Dimitri Papadimitriou <dpapadimitriou@psg> <dimitri.papadimitriou@alcatel-lucent.be>

1. (G)ELS - Ethernet VLAN-label Switching (ELS) Benchmarking Carrier Ethernet Technologies WorkshopSession MII.1Krakow, PolandApril 30, 2008 Dimitri Papadimitriou <dpapadimitriou@psg.com> <dimitri.papadimitriou@alcatel-lucent.be>

2. Evolution of Ethernet paradigms Ethernet LAN/MAN bridging branch • Two main scalability concerns: • VLAN ID space - can not be solved with Provider bridges (IEEE 802.1ad) • MAC address space & learning - (hierarchical) hash-based table lookup (=> simple but limited MAC table size due to memory consumption & non-deterministic lookup time) Main “networking” concern: • Loop avoidance (STP) - can not be solved with STP 802.1d or RSTP 802.1w • Convergence time of STP - idem Main performance concern: • STP “blocks” network trunks - not solved with MSTP 802.1s Spanning Tree Protocol (STP) (VLAN-)Bridges Multiple STP (MSTP) Provider Bridges (PB) Multiple STP (MSTP) Provider Backbone Bridges (PBB)

3. Ethernet MAC and Ethernet v2 • Ethernet 802.3 MAC Frame • Ethernet v2 Frame 6 1 6 2 4 7 Destination Address Source Address Information FCS Pad Preamble Length SD Synch Start frame 64 to 1518 bytes • MAC address (6 bytes) is either • Single address (0x0….) • Group address (broadcast = 111...111) • MAC addresses are defined • on local (0) or global (1) basis (second bit) • 246 possible global addresses No TTL (time to live) => impossible to detect looping Ethernet MAC frames 6 6 1 2 4 7 Destination Address Source Address Information FCS Pad Preamble Type SD Start frame Synch 64 to 1518 bytes

4. Spanning Tree Protocols: Count-to-infinity • Spanning tree: a connected, acyclic subgraph (no cycles) containing all the vertices of a graph • Minimum spanning tree (aka shortest spanning tree): a weighted graph which contains all of the graph's vertices • Count-to-infinity problem (as for any other Distance-Vector routing protocol) •  Temporary forwarding loop (cycle) that con persist for O(10s) •  (R)STP does not provide for fast convergence (and no - known - suitable technique to improve distance vector convergence properties) • Note: steiner tree = a minimum-weight tree connecting a designated set of vertices, called terminals, in an undirected, weighted graph or points in a space. The tree may include non-terminals. Root Root unreachable cycle Source: Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 17 July 2006.

5. Evolution of Ethernet paradigms: PBB Ethernet LAN/MAN Bridging branch • Two main scalability concerns: • VLAN ID space - solved: S-VID (12 bits) -> I-SID (24bits) • MAC address space & learning - solved: MAC-in-MAC tunneling (MAC learning still required) Main “networking” concern: • Loop avoidance (STP) - not solved • Convergence time of STP - not solved Main performance concern: • STP “blocks” network trunks - not solved Spanning Tree Protocol (STP) (VLAN-)Bridges Multiple STP (MSTP) Provider Bridges (PB) Multiple STP (MSTP) Provider Backbone Bridges (PBB)

6. Ethernet Transport technologies Ethernet packet-switched technology with two possible variants: • Ethernet Bridging: 802.1ah (PBB), 802.1aq (SPB) • Ethernet Switching (ongoing efforts): • MAC + VID based (domain-wide labels): 802.1Qay (PBB-TE) • VID based (link-local labels): Ethernet VLAN label switching

7. Problem statement Existing IEEE 802.1 forwarding components and their control does not fulfil requirements associated to Carrier Ethernet metro (and core) networks Management Provisioning (Policy, etc) Provisioning (Forwarding Components) Forwarding Plane Ethernet Control (MSTP) Spanning Tree, Learning, Filtering

8. Evolution of control and forwarding paradigms: Ethernet VLAN-label Switching (ELS) Ethernet Bridging branch (Distance vector) Ethernet Switching branch (Link State routing) Spanning Tree Protocol (STP) (VLAN-)Bridges Multiple STP (MSTP) Provider Bridges (PB) Multiple STP (MSTP) Provider Backbone Bridges (PBB) S-VID (encapsulation) + Constraint-based switched data paths Link-local labels

