Optical Waves Who needs them and why?

1. Optical WavesWho needs them and why? Some thoughts on how wave-based lightpath services can be effectively employed in emerging applications Jerry Sobieski Mid-Atlantic Crossroads Presented at the Internet2 Fall Member Meeting December 6th, 2006 Chicago, IL

2. “Optical Waves” vs “LightPaths” • Waves are subtly different from Light Paths • LPs are often provisioned thru switched or aggregated network infrastructure in ways that “privatize” traffic but often produce unexpected performance issues (e.g. buffer overruns) • LPs are often not optical at all (e.g. UTP Ethernet) • LPs often require only a portion of the capacity of an optical link (e.g. Fast Ethernet) • “Waves” imply a point-to-point optical signal that exists inside a very narrow spectral band and that typically exists in conjunction with many other similar waves on a single fiber. • While the photonic concept would lead one to assume that anything can be modulated onto a wave, there are many practical and engineering constraints that prevent this – thus the significant development that equipment vendors put into DWDM transport systems.

3. Optical Waves as LightPaths • LightPaths := Circuits broadly [re-]defined • LPs provide a mechanism by which the user or application can explicitly and apriori specify certain network service requirements and then access those services– i.e. they enable predictable and repeatable network services. • LPs (circuits) provide a mechanism by which the network can effectively manage network resources allocated (and dedicated to) many different users and applications. • This also allows the network to set resources aside for use at some future time… -> reservations and bookahead scheduling. • If your application has explicit network service requirements that must be met for the application to function properly or well, then your application should consider lightpath services to instantiate those service requirements. • LightPaths are complementary to conventional IP network services • IP networks employ circuits of some ilk underneath the IP layer • The vast majority of LightPaths use IP within those paths. • The LightPath is used to guarantee (or at least bound) the IP performance

4. Who needs ‘em? Isolation of application components • Waves/circuits (hybrid networks) can be used to segregate traffic bewteen/among certain facilities in order to provide that traffic with specific guarrantees • Example: A regional GRID cooperative may wish to provision a full mesh of high capacity network links between the participating computational clusters and data storage facilities. • The core components may be separated by geographically significant distances or might otherwise share network resources with unrelated and interfering traffic. • Communications capabilities between clusters should be predictable and repeatable in order to allow effective mapping of the computational tasks/workflow across the available resources • Access to a large distributed data repository by different computational layouts should be independent of other incident network traffic.

5. Real Time and nearRT Applications • Some applications have a real-time or near real-time component: • Example: Distributed Interactive Simulations; Gaming • Agents participating in the simulation (potentially thousands) require realtime notification of events that affect them; (Often all events must be broadcast in order for automated simulation agents to identify those that are relevant) • Architecting the distribution tree and providing adequate network performance at each branch is critical • Example: Very Long Baseline Interferometry – Capturing simultaneously sampled sensor data in realtime to intermediate storage from many globally distributed radio telescope facilities. • And then subsequently streaming that captured data to computational facilities for analysis

6. Traffic Engineering • In order to effectively utilize all available backbone transport capacity, LSPs can be established and forwarding adjacencies created to forward particular IP traffic flows along alternate (underutilized) paths • TE provides a degree of load balancing and more efficient use of network resources • Large flows (near or exceeding backbone capacity) require provisioned path(s) in order to provide the necessary overall capacity end-to-end. • Otherwise saturation of conventional IP forwarding paths will occur and network users as a whole will experience desiccated performance

7. Where do “Optics” play? • Emerging technologies are enabling the dynamic allocation of wave-based connections to add raw capacity when and where it is needed • ITU compliant XFPs can be inexpensively deployed into end user facilities (Ethernet switches, NICs, etc.) for activation when needed • Tunable lasers, tunable filters, multi-degree ROADMs allow hands-free, high service velocity provisioning • Dynamic on-demand photonics is doable in limited environments, but still very complex and technically challenging • Well engineered DWDM systems can provide wave based transport for almost any anticipated link technology • Ethernet, SONET/SDH, IB, FiberChannel, • Even 2R regeneration of non-standard digital streams such as SMPTE-292 (raw HDTV) • Forward Error Correction found on transponder cards can add significant distant or overcome significant impairments • Features such as FEC can provide “soft failover” capabilities - indicate impending failure before a hard (unrecoverable) failure occurs. • These types of features, when integrated with higher layer routing and VCAT + LCAS capabilities can allow the network to groom at-risk circuits from bad paths to better paths hitlessly and before unrecoverable bit errors are expressed to the user.

8. Summary • Waves - as connection oriented LightPaths- can provide customized collaboration and application environments • Predictable • Repeatable • Schedulable • Deternministic Network Performance • (when provisioned well)