Routing in Optical Networks

1. Routing in Optical Networks IP and MPLS in Optical Domain Markus Isomäki

2. Agenda • Trends in IP over optical networking • Traditional and new models • Optical network terminology and evolution • Future expectations • IP routing in optical domain • Different models • Requirements & possible solution frameworks • MPLS in optical domain - MPLambdaS • Proposed enhancements for routing and signaling • OSPF/IS-IS and RSVP/CR-LDP

3. Standardization Organizations and Industry Foras • Internet Engineering Task Force (IETF) • MPLS Working Group • IP over Optical Working Group starting • ITU-T SG 13 • Optical Transport Network architecture and requirements • ODSI • Allow IP routers to make dynamic bandwidth requests to the optical network • Started in January 2000 • Optical Internetworking Forum (OIF)

4. Traditional Model - IP over ATM over SDH • IP routers connected to each other via ATM switches which are connected to each other over SDH • Known problems • Different management (fault, configuration, …) at each layer adds complexity • Each layer has independent routing = Overlay • Different physical & logical topology • Redundant functionality at each layer • Multiplexing, QoS (mapping mismatch), protection… => ATM will not survive in the backbone

5. Current Model - IP over SDH

6. IP over SDH Pros & Cons • Advantages compared to IP over ATM over SDH • Easier management • No “cell tax” • IP QoS mapping straightforward • Major drawbacks • Protection switching consumes half of the capacity • Cumbersome provision of connections - no dynamics • Still two layers of management • Circuit switched!!! • May stop at 9.9 Gbps (STM-64 / OC-192) => More flexible & dynamic methods needed • IP Optimization wanted!!!

7. Other Existing Models • Gigabit Ethernet in Metro networks (10GE in 2001?) • Simple & cheap • No standard protection technology • Reach may cause problems • Cisco Systems’ Dynamic Packet Transfer (DPT) • Dual ring like FDDI • Spatial reuse of capacity • No unused protection capacity • Good for multicast • Proprietary

8. Toward IP over Optical Networking The common view is this But how to do routing, path setup, QoS, traffic engineering, protection & restoration etc. => Basic IP has not enough intelligence!

9. Optical Network Evolution & Terminology • Wavelength Division Multiplexing (WDM) • Multiple colors in a single fiber, each color carries SDH, Gigabit Ethernet etc. • Density grows every year • Optical Cross-Connects (OXC) • A box that switches a wavelength from an incoming fiber to an outgoing fiber • Wavelength continuity or conversion • All-optical (transparent) or electro-optical (opaque) • Erbium doped fiber amplifiers (EDFA)

10. Composite Link4 λ Optical Switches Composite Link3 λ IP Router IP over Optical Vision Routers connected to each other over OXC core using WDM wavelenghts

11. Router Interconnection Requirements • The routers have to be able to dynamically (on-demand) make connections to each other • Fast provision!!! • Connection capacity • Protection and restoration needed • Ask for a protected connection (1+1, 1:1, M:N) • Traffic engineering • Constraint-based and explicit routing => Use IP routing in the optical domain?!!!

12. Routing Models • Overlay • Independent routing on different layers • Router is client to optical network (some kind of UNI), optical switch computes the path (IP router does not “see” the topology of the optical network) • Similar to Classical IP over ATM or MPOA • Good when optical network owned by different organization than the router network • Integrated / Peer • Single routing instance run over both networks • Router is able to compute the path • Augmented • Separate routing instances, some information leaked

13. MultiProtocol Lambda Switching • IDEA: Use MPLS control plane machinery to implement traffic engineering, restoration etc. in OXCs (also SDH equipment) - Wavelength ~ Label MPLS Control Plane Control Adaptation OXC Switch Controller OXC Switch Fabric OXC Data Plane

14. MPLambdaS Benefits & Specialities • Real-time provisioning of connections • Distributed IP routing control • No need for new control protocols Optical domain (Like nested LSPs) OXCs unable to terminate LSPs

15. MPLambdaS & OXC Requirements • OXCs should be able exchange control information • Control plane topology may be different from data plane (in-band or out-of-band control); (Similar to SS7) • Automatic neighbor discovery and registration • Neighboring nodes should know which fiber ports are connected to each other • Robustness • A transient fault at the control plane should not affect the existing connections (soft state unacceptable?) • Fast restoration (fault handling)

16. Enhancements for Routing ProtocolsOSPF and IS-IS • New link attributes (TLVs) • Link type • Packet switch capable • TDM capable • Lambda switch capable • Fiber switch capable • Forwarding adjacency • Link media type • SDH, Gigabit Ethernet etc. • Termination capability • Shared Risk Link Group information • For example, if two fibers are in the same conduit they are in the same SRLG => Cannot be used for each other’s protection • Also information • on physical properties • BER • Wavelength conversion

17. Enhancements for Signaling ProtocolsRSVP and CR-LDP At least two proposals submitted • Label objects should contain information on • Fiber • Lambda • Channel • Convey information on requested media type • Capability to request protected connections! • For RSVP reservation confirmation should be used

18. Conclusions • Future networks based on IP routers connected to each other via Optical Cross-connects • IP routing and MPLS good candidates for controlling OXCs - IP optimization & synergy • Enhancements needed for routing & signaling protocols => Will happen because major support: Cisco, Nortel, ... • Other solutions possible • Use of GSMP • Use of traffic driven connection setup