MPLS MultiProtocol Label Switching. Overview Drawbacks of Traditional IP Routing Basic MPLS...

MPLSMPLS

MultiProtocol Label Switching

OverviewOverview

Drawbacks of Traditional IP Routing

Basic MPLS Concepts

MPLS Labels

Traffic Engineering with MPLS

MPLS Architecture

Routing protocols are used to distribute Layer 3 routing information.

Forwarding is based on the destination address only.

Routing lookups are performed on every hop.

Drawbacks of Traditional IP Drawbacks of Traditional IP ForwardingForwarding

Drawbacks of Traditional IP Forwarding Drawbacks of Traditional IP Forwarding (Cont.)(Cont.)Traditional IP ForwardingTraditional IP Forwarding

Every router may need full Internet routing information (more than 100,000 routes).

Drawbacks of Traditional IP Forwarding Drawbacks of Traditional IP Forwarding (Cont.)(Cont.)Traditional IP ForwardingTraditional IP Forwarding

Every router may need full Internet routing information (more than 100,000 routes).

Destination-based routing lookup is needed on every hop.

Most traffic goes between large sites A and B, and uses only the primary link.

Destination-based routing does not provide any mechanism for load balancing across unequal paths.

Drawbacks of Traditional IP Forwarding Drawbacks of Traditional IP Forwarding (Cont.) (Cont.) Traffic EngineeringTraffic Engineering

Basic MPLS ConceptsBasic MPLS Concepts

MPLS is a new forwarding mechanism in which packets are forwarded based on labels.

Labels usually correspond to IP destination networks (equal to traditional IP forwarding).

Labels can also correspond to other parameters, such as QoS or source address.

MPLS was designed to support forwarding of other protocols as well.

Basic MPLS Concepts (Cont.)Basic MPLS Concepts (Cont.) ExampleExample


• Only edge routers must perform a routing lookup.


• Only edge routers must perform a routing lookup.

• Core routers switch packets based on simple label lookups and swap labels.

Traffic Engineering with MPLSTraffic Engineering with MPLS

Traffic can be forwarded based on other parameters (QoS, source, ...).

Load sharing across unequal paths can be achieved.

SHIM LayerSHIM Layer

N

D

P

3

2

1

MPLS

MPLS LabelsMPLS Labels

MPLS technology is intended to be used anywhere regardless of Layer 1 media and Layer 2 protocol.

MPLS uses a 32-bit label field that is inserted between Layer 2 and Layer 3 headers

MPLS Labels (Cont.) MPLS Labels (Cont.) Label FormatLabel Format

MPLS uses a 32-bit label field that contains the following information: 20-bit label 3-bit experimental field 1-bit bottom-of-stack indicator 8-bit TTL field

MPLS Label StackMPLS Label Stack

Protocol identifier in a Layer 2 header specifies that the payload starts with a label (labels) and is followed by an IP header.

Bottom-of-stack bit indicates whether the next header is another label or a Layer 3 header.

If s=0, then label stack implementation is in use.

If s=1, then last label

Receiving router uses the top label only.

MPLS Label StackMPLS Label Stack (Cont.) (Cont.)

Usually only one label is assigned to a packet.

The following scenarios may produce more than one label: MPLS VPNs (two labels: The top label points to the

egress router and the second label identifies the VPN.)

MPLS TE (two or more labels: The top label points to the endpoint of the traffic engineering tunnel and the second label points to the destination.)

MPLS VPNs combined with MPLS TE (three or more labels.)

MPLS Labels (Cont.)MPLS Labels (Cont.)

Some MPLS Terms...Some MPLS Terms...

FEC - Forward Equivalence Class LER - Label Edge Router LSR - Label Switch Router Label – 20 bit value Label Stack - Multiple labels containing

information on how a packet is forwarded. 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

•A packet can be mapped to a particular FEC based on the following criteria:

- Destination IP address- Source IP address

- TCP/UDP port- Class of service,- Application used etc…

Any combination of the previous criteria.

FEC

Label Switch RoutersLabel Switch Routers

LSR primarily forwards labeled packets (label swapping).

Edge LSR primarily labels IP packets and forwards them into the MPLS domain, or removes labels and forwards IP packets out of the MPLS domain.

