Advances in Optical Technology & FI 2007.5.30 김종권

OCS, DOCS, OPS, OBS OCS (Optical Circuit Switching) Limited circuit Low efficiency (due to fixed bandwidth) Unfashionable DCS (Dynamic Circuit Switching) Well-suited to optics Circuit switches are simple Higher capacity per unit volume/watt Lower cost per Gb/s OBS (Optical Burst Switching) Assemble the packets (have same destination) make bursts at the edge Switched through transparently without any conversion No need for Optical buffer. OPS (Optical Packet Switching) Using Packet ( = Header (for routing) + Data ) Need buffers, Long Switching time, difficulty of bit-level processing EPS : IP packet이 electronics line electronics router (processing) electronics line 현재 기술? GMPLS : core망은 확실히 all-optical control packet은 electronics/optical line electronics router (processing) electronics/optical line (out-of-band/in-band) data packet은 optical line optical router (processing) optical line OCS/OBS/OFS : core망, metro, access망 모두 all-optical 궁극적인 목표 OPS : IP packet이 optical line optical router (processing) optical line

Comparison Low High Slow (ms) Fast (ns) Medium ? contention Optical Switching Bandwidth Utilization Setup Latency Switching Speed Required Proc/Sync Overhead Traffic Adaptive Capability Optical Buffer Main Problem Optical Circuit Switching (OCS) Low High Slow (ms) Not Required Not Very Dynamic Optical Packet Switching (OPS) Fast (ns) Required No Optical RAM Optical Burst Switching (OBS) Medium ? contention

DOCS Network Example DOCS Node DOCS : Fiber port, 파장, time slot으로 dynamic circuit reservation을 해서 한 방향으로 data를 보내는 방식이다. 이 그림은 일단 core망에서의 데이터 전송만 고려하고 있다. WB는 1개의 Fiber라고 보면 된다.

OFS-MIT, Chan (scheduled flow-based transport architecture) Physical and logical architecture Transport mechanisms –flow switching Routing: separate IP and optical control planes Very fast dynamics < 100mS Scalable Low cost MIT의 chan교수는 centralized방식인 OFS를 제안했다. 이는 band width utilization을 높이면서 cost를 줄이는 방식으로 packet switched networks와 다르게 all queuing data는 end users에서 발생하여 core망에는 buffer가 필요 없으며 convert가 없고(1개의 고정된 파장만 사용), OXC로만 이루어져 있다고 가정하였다. 또한 Metro/access망은 feeder라는 링 구조로 되어 있는데 이 구조에서 access망들은 millisecond time scales 단위에서 작동할 수 있는 optical switches로 구성되어 있기 때문에 원하는 파장을 매우 빠르게 선택해서 사용할 수 있다. 예를 들어, 먼저 1번 feeder에서 aggregated 된 flow를 다른 feeder의 어떤 Access Node (AN)으로 해당되는지 group formation해서 보내는데 이 속도가 <100ms이기에 매우 빠른 편이다. Each access node has three entities that perform three functions, but they can be incorporated into one processor unit instead of being physically separated. The first is an entity that runs a media access control (MAC) protocol for users in the distribution network to gain access to resources in the access node, the feeder network, and the distribution network. In a hybrid network architecture, the user can choose between IP packet service or OFS service and this entity coordinates this choice. The second entity is a router that accepts IP packets and acts as an aggregator for IP packet traffic. It also conveys network resource requests from users to the first and third functional processor blocks. This third block is a network configuration manager and an OFS scheduler which manages optical network functions such as formation of dynamic broadcast groups to gain access to WAN wavelengths for OFS, as well as path set-up and tear-down for OFS flows. 1 1

References [Clark2005] David D. Clark, What is "Architecture"?, Background Paper for FIND Informational Meeting AGENDA presentation, November 2005 [Bannister2000] Joe Bannister and et al., Optical Networks: Will Future Networks Be Structured Differently Than Today's Networks?, NSF Workshop on The Future Revolution in Optical Communications and Networking, December 2000 [2007] Blumenthal-“Optical Techniques For Circuits And Packet-Based Networking” [Broadnets 2006] Nick McKeown-“Dynamic Optical Circuit Switched (DOCS) Networks for Future Large Scale Dynamic Networking Environments” [The Stanford Clean Slate Program] Nick McKeown [ECOC 2005] Nick McKeown-“Introducing optical switching into the network”