graduate School of Engineering, Osaka Prefecture University, Japan

Shogo Kawai

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ContentsIntroductionExperimental IP-over-CWDM Network with ROADMSRecovery Time of Degraded Throughput When Removing Congestion Congestion Removing by Adding a

Lightpath Congestion Removing by Adding a

Static Bypass Route

Conclusion

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IntroductionRapid increase of traffic demandsNetwork types Optical LAN, Campus networks

and factory networksCWDM technologies are effective No wavelength stability control The devices are low costImportant tasks by the network administrators Avoid traffic congestion

The demand changes

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ROADM (Reconfigurable Optical Add/Drop Multiplexer)

Optical couplers and splitters The wavelength number was

limited We proposed stackable ROADM

(S-ROADM) [5]

Evaluate the traffic congestion removing performance Lightpath reconfiguration IP routing reconfiguration

[5] Md. Nooruzzaman, Y. Harada, O. Koyama, and Y. Katsuyama, “Proposal of stackable ROADM for wavelength transparent IP-over-CWDM networks”, IEICE

Trans. Commun, vol. E91-B, No.10, pp. 3330-3333, 2008.

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Performance required to the Network

SLA (Service Level Agreement) Transmission services should satisfySLS (Service Level Specification) Performance parameters

throughputs, delay, packet loss, connection setup time, service availability, routing stability and recovery time

User classifications[10] Premium, Gold, Silver and Bronze

When the Ethernet-based IP transmissions are assumed in the IP-over-CWDM network, the service level class belongs to Bronze

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Experimental IP-over-CWDM Network with ROADMS

S-ROADM

Common-ROADM with couplers and

splitters

ROADM

Optical Trancivers

Layer 3 Switch

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Recovery Time of Degraded Throughput When Removing Congestion

The congestion removing performance Recovery time to keep throughput

The recovery time is 10s for Bronze users [10] IP Packets are routed by OSPF (Open Shortest

Path First)

CS (Control System) connected to Node1 monitor the port throughput of the L3SWs send control signal to ROADMs and L3SWs

2 possibilities Lightpath reconfiguration by ROADMs IP routing reconfiguration

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Congestion Removing by Adding a Lightpath

Lightpath set LS0

Only one direct lightpath L2 connects Node1 and 3

congestion occurs in L2

L11 and L12 are reconfigured to make L’11

If the traffics can be transmitted without L11 and L12

(a) Lightpath set LS0 (b) Lightpath set LS1

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Experimental Results

Packet Stream S1

TX1(Node1)→Rx1(Node3)

Increased by 0.1Gbps every 5s

Packet Stream S2

Tx2(Node1)→Rx2(Node3)

0.5Gbps (constant)

Threshold ＝ 0.95Gbps

0

200

400

600

800

1000

1200

1400

15 20 25 30 35 40 45

Thr

ough

put (

Mbp

s)

Time (s)

S1 Receivedat Node 3

S2 Received at Node 3

Total ThroughputSent from Node 1 Total Throughput

Received atNode 3

Port ThroughputMonitored

at A2

Port ThroughputMonitored

at A1

8 s

10sControl & Conf.Signals

Threshold

5 s

A1(L2)=1Gbps Control signal sent

by CS

Congestions were removed A1(L2)=0.5Gbps=S2 A2(L’11)=S1 The routing for S1

was changed by the CS

Total throughput sent from Node1=1.1Gbps Total throughput

received at Node3 = 1Gbps

Congestion occurred Single lightpath had

a bit rate of 1Gbps

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Congestion Removing by Adding a Lightpath

After the control signals were observed It took 8s on a packet detection base

to remove the congestion, includes the establishing time by

OSPF.

10s after the port throughput exceeded the threshold The congestion related time was 10s

at longest The recovery time specified for Bronze

users

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Congestion Removing by Adding a Static Bypass Route

Streams S1 and S2 Congestion occurs in L2

The routing for S2 is changed so as to send S2 through a bypass route

Sending a file containing the commands to add the destination, nexthop, and the

preference to the L3SWs

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Experimental Results

0

200

400

600

800

1000

1200

1400

5 10 15 20

Th

rou

ghp

ut (

Mb

ps)

Time (s)

S1 Received at Node 3

S2 Received at Node 3

Port ThroughputMonitored at A2

Port ThroughputMonitored at A1

Threshold

Control Signal

3 sTotal ThroughputSent from Node 1

Total ThroughputReceived at Node 3

S1 : Increased by 0.2GbpsS2 : Constant at 0.2GbpsControl signal sent

Static bypass route was created

Total throughput received at Node 3 was below 1.1Gbps

The routing for S2 was changedCongestion

occurred in L2 for about 3s

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ConclusionCongestion removing performance has been investigated and examined in an experimental 5-node IP-over-CWDM network with S-ROADMs

By adding a new lightpath can provide effective adjustment of large traffic

By adding a static bypass route can provide fine granularity adjustment of traffic

It is found that the congestion related time was 10 s at longest, which is equal to the recovery time specified by the SLA

Thus, the S-ROADMs enable us to keep the throughput by the lightpath reconfigurations or adding a static bypass route within the recovery time by the SLA

Further Study : the recovery time depends on the traffic pattern, the control procedures and others, requiring further study to satisfy the SLA in more general traffic