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MPLS

MPLS. Evan Roggenkamp. Introduction. Multiprotocol Label Switching High-performance Found in telecommunications networks Directs data from one network node to the next based on short path labels rather then long network addresses, avoiding complex lookups in a routing table.

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MPLS

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  1. MPLS Evan Roggenkamp

  2. Introduction • Multiprotocol Label Switching • High-performance • Found in telecommunications networks • Directs data from one network node to the next based on short path labels rather then long network addresses, avoiding complex lookups in a routing table. • MPLS supports a range of access technologies: T1/E1, ATM, Frame Relay, and DSL • MPLS is agnostic of Layer 1 or Layer 2 protocols and can be used on any type of links. • Inserts a 32-bit label in between the Layer 2 and Layer 3 headers which dubbed it as a Layer 2.5 protocol. These labels number range is 0-1,048,575. Labels 0-15 for reserved purposes therefore the useable range is 16-1,048,575. • MPLS provides: traffic engineering, network convergence, failure protection, and the ability to guarantee Quality of Service (QoS) over IP. • Routing information obtained using a common intra domain routing protocol such as OSPF

  3. The Label • Label: 20 bits • Experimental/CoS: 3 bits • TTL: 8 bits • BOS (bottom-of-stack) • RFC 3031 “Multiprotocol Label Switching Architecture,” lists 3 bits as “experimental.” In reality, Cisco IOS uses those bits for Code of Service

  4. Modes • MPLS can run in Frame or Cell mode. • In Frame mode, it’s a packet that will have labels applied or removed. • In Cell mode, it is an ATM cell.

  5. Router Roles • Label switching routers • Edge Label switching routers • Edge LSR’s perform lookup using routing table, and then attach a label to the packet before sending it downstream to an LSR • LSR’s keep a routing table but do not perform a routing table lookup; instead, LSR’s use the contents of the label to determine the next hop.

  6. Another look

  7. Components • Control Plane – takes care of the routing table; also where label bindings are exchanged • Data Plane – takes care of the actual forwarding of traffic • In the control plane we will find many common routing protocols: • OSPF (popular with MPLS service providers} • ISIS (also popular) • EIGRP • RIP • BGP • Also supports: • Label Distribution Protocol (LDP); Industry standard, not proprietary • Tag Distribution Protocol (TDP); Cisco-proprietary; depreciated • Resource Reservation Protocol (RSVP); reservation of bandwidth; traffic engineering

  8. Misc • Packets can use more than one label: this is called a label stack. • MPLS VPN’s use label stacks as their form of encapsulation. • Attaching a label is called a “push” or label imposition • Removing a label is called a “pop” or label disposition • RFC 3031: rfc3031.pdf • Basic MPLS Lab with OSPF: mplsospf_basic_lab.pdf

  9. Sources • MPLS faq cisco.com • RFC 3031 • http://www.cisco.com/application/pdf/paws/13736/mplsospf.pdf MPLS OSPF Lab • http://eecourses.technion.ac.il/046992/files/Ex13MPLS.pdf Excellent/In-Depth MPLS Power Point • http://www.youtube.com/watch?v=MEWIdO40U54 Excellent video on MPLS • http://www.youtube.com/watch?v=pia2WceaevQ&annotation_id=annotation_319417&feature=iv&src_vid=MEWIdO40U54&hd=1 Better video on MPLS

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