Ch2 MPLS Overview

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2001, Cisco Systems, Inc. Chapter2-1

Chapter 2

MPLS Overview


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MLSTE 1.0Chapter2-2 2001, Cisco Systems, Inc.

Objectives

Upon completion of this chapter, you willbe able to:

Place MPLS technology within the network. Provide a high-level description of MPLS

technology.

Identify services provided by MPLS

technology.

Explain the features and benefits of MPLStechnology.


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2001, Cisco Systems, Inc. Chapter2-3

Driving Business Forces

from Old World to New


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Business Perspective

Businesses are building on IPBusinesses need private

IP services

CustomersSuppliersPartners

Telecommuters

Mobile Users

RemoteOffices

IP Intranet IP Extranet


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Virtual Private Networking:A $24 Billion Opportunity

35%

6%

5%

54%

ATM/FR Managed Svcs

IP VPNs Unrealized

1998 VPN Service Distribution

0

5

10

15

20

25

1998 2001 2004

ATM/FR Managed Svcs IP VPNs Total

Worldwide VPN Service Revenues

(Billions of Dollars)

Source: CIMI Corp.

Barriers?IP+ATM Opportunity


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New World Requirements

Transport Services Leased line, Frame Relay, ATM

(current business processes)

Revenue

IP Connectivity Services Internet Intranet Extranet

Growth

IP Valued-Added Services Content hosting Collaboration Voice Video

Profit


7/50MLSTE 1.0Chapter2-7 2001, Cisco Systems, Inc.

IP/VPN SLA

requirementscannot be met with

todays

technology!

Customer Perspective

Current Requirements

QoS

Privacy

Availability

Reliability

New Requirements

Multiple service classes

Multiple service options

ATM, Frame Relay,Private IP, Public IP

Multiple VPN options

Lower-cost managedservices

Any-to-any connectivity

Extranets, COINS(Community of InterestNetworks)

Seamless integration



The Problem

We cant get there from here using traditionaltechnologies:

ATM or Frame Relay virtual circuits

IP tunneling Encryption

Network address translation

Why?

Functionality trade-offs

Complexity

Cost

Service degradation



The Solution: MPLS

A new paradigm that delivers the best of bothworlds:

Privacy and QoS of ATM and Frame Relay

Flexibility and scalability of IP

Foundation for IP business services:

Flexible grouping of users and value-added

services Low-cost managed IP services:

Scalabilitysmall to large private networks



MPLS: New Industry Standardfor Carrier Networks

What is it? Multiprotocol Label Switching

Emerging IETF industry standard

Based on Ciscos tag switching

How does it work? Forwards packets based on labels

Packets are switched, not routed

Labels represent destination and service attributes

(CoS, PrivacyVPNs, traffic engineering) Multiple mechanisms for assigning and distribution labels

(Tag Distribution Protocol, Label Distribution Protocol,Resource Reservation Protocol, Border Gateway ProtocolVersion 4)



MPLS: The First CompleteIP Solution

Any-to-Any Connectivity

Leased Lines

Frame Relay/ATM

IP

MPLS

UserN2

N2(logical)

N

N

NetworkN2

N2(logical)

N

N

QoS

Privacy

Low-CostManagedServices

MPLS is the firstsolution that delivers on all the requirementsfor New World private IP networks.


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MPLS Technology

Overview



Why MPLS in the Internet?

Integrate best of Layer 2and Layer 3

Keep up with growth

Reduce operations costs

Increase reliability

Create foundation for newrevenue from advanced IPservices



MPLS Routing Scalability

Internal routingscalability

Limited adjacencies

External routingscalability

Full BGP4 support, with

extensionsVC merge for very largenetworks



MPLS: End-to-End IPServices over ATM

IP services mappeddirectly onto ATMswitches

MPLS label tocell stream

Avoids complextranslation

Full support for IP QoS,VPN, and TrafficEngineering

IPMulticast IPCoS

RSVP

IP Multicast

IP Multicast

IP CoS

RSVP

IP

Multicast

R12

R45



MPLS and ATM ServicesCoexisting on Same Platform

ATM standard services Private Network-

Network Interface /User-Network

Interface Signaling Voice trunking

Circuit emulation

MPLS Services

VPN CoS Traffic engineering

FR

IPATM

ATM MPLS

MPLS

IPFR

IP



MPLS Across Non-MPLSATM Networks

ATM Network

MPLS Network

Labeled cellsaretransported ina virtual path

ATM VCsare createdas needed;

virtualchannelidentifiersare mappedto labels.

