MultiProtocol Label Switching (MPLS) July 29, 2000TECON 2000 Pramoda Nallur Alcatel Internetworking Division

MultiProtocol Label Switching (MPLS)

July 29, 2000 TECON 2000

Pramoda Nallur

Alcatel Internetworking Division

July 29, 2000 TECON 2000July 29, 2000 TECON 2000 2

Agenda

• MPLS - The Motivation

• How MPLS Works !

• MPLS Technology

• MPLS Application


MPLS - The Motivation

• IP Protocol Suite - the most predominant networking technology.

• Voice & Data convergence on a single network infrastructure.

• Continual increase in number of users.

• Demand for higher connection speeds.

• Increase in traffic volumes.• Ever-increasing number of ISP networks.


MPLS Working Groups and Standards

• Standardized by the IETF - currently in Draft stage.• MPLS recommendations are done by IP players for IP

services• MPLS core components are generic• MPLS doesn’t use specific technology process (e.g.

ATM/FR signaling protocol PNNI or ATM OAM flow)


MPLS and ISO model

PPP

Physical (Optical - Electrical) 1

2

IP 3

4

Applications7to5

FrameRelay

ATM (*)

TCP UDP

PPP FR ATM (*)

MPLS

(*) ATM overlay model (without addressing and P-NNI) is considered as an ISO layer 2 protocol.

IETF main goal is that when a layer is added, no modification is needed on the existing layers.All new protocol must be backward compatible


Agenda

• Motivation for MPLS


• MPLS Technology



MPLS Architecture

Routing protocol OSPF OSPF OSPF

Attributes Precedence

Local tableLabel table Local table Local table

LSP Label swapping Label removalClassificationLabel assignment

IngressNode

CoreNode

EgressNode

Label SwitchLayer 2

Layer 1

Layer 2

Layer 1

Layer 2

Layer 1

Layer 2

Layer 1

Layer 2

Layer 1

FEC table Local table Local table Local table


Label swapping

Label removal

ClassificationLabel assignment

Label swapping

Label removal

ClassificationLabel assignment

OSPF / RIP / IS-IS

Label Switch Path

Label table

IngressNode

CoreNode

EgressNode

Layer 2

Layer 1

Layer 2

Layer 1

Layer 2

Layer 1

Precedence

Label table Label table

Layer 2

Layer 1

Layer 2

Layer 1

FEC FEC FEC

MPLS process


MPLS Cloud

LSR

LER

LSR

LER

IP PacketIP Packet w/ Label

L3 RoutingL3 Routing

Label SwappingLabel Swapping

LER

LERLER

L3 RoutingL3 Routing

L3 Routing


MPLS Link Layers & Label Encapsulation

ATM FR Ethernet PPP

VPI VCI DLCI “Shim Label”

Layer2

“Shim header” …….

IP | PAYLOAD


Agenda



• MPLS Technology



Some MPLS Terms...

• LER - Label Edge Router

• LSR - Label Switch Router

• FEC - Forward Equivalence Class

• Label - Associates a packet to a FEC

• Label Stack - Multiple labels containing information on how a packet is forwarded.

• Shim - Header containing a Label Stack

• Label Switch Path - path that a packet follows for a specific FEC

• LDP - Label Distribution Protocol, used to distribute Label information between MPLS-aware network devices

• Label Swapping - manipulation of labels to forward packets towards the destination.


Ingress Label FEC Egress Label

6 138.120.6/24 - xxxx 9

Ingress Label AttributeFEC Egress LabelIngress Label FEC Egress Label

6 138.120.6/24 - xxxx 9

Attribute

A

6 138.120.6/24 - xxxx 12B

•FECs are manually initiated by the operator

•A FEC is associated at least one Label

•A packet can be mapped to a particular FEC based on the following criteria:•destination IP address,•source IP address,•TCP/UDP port,•in case of inter AS-MPLS, Source-AS and Dest-AS,•class of service, •application used,•…•any combination of the previous criteria.

FEC Classification


What is a Label ?

• A short, fixed length, locally significant identifier used to identify a FEC.

• The label can be identified by the L2 technology identifier (e.g. VPI/VCI for ATM, DLCI for FR or MPLS label for PPP/Ethernet).

L2 Type L2 TypePort PortIngress Label Egress LabelFEC

ATM 1-1 12 (i.e. 4/65) F1 22 (i.e. 5/65)3-4ATM

ATM 1-1 15 (i.e. 0/25) F4 9 (i.e. 101) 5-1FR

Gig Eth 5-1 7 F1 22 (i.e. 4/65)3-4ATM


MPLS Label Assignment Schemes

• Topology Driven – Label assignment in response to routing

protocols (OSPF and BGP) updates

• Control Driven – Label assignment in response to RSVP, CR-

LDP requests

• Traffic Driven – Label assignment in response to flow detection

& triggering


The MPLS Shim Header• The Label (Shim Header) is represented as a sequence of

Label Stack Entry• Each Label Stack Entry is coded by 4 bytes (32 bits) as

described• 20 Bits is reserved for the Label Identifier (also named Label)

Label(20 bits)

Exp(3 bits)

S(1 bit)

TTL(8bits)

Label : Label value (0 to 15 are reserved for special use)

Exp : Experimental UseS : Bottom of Stack (set to 1 for the last entry in the label)

TTL : Time To Live


Label Switched Path

5 12

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 312

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 x4

53

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 x 138.120

MPLS switch

MPLS switch

MPLS switch

MPLS switch1

2

3

1 2

3

1

2

3

41

2

3

138.120

192.168127.20


MPLS switch

MPLS switch

MPLS switch

MPLS switch1

2

3

1 2

3

1

2

3

41

2

3

138.120

192.168127.20

138.120.6.12

138.120.6.12138.120.6.12

138.120.6.12 138.120.6.12

138.120.6.12

??138.120.6.12

Default3

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 x None

??138.120.6.12

??