9. Ethernet LSP Ethernet VLAN-label Switching (ELS) - Overview • Ethernet LER (E-LER) function: take an incoming Ethernet MAC frame, add or remove the label (encoded in the TAG field) • Ethernet LSR (E-LSR): take incoming labelled Ethernet MAC frame and perform label swap (VID in  VID out) => forwarding independent of destination MAC address • Ethernet: point-to-point and point-to-multipoint data paths Payload (Eth, X, Y) MAC header + S=VID PHY E-LSR E-LSR E-LSR Ethernet MAC frame Ethernet MAC frame Source Dest S-VID push S-VID swap S-VID pop Router Router Ethernet 802.1ad Switch Ethernet 802.1ad Switch Ethernet 802.1ad Switch Eth. PHY Eth. PHY

10. Ethernet VLAN-label Switching (ELS) - Framing

11. ELS Control Paradigm: Traffic Engineering • Traffic engineering adapt traffic routing to network conditions with joint traffic and resource-oriented performance objectives • Effectively control usage of available network resources (put traffic where unused capacity is) • Efficiently re-/direct selected traffic flows from IGP shortest path onto an alternative path • Rapidly redistribute traffic in response to changes in network topology • Performance objectives (provisioning and recovery) • Resource-oriented • Traffic-oriented: packet loss, delay (and variation) • Approaches • Proactive (longer-term): anticipating traffic changes • Reactive/adaptive (shorter-term): responsive to traffic changes

12. Constrain-based Routing (Policy-based + QoS source routing) Operations performed by a LSP head-end (G)MPLS-TE capable node (GMPLS) OSPF-TE 1 2 4 3 Traffic engineering Database (TEDB) Constrained-SPF Computation Use Request Constraints Routing table (GMPLS) OSPF-TE Extensions Distributed (piggybacked) using Opaque Link State Advertisements (LSA) & encoded as Link sub-TLV Metrics: Unreserved Bandwidth, Maximum Reservable Bandwidth, TE Metric, Resource Class and ISCD (Max. LSP Bandwidth, Switching Cap., LSP Enc. Type) 5 6 (GMPLS) RSVP-TE Signaling Explicit Route Representation • Store information from IGP flooding in the Link State DB (LSDB) • Store traffic engineering information in the TE Link State DB (TEDB) • Examine user defined constraints for the incoming connectivity requests (=> QoS routing) • Path computation for the data path (LSP) through the TE link topology (=> Policy routing) • Representation of the computed path as an Explicit Route (=> Source routing) • Pass Explicit Route to (GMPLS) RSVP-TE engine for signaling

13. Positioning ELS Ethernet VLAN-label Switching (ELS) Ethernet PW over MPLS IEEE: PBB/PBB-TE Payload Payload Payload Ethernet (Untagged, C-/S-VID) Ethernet (Untagged, C-VID) Ethernet (Untagged, C-/S-VID) Shim (I-SID) Shim (CW + PW label) Ethernet + B-VID [Ethernet] + S-VID PSN Tunnel (MPLS) Ethernet VLAN-Label Switching (ELS) S-VID Label (link local) Ethernet PW over MPLS MPLS Label (link local) Provider Backbone Bridges (PBB) Provider Backbone Bridges (PBB-TE) PBB: same issues as for any other 802.1 based technology PBB-TE: Single domain (MAC unicity) and no multicast support (single VID space segmentation) Unique payload type per LSP Encapsulating LSP can not be merged (as PW labels are node specific) 4k LSP per port (max.) LSP merging

14. Positioning ELS vs PBB-TE (1)

15. Positioning ELS vs PBB-TE (2) Ethernet Transport IP/MPLS ETH + S-VID PBB (BEB) Router Disjoint Ethernet MAC address spaces PB (BCB) IP/MPLS ETH PHY ETH + S-VID I-SID IP/MPLS B-VID Ethernet Label Switching <B-DA, B-VID> ETH + S-VID B-SA Frame Filtering B-DA Ethernet Transport IP/MPLS ETH Router VLAN label Switching Ethernet LSR Same Ethernet MAC address space IP/MPLS S-VID Label Switching Frame forwarding independent of MAC address ETH+S-VID IP/MPLS PWoMPLS LER ETH

16. Positioning ELS vs Ethernet PW over PSN (1) Ethernet (Untagged, C-VID) Ethernet (Untagged, C-/S-VID) Shim (CW + PW label) [Ethernet] + S-VID PSN Tunnel (MPLS) Ethernet Label Switching (ELS) Ethernet Pseudo-Wires (PW) Ethernet Transport Ethernet PW over PSN Client Payload IP, IP/MPLS, etc. Outside scope Connectivity Service Ethernet P2P, P2MP Segment Ethernet P2P, P2MP, MP Segment Network Emulation & Adaptation Ethernet Path (PE-to-PE) Append S-VID to Ethernet frames Pseudo-Wire (PW) label Network PE-to-PE Connection MPLS/T-MPLS Network Intermediate Trunks MPLS Tunnel/T-MPLS Tunnel Data link layer Ethernet MAC/PPP-HDLC Physical layer Ethernet PHY/SONET-SDH Ethernet PHY/SONET-SDH