Label Switch Routers (Cont.) Label Switch Routers (Cont.) Architecture of LSRsArchitecture of LSRs

LSRs, regardless of the type, perform these functions:

Exchange routing information

Exchange labels

Forward packets

The first two functions are part of the control plane.

The last function is part of the data plane.

LSPLSP

Label-Switched Path Simplex L2 tunnel across a network Concatenation of one or more label switched hops Analogous to an ATM PVC

New DelhiNew Delhi

MumbaiMumbai

LSPLSP

LSRLSR

MPLS enabled router is called label Switching Router Forwards MPLS packets using label-switching Executes one or more IP routing protocols Participates in MPLS control protocols

New DelhiNew Delhi

MumbaiMumbai

LSPLSP

LSRLSR

LSRLSR

LSRLSRLSRLSR

MPLS TerminologyMPLS Terminology

SanSanFranciscoFrancisco

New New YorkYork

LSPLSP

Ingress LSR (“head-end LSR”) Examines inbound IP packets and assigns them to an

FEC Generates MPLS header and assigns initial label

Transit LSR Forwards MPLS packets using label swapping

Egress LSR (“tail-end LSR”) Removes the MPLS header

IngressIngressLSRLSR TransitTransit

LSRLSR TransitTransitLSRLSR

EgressEgressLSRLSR

MPLS Label Assignment/BindingMPLS Label Assignment/Binding

Assign labelLabel

assignedDataData

Control

Data

Control

Upstream Node

Downstream Node

Label Request for FEC10.0.0.0

MPLS Label Assignment/BindingMPLS Label Assignment/Binding

UpstreamUpstreamLDP peerLDP peer

DownstreamDownstreamLDP peerLDP peerLSRLSR

325413

Net: 10.0.0.0 Net: 10.0.0.0 Label: 52Label: 52

(3, 29)

Net: Net: 10.0.0.0 10.0.0.0 Label: 29Label: 29

MPLS TableMPLS TableIn Out

(2, 52)


(1, 17)


(5, 52)

ReceiveReceiveoutgoingoutgoing

labellabel(4, 17)

Net: 10.0.0.0 Net: 10.0.0.0

Label: 17Label: 17

AdvertiseAdvertiseincomingincoming

labellabel(3, 35)

Label OperationsLabel Operations

Label PushingLabel Pushing

S0

S1

N

D

P

3

2

1

Routing Information Base

Receive Logic Transmit Logic

Input port Output port

Forwarding Information Base

MPLS

Ingress Node

DH4H3H2 T2

DH4H3

101001001 11S

DH4H3H2 T2S

DH4H3S

101001001 11

DH4H3

Label SwappingLabel Swapping

S0

S1

N

D

P

3

2

1





MPLS

Transit Node

101001001 11S

DH4H3S

101001001 11S

DH4H3H2 T2S

DH4H3S

DH4H3H2 T2S

Label PoppingLabel Popping

S0

S1

N

D

P

3

2

1





MPLS

Egress Node

DH4H3H2 T2S

101001001 11

DH4H3H2 T2

101001001 11S

DH4H3

DH4H3S

DH4H3

Label databasesLabel databases

LSR OperationLSR Operation

Each LSR maintains a connection table

Port 1

Port 3

Port 2

Port 4

Connection TableConnection TableIn

(port, label)Out

(port, label)

(1, 22)

(1, 24)

(1, 25)

(2, 23)

(2, 17)

(3, 17)

(4, 19)

(3, 12)

LabelOperation

Swap

Swap

Swap

Swap

25IP

19IP

1 2Ingress Routing TableIngress Routing TableDestination Next Hop

134.5/16

200.3.2/24

(2, 84)

(3, 99)


(2, 84) (6, 0)


(1, 99) (2, 56)


(3, 56) (5, 0)

3 5

2

3

2 6134.5.1.5134.5.1.5

200.3.2.7200.3.2.7200.3.2.1200.3.2.1

134.5.6.1134.5.6.1

DestinationEgress Routing TableEgress Routing Table

Next Hop

134.5/16

200.3.2/24

134.5.6.1

200.3.2.1

200.3.2.7

MPLS Forwarding Example MPLS Forwarding Example

200.3.2.7

9999200.3.2.7 00200.3.2.7

200.3.2.75656200.3.2.7

MPLS ArchitectureMPLS Architecture

MPLS has two major components: Control plane: Exchanges Layer 3 routing

information and labels

Data plane: Forwards packets based on labels

Control plane contains complex mechanisms to exchange routing information, such as OSPF, EIGRP, IS-IS, and BGP, and to exchange labels, such as TDP, LDP, BGP, and RSVP.