138.120.6.12

Default Default

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 None 3

??

138.120.6.12 ??138.120.6.12

Default

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 None x4

??138.120.6.12

Hop by Hop IP forwarding


5 12

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 312

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 x4

53

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 x 138.120

MPLS switch

MPLS switch

MPLS switch

MPLS switch1

2

3

1 2

3

1

2

3

41

2

3

138.120

192.168127.20

138.120.6.12

138.120.6.12

138.120.6.12

138.120.6.12 138.120.6.12

IP forwarding using LSP


MPLS Label Distribution Protocol

• LDP - a set of procedures by which one LSR informs the other of the FEC-to-Label binding it has made.

• Currently, several protocols used as Label Distribution Protocol (LDP) are available:– RSVP-TE (MPLS extension)

– LDP and CR-LDP

– BGP-4 MPLS extensions

• Label Distribution schemes


Downstream stream on demand

Mapping 12Mapping 5

5 12

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 312

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 x4

53

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 x 138.120

Request 138.120Request 138.120

MPLS switch

MPLS switch

MPLS switch

MPLS switch1

2

3

1 2

3

1

2

3

41

2

3

138.120

192.168127.20

The label is requested by the upstream node and the downstream node defines the

label used.


Unsolicited Downstream

MPLS switch

MPLS switch

MPLS switch

MPLS switch1

2

3

1 2

3

1

2

3

41

2

3

138.120

192.168127.20

Mapping 12Mapping 5

5 1212

5

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 3

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 138.120 x4

3

IngressInterface

IngressLabel

FEC EgressInterface

EgressLabel

1 x 138.120

The downstream node defines the label and advertises it to the upstream node.


Edge LSR Features

– Routing protocols

– FEC Classification

– Initiates LSP setup for Downstream On Demand method

– Adaptation of non-MPLS data to MPLS data

– Layer 2 translation for MPLS data

– Terminated MPLS-VPN

– At least one LDP protocol

– Edge LSR is counted into the TTL count as a regular router


Core LSR Features– Routing protocols

– Propagates Downstream On Demand method (request and mapping)

– Layer 2 translation

– High speed label forwarding/switching

– At least one LDP protocol


Agenda



• MPLS Technology



MPLS Advantages

• Simplified Forwarding• Efficient Explicit Routing• Traffic Engineering• QoS Routing• Mappings from IP Packet to Forwarding

Equivalence Class (FEC)• Partitioning of Functionality• Common Operation over Packet and Cell media


MPLS - the Future

• Who will use MPLS?– Large-scale data networks used by Enterprises,

Carriers and ISPs.

• Why MPLS?– Delivers high speed L2 (really “Label”) switching

at low cost vs. traditional L3 routing – Provides Traffic Engineering - allows the user to

direct traffic based on network utilization and demand.

– Ease of provisioning QoS– Support for VPNs


Explicitly Routed LSP

• End-to-End forwarding decision determined by ingress node.

• Enables Traffic Engineering

LER 1

LSR 2 LSR 3

LER 4

Forward toLSR 2LSR 3LSR 4LSR X

Overload !!

Overload !!


MPLS Traffic Engineering

• MPLS Traffic Engineering (TE) provides high quality IP service.

• TE defines :– LSP Admission Control (LAC)

– IP traffic (policing or shaping)

– IP service prioritization

– Network capacity and growth capacity

• TE is primary done by external tools. This solution allows flexibility and customization.


MPLS VPN : MPLS topology

Site A

138.120.8.0/24

VPN 2

Site B

138.120.6.0/24

VPN 2

ISP BackboneLSR LSR

LSR

LSR

LSR

LSR

Site A

138.120.8.0/24

VPN 1

Site B

138.120.6.0/24 VPN 1

LSP 32

LSP 47


MPLS - Some Major Vendors

• Alcatel

• Cisco

• Juniper Networks

• Nortel

• Lucent


MPLS - More Information @

• MPLS Charter http://www.ietf.org/html.charters/mpls-charter.html

• MPLS Resource Centerhttp://www.mplsrc.com

• MPLS Forum http://www.mplsforum.org

http://www.mplsrc.com/




http://www.mplsforum.org/



Any Questions ?

Thanks for your time !

Email [email protected]


MPLS - An Analysis

UDP Rate (in Mbps)

Th

rou

ghp

ut

(in

Mb

ps)

TCP 1

UDP

TCP 2

TCP & UDP Flows without MPLS


MPLS - An Analysis

UDP Rate (in Mbps)

Th

rou

ghp

ut

(in

Mb

ps)

TCP 1

UDP

TCP 2

TCP & UDP Flows with MPLS Trunks (LSPs)

Documents

MultiProtocol Label Switching (MPLS) July 29, 2000TECON 2000 Pramoda Nallur Alcatel Internetworking Division