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MultiProtocol Label Switching (MPLS)

MultiProtocol Label Switching (MPLS). July 29, 2000 TECON 2000. Pramoda Nallur Alcatel Internetworking Division. Agenda. MPLS - The Motivation How MPLS Works ! MPLS Technology MPLS Application. MPLS - The Motivation. IP Protocol Suite - the most predominant networking technology.

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MultiProtocol Label Switching (MPLS)

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  1. MultiProtocol Label Switching (MPLS) July 29, 2000 TECON 2000 Pramoda Nallur Alcatel Internetworking Division

  2. Agenda • MPLS - The Motivation • How MPLS Works ! • MPLS Technology • MPLS Application

  3. MPLS - The Motivation • IP Protocol Suite - the most predominant networking technology. • Voice & Data convergence on a single network infrastructure. • Continual increase in number of users. • Demand for higher connection speeds. • Increase in traffic volumes. • Ever-increasing number of ISP networks.

  4. MPLS Working Groups and Standards • Standardized by the IETF - currently in Draft stage. • MPLS recommendations are done by IP players for IP services • MPLS core components are generic • MPLS doesn’t use specific technology process (e.g. ATM/FR signaling protocol PNNI or ATM OAM flow)

  5. Applications 7to5 IP 3 PPP FR ATM (*) Physical (Optical - Electrical) 1 MPLS and ISO model IETF main goal is that when a layer is added, no modification is needed on the existing layers. All new protocol must be backward compatible TCP UDP 4 MPLS PPP Frame Relay ATM (*) 2 (*) ATM overlay model (without addressing and P-NNI) is considered as an ISO layer 2 protocol.

  6. Agenda • Motivation for MPLS • How MPLS Works ! • MPLS Technology • MPLS Application

  7. Classification Label assignment LSP Label swapping Label removal Routing protocol OSPF OSPF OSPF FEC table Local table Local table Local table Attributes Precedence Label table Local table Local table Local table Layer 2 Layer 2 Layer 2 Layer 2 Layer 2 Label Switch Layer 1 Layer 1 Layer 1 Layer 1 Layer 1 Ingress Node Core Node Egress Node MPLS Architecture

  8. Label Switch Path OSPF / RIP / IS-IS FEC FEC FEC Precedence Label table Label table Label table Layer 2 Layer 2 Layer 2 Layer 2 Layer 2 Layer 1 Layer 1 Layer 1 Layer 1 Layer 1 Ingress Node Core Node Egress Node MPLS process Label removal Label removal Label swapping Label swapping Classification Label assignment Classification Label assignment

  9. MPLS Cloud LER L3 Routing LER LER L3 Routing L3 Routing LSR LSR LER Label Swapping Label Swapping LER L3 Routing L3 Routing IP Packet IP Packet w/ Label

  10. MPLS Link Layers & Label Encapsulation ATM FR Ethernet PPP Layer2 VPI VCI DLCI “Shim Label” “Shim header” ……. IP | PAYLOAD

  11. Agenda • Motivation for MPLS • How MPLS Works ! • MPLS Technology • MPLS Application

  12. Some MPLS Terms... • LER - Label Edge Router • LSR - Label Switch Router • FEC - Forward Equivalence Class • Label - Associates a packet to a FEC • Label Stack - Multiple labels containing information on how a packet is forwarded. • Shim - Header containing a Label Stack • Label Switch Path - path that a packet follows for a specific FEC • LDP - Label Distribution Protocol, used to distribute Label information between MPLS-aware network devices • Label Swapping - manipulation of labels to forward packets towards the destination.

  13. A packet can be mapped to a particular FEC based on the following criteria: • destination IP address, • source IP address, • TCP/UDP port, • in case of inter AS-MPLS, Source-AS and Dest-AS, • class of service, • application used, • … • any combination of the previous criteria. Ingress Label FEC Egress Label 6 138.120.6/24 - xxxx 9 Ingress Label FEC Attribute Egress Label Ingress Label FEC Attribute Egress Label • FECs are manually initiated by the operator 6 138.120.6/24 - xxxx A 9 • A FEC is associated at least one Label 6 138.120.6/24 - xxxx B 12 FEC Classification

  14. L2 Type Port Ingress Label FEC L2 Type Egress Label Port ATM 1-1 12 (i.e. 4/65) F1 22 (i.e. 5/65) 3-4 ATM ATM 1-1 15 (i.e. 0/25) F4 9 (i.e. 101) 5-1 FR Gig Eth 5-1 7 F1 22 (i.e. 4/65) 3-4 ATM What is a Label ? • A short, fixed length, locally significant identifier used to identify a FEC. • The label can be identified by the L2 technology identifier (e.g. VPI/VCI for ATM, DLCI for FR or MPLS label for PPP/Ethernet).

  15. MPLS Label Assignment Schemes • Topology Driven • Label assignment in response to routing protocols (OSPF and BGP) updates • Control Driven • Label assignment in response to RSVP, CR-LDP requests • Traffic Driven • Label assignment in response to flow detection & triggering

  16. Label(20 bits) Exp(3 bits) S (1 bit) TTL (8bits) The MPLS Shim Header • The Label (Shim Header) is represented as a sequence of Label Stack Entry • Each Label Stack Entry is coded by 4 bytes (32 bits) as described • 20 Bits is reserved for the Label Identifier (also named Label) Label : Label value (0 to 15 are reserved for special use) Exp : Experimental Use S : Bottom of Stack (set to 1 for the last entry in the label) TTL : Time To Live

  17. Ingress Interface Ingress Label Egress Label FEC Egress Interface Ingress Interface Ingress Label Egress Label 12 FEC Egress Interface 5 12 1 4 138.120 x 1 3 138.120 Ingress Interface Ingress Label Egress Label FEC Egress Interface 5 1 x 3 138.120 Label Switched Path MPLS switch 3 1 138.120 4 1 2 MPLS switch 3 127.20 1 2 3 3 MPLS switch 192.168 2 1 2 MPLS switch

