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M ulti P rotocol L abel S witching

M ulti P rotocol L abel S witching. Presented by: Petros Ioannou Dept. of Electrical and Computer Engineering, UCY. What is MPLS?. Multi Protocol: Because it works with the Internet Protocol(IP), Asynchronous Transport Mode(ATM) and Frame Relay network protocols Label Switching:

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M ulti P rotocol L abel S witching

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  1. Multi Protocol Label Switching • Presented by: Petros Ioannou • Dept. of Electrical and Computer Engineering, UCY

  2. What is MPLS? • Multi Protocol: • Because it works with the Internet Protocol(IP), Asynchronous Transport Mode(ATM) and Frame Relay network protocols • Label Switching: • Because it use fixed length label switching similar to ATM or FR • MPLS forwards packets based on labels • MPLS simplifies and improve the forwarding function by introducing a connection oriented mechanism inside the connectionless IP networks • Packets are switched, not routed

  3. Why MPLS? • IP Routing Disadvantages: • Connectionless • No QoS • Each router has to make independent forwarding decisions based on the IP address • Routing in Network Layer • Slower than switching • Usually designed to obtain shortest path • Don’t take into account additional metrics

  4. Why MPLS? Traffic Engineering

  5. Why MPLS? • ATM Advantages: • Connection oriented • Supports QoS • Fast packet switching with fixed length packets (cells) • Integration of different traffic types (voice, data, video) • ATM Disadvantages: • Complex • Expensive • Not widely adopted

  6. Why MPLS?

  7. The Idea

  8. MPLS Label Format • MPLS uses a 32-bit label field: • 20-bit label (a number) • 3-bit experimental field (usually used to carry IP precedence value) • 1-bit bottom-of-stack indicator (indicates whether this is the last label before the IP header) • 8-bit TTL (equal to the TTL in the IP header)

  9. MPLS Label Format

  10. MPLS Terminology • LSP: Label Switched Path • An MPLS virtual circuit • A path established before the data transmission starts • FEC: Forwarding Equivalence Class • A group of IP packets which are forwarded in the same manner (over the same path with the same forwarding treatment) • LSR: Label Switching Router • Any router in network who supports MPLS • LER: Label Edge Router • Resides at the edge of an MPLS network and assigns and removes the labels from the packets

  11. MPLS Operation Ingress Router Egress Router PUSH SWAP POP

  12. Establishing a Label Switched Path • Each LSR negotiates a label for each Forwarding Equivalence Class (FEC) with its neighbors using a distribution method • The result of negotiation is a Label Information Base (LIB) • Each LSR maintains a Label Information Base (LIB) and learns labels from there • When next hop changes for a FEC, LSR will retrieve the label for the new next hop from the LIB

  13. Label Distribution Protocols • Label Distribution Protocol (LDP) • Hop-by-Hop label distribution • Follows IGP-OSPF best path • No traffic engineering capabilities • Highly scalable • Best suited for apps using thousands of LSPs (VPNs) • Resource Reservation Protocol with Traffic Engineering Extensions (RSVP-TE) • End-to-End LSP signaling • Enables different specifications on each path • Less scalable • Best suited for traffic engineering in the core • Constraint-Based Routed LDP (CR-LDP) • TE-capable LDP • Never widely deployed

  14. Label Distribution Protocol (LDP) • A protocol which it is used to map FECs to labels • In order to do that LDP sessions are established between LDP peers in the MPLS network • LDP message types: • discovery messages:announce and maintain the presence of an LSR in a network • session messages:establish, maintain, and terminate sessions between LDP peers • advertisement messages: create, change, and delete label mappings for FECs • notification messages: provide advisory information and signal error information

  15. Label Distribution Protocol (LDP)

  16. Traffic Engineering • A way to achieve required delay, grade-of-service and to meet policy requirements imposed by the network operator • Traffic Engineering ensure available spare link capacity for re-routing traffic on failure • In case of single failure the network traffic is spread across network backup links • The LSPs are created independently, specifying different paths that are based on user-defined policies

  17. Traffic Engineering

  18. Resource Reservation Protocol with Traffic Engineering Extensions (RSVP-TE) • Request bandwidth and traffic conditions on a defined path • Uses two types of massages: RSVP PATH msg and RSVP RESERVATION msg • Calculates best path based on the specified constraints • TE interface parameters: • Maximum Bandwidth • Maximum Reservable Bandwidth • Unreserved Bandwidth • TE Metric (given by IGP protocol) • Administrative Group (Link Affinity or “Link Coloring”) • Drawback: • Requires regular refreshes • Scalability

  19. Resource Reservation Protocol with Traffic Engineering Extensions (RSVP-TE)

  20. Benefits from MPLS • MPLS combines the performance characteristics of layer 2 networks and the connectivity and network services of layer 3 networks • Combines IP and ATM in the network • Improves packet-forwarding performance in the network • Supports network scalability • Improves the possibilities for traffic engineering • Supports the delivery of services with QoS guarantees

  21. Thank You! • w

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