April 8, 2023

BY :-SAJIDULLAH S.KHANANUJA KHODUSKARDr. N A.KOLIIJAET/Vol.II/ Issue II/April-June, 2011/150-153

Shah Vatsalkumar Nikhilkumar M.Tech Network Engg vatsalshah90@gmail.com

NOVEL APPROACH OF MULTI PROTOCOL LABEL SWITCHING FOR ASCYNCHRONUS TRANSFER MODE OR ROUTED NETWORKS

April 8, 20231

Drawbacks of Traditional IP Routing

Basic MPLS Concepts

MPLS Vs IP Over ATM

Advantages of using MPLS TE

MPLS Label Format

Architecture of MPLS

MPLS Applications

Conclusion

Objectives

April 8, 20232

Routing protocols are used to distribute Layer 3 routing information

Forwarding is based on Destination Address only

Routing lookups are performed on every hop

Drawbacks of Traditional Ip Routing

April 8, 20233

Destination-based routing lookup is needed on every hop.

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

Traditional IP Forwarding

Update: 10.0.0.0/8

Update: 10.0.0.0/8 Update: 10.0.0.0/8

Update: 10.0.0.0/8

10.1.1.1

10.1.1.110.1.1.1

10.1.1.1

10.1.1.110.1.1.110.1.1.110.1.1.1

Routing

lookup

Routing

lookup

Routing

lookup

April 8, 20234

MPLS BUILT ON STANDARD IP

47.1

47.247.3

Dest Out

47.1 147.2 2

47.3 3

1

23

Dest Out

47.1 147.2 2

47.3 3

Dest Out

47.1 147.2 2

47.3 3

1

23

1

2

3

• Destination based forwarding tables as built by OSPF, IS-IS, RIP, etc.

April 8, 20235

IP FORWARDING USED BY HOP-BY-HOP CONTROL

47.1

47.247.3

IP 47.1.1.1

Dest Out

47.1 147.2 2

47.3 3

1

23

Dest Out

47.1 147.2 2

47.3 3

1

2

1

2

3

IP 47.1.1.1

IP 47.1.1.1IP 47.1.1.1

Dest Out

47.1 147.2 2

47.3 3

April 8, 20236

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.

Traffic Engineering with Traditional IP Forwarding

Primary OC 192 linkPrimary

OC 192 linkLarge Site A Large Site B

Small Site C

BackupOC 48 linkBackup

OC 48 link

April 8, 20237

MPLS is a new forwarding mechanism in which

packets are forwarded based on labels.

Labels may correspond to IP destination networks

(equal to traditional IP forwarding).

Labels can also correspond to other parameters,

such as quality of service (QoS) or source

address.

MPLS was designed to support forwarding of other

protocols as well.

Basic MPLS Concepts

April 8, 20238

Only edge routers must perform a routing lookup. Core routers switch packets based on simple

label lookups and swap labels.

MPLS Example

L=5L=3

10.1.1.110.1.1.1

Routing lookup andlabel

assignment10.0.0.0/8

L=5Label

swappingL=5 L=3

Label removal and

routing lookup

L=3

April 8, 20239

Layer 2 devices are IP-aware and run a routing protocol.

There is no need to manually establish virtual circuits.

MPLS provides a virtual full mesh topology.

MPLS Versus IP over ATM

10.1.1.110.1.1.1L=5L=5L=3L=3

L=17L=1710.1.1.110.1.1.1

Layer 2 devices run a Layer 3 routing

protocol and establish virtual circuits

dynamically based on Layer 3 information

April 8, 202310

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

Load sharing across unequal paths can be achieved.

Traffic Engineering with MPLS

Primary OC 192 linkPrimary

OC 192 linkLarge Site A

Large Site B

Small Site C

SecondaryOC 48 linkSecondaryOC 48 link

April 8, 202311

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, and BGP, and to exchange labels, such as TDP, LDP, MP-BGP, and RSVP.Data plane has a simple forwarding engine.Control plane maintains contents of the label-switching table (label forwarding information base, or LFIB).

MPLS Architecture

April 8, 202312

MPLS Architecture

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

April 8, 202313

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 (frame-mode).

MPLS over ATM uses the ATM header as the label (cell-mode).

