MPLS is a technology that allows traffic to be forwarded through networks based on short fixed length labels rather than long network addresses, enabling traffic engineering and quality of service. It works by classifying packets into forwarding equivalency classes, assigning labels when packets enter the MPLS domain, and using label switching to forward packets along label switched paths. MPLS provides advantages like simplified packet forwarding, efficient traffic engineering capabilities, and virtual private networks.

1. MPLS
Technology

2. Agenda
 MPLS - The Motivation
 How MPLS Works !
 MPLS Technology
 MPLS Application
 Advantages of MPLS
 Future of MPLS
 Conclusion
 Refrences
July 29, 2000 TECON 2000 2

3. 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.
July 29, 2000 TECON 2000 3

4. 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

5. MPLS BlOCK DIAGRAM
Classification
LSP Label assignment
Label swapping Label removal
Routing protocol OSPF OSPF OSPF
FEC table Local table Local table Local table
Attributes Precedence
Label table Local table Local table Local table
Layer 2 Layer 2 Layer 2
Label Switch
Layer 1 Layer 1 Layer 1
Ingress Core Egress
Node Node Node
July 29, 2000 TECON 2000 5

6. MPLS Architecture: Control Plane

7. MPLS Architecture: Data Plane

8. Basic Model for MPLS Network
 Existing routing protocols establish routes
 LDP establishes label to route mappings
 LDP creates LIB entries for each LSR
 Ingress LER receives packet,adds a label
 LSRs forward labeled packets using label swapping
 Egress LER removes the label and delivers the packet
Internet
LER
LER
IP
LSR
LSR
LSR LSR
MPLS
LER IP
LSR = Label Switched
RouterLER = Label Edge Router

9. MPLS FORWORDING PROCESS
LER
L3 Routing LER
LER
Interne
t
L3 Routing L3 Routing
LER LSR LSR
Label Swapping Label Swapping LER
L3 Routing
L3 Routing
IP Packet
IP Packet w/ Label

10. MPLS Terminology
• LDP: Label Distribution Protocol
• FEC: Forwarding Equivalence Class
• LSP: Label Switched Path
• LSR: Label Switching Router
• LER: Label Edge Router

11. 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)

12. Forwarding Equivalence Classes
LSR LSR
LER LER
LSP
IP1 IP1
IP1 #L1 IP1 #L2 IP1 #L3
IP2 #L1 IP2 #L2 IP2 #L3
IP2 IP2
Packets are destined for different address prefixes, but can be
mapped to common path
• 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

13. FEC Classification
•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,
Ingress Label FEC Egress Label
6 138.120.6/24 - xxxx 9
•FECs are manually initiated by the operator
•A FEC is associated at least one Label
Ingress Label
Ingress Label FEC FEC Attribute Egress Label
Attribute Egress Label
6 138.120.6/24 - xxxx A 9
6 138.120.6/24 - xxxx B 12

14. Label Switched Path (LSP)
Intf Label Dest Intf Label Intf Label Dest Intf
In In Out Out In In Out
3 0.50 47.1 1 0.40 3 0.40 47.1 1
IP 47.1.1.1
1 47.1
Intf Dest Intf Label 3
In Out Out 3
3 47.1 1 0.50 2
1
1 2
47.3 3 47.2
2
IP 47.1.1.1
Two types of Label Switched Paths:
• Hop by hop)
• Explicit Routing (LDP+”ER”)

15. Hop by Hop Routing
Route=
{A,B,C} #14 #972
#216
B
#14 C
A
#972
#462
It follows route that source chooses. In other
words, the control message to establish the LSP
(label request) is source routed.

16. EXPLICITLY ROUTED LSP ER-LSP
Intf Label Dest Intf Label Intf Label Dest Intf
In In Out Out In In Out
3 0.50 47.1 1 0.40 3 0.40 47.1 1
Intf Dest Intf Label
In Out Out IP 47.1.1.1
1 47.1
3 47.1.1 2 1.33 3 3
3 47.1 1 0.50
2
1
1 2
47.3 3 47.2
2
IP 47.1.1.1

17.  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.

18. Traffic Engineering
B C
Demand
A D
Traffic engineering is the process of mapping traffic demand onto a network it’s a main
APPLICATION of mpls.
Network
Topology
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

19. MPLS VPN : MPLS topology
VPN 2
138.120.6.0/24
LSR
138.120.8.0/24 Site B
VPN 1 Site A LSP 47
ISP Backbone
LSR
LSR
LSR
LSR
LSP 32
LSR
Site A
Site B
138.120.8.0/24
VPN 2 138.120.6.0/24 VPN 1

20. Loop Handling
 Routing protocols used in conjunction with MPLS
are based on distributed computation which may
contain loops.
Loop Handling
 Ensures that loops are never set up
 labels are not used until it is sure to be loop free
 Methods
◦ labels are propagated starting at the egress switch
◦ use source routing to set up label bindings from the
egress switch to each ingress switch
Contd
.

21. Leaf Leaf
Leaf
Detects loop
immediately
Link removed Change in Link
from tree
LSR
Ingress Node
Egress Node

22. 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

23. 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

24. 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 …...

25. 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.