OPTICAL PACKET SWITCHING

Done by : ARUN JOY

R7A11

WHAT IS A SWITCH ?? Device that channels incoming data from any of the multiple input

ports to any of the output ports.

SWITCHING TYPES

CIRCUIT SWITCHING

PACKET SWITCHING

o In circuit switching a dedicated path is established for communication. E.g.: telephone networks

o In packet switching, the messages to be transmitted is broken to small PACKETS.

Today’s switching networks

ROUTING and TRANSMISSION are the two functions required to move packets through networks

The router uses the information in the packet-(IP header, Type, Priority) to

route the packets from input to output

with minimal packet loss

Optic fibers

A medium for transmitting information in the form of light pulses along a glass/fiber

Also known as LIGHT PIPE Provides greater bandwidth

WAVE LENGTH DIVISION MULTIPLEXING (WDM)

• A technology used to increase the information rate

• Here multiple signals can traverse through a single strand of optic fiber

USE

• By the use of this technology, optic fiber transmission system can carry 32-80 wavelengths modulated @ 2.5gbps-10gbps per wavelength

OPTICAL TRANSMISSION MEDIA

• In MAN, links between the nodes are optical fibers

• Here packets are in the optical format• O-E-O conversion are required at the interface

LIMITATIONS

• LIMITED PACKET PROCESSING• SLOW OPERATION• COST AND COMPLEXITY• CROSS TALK

These limitations degrades the performance of the system affecting the bandwidth

SOLUTION!

• The solution is OPTICAL PACKET SWITCHING

• The signals are being processed by means of OPTICAL SWITCH FABRIC

OPTICAL SWITCH FABRIC

OPTICAL SIGNALS OPTICAL SIGNALS

SWITCH ARCHITECTURE

An OPS node consists of following components

1. INPUT INTERFACE

2. SWITCHING MATRIX

3. BUFFER

4. OUTPUT INTERFACE

5. ELECTRONIC CONTROL UNIT

1.INPUT INTERFACE

• Wave length conversion

->conversion of external to internal wavelengths

->identification of the beginning and end of the header and payload

• Provides synchronization• Header processing

CONTROL UNIT

• Processing routing information• Updates header information• Forwards header to output interface

SWITCHING MATRIX

• Optical switching of the payloads according to the commands from the control unit

OUTPUT INTERFACE

• Provides 3R(reamplification,reshaping,retiming) regeneration

• Attaches updated header to corresponding optical payload

• Conversion of internal to external wavelength• resynchronization

GENERAL PACKET FORMAT

• A generic packet format consists of Header Payload Additional GUARD BANDS before and after

payload

PACKET HEADER

• A packet header may comprise of following fields

Sync- provides synchronization

Source Label-provides source node address

Destination Label-provides destination node address Type-type and priority of the carried payload

continued…

Sequence Number: Packet sequence number to reorder packets arriving out of order

and guarantee in-order packet delivery

OAM: Operation, Administration, Maintenance

HEC: Head Error Correction

OPTICAL SWITCHING TECHNIQUES

• Two types of optical switching techniques

1.ALL OPTICAL LABEL SWAPPING (AOLS)

2.LIQUID CRYSTAL SWITCHES

ALL OPTICAL LABEL SWAPPING

Consists of Optical Core Networks

1.Edge Router

2.Core Router

Here Packets can be routed independent of Payload Bit Rate, Coding format ,length etc

Can handle IP packets as well as ATM cells

LABEL

• A Lower Bit Rate (LABEL) is attached to the front of the packet

• A LABEL contains-

1.Error checking information

2. Source Information

3. Destination Information

4. Framing and timing information

PROCESS

• Packets entered through EDGE nodes (source side) is encapsulated with the optical label

• Header is removed.• At internal CORE nodes, the label is optically

erased, embedded with a new label• The payloads with the label gets routed in the

networks• At the Edge nodes (destination side) ,the label is

Erased back to packet payload• Updated header is encapsulated to the payload

All optical label swapping

2.LIQUID CRYSTAL SWITCHES

• Principle : -when an electric field is applied to liquid crystal, the molecules line up and become opaque

• The molecules are so thin and straight, will allow light of a particular orientation to pass through the liquid crystal

• It consists of 2 components

1. CELL

2. DISPLACER

CELL AND DISPLACER

CELL: Formed by placing the liquid crystal between 2 plates of glass

• Glass is coated with oxide materials that conducts electricity

• The function is to REORIENT the polarized light entering the cell

DISPLACER: • It is a composite crystal that directs the polarized light

leaving the cell

conclusion

• The new technology –regarded as ULTIMATE SOLUTION to bandwidth needs PROVIDING

->IMPROVED EFFICIENCY

->LOW COSTS

->UTILISE DWDM

THANK YOU!!!

•

QUESTIONS ????

DONE BY

• ARUN JOY

• 7TH SEMESTER,DEPARTMENT OF COMPUTER SCIENCE AND ENGG,

SREE NARAYANA GURUKULAM COLLAGE OF ENGINEERING,KADAYIRUPPU.