1. IP over Optical Networks Debanjan Saha Bala Rajagopalan {dsaha, braja}@tellium.com

2. NANOG, 10/2000 2 BOF Objectives Determine areas of priority for operators in  IP-centric control of optical networks  IP over optical network service architectures  New services & applications –Traffic engineering & network re-configuration –Others

3. NANOG, 10/2000 3 Summary Motivation IP over optical network model IP-centric control plane for optical networks  MPLS signaling for optical networks  IP routing protocol extensions for optical networks  Optical internetworking IP over optical networks  Service models  Traffic engineering Discussion

4. NANOG, 10/2000 4 Benefits of Optical Networking Build Networks for 2/3’s less  Optical Meshes are 50% more efficient than TDM Rings  Eliminate SONET/DCS Equipment Layer Dynamic Lambdas  Fast provisioning  Automatic restoration

5. NANOG, 10/2000 5 Applications for Dynamic Lambdas Reconfigure Network to changing traffics  Add lambdas on demand between IP Routers  “Tune” IP layer topology with changing traffic patterns  Just in time lambdas Dynamic Optical Virtual Private Network (OVPNs)  Shared s for bandwidth efficiency Automatic lightpath restoration  Restore at Layer 1 instead of Layer 3  Simplify restoration from large scale failures –e.g. 100s of lambdas

6. NANOG, 10/2000 6 Routers experience congestion  Step 1 - Router requests additional to relieve congestion  Step 2 - Optical Switches dynamically add  between congested routers Traffic Demand Changes  Step 3 - Optical Switches reconfigure Dynamic Lambdas: Routers request Dynamic Router Network Step 1 - Request Step 3 - Release Step 2 - OXC Provides Optical Subnet

7. NANOG, 10/2000 7 Tune IP layer topology to changing traffics IP Layer Traffic Patterns Change  Step 1- Add new from A to B  Step 2 - Delete from A to C Optical Network Subnet B Subnet C Subnet A Subnet B Subnet C Optical Network

8. NANOG, 10/2000 8 IP over Optical: Network Model Optical subnet Optical subnet Optical Subnet Router Network Optical Network End-to-end path (LSP) Optical Path NNI MP S for signaling and routing within the optical network NNI

9. NANOG, 10/2000 9 IP-Centric Control of Optical Networks Ingredients  IP addressing for optical network nodes (and termination points)  MPLS-based signaling for lightpath provisioning  IP routing protocols adapted for resource discovery  Route computation with resource optimization  Restoration signaling???

10. NANOG, 10/2000 10 What is the MP S approach? Each OXC is considered the equivalent of an MPLS Label- Switching Router (LSR)  MPLS control plane is implemented in each OXC Lightpaths are considered similar to MPLS Label-Switched Paths (LSPs)  Selection of s and OXC ports are considered similar to selection of labels MPLS signaling protocols (e.g., RSVP-TE, CR-LDP) adapted for lightpath establishment IGPs (e.g., OSPF, ISIS) with “optical” extensions used for topology and resource discovery

11. NANOG, 10/2000 11 Optical Network Functions Dynamic provisioning of lightpaths  Just-in-time provisioning  Path selection with constraints Protection & restoration of lightpaths  Protection paths with appropriate service levels –Node & link disjoint primary & protection paths for resiliency –Shared protection paths for cost savings  Fast restoration of lightpaths after the failure

12. NANOG, 10/2000 12 Protocols for Realizing Optical Network Functions Provisioning protocols  Automatic neighbor discovery –Neighbor Discovery Protocol –Link Management Protocol  Topology discovery –OSPF with optical extension –IS-IS with optical extensions  Signaling for path establishment –RSVP-TE, CR-LDP with optical extensions –Generalized MPLS Restoration Protocols  Proprietary techniques

13. NANOG, 10/2000 13 Physical Topology O3 O1 O5 O4 O2 Router Network Router Network Optical Network Optical Network

14. NANOG, 10/2000 14 Topology Abstraction O3 O1 O5 O4 O2 Router Network Router Network Optical Network Optical Network UNI SRG #1 SRG #2 SRG #3 SRG #4 SRG #5 SRG #6 NDP UNI

