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-PRESENTED BY-
SUNAME PRASHARROLL NO : 296|ECE|2007
COLLEGE : MIET/ JAMMU UNIVERSITY
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MPLS Introduction
Motivation
MPLS Basics
Components and Protocols Operation
Applications including GMPLS
Advantages and Disadvantages
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Motivation
IP
The first defined and used protocol
It usually works in packet switching environment.
but there are disadvantages
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Motivation (cont.)
IP Routing disadvantages
Connectionless
- e.g. no QoS Each router has to make independent forwarding decisions
based on the IP-address
Large IP Header
- At least 20 bytes
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Motivation (cont.)
ATM
connection oriented
- Supports QOS
Fast circuit switching with fixed length packets(cells)
integration of different traffic types (voice, data,video)
but there are also disadvantages
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Motivation (cont.)
ATM disadvantages
Complex
Expensive Not widely adopted
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Motivation (cont.)
Idea: Combine the
forwarding algorithm
used in ATM with IP.
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MPLS BASICS
MPLS is a versatile solution to address the
problems faced by present day
networks(usually IP networks) including speed,
scalability, QOS and traffic engineering.
Standard approved technology by IETF
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MPLS BASICS
Multi Protocol Label Switching is arranged
between Layer 2 and Layer 3
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MPLS BASICS (cont.)
MPLS is arranged between layer 2 and layer 3 protocols of
the OSI
model thats why it is also called as layer 2.5protocol.
Works with IP,ATM and frame relay network protocols
thats why it is called as multiprotocol.
It can works in both circuit switching and packet switchingenvironment.
Unlike IP networks , MPLS are connection oriented and
packets are routed along pre-configured LSPs.
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MPLS BASICS(cont..)
- MPLS is based on the concept of label
switching : an independent and unique
label is added to each data packet and this
label is used to switch and route the packet
through the network
- MPLS uses the same routing and hostaddressing schemes as IP networks.
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COMPONENTS AND PROTOCOLS
LER label edge router
LSR label switching router
FEC - forward equivalence class Label- associates a packet to a FEC
LSP- label switched path
LDP- label distribution protocol.
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Label edge router
LER LER is the device that operates at the edge of
the MPLS network.
LER plays a very important role in theassignment and removal of labels, as traffic
enters or exits an MPLS network.
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Label Switching Router -
LSR
An LSR is a high speed router in the core of an
MPLS network that participates in the
establishment of the LSPs(label switched path)
using appropriate label signaling protocol.
ATM switches can be used as LSRs without
changing their hardware.
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Label
A labelis a short, fixed-length value carried in thepacket's header to identify a forwarding
equivalence class (FEC). These labels are arranged in the form of stack
known as label stack.
Label associates a packet to a FEC.
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Label
Generic label format
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Forward Equivalence Class
-FEC
Is a representation of a group of packets that
share the same requirements for their
transport.
The assignment of a particular packet to a
particular FEC is done just once (when the
packet enters the network).
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Label-Switched Paths -LSPs
Within an MPLS domain, a path is set up for a
given packet to travel based on an FEC.
The LSP is set up prior to data transmission.
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LSP Details
MPLS provides two options to set up an LSP
hop-by-hop routing
Each LSR independently selects the next hop for a given FEC.LSRs support any available routing protocols (OSPF, ATM ).
explicit routing
Is similar to source routing. The ingress LER specifies the list of
nodes through which the packet traverses.
The LSP setup for an FEC is unidirectional. The return
traffic must take another LSP!
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MPLS Operation
The following steps must be taken for a data
packet to travel through an MPLS domain.
label creation and distribution
Label information base creation using LDP
label-switched path creation
Label information base creation
packet forwarding
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MPLS Operation Example
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Packet Forwarding
Packet forwarding
LER1 may not have any labels for this packet as it is
the first occurrence of this request. In an IP
network, it will find the longest address match to
find the next hop. Let LSR1 be the next hop for
LER1.
LER1 will initiate a label request toward LSR1.
This request will propagate through the network as
indicated by the broken green lines.
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Packet Forwarding (cont.)
Each intermediary router will receive a label from itsdownstream router starting from LER4 and going
upstream till LER1. All these routers will update their LIB table for this FEC.
The LSP setup is indicated by the broken blue linesusing LDP or any other signaling protocol.
LER1 will insert the label and forward the packet toLSR1.
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Packet Forwarding (cont.)
Each subsequent LSR, i.e., LSR2 and LSR3, will
examine the label in the received packet, replace it
with the outgoing label and forward it. When the packet reaches LER4, it will remove the
label because the packet is departing from an MPLS
domain and deliver it to the destination.
The actual data path followed by the packet is
indicated by the broken red lines.
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APPLICATIONS
Traffic engineering ( the ability of network
operators to dictate the path that traffic takes
through their network) and VPN support are
the examples of two key applications where
MPLS is superior to any currently available IP
technology.
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GMPLS
MPLS is being expanded for more general
applications in the form of GMPLS with the
application in optical and time-division
multiplexing network.
GMPLS is conceptually similar to MPLS, but
instead of using an explicit label for a given
FEC , some physical properties(time slot,wavelength etc..) of the received data stream
is used to deduce which LSP it belongs to.
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MPLS Advantages
Improves packet-forwarding performance in
the network
Supports QOS and COS for servicedifferentiation
Supports network scalability
I
ntegratesI
P and ATM in the network
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MPLS Disadvantages
An additional layer is added
The router has to understand MPLS
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Thank you..!
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