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 = 220 = 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?