15. NANOG, 10/2000 15 Neighbor Discovery NDP allows adjacent OXCs to determine IP addresses of each other and port-level local connectivity information (i.e., port X in OXC O1 connected to port Y in OXC O2) (IETF Status: Link Management Protocol (LMP) is being considered) Port State Database of O1 Type ID Remote Port Speed Resource Class Remote Node Status SROG 1 2 1024 1023 Drop Network Up SF Up OC-48 OC-192 F123, C231 F234, C251 F234, C231 F123, C231 9.2.1.3 8.4.1.3 11.3.1.3 129.2.1.3 10 123 345 15 Primary Backup Primary

16. NANOG, 10/2000 16 Topology Discovery with OSPF O3 O1 O5 O4 O2 Router Network Router Network OSPF Area 0.0.0.3 UNI OSPF Area 0.0.0.2 OSPF Area 0.0.0.1 Summary LSA Summary LSA Router/ Optical LSA

17. NANOG, 10/2000 17 OSPF Extensions Recognition of optical link types Link bundling  Multiple, similar links between OXCs are abstracted as a single link bundle  Composition of link bundle described by parameters  Single adjacency maintained between OXCs regardless of the number of links  Bundling considerations in preliminary stages in IETF

18. NANOG, 10/2000 18 Example Scenario SRLG S1 SRLG S2 O1O2 5 OC-48, 2 OC-192, 2 10G E/N 5 OC-48, 5 OC-192

19. NANOG, 10/2000 19 Desired Bundling Structure 5 OC-48, S1 2 OC-192, S1 2 10G E/N, S1 5 OC-48, S2 5 OC-192, S2 O1O2 Single bundle between nodes Resource sub-bundle# 1 Resource sub-bundle# 2 Resource sub-bundle# 3 Resource sub-bundle# 4 Resource sub-bundle# 5

20. NANOG, 10/2000 20 OSPF Extensions New lightpath computation algorithms  Path computation based on lightpath attributes and constraints  Proprietary algorithms for efficiency  Algorithms not considered in IETF Source-routing methodology  Differs from traditional OSPF  Considered in IETF as part of RSVP-TE/CR-LDP extensions Reduction of link state propagation overhead  Thresholds for reducing link state propagation overhead  No framework yet in the IETF

21. NANOG, 10/2000 21 Link State Advertisements

22. NANOG, 10/2000 22 Link State Database

23. NANOG, 10/2000 23 Routing Across the NNI: BGP E-BGP is used between adjacent border OXCs in different sub- networks I-BGP is used between border OXCs in the same sub-network External addresses are passed between sub-networks, with indication of egress border OXC information Routing policies may be applied, as per BGP features Sub-network 1 Sub-network 2 E-BGP I-BGP Sub-network 3

24. NANOG, 10/2000 24 Some Issues to Consider What other information must be exchanged during neighbor discovery? The practicality of obtaining SRG information Resource metrics for OSPF Distributed vs centralized path computation Interdomain routing with resource constraints

25. NANOG, 10/2000 25 Multi-protocol Lambda Switching Each OXC is considered the equivalent of an MPLS Label- Switching Router (LSR). An IP control channel must exist between neighboring OXCs  MPLS control plane is implemented in each OXC The establishment of a lightpath from an ingress to an egress OXC requires the configuration of the cross-connect fabric in each OXC such that an input port is linked to an output port MP S signaling allows an OXC to convey to the next OXC in the route the selected output port (“label”) O3 O1 O5 O4 O2 Request (label) Response (P1) Request (label) Response (P4)

