multiprotocol label switching (mpls)

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)

multiprotocol label switching (mpls)

Documents

label identifier

label information

multiprotocol label

label value

mpls recommendations

mplshow mpls works

motivationhow mpls works

protocol pnni