17. Positioning ELS vs Ethernet PW over PSN (2) Ethernet (connectivity) Service IP/MPLS ETH Router Disjoint Ethernet MAC address spaces MPLS Label Switching MPLS LSR IP/MPLS ETH PHY ETH PW MPLS IP/MPLS MPLS Label Switching PWoMPLS LER MPLS ETH DLL Ethernet Transport IP/MPLS ETH Router VLAN label Switching Ethernet LSR Same Ethernet MAC address space IP/MPLS S-VID Label Switching Frame forwarding independent of MAC address ETH+S-VID IP/MPLS PWoMPLS LER ETH

18. Resolving the Ethernet Paradox • Ethernet Paradox • Ethernet evolves as intra-domain aggregation technology for metro & core networks (by better adapting transport to Ethernet as MPLS is adapted to IP) Ethernet forwarding plane Ethernet switching technology e.g. ELS • Moving Ethernet "networking" properties (linked to LAN / campus networks) toward metro-aggregation networks - but also core - definitely transform intrinsic nature of Ethernet Ethernet routing paradigm (control) use of unified control e.g. GMPLS • Consequences • Ethernet control: • From distance vector routing protocol (spanning tree protocol) to link state routing protocol • As IP routing evolved from RIP (distance vector) to OSPF (link state) • Ethernet forwarding: • Ethernet forwarding without specific mechanisms suitable/dedicated for LAN (campus, enterprise, etc.) environments • Mechanisms fitting specific needs of aggregation

19. ELS and Architectural evolution: IP over Optics  IP over Carrier Ethernet Ethernet (connectivity) between routers using OWS network IP/MPLS ETH Router Disjoint Ethernet MAC address spaces + Service boundary Optical Switching ETH PHY IP/MPLS ETH Optical Switching Optical IP/MPLS ETH Ethernet (connectivity) between routers using carrier Ethernet switching network IP/MPLS ETH Router VLAN label Switching Ethernet LSR Same Ethernet MAC address space + Same admin domain IP/MPLS S-VID VLAN Label Switching (802.1ad) ETH+S-VID IP/MPLS ETH

20. Architectural evolution: IP over Optics  IP over Carrier Ethernet • IP routers • traffic aggregation (level 1) • networking (single peering point), IP fast re-routing (not MPLS), and multi-topology routing, and BFD (OAM) • Carrier Ethernet: robust, resilient, flexible and cost-effective traffic aggregation (level 2) • Optical equipment/switching: (internal long distance) connectivity Domain boundary Domain boundary IP router IP router ETH PHY ETH PHY ETH PHY Carrier Ethernet ETH PHY ETH PHY Long distance, Ethernet switch interconnection Optical

21. SP1..i-1 Internet SPi…n Tomorrow’s situation Metro Access Core First Mile Metro-Aggregation Customer Premises Large CO Regional POP Ethernet aggregation Ethernet aggregation 100GbE 100GbE Ethernet core switch IP edge routers Ethernet metro switch IP Access router IP Access router < 10 nodes O(10) nodes < 100 km < O(100 km) < 5,5 km < 50 km

22. Conclusion: Evolution of Ethernet control and forwarding paradigms The ultimate goal toward Carrier Ethernet … Management Provisioning (TE data paths, re-routing, etc) Provisioning (Forwarding Components) Forwarding Plane Unified Ethernet Control (e.g. GMPLS) Forwarding component control

23. Several issues for further investigation • Ethernet Forwarding Plane • Ethernet label space and scalability ( Label/LSP merging ?) - specific to link-local label switching based Ethernet forwarding • Ethernet CoS mechanisms (DSCP to Ethernet PCP mapping  DCP ?) - common • Ethernet multicast traffic (connectivity and adaptation) - common • Ethernet Control - common • Unified traffic engineering (including fast re-routing)  lighter protocol suite(*) ? • Adaptive traffic engineering and resource allocation including Bandwidth Constraint Models (BCM) • Lightweight measurement/monitoring capabilities including performance (*) fundamental issue: developing, deploying and operating metro Ethernet using unified control must remain time-, resource- and cost-efficient (prevent over-engineering)

24. Thanks ! Acknowledgements This work was carried out within the framework of the IWT TIGER project sponsored by the Flemish government institute for Innovation through Science and Technology in Flanders (IWT)