LSRLabelSwitchRouter



Benefits of MPLSCoS with ATM

IP QoS over Standard ATM

Allocate resources:

Per-individual, edge-to-edge VCs

By kbps bandwidth Mesh of VCs to configure

Complex error recovery

Wasted/inaccessible bandwidth

CoS with MPLS

Allocate resources:

Per-class, per-link

By % bandwidth No VCs to configure

No wasted bandwidth

Contained error recovery

Simpler to provision and

engineer



A New Paradigm for VPNs

VPN A

VPN B

VPN C

VPN A VPN BVPN C

VPN A

VPN BVPN C

VPN A

VPN C

VPN B

MPLS-Based VPNs

Network privacy

Network-based (subnets)

IP and VPN-aware

groups users and services

Overlay VPN

Frame Relay/VC privacy

VC-based

Frame Relay/ATM aware

groups endpoints

extranet

intranet



MPLS-Based VPN Benefits

Frame Relay privacy In a connectionless IP network Without tunnels or encryption

VPN-aware networks

Flexible user and servicegrouping

Multiple COS service classes

Scales to large and small VPNs

Low-cost managed services

No inherent scalability limits

Secure Intranets and Extranets

Multiple customer

memberships Provides Internet access

Simplified managed networks

No new PVCs to provision

No traffic matrix to update

No PVC mesh to resize

No routing topology to update

Simpler for the customer

No new application paradigms

No translation required forprivate IP addresses

No special CPE requirements

Simplified routing

Support over any access orbackbone technology

Standards based



A New Paradigm forManaged Networks

Single-carrier networksupporting multiplecustomer IP VPNs

Separately engineeredcustomer private IPnetworks

MPLSNetwork

Vs.

Build once,sell many

Build once,

sell once



Overlay VPN MPLS-Based VPN

LSRCPE

Lower Operational Cost

Update traffic matrix

Add (N 1) PVCs for new CPE

Resize full PVC mesh

Update OSPF design

Reconfigure each CPE for new Layer 3topology

Configure new CPEUpdate Edge LSR


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Leveraging Todays IP QoSSolutions

Technology Function

IP precedence Prioritization (in IP header) Indicates service class

Committed Access Rate (CAR) Packet classification byapplication, protocol, etc.

Sets precedence Bandwidth management: discard

or change service class

WRED Weighted Random Early Detection Congestion avoidance Service-class enforcement

WFQ, CBQ Weighted Fair Queuing Class-based Queuing Queuing policies (e.g. latency)

MPLS IP +ATM CoS Integration Traffic Engineering


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MPLS Class of Service

CoS

Distinct service classes implemented by network

Traffic flows classified

Based on Layer 3

Simpler and more efficient than mesh VCs

Two methods to indicate service class:

IP precedence copied to MPLS header (CoS field)

Up to 8 classes can be defined (3 bits)

Separate labels used for different service classes


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Benefits of MPLS CoS

IP CoS over ATM/FrameRelay VPNs

Allocate resources:

Per-individual,edge-to-edge VCs

By kbps bandwidth

Mesh of VCs to configure

Wasted/inaccessible bandwidth

IP CoS with MPLS VPNs

Allocate resources efficiently:

Per-class, per-link by % of

bandwidth Maximize transport of paid traffic

No connections to configure

Flexibility without added overhead

No wasted bandwidth as with PVCs

No call setup overhead aswith SVCs

Add traffic engineering

Path route consistency per flow


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Motivations for TrafficEngineering

