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Graceful Label Numbering in Optical MPLS Networks Ibrahim C. Arkut [email protected] Refik C. Arkut [email protected] Nasir Ghani [email protected] What is MPLS? Multi Protocol Label Switching is a routing technique that imitate connection oriented forwarding method in a connectionless (IP) environment OptiComm 2000, October 24, 2000, Dallas, Texas Chart 2 What is MPLS? (cont.) • Hop-by-hop or source routing to establish labels - non-shortest paths • Uses label native to the media • Multi level label substitution transport OptiComm 2000, October 24, 2000, Dallas, Texas Chart 3 Why MPLS ? • Performance and scalability • Explicit routing and traffic engineering – Constraint-based Routing / QoS • Separation of control (routing) and forwarding • Virtual Private Networks – Controllable tunneling mechanism • Unified approach to routing functionality OptiComm 2000, October 24, 2000, Dallas, Texas Chart 4 Best of both Worlds Packet Forwarding IP HYBRID MPLS +IP Circuit Switching ATM • Flexibility and predictability • Performance - complexity trade-off OptiComm 2000, October 24, 2000, Dallas, Texas Chart 5 Forwarding Equivalence Classes (FEC) LER (ingress) IP1 LSR LSR LER (egress) IP1 IP1 #L1 IP1 #L2 IP1 #L3 IP2 #L1 IP2 #L2 IP2 #L3 IP2 IP2 LSP Flow of IP packets • over the same path • treated in the same manner • mapped to the same label OptiComm 2000, October 24, 2000, Dallas, Texas Chart 6 FEC / label binding mechanism • Binding is done once at the ingress LER / OXC • Currently based on destination IP address prefix • Future mappings based on SP-defined policy • In electronic MPLS domain Label <---> FEC (packet associated) • In photonic MPLS domain Label <---> Wavelength ( channel associated) OptiComm 2000, October 24, 2000, Dallas, Texas Chart 7 MPLS Signaling Protocols • • • • Hop-by-hop & Explicit Label Distribution Protocol (LDP) Constraint-based Routing LDP (CR-LDP) Extensions to RSVP OptiComm 2000, October 24, 2000, Dallas, Texas Chart 8 Packet Forwarding over LSP(Label swapping) Edge Core Edge Core Egress Label Switch Ingress label switch IP addr Out label 192.4/16 192.4.2.1 Layer 2 transport 5 Assign Initial Label IP label Next hop Core 5 Label Switch Label Switch In label Out label In label Out label 5 9 Label Swapping 9 9 2 2 2 21.9.1.1 Layer 2 Transport Remove label 192.4.2.1 Label Swapping Label-Switched Path Label swapping is ‘simple’, but is it simple enough? OptiComm 2000, October 24, 2000, Dallas, Texas Chart 9 Matching the Speeds? IP/MPLS-over-WDM IP/MPLS Electronic Speed Frame Monitoring Optical Speed Optical (Physical) Layer For increased speed, the mechanism must be simpler! OptiComm 2000, October 24, 2000, Dallas, Texas Chart 10 Graceful Numbering of Trees • It is a well-known labeling problem in graphs and trees. • Number the nodes of a graph G with 1, 2,…, e so that induce edge labels computed by absolute node number differences are all distinct. • Notorious conjecture of RingelKotzig [1963] asserts that “all trees are graceful” 9 7 6 10 4 7 3 14 8 6 2 13 1 12 1 13 5 2 14 8 9 15 11 4 3 12 11 10 5 Graceful numbering of a tree OptiComm 2000, October 24, 2000, Dallas, Texas Chart 11 MPLS unicast with graceful numbering DESTINATION 4 2 7 5 6 1 5 2 4 3 3 6 1 SOURCE OptiComm 2000, October 24, 