Optical + Ethernet: Converging the Transport Network

1. Optical + Ethernet:Converging the Transport Network An Overview

2. Trends • R&E Optical Networks • Locally-managed fiber termination points • Locally-organized peering relationships • Locally-controlled layer-0/1/2 services • Ubiquitous Ethernet • Most-requested client service interface • Both point-to-point and virtual-LAN topologies • Apps consuming bandwidth in Ethernet-sized increments • Unit of provisioning 100/1000/10000Mbps • Options: L2 WAN, Pseudowires, Converged

3. L2 WAN • Classical Bridged Network • Transparent handoff to optical transponders • Switches establish topology at L2 • Deployment issues are many • Wide-area spanning tree, ugh • Limited VLAN tag space, or go 802.1ad/ah • No Traffic Engineering, at mercy of STP Optical Core = L2 switch, 802.1q/ad/ah = OADM, transponding only = Ethernet service

4. Pseudowires • L2 Pseudowires over IP/MPLS Core • Ethernet encapsulated in IP at PE routers • Transport via IP/MPLS core, over optical WAN • VPLS-enabled Control Plane • Full mesh of MPLS LSPs, PE-to-PE • BGP/LDP assigns 802.1q flows to LSPs • Optical layer setup manually or via GMPLS IP/MPLS/Optical = PE routers, MPLS + 802.1Q = Multi-tenant unit (MTU) = OADM, transponding only = Ethernet service

5. Pseudowires (cont’d) • Benefits • If IP/MPLS already built out, service type is additive • Update IP/MPLS PEs and MTUs with VPLS functionality; software for signaling, possible fw/hw for L2-in-IP encapsulation • Issues • Several distinct control mechanisms • Manual or GMPLS control plane in optical transport • IP/MPLS between PEs to establish full mesh of tunnels • LDP/BGP between PE client ports, to map pseudowires to tunnels • Management complexity • How to coordinate indications/actions/repairs across mechanisms? • Multiple encapsulations • Ethernet, into IP, into perhaps something else, into optical, and out again • Many moving parts • Control planes are complex enough, without having three of them

6. Converged • Converged Optical + Ethernet • OADMs are adding L2 functionality • Ethernet client interface, Optical transport • Unified Control Method • Optical service established via GMPLS • L2 tunnel within Optical service, also established via GMPLS (PBB-TE/GELS) Optical Core = OADM + 802.1q/1ad/1ah = Multi-tenant unit (MTU) = Ethernet service

7. PBB-TE / GELS • GMPLS Control Plane for Ethernet • Ethernet as just another transport technology • VLAN or VLAN+MAC becomes the GMPLS “label” • Labels identify end-to-end path, distributed via signaling • Ethernet services become regular GMPLS tunnels • Integrates Ethernet into GMPLS management framework • Same tools (routing, signaling, pce) used by optical GMPLS • Eliminates need for other control mechanisms (RSTP, etc) • Benefits • Traffic Engineering for Ethernet – explicit control over path • Unified Control – eases coordination among layers • Automation – 802.1ad/ah forwarding tables populated via signaling rather than manually • Two methods: “short-label” and “long-label”

8. OADM+L2 OADM+L2 OADM+L2 OADM+L2 OADM+L2 OADM+L2 “Short Label” • Hardware • Optical DWDM transport • L2-aware client interfaces • Able to switch L2 frames between ports • Able to swap VLAN tags when transiting ports • Control Plane • Optical tunnels setup via GMPLS; label is Lambda • L2 tunnels also setup via GMPLS; label is VLAN tag • VLAN tag changes along service path – unique per-link only VLAN tag Y VLAN tag Z VLAN tag X = Optical LSP, lambda A = Optical LSP, lambda B = L2 LSP, VLAN X = L2 LSP, VLAN Y + Z = swap Y for Z = add/remove VLAN

9. OADM+L2 OADM+L2 OADM+L2 OADM+L2 OADM+L2 OADM+L2 “Long Label” • Hardware • Optical DWDM transport • “L2-aware” client interfaces • Able to switch L2 frames between ports • Able to encapsulate MAC-in-MAC (802.1ah) • Control Plane • Optical tunnel setup via GMPLS; label is Lambda • L2 tunnel also setup via GMPLS; label is VLAN + MAC • Local L2 forwarding tables provisioned with VLAN + MAC MAC B VLAN tag Y VLAN tag X MAC A = Optical LSP, lambda A = Optical LSP, lambda B = L2 LSP, VLAN X + MAC A = L2 LSP, VLAN Y + MAC B = forward per VLAN + MAC = add/remove VLAN + MAC

10. Converged Approach • Benefits • Fewer moving parts • Single element with optical transport and L2 capability • Native transport for most-requested traffic • Single, unified control mechanism across all layers • Unified control via GMPLS • Coexistence with existing 802.nnn infrastructure • No dataplane changes for long-label; ships-in-the-night with regular PBB • Traffic Engineering for Ethernet services • Explicit control over path taken; usual benefits • New deployments achieve greatest benefit; existing IP/MPLS less so • Issues • Short label requires VLAN tag swapping • Older switches may not be capable of doing this • Long label requires carrying 8-byte label in GMPLS signaling • Most implementations carry a 4-byte label; software only

11. Protocol Details • Signaling L2 Labels • Define short-label, long-label formats • Update label-related protocols objects in RSVP-TE: • Generalized Label, Label Request, Upstream Label, Suggested Label, Acceptable Label Set, Explicit Route, Record Route • TE Routing L2 Labels • Advertise L2 Label availability into OSPF-TE • Range of available VLAN tags (short-label) • VLAN+MAC pairs (long-label); under discussion • Hierarchical LSP setup • Lambda LSP setup establishes optical service • Lambda LSP forms L2SC FA-LSP, populates L2 TE database • L2 LSP paths computed on L2 TE database, established thru FA-LSP

12. References • IEEE • 802.1d – STP/RSTP (2004) • 802.1q – VLAN • 802.1s – Multi-STP • 802.1ad – PB (Q-in-Q) • 802.1ah – PBB (MAC-in-MAC) • PBB-TE – under discussion • IETF • draft-fedyk-gmpls-ethernet-pbt-01 (GELS)

13. Thank You wdoonan@advaoptical.com