Economics

Failure scenarios

Unanticipated traffic

300 MbpsTraffic Flow

155 Mbps Fiber Link

Link Failure


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MLSTE 1.0Chapter2-27 2001, Cisco Systems, Inc. 2001, Cisco Systems, Inc. Chapter2-27

MPLS Operation


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MPLS Terminology

Label Switch Router (LSR)= Router= ATM Switch + LSC

Label DistributionProtocol (LDP)

ATM EdgeLSR

Edge functions

Core Functions

Label Edge Router= LER


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Label Switched Path

Label DistributionProtocol (LDP)

ATM EdgeLSR

Edge Functions

Core FunctionsLSP

PE1

PE10


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MPLS Labels

Basic MPLS: destination-based unicast

Labels divorce forwarding from IP address

Many additional options for assigning labels

Labels define destination and service

The key: separation of routing and forwarding

Destination-

basedUnicastRouting

IP

CoS

Resource

Reservation(RSVP)

Multicast

Routing(PIM v2)

Explicit &

StaticRoutes

VPNs

Label Information Base (LIB)

Per-Label Forwarding, Queueing and Multicast Mechanisms


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MPLS Operation

CECE

PE

PE

1. Existing routing protocols (e.g., OSPF, IS-IS, BGP)establish reachability to destination networks.


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1. Existing routing protocols (e.g., OSPF, IS-IS)establish reachability to destination networks.

MPLS Operation (cont.)

2. Label Distribution Protocol (LDP)establishes label-to-destinationnetwork mappings.


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3. Ingress Edge LSR receivespacket, performs Layer 3 value-added services, and labels

packets.


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3. Ingress Edge LSRreceives packet, performsLayer 3 value-added services,

and labels packets.

4. LSR switchespackets using labelswapping.



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3. Ingress Edge LSRreceives packet, performsLayer 3 value-added services,

and labels packets.


4. LSR switches packets

using label swapping.

5. Egress LSR removes labeland forwards standard IP

packet to customer.


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Router Example: DistributingRouting Information


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Router Example: ForwardingPackets

Packets are forwarded on the

basis of IP address.


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MPLS Example: RoutingInformation


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MPLS Example: AssigningLabels

S


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MPLS Example: ForwardingPackets

LER LERLSR


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MPLS Example: Shared Labels

Prefixes that share apath can share a label.

MPLS E l


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MPLS Example:Label Disposition

MPLS NetworkEgress LER

CERouter

RemovesLabel

MPLS E l


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MPLS Example:Standard IP mode

MPLS NetworkEgress LER

Deaggregation Pointdoes Layer 3 Lookup

CERouter

L b l H d


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Label HeaderPacket Media

Can be used over Ethernet, 802.3, or PPP links

Contains everything needed at forwarding time

One word per label

Label = 20 bitsExperimental = Class of Service, 3 bitsS = Bottom of Stack, 1 bit

TTL = Time to Live, 8 bits


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Encapsulations

ATM Cell Header

PPP Header(Packet overSONET/Synchronous

Digital Hierarchy)

LAN MACLabel Header


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MPLS A N MPLS


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MPLS Across Non-MPLSATM Networks

Labeled cellsare transportedin a virtualpath.

ATM Network

MPLS Network

ATM VCs

are createdas needed;VCIs aremapped tolabels.

LSRLabelSwitchRouter


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Summary

MPLS is the enabling technology to supportNew World services.

Significant customer demand for IP+ATMcapabilities.

Build oncesell many.

MPLS combines the best features of Layer 2(ATM) and Layer 3 (IP).


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Review Questions (cont.)

1. Why do current (traditional) technologies

prove inadequate to deliver New WorldServices?

2. How do MPLS-forwarded packets carrydestination and service attributes such as

CoS, VPN, and Traffic Engineering?3. What MPLS mechanism allows IP services to

be mapped easily onto ATM switches?


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Review Questions (cont.)

4. What type of device is responsible for

adding or removing MPLS labels?5. Which field in the label is used to

map the IP precedence bits?

6. What technique is used to translate thepacket-based label for an ATMnetwork?

Documents

Ch2 MPLS Overview