  18. Ingress Interface Ingress Label Egress Label FEC Egress Interface Ingress Interface Ingress Label Egress Label FEC Egress Interface 1 Default 4 None x 1 Default 3 Default None ?? ?? MPLS switch ?? ?? 3 1 138.120 4 1 2 MPLS switch 3 127.20 1 2 3 3 MPLS switch 192.168 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 ?? ?? 2 1 2 MPLS switch Ingress Interface Ingress Label Egress Label FEC Egress Interface 1 x 3 Default None Hop by Hop IP forwarding

  19. Ingress Interface Ingress Label Egress Label FEC Egress Interface Ingress Interface Ingress Label Egress Label FEC Egress Interface 12 1 5 4 12 138.120 x 1 3 138.120 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 138.120.6.12 Ingress Interface Ingress Label Egress Label FEC Egress Interface 5 1 x 3 138.120 IP forwarding using LSP MPLS switch 3 1 138.120 4 1 2 MPLS switch 3 127.20 1 2 3 3 MPLS switch 192.168 2 1 2 MPLS switch

  20. MPLS Label Distribution Protocol • LDP - a set of procedures by which one LSR informs the other of the FEC-to-Label binding it has made. • Currently, several protocols used as Label Distribution Protocol (LDP) are available: • RSVP-TE (MPLS extension) • LDP and CR-LDP • BGP-4 MPLS extensions • Label Distribution schemes

  21. Ingress Interface Ingress Label Egress Label FEC Egress Interface Ingress Interface Ingress Label Egress Label FEC Egress Interface 1 4 138.120 x 1 3 138.120 MPLS switch 3 1 138.120 4 1 2 MPLS switch 3 127.20 1 2 3 3 MPLS switch 192.168 2 1 2 MPLS switch Ingress Interface Ingress Label Egress Label FEC Egress Interface 1 x 3 138.120 Downstream stream on demand 12 5 12 Request 138.120 Request 138.120 Mapping 12 Mapping 5 The label is requested by the upstream node and the downstream node defines the label used. 5

  22. Ingress Interface Ingress Label Egress Label FEC Egress Interface Ingress Interface Ingress Label Egress Label FEC Egress Interface 1 4 138.120 x 1 3 138.120 MPLS switch 3 1 138.120 4 1 2 MPLS switch 3 127.20 1 2 3 3 MPLS switch 192.168 2 1 2 MPLS switch Ingress Interface Ingress Label Egress Label FEC Egress Interface 1 x 3 138.120 Unsolicited Downstream 12 5 12 Mapping 12 Mapping 5 The downstream node defines the label and advertises it to the upstream node. 5

  23. Edge LSR Features • Routing protocols • FEC Classification • Initiates LSP setup for Downstream On Demand method • Adaptation of non-MPLS data to MPLS data • Layer 2 translation for MPLS data • Terminated MPLS-VPN • At least one LDP protocol • Edge LSR is counted into the TTL count as a regular router

  24. Core LSR Features • Routing protocols • Propagates Downstream On Demand method (request and mapping) • Layer 2 translation • High speed label forwarding/switching • At least one LDP protocol

  25. Agenda • Motivation for MPLS • How MPLS Works ! • MPLS Technology • MPLS Application

  26. MPLS Advantages • Simplified Forwarding • Efficient Explicit Routing • Traffic Engineering • QoS Routing • Mappings from IP Packet to Forwarding Equivalence Class (FEC) • Partitioning of Functionality • Common Operation over Packet and Cell media

  27. MPLS - the Future • Who will use MPLS? • Large-scale data networks used by Enterprises, Carriers and ISPs. • Why MPLS? • Delivers high speed L2 (really “Label”) switching at low cost vs. traditional L3 routing • Provides Traffic Engineering - allows the user to direct traffic based on network utilization and demand. • Ease of provisioning QoS • Support for VPNs

  28. Explicitly Routed LSP Overload !! LER 4 LER 1 Overload !! LSR 2 LSR 3 Forward to LSR 2 LSR 3 LSR 4 LSR X • End-to-End forwarding decision determined by ingress node. • Enables Traffic Engineering

  29. MPLS Traffic Engineering • MPLS Traffic Engineering (TE) provides high quality IP service. • TE defines : • LSP Admission Control (LAC) • IP traffic (policing or shaping) • IP service prioritization • Network capacity and growth capacity • TE is primary done by external tools. This solution allows flexibility and customization.

  30. VPN 2 138.120.6.0/24 LSR 138.120.8.0/24 Site B VPN 1 Site A LSR LSR LSR LSR LSR Site A Site B 138.120.8.0/24 VPN 1 VPN 2 138.120.6.0/24 MPLS VPN : MPLS topology LSP 47 ISP Backbone LSP 32

  31. MPLS - Some Major Vendors • Alcatel • Cisco • Juniper Networks • Nortel • Lucent

  32. MPLS - More Information @ • MPLS Charter http://www.ietf.org/html.charters/mpls-charter.html • MPLS Resource Center http://www.mplsrc.com • MPLS Forum http://www.mplsforum.org

  33. Any Questions ? Thanks for your time ! EmailPramoda.Nallur@ind.alcatel.com

  34. MPLS - An Analysis TCP & UDP Flows without MPLS UDP Throughput (in Mbps) TCP 2 TCP 1 UDP Rate (in Mbps)

  35. MPLS - An Analysis TCP & UDP Flows with MPLS Trunks (LSPs) UDP Throughput (in Mbps) TCP 2 TCP 1 UDP Rate (in Mbps)

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