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The Role of Ethernet in Optical Networks

Learn about innovative Ethernet technologies such as PBT, PBB, and GMPLS, and how they enhance the role of Ethernet in optical networks. Discover the benefits of these technologies in terms of scalability, utilization, and network engineering.

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The Role of Ethernet in Optical Networks

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  1. The Role of Ethernet in Optical Networks Dave Allan, Sr. Advisor, CTO office Nortel dallan@nortel.com

  2. PBT PBB Layer 2 networking GFP 802.3 RPR Link layer Physical layer What you should get out of this An appreciation of new innovations in the Ethernet networking space • “Ethernet” means many different things; this overview is about Ethernet as an networking technology Specifically: • 802.1ah Provider Backbone Bridging (PBB) • Provider Backbone Transport (PBT) • Applying GMPLS to PBT And what this means in the role of Ethernet in general YOU ARE HERE

  3. Ethernet Basics • Ethernet floods information on the data plane • No real concept of “need to know” • Flooding -> • Rigorous loop avoidance -> • Spanning-Tree protocol (STP) OR trivial bridged networks • Poor utilization of mesh & lack of determinism • Practical limits in number of end-systems supported • STP re-convergence is service interrupting • No topology database, convergence is incremental/transactional • Topology must stabilize before forwarding and flooding can resume

  4. Why Ethernet is perceived as needing help • STP is very topologically limited • VLAN tags allow better use of richer topologies, but : • are administratively complex, • VLAN identifiers are network global -> scaling limitations • Ethernet is not easily engineered in any real sense • Conclusion is that for smaller networks the plug and play and minimal implementation are useful properties but to extend Ethernet into larger networks, more is needed. To date this has restricted Ethernet to the role of link layer in large networks

  5. Why is Ethernet worth pursuing? • It is rapidly becoming the link layer of choice…everywhere! • Ethernet starts as a broadcast medium and then applies progressive filtering to achieve more selective behaviors • Unicast • Closed user groups etc. • All other modes of connectivity can be derived from basic Ethernet behavior • Adding new functionality is actually subtractive from the basic behavior… turn something or other off Ethernet has the potential to be THE most flexible networking technology

  6. Ethertype B-VID Ethertype B-DA B-SA A brief history of Ethernet stacking Payload Payload Payload Ethertype Ethertype Payload Non-Ethernet payloads C-VID C-VID Ethertype Ethertype Ethertype VID S-VID S-VID Ethertype Ethertype Ethertype Ethertype DA DA DA DA Separating infrastructure end points from service end points has profound implications as to what Ethernet is capable of SA SA SA SA 802.1 802.1q 802.1ad Provider Bridges I-SID SA = Source MAC address DA = Destination MAC address VID = VLAN ID C-VID = Customer VID S-VID = Service VID I-SID = Service ID B-VID = Backbone VID B-DA = Backbone DA B-SA = Backbone SA 802.1ah Provider Backbone Bridges

  7. A 20 year journey from discovery…. • Ethernet depends on loop free topology for learning and discovery to work • Flood unknown information • Observe where traffic comes from and optimize forwarding • Useful where the set of MAC terminations in the network is either not known, not under control, or desired to simply be auto-discovered • MACinMAC is one scenario where the set of MAC addresses is known and could be controlled • Doing something other than learning and discovery is an option

  8. ….to Configuration • A cornerstone • IVL switches can have a unique forwarding entry per MAC per VLAN • Full 60 bit lookup • These entries can be configured instead of learned… • Another cornerstone • A VID in an IVL switch today identifies a loop free spanning tree • A VID can refer to the whole mesh… • If VID refers to the whole mesh, loop free is a configuredMAC problem • Control planes are good at loop free and autodiscovery • A control plane can configure a unique loop free MP2P unicast or P2MP multicast tree per VID per DA-MAC This technique has been introduced to the industry under the name of Provider Backbone Transport (PBT)

  9. Dataplane Example 1/X & 2/X can diverge VIDs 1+2 delegated to PBT 1/X&1/Y can diverge VID(1)/MAC(X) MAC ‘X’ MAC’B’ VID(2)/MAC(X) MAC ‘Y’ VID(2)/MAC(Y) VID(1)/MAC(Y) Note that MACs and VIDs can overlap, it is the combination of both that is unique and allows diverse routing

  10. Useful Properties • Destination based forward • Scales O(N) in the core • Only need to borrow a dozen or so VLANs or so for massive connection capacity • Class based Queuing (.1P) • Packet level pre-emption, • Connectivity and QoS decoupled, analogous to E-ESPs • Knowledge of source preserved (SA-MAC) • Can instrument connectivity as if P2P • Levers emerging “strong OAM” (802.1ag/Y.1731) • How FIB gets populated has changed, not how bridges actually forward • Global 60 bit label (VID+DA-MAC) • dataplane forwards directly on “connection ID” All of this is largely for free! …known capabilities simply used in a new way!

  11. Applying GMPLS to PBT Relatively few modifications are required to GMPLS in order to apply it to PBT • 60 bit VLAN/DA MAC “label” is invariant • Different from GMPLS today • VLAN (local to DA), DA (global to network) means destination can administer labels • Destination label administration as per GMPLS today • Bi-directional ESPs w. common routing preferred • GMPLS supports today (Upstream label) • Full 108 bit label SA/VID/DA inferred from upstream label (which will be mandatory) Ethernet assumes some of the mantle of MPLS-TE and SONET/SDH

  12. Other control planes…? • Global destination based label (VID/MAC) means label information can be piggybacked on routing system… • For example: • Allocate a VID for use by a link-state routing system • Globally unique/destination offered 60 bit labels mean “routing prefix to L2 binding” does not require any link local personalization and can simply be flooded in routing system advertisements • One….yes one (1) control protocol • Local configuration of bridge tables is to point 60 bit label to next hop for the prefix as determined by the routing system • …and the result is: • Converged network has built required L3 connectivity with vanilla Ethernet forwarding Very simple L2<->L3 integration

  13. The implications are…. In a world where all neighbors grow up to eat each other’s lunch, Ethernet becomes the hungry gorilla…. Data Services IP/MPLS Ethernet L0/L1

  14. Summary • Ethernet is a commodity with vast untapped capabilities • We can re-purpose Ethernet switches with new control software to broaden their role in the network • TE, SPF in addition to bridging and multicast…. • This can be done with minimal changes to Ethernet standards • And they are well underway • This provides an opportunity to radically delayer the network

  15. Questions?

  16. For Further Reading • “GMPLS Control of Ethernet IVL Switches”. April 2006 • http://www.ietf.org/internet-drafts/draft-fedyk-gmpls-ethernet-ivl-01.txt • Pseudo Wires over PBT, March 2006 • http://www.ietf.org/internet-drafts/draft-allan-pw-o-pbt-00.txt • “Ethernet as Carrier Transport Infrastructure” • IEEE Communications magazine, February 2006 • www.ieee802.org/1/files/public/docs2005/ah-bottorff-pbt-for-iee-v41-0905.pdf

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