MPLS (Multi-Protocol Label Switching)

1. MPLS - MULTI-PROTOCOL LABEL SWITCHING
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2. • Multi-Protocol Label Switching (MPLS) was originally presented as a way of
improving the forwarding speed of routers but is now emerging as a crucial
standard technology that offers new capabilities for large scale IP
networks. Traffic engineering, the ability of network operators to dictate
the path that traffic takes through their network, and Virtual Private
Network support are examples of two key applications where MPLS is
superior to any currently available IP technology.
• Although MPLS was conceived as being independent of Layer 2, much of
the excitement generated by MPLS revolves around its promise to provide
a more effective means of deploying IP networks across ATM-based WAN
backbones. The Internet Engineering Task Force is developing MPLS with
draft standards expected by the end of 1998. MPLS is viewed by some as
one of the most important network developments of the 1990's

3. • The essence of MPLS is the generation of a short fixed-length label that acts as a
shorthand representation of an IP packet's header. This is much the same way as a
ZIP code is shorthand for the house, street and city in a postal address, and the use
of that label to make forwarding decisions about the packet. IP packets have a
field in their 'header' that contains the address to which the packet is to be routed.
Traditional routed networks process this information at every router in a packet's
path through the network (hop by hop routing).
• In MPLS, the IP packets are encapsulated with these labels by the first MPLS
device they encounter as they enter the network. The MPLS edge router analyses
the contents of the IP header and selects an appropriate label with which to
encapsulate the packet. Part of the great power of MPLS comes from the fact
that, in contrast to conventional IP routing, this analysis can be based on more
than just the destination address carried in the IP header. At all the subsequent
nodes within the network the MPLS label, and not the IP header, is used to make
the forwarding decision for the packet. Finally, as MPLS labelled packets leave the
network, another edge router removes the labels.

4. • In MPLS terminology, the packet handling nodes or routers are called Label
Switched Routers (LSRs). The derivation of the term should be obvious; MPLS
routers forward packets by making switching decisions based on the MPLS label.
This illustrates another of the key concepts in MPLS. Conventional IP routers
contain routing tables which are looked up using the IP header from a packet to
decide how to forward that packet. These tables are built by IP routing protocols
(e.g., RIP or OSPF) which carry around IP reachability information in the form of IP
addresses. In practice, we find that forwarding (IP header lookup) and control
planes (generation of the routing tables) are tightly coupled. Since MPLS
forwarding is based on labels it is possible to cleanly separate the (label-based)
forwarding plane from the routing protocol control plane. By separating the two,
each can be modified independently. With such a separation, we don't need to
change the forwarding machinery, for example, to migrate a new routing strategy
into the network.

5. • There are two broad categories of LSR. At the edge of the network, we
require high performance packet classifiers that can apply (and remove) the
requisite labels: we call these MPLS edge routers. Core LSRs need to be
capable of processing the labelled packets at extremely high bandwidths.

6.  Multi Protocol Label Switching is arranged between
Layer 2 and Layer 3
 Versatile solution:-speed ,QOS ,traffic management
Security management.

7.  Mechanisms to manage traffic flows of various
granularities (Flow Management)
 Is independent of Layer-2 and Layer-3 protocols
 Maps IP-addresses to fixed length labels
 Supports ATM, Frame-Relay and Ethernet

8. • Label
• Label Edge Router (LER)
• Forwarding Equivalence Router (FER)
• Label Switching Router (LSR)
• Label Distribution Protocol (LDP)

9. • Short fixed length entity
 20-bits label value
 Each label head contain four fields
Label Format

10. MPLS: HOW DOES ITWORK
UDP-Hello
UDP-Hello
TCP-open
TIME
TIME
Label request
IP
Label mapping
#L2
Initialization(s)

11. • Resides at the edge of an MPLS network and assigns and
removes the labels from the packets.
• Support multiple ports connected to dissimilar networks (such
as frame relay, ATM, and Ethernet).

12. • Is a high speed router in the core on an MPLS network.
• ATM switches can be used as LSRs without changing their
hardware. Label switching is equivalent to VP/VC switching.

14. • An application layer protocol for the distribution of label
binding information to LSRs.
• It is used to map FECs to labels, which, in turn, create LSPs.
• LDP sessions are established between LDP peers in the
MPLS network (not necessarily adjacent).

15. Configuration

16. R1
• !
• interface Serial1/0
• ip address 192.168.12.1 255.255.255.0
• no shut
• !
• interface Serial1/1
• ip address 192.168.13.1 255.255.255.0
• no shut
• !
• router ospf 1
• log-adjacency-changes
• network 0.0.0.0 255.255.255.255 area 0
R2
• !
• interface Serial1/0
• ip address 192.168.12.2 255.255.255.0
• no shut
• !
• interface Serial1/1
• ip address 192.168.23.2 255.255.255.0
• no shut
• !
• router ospf 1
• log-adjacency-changes
• network 0.0.0.0 255.255.255.255 area 0

17. R3
• !
• interface Serial1/0
• ip address 192.168.13.3 255.255.255.0
• no shut
• !
• interface Serial1/1
• ip address 192.168.23.3 255.255.255.0
• no shut
• !
• router ospf 1
• log-adjacency-changes
• network 0.0.0.0 255.255.255.255 area 0

18. Enabling MPLS
• Once you have done this the OSPF adjacencies should be up and running. Now what we need
to do is apply the necessary MPLS command to enable MPLS on network.
R1(config)#int se1/0
R1(config-if)#mpls ip
R1(config-if)#int se1/1
R1(config-if)#mpls ip
R2(config)#int se1/0
R2(config-if)#mpls ip
R2(config-if)#int se1/1
R2(config-if)#mpls ip
R3(config)#int se1/0
R3(config-if)#mpls ip
R3(config-if)#int se1/1
R3(config-if)#mpls ip

19. • Once you have applied the single command "mpls ip" on the both sides of
the link, an LDP adjacency will be formed and will display a log shown
below:
• *Feb 21 04:15:51.811: %SYS-5-CONFIG_I: Configured from console by console
• *Feb 21 04:15:52.135: %LDP-5-NBRCHG: LDP Neighbor 192.168.13.1:0 (2) is UP
• This means that MPLS is enabled on both sides and the neighbors are
exchanging label information. The LFIB, FIB and LIB are created after the
neighborships are formed.

20. Verifying MPLS Interfaces
• In order to get which interfaces are mpls enabled the command "show mpls
interfaces" is used. Operational state is "Yes" if the command "mpls ip" is
enabled on the interface.
R3#sh mpls interfaces
• Interface IP Tunnel Operational
• Serial1/0 Yes (ldp) No Yes
• Serial1/1 Yes (ldp) No Yes

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