26. NANOG, 10/2000 26 Generalized MPLS GMPLS is based on the premise that MPLS can be used as the control plane for different switching applications:  TDM where time slots are labels (e.g., SONET)  FDM where frequencies (or s) are labels (e.g., WDM)  Space-division multiplexing where ports are labels (e.g., OXCs)  Generalized labels used in MPLS messaging: Request Resv/Request Allocate/Port=43 Allocate/Port= 5 Allocate/Port= 21 (OXC example) Allocate/Fiber=43 = 9 Allocate/Fiber= 5 = 18 Allocate/Fiber= 21, = 8 (OXC with built-in WDM)

27. NANOG, 10/2000 27 Generalized Label Used in place of traditional labels in MPLS signaling messages May contain a Link ID in addition to the label value  Link ID used when a single control channel is used to control multiple data channels  Label format depends on the link type. Presently label formats have been defined for SONET/SDH, port,, waveband and generic

28. NANOG, 10/2000 28 GMPLS Actions Generalized Label Request  Indicates the type of label being requested Generalized Label  Response to label request. Format depends on the type of label Label Suggestion  Sent along with label request, to aid in certain optimizations Label Set  Sent along with label request. Constrains the allocation of labels to those in the set to support OXCs without wavelength conversion capability

29. NANOG, 10/2000 29 Signaling Requirements: Bi-directional Lightpaths Why not use two unidirectional paths?  Signaling twice is expensive  SONET requires the forward and backward paths to be on the same circuit pack Who owns the label space?  Avoid label assignment collision  Resolve collision after in happens A B C D E F L1 L2

30. NANOG, 10/2000 30 Signaling Requirements: Fault-Tolerance Lightpaths must not be deleted due to failures in the control plane  Present RSVP/CR-LDP mechanisms associate the control path with data paths –Failure in the control path is assumed to affect the data path –Data path is therefore deleted or rerouted  In optical networks, the fabric cross-connects must remain if control path is affected –Enhancements to RSVP/CR-LDP needed for this.

31. NANOG, 10/2000 31 Dynamic Provisioning Across the NNI Lightpath request is routed inside source sub-network to border OXC (D) based on destination address and local routing scheme  D routes request to border OXC K in dest. sub-network (NNI signaling)  K routes request to destination, N based on destination address  Response routed along the reverse path F E A B C D Req Resp K L M N Req Resp NNI Path Request NNI Path Resp

32. NANOG, 10/2000 32 Some Issues to Consider Service definition and GMPLS semantics for different layer technologies Optimization of optical layer signaling

33. NANOG, 10/2000 33 Restoration Objectives  Low restoration latency  High restoration capacity efficiency by sharing capacity among the backup paths  High degree of robustness of the restoration protocols and the related algorithms Scope  Fast and guaranteed restoration of lightpaths after “single failure” events  Best-effort restoration after multiple concurrent failures

34. NANOG, 10/2000 34 Supported Classes of Service 1+1 path protected  Each primary path is protected by a dedicated backup path  No signaling is necessary during switching from the primary path to the backup path Mesh restorable  Each primary path is protected by a shared backup path  Restoration signaling is necessary during switching from the primary to the backup path

35. NANOG, 10/2000 35 Restoration Protocol Components Primary and backup path setup  Path computation from OSPF generated link state database  Path setup using RSVP-TE/CR-LDP signaling protocol  May be done through the Wavelength Management System (WMS) Link-level restoration protocol  Using SONET bit-oriented signaling at the link-level Path-level restoration protocol  Using SONET bit-oriented signaling at the end-to-end path level

36. NANOG, 10/2000 36 Link-Level Restoration Overview  A lightpaths is locally restored by selecting an available pair of channels within the same link  If no channel is available then the end-to-end restoration is invoked 310757 12 754 7 19 4 A BCD E Drop port 14 Original Channel Pair New Channel Pair

37. NANOG, 10/2000 37 End-to-End Restoration Overview  A shared backup path is “soft-setup” for each restorable primary path  When local restoration fails, triggers are sent to the end-nodes  End-to-end signaling over the backup path activates it and completes end-to-end restoration 310757 12 754 8794 85 7 19 4 A BCD E HGF Drop port 14 Primary Path Shared Backup Path Local Restoration Failure