Data plane has a simple forwarding engine.

MPLS Architecture (Cont.)MPLS Architecture (Cont.)

Router functionality is divided into two major parts: control plane and data plane

Network Architecture of Project 1Network Architecture of Project 1

Depending on the traffic expectations, the locations are divided into two categories, A & B.

A locations are provided with core routers.

B locations are provided with only edge routers.

Location ALocation A

A is further divided into four categories viz A1, A2, A3, A4

All A nodes are provided with Cisco routers.

BSNL NIB-II CORE ROUTER A1,A2,A3 &A4 CONNECTIVITY DIAGRAM

STM-16 LINK

STM-1 LINK

SiSi

CISCO ROUTER

JUNIPER ROUTER(Existing with BSNL)

LEGENDS

Jullundar

Jaipur

Pune

Ahmedabad

Indore

Lucknow

Patna

Noida

Kolkata

ChennaiBanglore

Mumbai

Ernakulam

Hyderabad

SiSi

Chandigarh

SiSi

Manglore

SiSi

Nagpur

SiSi

Vijaywada

SiSi

Raipur

SiSi

Coimbtore

SiSi

Bhubneshwar

SiSi

Ranchi

SiSi

Guwahati

SiSi

Allahabad

A1 Nodes - 5

A2+A3 Nodes - 9

A4 Nodes - 10

B NodesB Nodes

B locations are divided into B1 & B2 categories.

Provided with only edge routers Cisco 7613

B1 & B2 are dual homed to nearest A node on STM-1 link.

NIB-II A1,A2,A3,A4,B1& B2 ROUTER CONNECTIVITY DIAGRAM

A1 Nodes - 5

A2+A3 Nodes - 9

A4 Nodes - 10

B1 + B2 Nodes - 47

Jullundar

Jaipur

Pune

Ahmedabad

Indore

Lucknow

Patna

Noida

Kolkata

ChennaiBanglore

Mumbai

Ernakulam

Hyderabad

Chandigarh

Manglore

SiSi

Bhubneshwar

SiSi

Ranchi

Allahabad

SiSi

Coimbtore

Madurai

Trichy

Palghat

TrivandrumTrichur

Kalikat

SiSi

Vijaywada

Rajmundary

Vizag

Tirupati

Durgapur

Siliguri

DimapurSiSi

Guwahati

Kalyan

Panjim

Aurangabad

Kolhapur

Nashik

SiSi

Nagpur

Bhopal

Gwalior

Mehsana

Ambala Faridabad Gurgaon

Meerut

Agra

Dehradun

Ludhiana

Ferozpur

Shimla

Amritsar

SiSi

SiSi

Ajmer Jodhpur

MysoreHubli

Jamshedpur

Surat

Vadodara

Rajkot

Jabalpur

Shilong

Ghaziabad Noida

Varanasi Kanpur

Pondicherry

Belgaum

SiSi

Raipur

SiSi

Chennai

Ernakulam

Hyderabad

Pune

Indore

Ahmedabad

Jaipur Jallandar Lucknow

Patna

Kolkata

Noida

Mumbai

Bangalore

1

3

NIB - II Core Router

IXP Router Route Reflector

IDC Router

IGW Router

Routers ConnectivityRouters Connectivity

51

ReviewReview

Drawbacks of Traditional IP Routing

Basic MPLS Concepts

MPLS Labels

MPLS Architecture

Label Switch Routers

Label database

Label operations

Thank YouThank You

MPLS MultiProtocol Label Switching. Overview Drawbacks of Traditional IP Routing Basic MPLS...

Documents

Transcript of MPLS MultiProtocol Label Switching. Overview Drawbacks of Traditional IP Routing Basic MPLS...