Contention Resolution for Optical Burst Switching Networks Using ...

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Mar 11, 2003 - Alternative routing based intra-contention resolution scheme by suggesting a control header packet format. ✓The blocking probability is ...
Contention Resolution for Optical Burst Switching Networks Using Alternative Routing (Mar. 11, 2003) Yonsei Univ. Computer Communication Lab. Kim Hyo Jin NGI seminar

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Contents Abstract & INTRODUCTION OPTICAL BURST SWITCHING ALTERNATIVE ROUTING IN OBS NETWORKS SIMULATION AND RESULTS CONCLUSION NGI seminar

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Abstract & INTRODUCTION Dense Wavelength Division Multiplexing(DWDM) technology Exploit the huge potential bandwidth 9 Without any opto-electro-optic(O/E/O) conversions. 9

Optical Burst Switching(OBS) 9 9 9

To build very high capacity routing switches. Good solution in high-speed optical Internet backbone. Eliminate the electronic bottleneck 9

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at switching node without O/E/O conversion

Guarantee the Class of Service(CoS) 9

without any buffering. NGI seminar

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Propose : 9 Alternative

routing based intra-contention resolution scheme by suggesting a control header packet format 9 The

blocking probability is significantly reduced. Additional delay

< 10% x Basic offset time

for the alternative path

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OPTICAL BURST SWITCHING OBS composition 9

OBS network

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Each burst

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Optical core routers and electronic edge routers Control header packet and a data burst

Control header contains 9

Information of the data burst length and offset time

Packets are 9 9

Assembled into bursts at the network ingress. Disassembled back into packets at the network egress. NGI seminar

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Two coupled overlay networks 9

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A pure optical network transferring data bursts and a hybrid control network transferring control header packets. Control network 9

A packet switched network Controls the routing and scheduling of data bursts in the all optical network

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Advantages

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9 9

based on the control header packet’s information Mature electronic control technologies Promising optical transport technologies NGI seminar

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Fig. 1 : three burst switching techniques 9A

burst can cut through intermediate routers. NGI seminar

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(a) In-Band Terminator(IBT) based burst switching 9 Bandwidth 9 9

is reserved

As soon as IBT Followed end of the data burst

9 Limitation 9

Be processed all optically 9 Not support optical processing

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(b) Tell-And-Go(TAG) based burst switching 9

Operating steps ① ② ③

9 9

Source node sends a control packet over the control channel to reserve a bandwidth. Corresponding data burst is transmitted without waiting for the acknowledgement. The source node sends a release packet to the destination.

Ex) Just-In-Time(JIT) protocol Disadvantage 9

Large signaling overhead NGI seminar

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(c) Reserve-Fixed-Duration(RFD) based burst switching 9

Bandwidth is reserved 9

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Information of reservation time 9

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Carried by control packet

Ex) Just-Enough-Time(JET) protocol 9 9

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fixed time duration at each router

Eliminates the signaling overhead Improve the resource utilization

Disadvantage 9

Complexity increased. NGI seminar

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Many challenges to implement the OBS network 9 Edge

router

9 Burst

offset time management, burstification and burst assembly mechanism

9 Core

router

9 Data

burst and control header packet scheduling, protection and restoration mechanism and contention resolution scheme NGI seminar

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We focused… 9

Contention resolution 9

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The core router has no fiber delay line(FDL) and the offset time is fixed at the ingress router.

Classify the contention in intermediate core routers. The inter-class contention caused by different class bursts. 9 The intra-class contention caused by same class bursts. 9

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To prevent the inter-class contention Additional QoS offset time can be used and high priority bursts can avoid blocking caused by low priority bursts. 9 No published result yet. 9

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ALTERNATIVE ROUTING IN OBS NETWORKS Our three methods for solving the intra-contention problem in core routers ① ② ③

The wavelength converter FDL The deflection routing

We proposed.. 9

An alternative routing scheme 9

Combines wavelength converters and the enhanced deflection routing algorithm. NGI seminar

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If contention occurs at intermediate core routers, the data burst is blocked. 9 Because

it can’t change its path.

In our algorithm 9 Every

core router has hop by hop routing functions. 9 The routing table has two different paths for each destination. NGI seminar

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Operating steps 9

If contention occurs at certain intermediate core router, the hop by hop routing functions are performed. 9

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One is routed through the short path and the other is routed through the alternative path obeying certain policy(time critical burst, number of hops, etc.)

If next node does not encounter any contention, the rerouted data burst will be routed through the shortest path. The control packets contain the number of rerouting times 9

Thus if the number of rerouting is over the threshold value, the rerouted bursts are just drop to prevent looping and early arrival of data bursts.

Better than deflection routing NGI seminar

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“Routing offset time” 9 The 9 to

additional offset time make up the time by alternative routing.

9 Depends

on

9 the

network size and the header processing time 9 Ingress edge routers decide the offset time 9 Prevents

the data burst surpasses the control header. NGI seminar

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Message type 9 9

The header packet type Uniquely determines the exact layout of the message.

QoS 9

Following data burst’s priority.

Input port and Input wavelength identifier 9

Indicate the incoming data burst’s port and wavelength.

Offset time 9

The separation time between control header and data burst 9

Consists of the basic offset time and routing offset time.

Burst length 9

Length of data burst

Hop count 9

Prevent bursts not to lose their destination router or the looping environment.

Source address and Destination address 9

Addresses of the source and the destination. NGI seminar

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SIMULATION AND RESULTS Java language 9

To evaluate the performance of blocking probability 9

in the slotted 4x4 Manhattan Street network.

In fig. 2 9

Assumed 9

Nodes 9 9

0,3,12,15 nodes – edge routers Others – core routers

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The bursts arrive synchronously.

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Available wavelength at each node is one.

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Input traffic

9 9 9

Each time slot is equal to the burst duration. For simplify the simulation Exponential distribution and Pareto distribution with Hurst parameter H=0.9. NGI seminar 20

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Fig. 5 and Fig. 6 9

Blocking probability is reduced by 10 and 2 times 9

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When offered load is 0.1 and 0.9.

Self-similar traffic with H=0.9, 9

The proposed alternative routing scheme performs very well. NGI seminar

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Fig. 7 9

Alternative Path makes the additional delay(additional hop counts) performance. NGI seminar

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CONCLUSION An intra-contention resolution scheme 9 By

introducing additional routing offset time in bufferless intermediate core routers in the OBS network. 9 Using “Routing offset time” 9 Effective

to significantly reduce the blocking probability for the exponential NGI seminar

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