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Title: Optical Burst Switching

1Optical Burst Switching

An optical transport technology with the

capability of transmitting data in the form ofbursts in an all-optical bufferless networkusing either circuit switching (light paths)flow switching (persistent connection) orper-hop switching (single burst) servicesdepending on connection set-up message.

The network is transparent to the content of aburst (analog or any digital format) as well asto the data rate by separating the control plane(electrical) from the data plane (optical).

2Burst definition

A burst can be defined as a continous set ofdata bytes or packets. It can be as short as afew microseconds or as long as several hours.

3Control plane vs. data plane

The fundamental premise of OBS is the separationof the control and data planes and thesegregation of functionality within theappropriate domain (electronic or optical).

a set-up message (control message) to an OBSingress switch. The control processor forwards

the message along the data transmission pathtoward the destination.

Control messages are processed at each node(requiring OEO conversions) they inform eachnode of the impending data burst and initiateswitch configurations to accommodate the databurst.

The data burst is launched after a small offsetdelay. Bursts remain in the optical planeend-to-end and are typically not buffered asthey transit the network core.

4OBS features

OBS has the potential of meeting severalimportant objectives

high bandwidth low latency deterministic (verylittle if any network elasticity no buffers)transport required for high demand (grid)applications

all-optical data transmission with ultra-fastuser/application-initiated light path setup


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implementable with cost effective COTS opticaldevices.

5E2E burst transmissionApplication/user initiated Control message

OEOOEO- -XControl signal created Cross connection awaitingburstControl signal has not been processed yet butwill arrive ahead off burst by time offset delay6When will carriers have it

Many in the networking research community believethat optical burst switching (OBS) can meet theneeds of the scientific community in the nearterm (2-3 years).

Research test beds in several Labs globally ATDnet MAN testbed

The opportunity work on a networking technologyduring pre-standardization development for thepurpose of meeting service management needs andrequirements (not an after thought!).

7Optical Packet Switching (OPS)

OPS is the ultimate optical switching technology requires optical buffering (beyond todays coarse

fiber delay lines)

also requires line-rate header parsing. Many experts do not expect OPS to be commercially

feasible for at least a decade.

8OBS Network Architectures

Most OBS research has focused on edge-coreoverlay architectures.

Few (myself included) are looking at e2euser/application initiated connections.

Working on OBS NICs User/application initiated optical network

connections.

Use Just In Time (JIT) protocol for connectionsignaling.

9OBS and QoS


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1) Application layer QoS (latency jitterdatarate)

Handled at edges during burstification (similarto SAR in ATM) and scheduling not incut-through optical network (no buffering)

2) Physical layer QoS (BER) Function of optical components optical fiber

length of transmission controlled and monitoredat the optical layer

3) QoS and priority

Pre-emption during congestion

10OBS Service Requirements

Network feedback mechanisms to user Status Alarms Availability and reach


Policy based routing algorithms user orcarriers decide on how forwarding tables arecreated.

Integrating security concerns at both theprotocol level as well as control and managementplane.

Incorporating necessary inter-domain informationexchange in protocol definitions.

Providing necessary flexibility in architectures

to meet both carrier-owned and user-ownednetworks.


Understanding the requirements for both physicallayer QoS and application layer QoS andincorporating them into protocol definitions.

Determine how users will get billed for thenetwork service.

Determine what is meant by SLAs and how thenetwork can provide them.

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