38. NANOG, 10/2000 38 Optical Control Plane: Restoration Multi-domain restoration:  Allow possibility of proprietary restoration in each sub-network  Specify an overall end-to-end restoration scheme as backup.  Signaling and routing for end-to-end restoration

39. NANOG, 10/2000 39 Issues to Consider IP-based restoration protocol  Protocol must satisfy time constraints  Should a new “fast” protocol be developed? Inter-domain restoration  Is there a need for end-to-end restoration across domains?  Can this need be satisfied by domain-local restoration plus re-provisioning as a fall-back? Restoration time requirements

40. IP-Optical Internetworking

41. NANOG, 10/2000 41 IP over Optical Service Models: Domain Services Model Optical network provides well-defined services (e.g., lightpath set-up) IP-optical interface is defined by actions for service invocation IP and optical domains operate independently; need not have any routing information exchange across the interface Lightpaths may be treated as point-to-point links at the IP layer after set- up Optical Cloud Router Network Service Invocation Interface Physical connectivity

42. NANOG, 10/2000 42 Optical Network Services Discrete capacity, high-bandwidth connectivity (lightpaths)  Lightpath Creation, Deletion, Modification, Status Enquiry Directory Services  Determine client devices of interest Supporting Mechanisms  Neighbor discovery  Service discovery

43. NANOG, 10/2000 43 UNI Abstract Messages Lightpath Create Request - UNI-C  UNI-N Lightpath Create Response - UNI-N  UNI-C Lightpath Delete Request - UNI-C  UNI-N Lightpath Delete Response - UNI-N  UNI-C Lightpath Modify Request - UNI-C  UNI-N Lightpath Modify Response - UNI-N  UNI-C Lightpath Status Enquiry - UNI-C  UNI-N Lightpath Status Response - UNI-N  UNI-C Notification - UNI-N  UNI-C Concrete realization based on MPλS signaling constructs

44. NANOG, 10/2000 44 Signaling Example Optical Network Lightpath Create Request UNI-C (Terminating) Lightpath Create Response UNI-C (Initiating) UNI-C (Initiating) UNI-C (Terminating) 1 2 3 4 Lightpath Create Request Lightpath Create Response

45. NANOG, 10/2000 45 UNI Parameters Identification-related Service-related Routing-related Security-related Administrative Miscellaneous

46. NANOG, 10/2000 46 Service Models: Unified Service Model No distinction between UNI, NNI and router-router (MPLS) control plane Services are not specifically defined at IP-optical interface, but folded into end-to-end MPLS services. Routers may control end-to-end path using TE-extended routing protocols deployed in IP and optical networks. Decision about lightpath set-up, end-point selection, etc similar in both models. Optical Network Router Network

47. NANOG, 10/2000 47 IP over Optical Services Evolution Scenario First phase: Domain services model realized using appropriate MPλS signaling constructs Optical Cloud (with or w/o internal MPλS capability) MPλS-based signaling for service invocation, No routing exchange Router Network

48. NANOG, 10/2000 48 Evolution Scenario Second phase: Enhanced MPλS signaling constructs for greater path control outside of the optical network. Abstracted routing information exchange between optical and IP domains. MPλS-based signaling for service invocation (enhanced). Abstracted routing information exchange Router Network Optical Cloud (with internal MPλS capability)

49. NANOG, 10/2000 49 Evolution Scenario Third Phase: Peer organization with the full set of MPλS mechanisms. MPλS-based signaling for end-to-end path set-up. MPλS-based signaling within IP and optical networks. Full routing information exchange. Router Network Optical Cloud (with internal MPλS capability)

50. NANOG, 10/2000 50 Routing for Interworking: BGP Client network sites belong to a VPN. Client border devices and border OXCs run E-BGP. Routing in optical and client networks can be different Address prefixes in each site (along with VPN id) are advertised by border devices to optical network. Optical network passes these addresses to border devices in other sites of the same VPN (along with egress OXC address) Network N1 Network N3 Network N2 R1 R2 R3 R6 R5 R4 x.y.a.*, x.y.b.* x.y.c.* a.b.c.* O1 O2 O3 O4 O5

51. NANOG, 10/2000 51 Issues to Consider Which service model?  Determines complexity of signaling at the IP- optical interface What are the service requirements on routing and signaling?