MPLS Modes of Operation

April 8, 202314

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 time-to-live (TTL) field

Label Format

LABEL EXP S TTL

0 19 2223 3120 24

April 8, 202315

Frame-Mode MPLS

FrameHeaderFrameHeader

IP HeaderIP Header PayloadPayload

Layer 2Layer 2 Layer 3Layer 3

FrameHeader

Label IP Header Payload

Layer 2Layer 2½ Layer 3

Routing lookup

andlabel

assignment

Shim Header

April 8, 202316

IP Header

Cell_Mode MPLSFrameHeader

IP Header Payload

Layer 2 Layer 3

FrameHeader

Label IP Header Payload

Layer 2Layer 2½ Layer 3

ATM Adaptation Layer 5 (AAL5) Header

Label Payload

Layer 2 Layer 2½ Layer 3

ATMHeader

Cell 1

PayloadATM

HeaderCell 2

VPI/VCI fields

arused for label

switching

April 8, 202317

MPLS: HOW DOES IT WORK

UDP-Hello

UDP-Hello

TCP-open

TIME

TIME

Label requestIP

Label mapping#L2

Initialization(s)

April 8, 202318

MPLS Terminology

• LDP: Label Distribution Protocol

• LSP: Label Switched Path

• FEC: Forwarding Equivalence Class

• LSR: Label Switching Router

• LER: Label Edge Router

April 8, 202319

Forwarding Equivalence Classes

•FEC = “A subset of packets that are all treated the same way by a router”• In conventional routing, a packet is assigned to a FEC at each hop in MPLS it is only done once at the LER

Packets are destined for different address prefixes, but can be mapped to common pathPackets are destined for different address prefixes, but can be mapped to common path

IP1

IP2

IP1

IP2

LSRLSRLER LER

LSP

IP1 #L1

IP2 #L1

IP1 #L2

IP2 #L2

IP1 #L3

IP2 #L3

April 8, 202320

IntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

MPLS Label Distribution

47.1

47.247.3

1

2

31

2

1

23

3IntfIn

Dest IntfOut

LabelOut

3 47.1 1 0.50 Mapping: 0.40

Request: 47.1

Mapping: 0.50Request: 47.1

April 8, 202321

Label Switched Path (LSP)

IntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

47.1

47.247.3

1

2

31

2

1

23

3IntfIn

Dest IntfOut

LabelOut

3 47.1 1 0.50

IP 47.1.1.1

IP 47.1.1.1

April 8, 202322

IntfIn

LabelIn

Dest IntfOut

3 0.40 47.1 1

IntfIn

LabelIn

Dest IntfOut

LabelOut

3 0.50 47.1 1 0.40

47.1

47.247.3

1

2

31

2

1

23

3

IntfIn

Dest IntfOut

LabelOut

3 47.1.1 2 1.333 47.1 1 0.50

IP 47.1.1.1

IP 47.1.1.1

EXPLICITLY ROUTED LSP ER-LSP

April 8, 202323

Label switch router (LSR) primarily forwards labeled packets (label swapping)

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

Label Switch Router

MPLS Domain

Edge LSR

LSR

10.1.1.1 L=3 L=5

L=43L=3120.1.1.1

10.1.1.1

20.1.1.1

April 8, 202324

LSR performs the following three functions:◦ Exchange routing information◦ Exchange labels◦ Forward packets (LSRs and edge LSRs) or cells

(ATM LSRs and ATM edge LSRs)

The first two functions are part of the control plane.The last function is part of the data plane.

Architecture of LSRs

April 8, 202325

Architecture of Edge LSRs

Note: ATM edge LSRs can only forward cells.

Edge LSREdge LSR

Control Plane

Data Plane

Routing Protocol

Label Distribution Protocol

Label Forwarding Table

IP Routing Table

Exchange ofrouting information

Exchange oflabels

Incoming labeled packets

Outgoing labeled packets

IP Forwarding Table

Incoming IP packets

Outgoing IP packets

April 8, 202326

MPLS Applications

MPLS is already used in many different applications:

◦ Unicast IP routing

◦ Multicast IP routing

◦ Traffic Engineering (MPLS TE)

◦ QoS

◦ Virtual private networks (MPLS VPN)

April 8, 202327

Improved up-time – By providing alternative network paths

Improved bandwidth utilization – By allowing for multiple traffic types to traverse the network

Reduced network congestion 

One potential drawback of MPLS is the network administrator has to play a role in configuration of the overall network.

Advantages and Disadvantages of MPLS

April 8, 202328

MPLS is specifically designed for highly scalable networks

Multiprotocol label switching is the convergenceof connection-oriented forwarding techniquesand the Internet’s routing protocols

MPLS provides load balancing between unequalpaths and it’s an advantage for MPLS Traffic Engineering

Conclusion

April 8, 202329

Rosen, E., Viswanathan, A., and Callon, R.:‘Multiprotocol label switching architecture’, RFC-3031, January 2001.

Armitage, G.: ‘MPLS: the magic behind the myths’,IEEE Commun. Mag., 2000, 38, (1), pp. 124–131.

Zhon, H., Yeh, C., and Mouftah, H.T.: ‘Dynamichierarchical mobile MPLS for next generation all-IPwireless network’. IEEE 61st Vehicular TechnologyConf., 30 May–1 June 2005, vol. 4, pp. 2230–2234

REFRENCES

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