Optical Burst Switching (OBS)

Definition

• Optical Burst Switching (OBS) is an optical network technology that aims to improve the use of optical networks resources when compared to optical circuit switching (OCS).
• OBS is implemented using Wavelength Division Multiplexing (WDM), a data transmission technology that transmits data in an optical fibre by establishing several channels, each channel corresponding to a specific light wavelength.
• Optical Burst Switching is used in core networks, and viewed as a feasible compromise between the existing Optical Circuit Switching (OCS) and the yet not viable Optical Packet Switching (OPS).

OBS network

• Control and data information travel separately on different channels
• Data coming from legacy networks are aggregated into a burst unit in edge node
• The control packet is sent first in order to reserve the resources in intermediate nodes
• The burst follows the control packet with some offset time, and it crosses the nodes remaining in the optical domain

OBS principles

• Variable-length packets, named bursts
• Asynchronous node operation
• A strong separation between the control and data planes
  • control burst (with control information)transmitted on dedicated control channel andprocessed electronically
  • Data burst transmitted and switched all-optical way

Edge Node

Consist of electronic router and OBS interface

Functions

•  Electronic data buffering and processing
•  Burst  Aggregation (BA), responsible for collecting data from legacy networks and building the burst unit
• impact on the overall network operation by the control of the burst characteristics
• in order to reduce the burst loss probabilities in the network the aggregation function can segmentate data bursts for the purpose of their partially dropping in core nodes when contention occurs
• Setting up the pre-transmission offset time
• in simple fixed offset scheme, the offset time is calculated as a sum of the total processing time at all the intermediate hops
• offset time is one of the crucial OBS network parameter, since his incorrect estimation has impact on data lost
• Sending the control packet
• Sending the burst