52. Traffic Engineering

53. NANOG, 10/2000 53 IP-over-Optical TE Example : Peer Model Optical network links are OC-48 (2.5 Gbps) Sequence: 1. 100 Mbps LSP from R3 to R8 2. 300 Mbps LSP from R1 to R6 3. 200 Mbps LSP from R2 to R12

54. NANOG, 10/2000 54 TE Example Cont. To set up LSP1: 1. R3 computes path R3-R2-O12-R7-R8 2. R2 establishes an OC-48 FA to R7 3. LSP occupies 100 Mbps on the FA 4. Links R2-O12, R7-O12 must be removed from database when FA R2-R7 is advertised.

55. NANOG, 10/2000 55 TE Example Cont. To set up LSP2 (R1-R6): 1. Path: R1-R2-O11-O13-O14-R4-R6 2. R2 establishes an OC-48 FA to R4 3. LSP occupies 300 Mbps on the FA 4. Link R2-OC11 removed from database FA, 2.5G Optical Network R9 R8 R7 R1 R2 R3 O12 O15 O14 O13 R10 R11 R12 R4 R5 R6 O10 O11

56. NANOG, 10/2000 56 TE Example Cont. R9 R8 R7 R1 R2 R3 To set up LSP3 (R2-R12): 1. Path: R2-R7-R9-O15-O14-O13-O10-R10-R12 2. R9 establishes an OC-48 FA to R10 3. LSP occupies 200 Mbps on the FA 4. Link R9-O15 & R10-O10 removed from database. The next LSP set-up utilizes an overlay topology of FAs only! It may make sense to change this topology based on observed traffic pattern between routers Thus, the design of this overlay is an important TE issue. R10 R11 R12 R5 R4 R6

57. NANOG, 10/2000 57 Topology Design General objective  Design topology of least cost that accommodates traffic demand When LSPs are routed over an FA topology  Routers may have to optimize overlay topology to utilize available resources (ports, etc) efficiently and minimize cost  Co-ordination among routers may be required for this Internally, some optimizations are possible in the optical network to minimize capacity usage, based on overall view of lightpaths routed. It is difficult to push this functionality outside of the optical network

58. NANOG, 10/2000 58 IP-over-Optical TE Example : Domain Model 1. Each border router gets reachability of others 2. Each border router keeps track of availability of edge links 3. Lightpaths are set up internally in optical network 4. Overlay virtual link (VL) topology is formed based on LSP demand between router networks.

59. NANOG, 10/2000 59 TE Example - Domain Model To set up LSP1: 1. R3 computes path R3-R2- -R8 2. R2 sends a request to optical net to set-up a path to R7 3. Lightpath is established from R2 to R7 4. LSP occupies 100 Mbps on the virtual link 5. The VL is also a new routing adjacency FA, 2.5G Optical Network Router Network R5 R4 R6 R9 R8 R7 Router Network R1 R2 R3 O12 O15 O14 O13 Router Network R10 R11 R12 O10 O11

60. NANOG, 10/2000 60 IP-over-Optical TE Issues TE rules should be incorporated in all routers to decide when to select new optical paths, as opposed to using existing FAs or VLs Should resource optimization in optical network be an objective of LSP routing? (This requirement may be handled best internally in the optical network) TE work must investigate to what degree internal optical network information (topology, etc) aid in IP over optical TE decisions. Specifically, with regard to protection, requiring physical topology characteristics (e.g. SRLG) of optical network at the IP layer for computing alternate paths may be impractical.

61. NANOG, 10/2000 61 Finally…. What applications may be built based on dynamic bandwidth provisioning?