MPLS Technology

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Agenda

MPLS - The MotivationHow MPLS Works !MPLS TechnologyMPLS ApplicationAdvantages of MPLSFuture of MPLSConclusionRefrences

July 29, 2000 TECON 2000

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MPLS - The MotivationIP 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.

July 29, 2000 TECON 2000

What is MPLS?

Multi Protocol – supports protocols even other than IP Supports IPv4, IPv6, IPX, AppleTalk at the network layer Supports Ethernet, Token Ring, FDDI, ATM, Frame Relay, PPP

at the link layer

Label – short fixed length identifier to determine a route Labels are added to the top of the IP packet Labels are assigned when the packet enters the MPLS domain

Switching – forwarding a packet Packets are forwarded based on the label value NOT on the basis of IP header information

5July 29, 2000 TECON

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MPLS BlOCK DIAGRAM

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

MPLS Architecture: Control Plane

MPLS Architecture: Data Plane

Basic Model for MPLS Network

Existing routing protocols establish routesLDP establishes label to route mappingsLDP creates LIB entries for each LSR Ingress LER receives packet,adds a labelLSRs forward labeled packets using label swappingEgress LER removes the label and delivers the packet

LERLER

LSR

LER

LSRLSR

IP

MPLS

IP

Internet

LSR

LSR = Label Switched RouterLER = Label Edge Router

MPLS FORWORDING PROCESS

LSR

LER

LSR

LER

IP PacketIP Packet w/ Label

L3 RoutingL3 Routing

Label SwappingLabel Swapping

LER

LERLER

L3 RoutingL3 Routing

L3 Routing

Internet

MPLS Terminology

• LDP: Label Distribution Protocol

• FEC: Forwarding Equivalence Class

• LSP: Label Switched Path

• LSR: Label Switching Router

• LER: Label Edge Router

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) —used for traffic engineering

and resource reservation. – LDP and CR-LDP—maps unicast IP destinations into labels.– BGP—external labels (VPN)

Forwarding Equivalence Classes

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

IP1

IP2

IP1

IP2

LSRLSRLER LER

LSP

IP1 #L1

IP2 #L1

IP1 #L2

IP2 #L2

IP1 #L3

IP2 #L3

• A group of packets that require the same forwarding treatment across the same path• Packets are grouped based on any of the following

Address prefix Host address Quality of Service (QoS)

• FEC is encoded as the label

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,

FEC Classification

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

Two types of Label Switched Paths:• Hop by hop)• Explicit Routing (LDP+”ER”)

#216

#14

#462

It follows route that source chooses. In other words, the control message to establish the LSP (label request) is source routed.

#972

#14 #972

A

B

C

Route={A,B,C}

Hop by Hop Routing

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

Label Switch Router-

An LSR is a high-speed router device in the core of an MPLS network that participates in the establishment of LSPs using the appropriate label signaling protocol and high-speed switching of the data traffic based on the established path.

• Label Edge Router-

An LER is a device that operates at the edge of the access network and MPLS network. LER’s support multiple port connected to dissimilar networks(such as frame relay ,ATM, and Ethernet) and forward this traffic on the MPLS.

Traffic Engineering

A

B C

D

Traffic engineering is the process of mapping traffic demand onto a network it’s a main APPLICATION of mpls.Traffic engineering is the process of mapping traffic demand onto a network it’s a main APPLICATION of mpls.

Demand

NetworkTopology

Purpose of traffic engineering:

• Maximize utilization of links and nodes throughout the network• Engineer links to achieve required delay, grade-of-service• Spread the network traffic across network links, minimize impact of single failure• Ensure available spare link capacity for re-routing traffic on failure• Meet policy requirements imposed by the network operator

Traffic engineering key to optimizing cost/performance

MPLS VPN : MPLS topology

Site A

138.120.8.0/24VPN 2

Site B

138.120.6.0/24

VPN 2

ISP Backbone

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

LSR

LSR

LSR

Loop Handling

Routing protocols used in conjunction with MPLS are based on distributed computation which may contain loops.

Ensures that loops are never set uplabels are not used until it is sure to be loop freeMethods

◦ labels are propagated starting at the egress switch◦ use source routing to set up label bindings from the egress switch

to each ingress switch

Loop Handling

Contd.

Detects loop

immediately

LeafLeaf

Leaf

LSR

Ingress Node

Egress Node

Change in LinkLink removedfrom tree

MPLS Advantages

Simplified ForwardingEfficient Explicit RoutingTraffic EngineeringQoS RoutingMappings from IP Packet to Forwarding Equivalence

Class (FEC)Partitioning of FunctionalityCommon 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?

-Leverage existing ATM hardware-Ultra fast forwarding -IP Traffic Engineering-Constraint-based Routing-Virtual Private Networks-Controllable tunneling mechanism-Voice/Video on IP-Delay variation + QoS constraints

Summary

MPLS is an exciting promising emerging technology

Basic functionality (Encapsulation and basic Label Distribution) has been defined by the IETF

Traffic engineering based on MPLS/IP is just round the corner.

Convergence is one step closer …...

Conclusion

Providing QoS and traffic engineering capabilities in the Internet is very essential.

For this purpose, the current Internet must be enhanced with new technologies such as MPLS.

MPLS will play a key role in future service providers and carriers IP backbone networks.

The use of MPLS in IP backbone networks will facilitate the development of new services such as real-time applications in the Internet.