SEMINAR ON

OPTICAL BURST SWITCHING

Presented By Kadlag Priti

Under guidance of Prof G.D.Puri

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Optical Switching Techniques Problems and solution for OCS and OPS What is OBS Why OBS? A Comparison OBS Fundamental OBS Network Edge Actual Data Transmission In OBS One-way vs. two-way reservation One way reservation Packet and OBS switching mechanism Just Enough Time Advantages And Disadvantages Applications Conclusion

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Optical Circuit Switching Bandwidth inefficient for bursty data (internet

traffic). Frequent long circuit setup Waste bandwidth during off/low-traffic periods

Optical Packet Switch A packet contains a header and the

payload(variable or fixed length). Each node needs to buffer, process the header,

and send it to the next switch.

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• Problems:– Explosive traffic growth and bursty Traffic pattern– Lack of optical buffer (RAM) for packet switching.– Fiber delay lines (FDLs) are bulky and provide only

limited delays– Need fast processing of header and payload

• Solution:– Find a method between circuit switching and

packet switching.– To increase the Bandwidth efficiency.– That’s Optical Burst Switching comes into the

picture

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• OBS combines benefits of OCS and OPS.• OBS is an attempt at a new synthesis of

optical and electronic technologies.• OBS lies between OPS and WRN.• In OBS, data is transmitted in variable size

packets called Burst. • A burst is switched to next node before its

last bit arrives which will reduce offset time.• No store and forward is required.• It provides strong separation between

control and data plane.• It will reduce the problem of bursty traffic.

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OBS combines the best of circuit-switching and packet-switching

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• In an OBS network, various types of client data are aggregated at the ingress (an edge node) and transmitted as data bursts which later will be disassembled at the egress node.• The process of burst assembly is called as the burstification.

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Network Edge OBS users perform the following four functions

1. Burst assembly2. Signaling3. Routing & wavelength assignment4. Computation of offset time for control packet

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Data is transported in variable sized units called bursts.

When a burst is ready, reservation request is sent to the next resource.

Data is sent shortly after the reservation request, without receiving an acknowledgement of successful reservation.

Control and data signals are send on different channels.

There are two protocols for data transmission in OBS namely JET and JIT.

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In one-way reservation, burst is sent out after prespecified delay, called offset, without waiting for acknowledgment (ACK) that connection has been established.

In conventional two-way reservation, source OBS user would wait for ACK before sending any data.

Benefit of one-way reservation Significantly decreases connection set-up time to one-

way end-to-end propagation delay plus time required to process control packet & configure optical switch fabric at intermediate OBS nodes.

Shortcoming of one-way reservation Burst can be lost since control packets may not be

successful in setting up connections due to congestion on data wavelength channels.

Retransmission of lost bursts is complex.

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ONE WAY RESERVATION

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Incomingfibers

Fixed-length(but unaligned) FDL’s

Synchronizer

Header

Payload

Setup

Header recognition,processing, and generation

Switch1

B

C

DNewheaders

2

1

2 2

1

(a)

A

Switch

2

1 1

2

(b)

O/E/O

Control packet processing(setup/bandwidth reservation)

2 2

1 1

Controlpackets

Data bursts

Controlwavelengths

A

B

C

D

Datawavelengths

Offset time

• JET is a special protocol for reservation of resources for burst.

• Basic ideas– Each control packet carries the information

like offset time and burst length.– The offset time is chosen so that no optical

buffering or delay is required at the intermediate nodes.

– Delayed reservation: the reservation starts at the expected arrival time of the burst

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Connection establishment. Connection tear down. Connection failure due to request

rejection. Connection failure due to data lost.

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Advantages…• More efficient bandwidth utilization.• Remove throughput limitation.• Guard band between burst and header.• Reduce processing requirements. Energy consumption.   Disadvantages…• Limited/No QoS.• Less processing speed.• Noise Problem

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OBS supports multiservice traffic offering high bandwidth efficiency and low latency. File transfers. Multimedia Application like restore films, add videos, edit video clips etc.

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Optical packet and circuit switching were discussed and compared to the new OBS switching technique.

OBS is a very promising switching technique that will most likely be adopted in the future.

Optical burst switching (OBS) as an efficient way to resolve the problem of congestion that the Internet is suffering from.

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Thank You

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Any Questions ?