2000, Dallas, Texas Chart 12 MPLS+Graceful Numbering Edge Core Ingress label switch Egress Label Switch IP addr Out label 192.4/16 192.4.2.1 Layer 2 transport 1 IP label Next hop Core 3 Assign Initial Label Edge Core 3 Label Switch Label Switch In label Out label In label Out label 3 2 2 2 1 Label Swaping Label Swaping 4 2 L a b e l -S w i t c h e d P a t h OptiComm 2000, October 24, 2000, Dallas, Texas 1 1 21.9.1.1 Layer 2 Transport Remove label 192.4.2.1 3 Chart 13 MPLS multicast caterpillar using graceful numbering 3 9 8 12 4 10 11 1 SOURCE 2 SOURCE N={1,2,3,4,5,6,7,8,9,10,11,12} 11 3 N={1,2,3,4,5,6,7,8,9,10,11,12} 10 7 9 11 3 8 11 4 10 6 4 11 9 1 SOURCE 2 N={1,2,3,4,5,6,7,8,9,10,11,12} OptiComm 2000, October 24, 2000, Dallas, Texas 8 12 8 5 1 SOURCE 6 7 9 6 12 10 2 4 4 10 5 3 8 5 9 2 1 7 N={1,2,3,4,5,6,7,8,9,10,11,12} Chart 14 Graceful numbering of paths and caterpillars (*) are not complex and resembles label assignment in PATH MPLS N 1 2 N-1 3 N-3 N-2 N-1 N-2 N-5 N-4 etc. CATERPILLAR backbone path N-3 1 N-5 N-2 N-6 3 N-14 N-13 N-10 N-3 N-6 7 etc. N-1 N-2 N-4 N-7 N-9 N-11 N-12 N-8 N N-1 2 4 5 6 N-4 N-5 (*)I. Cahit and R. Cahit, “On Graceful Numbering of Spanning Trees”, Info. Proc. Lett., 3(4), March 1975, OptiComm 2000, October 24, 2000, Dallas, Texas Chart 15 MPLS Roles MPLS SONET Optical Present MPLS Adaptation Optical Future IP/MPLS:Service and addressing, Quality of service, TE, Protection Efficient logical Sonet: Multiplexing, Protection overlay over Optical: Bandwidth Sonet IP/MPLS: Service and addressing Quality of service, TE, Protection, Multiplexing, Efficient Peer Optical: Protection, Multiplexing model and Bandwidth transport topology aware OptiComm 2000, October 24, 2000, Dallas, Texas Chart 16 One Control (MPLS) - End to End VPI/VCI /DLCI/ Label MPLS Control Plane Label Lambda OptiComm 2000, October 24, 2000, Dallas, Texas Lambda Label VPI/VCI /DLCI/ Label Chart 17 Lambda-Labeling with Graceful Numbering (IP-Over-WDM) • Graceful Lambda (Gl) Labeling in Optical Core Network IP/MPLS network (electronic) ”Gl - labeling" Optical MPLS Core I1 I6 M12 M8 Large bandwidth lambda LSP's explicit routing I2 M11 I5 M9 M10 I3 I4 Lambda-labeling approach: multiple MPLS network node types OptiComm 2000, October 24, 2000, Dallas, Texas Chart 18 Graceful Numbering of Two Light-paths (without lambda conversion) • IF the light-paths from C to B and from A to D arrive to node X with the same label but different wavelengths • THEN no need to convert any wavelength at node X OptiComm 2000, October 24, 2000, Dallas, Texas C B 5 4 1 merging is not possible X 2 3 3 4 2 1 A D Chart 19 Graceful Numbering of Two Light-paths with wavelength conversion • IF the light-path from C to B and from A to D arrive to node X with the same labels and wavelengths • THEN one of the wavelength is to be converted at node X C B 5 4 1 merging is not possible X 2 3 3 4 2 1 A D OptiComm 2000, October 24, 2000, Dallas, Texas Chart 20 Summary • Topology associated labeling • Distinct labels per LSP or MC Caterpillar • Label conflict resolution by central control • Source controlled Graceful Number assignments • Labels generation automatic and simple • Efficient O(n) algorithms • Minimum label-process time • Distributed algorithm to assign Gl-labels OptiComm 2000, October 24, 2000, Dallas, Texas Chart 21