MULTI-PROTOCOL LABEL SWITCHING Brandon Wagner

Lecture Outline  Precursor to MPLS  MPLS Definitions  The Forwarding Process  MPLS VPN  MPLS Traffic Engineering  Any Transport over MPLS

Precursor to MPLS: Asynchronous Transfer Mode (ATM)  A cell-based switching method.  Size of cell’s is fixed.  Doesn’t encounter queuing problems like packet-switched networks.  Provides less jitter for Voice / Video  Utilizes Time-Division-Multiplexing  Each circuit is given dedicated “time” on physical interface and therefore provides true dedicated bandwidth.  Creates Virtual Paths/Channels  12 bit VPI (Virtual Path Identifier)  16 bit VCI (Virtual Channel Identifier)  LANE (LAN Emulation)  Consists of LAN clients and LAN services.  All clients communicate through central LES (LAN emulation server)

MPLS Definition  Multi-protocol Label Switching for Ethernet/IP.  Method to classify and forward traffic at Layer 2.5.  Segments a Layer 3 network much like VLANs segment a layer 2 network.  Done by attaching labels to traffic  Independent of routing protocols.  Is NOT a routing protocol itself.

MPLS Label  Label Key Terms  Push – adding a label.  Pop – removing a label.  Swap – replacing one label for another.  Number of Labels = 2 20 = 1,048,576 Labels  Experimental Field is used for QoS

MPLS Setup  LDP – Label Distribution Protocol  Responsible for exchanging label mappings between routers.  Builds LFIB (Label Forwarding Information Base), which maps labels to labels.  FEC’s are determined  Forwarding Equivalency Class provide a map between IP routing and labels.  Routing Protocols in place  MPLS works on top of an existing routed network.  Must still use RIP, EIGRP, OSPF, IS-IS, BGP.

MPLS Routers  Label Switch Router (LSR)  All interfaces are MPLS switching/forwarding  Edge Label Switch Router (Edge LSR)  Provides the bridge between an MPLS network and a traditional IP network.

MPLS Forwarding Process

MPLS Project Example

MPLS Router Planes

MPLS for Service Providers  Purpose of LSR – forward traffic according to labels.  Internal forwarding means no need to run BGP.  What are the benefits of not running BGP?

MPLS Implementations  MPLS VPNs  Creates virtual L2 and L3 networks over an existing routed network.  MPLS Traffic Engineering (TE)  Enables the control of which forwarding path traffic will take based on policy’s.  Any Transport over MPLS (AToM)  Can create a “pseudowire” path (Layer 2) over an MPLS backbone

MPLS VPNs  Terms  P = Provider  PE = Provider Edge  CE = Customer Edge  VRF = Virtual Routing/Forwarding  Controls access to available routes and therefore network reachability and exposure.  Requires BGP to exchange routes  BGP VPN extensions utilized

MPLS Traffic Engineering  Source based routing instead of IP destination based routing.  Forwarding is determined by “Head-end” LSR.  Calculates the best LSP (Label switched path) from source point to end point and creates tunnels.  Requires link-state routing protocol to be running – why?  Can be based on user metrics, auto-bandwidth, reliability, etc.  Can use multiple labels: 1 for endpoint of tunnel, 1 for destination  Tunnels are:  Unidirectional – one way only  Not necessarily based on IGP metrics.

Any Transport over MPLS (AToM)  Pseudowire – creating a point to point connection.  Can provide console ports to equipment thousands of miles away.  Provide a monitor port (snif) on a port anywhere in the network.  Private Layer 2 Networks  Effectively create a virtual switch that traverses providers or tens of hops.

Questions?