Transcript Introducing a New Product

IP/MPLS
Multiprotocol Label Switching
Isaicu Monica
ES an I
Contents
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Overview
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Need for MPLS
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MPLS Basics
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MPLS Components and Protocols
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MPLS Operation
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Advantages and Disadvantages
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Evolution of MPLS
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References
Overview
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MPLS is a standard from the IETF for including
routing information in the packets of an IP network.
The first IETF MPLS Working Group Meeting
occurred in April of 1997
Widely deployed by many telcos and service
providers for their Internet backbones, MPLS delivers
the quality of service (QoS) required to support realtime voice and video as well as service level
agreements (SLAs) that guarantee bandwidth. Large
enterprises also use MPLS in their national private
networks.
Need for MPLS
IP Routing disadvantages
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Connectionless
- e.g. no QoS
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Each router has to make independent forwarding decisions
based on the IP-address
Large IP Header
- At least 20 bytes
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Routing in Network Layer
- Slower than Switching
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Usually designed to obtain shortest path
- Do not take into account additional metrics
Need for MPLS
ATM (Asynchronous Transfer Mode)
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connection oriented
- Supports QoS
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fast packet switching with fixed length packets (cells)
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integration of different traffic types (voice, data, video)
But there are also disadvantages:
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Complex
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Expensive
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Not widely adopted
Need for MPLS
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MPLS effectively pulls together the best of two different
networking worlds. It allows an IP network to be operated
in a controlled manner - in a similar way to legacy ATM,
DTM - while maintaining the flexibility and versatility of an
IP network
MPLS networks meet and exceed quality and reliability
levels of legacy networks, while opening up a whole new
world of networking flexibility.
MPLS Basics
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Multi Protocol Label Switching is arranged
between Layer 2 and Layer 3
MPLS combines the performance and
capabilities of Layer 2 (data link layer)
switching with the proven scalability of Layer 3
(network layer) routing.
MPLS Basics
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Characteristics:
Provides means to map IP addresses to simple,
fixed-length labels
Remains independent of Layer-2 and Layer-3
protocols
Provides interfaces to existing routing protocols
such as OSPF (Open Shortest path first) and
RSVP (Resource reservation protocol)
MPLS packets can run on other Layer 2
technologies such as ATM, FR, PPP, POS,
Ethernet
Other Layer 2 technologies can be run over an
MPLS network
MPLS Components and Protocols
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Label Header
A label is a short, fixed length, locally significant identifier which is
used to identify a FEC (Forwarding Equivalence Class - a group
of IP packets which are forwarded in the same manner - over the
same path, with the same forwarding treatment)
The label which is put on a particular packet represents the FEC
to which that packet is assigned.
MPLS Components and Protocols
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LER (label edge routers)
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The entry and exit points of an MPLS
network
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Support multiple ports connected to
dissimilar networks (such as frame relay,
ATM, and Ethernet).
LSR (label switching routers)
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High speed routers in the core on an MPLS
network, that perform routing based only on
the label
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ATM switches can be used as LSRs without
changing their hardware
MPLS Components and Protocols
MPLS Components and Protocols
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LSP (Label switching Path) - within an MPLS domain, a path is
set up for a given packet by LSRs to travel based on a FEC
MPLS provides two options to set up an LSP
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hop-by-hop routing
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explicit routing
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Each LSR independently selects the next hop for
a given FEC. LSRs support any available routing
protocols (OSPF, ISIS,BGP).
Is similar to source routing. The ingress LSR
specifies the list of nodes through which the
packet traverses.
The LSP setup for a FEC is unidirectional. The return traffic must
take another LSP!
MPLS Protocols
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MPLS signaling protocols are used to establish,
maintain, and release label-switched paths
(LSP).
Examples of MPLS signaling protocols include
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Existing protocols have been extended so that
label distribution can be piggybacked on them
Border Gateway Protocol (BGP) and Resource
Reservation Protocol (RSVP)
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New protocols have also been defined Label
Distribution Protocol (LDP) and Constraintbased Routing Label Distribution Protocol
(CR-LDP)
MPLS Protocols - LDP
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LDP associates a Forwarding Equivalence Class (FEC)
with each label it distributes. Two LSRs which use LDP to
exchange FEC - label binding information are known as
"LDP Peers", and we speak of there being an "LDP
Session" between them.
LDP uses TCP for session communication. Use of TCP
ensures that session messages are reliably delivered, and
that distributed labels and state information associated with
LSPs need not be refreshed periodically.
LDP includes a mechanism by which an LSR can discover
potential LDP peers. The discovery mechanism makes it
unnecessary for operators to explicitly configure each LSR
with its LDP peers.
LDP Details
LDP message types:
discovery messages - announce and maintain
the presence of an LSR in a network
session messages - establish, maintain, and
terminate sessions between LDP peers
advertisement messages - create, change, and
delete label mappings for FECs
notification messages - provide advisory
information and signal error information
All LDP messages have a common structure that uses a
Type-Length-Value (TLV) encoding scheme. The Value
part of a TLV - encoded object, or TLV for short, may
itself contain one or more TLVs.
IP/MPLS networks
MPLS Operation
Advantages
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Flexibility - as a technology, MPLS imposes few restrictions on
interoperability with other technologies.
Improves packet-forwarding performance in the network
Supports QoS and CoS for service differentiation - with multimedia
applications gaining popularity it is essential to have QoS in place. IP
based voice service needs to have more priority as it is very sensitive to
delay, jitter etc. Also, video applications are used in enterprise networks as
Video Conferencing and Telepresence. Such applications also need to be
given priority in addition to the business critical applications. Earlier, ATM
was the answer for many people to have QoS. But the things have
changed and MPLS can provide ATM like QoS features. MPLS label has a
3 bit field called Traffic Class (TC) which was formerly known as EXP
(Experimental) field. Core routers can provide different set of treatment for
each MPLS frame based on the value of TC.
Advantages
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MPLS is used to create cost effective, private Wide Area Networks
(WANs)
Traffic Engineering - this is a feature that every Service Provider would
love to use. Mostly, SPs would be having more than one link between
different routers, both for redundancy and for meeting customer
requirements. The problem arises, when the bandwidth of these links are
different. SP can configure the load sharing between these links using
various IGP features, but that may prove to be very difficult and the model
itself is not scalable. If the configurations are not properly documented,
troubleshooting can be a pain. MPLS traffic Engineering can address such
scenarios. The use of TE along with IGP can provide better solution.
It's inexpensive compared with "private" IP networks like point to point
technologies.
As a "fully meshed" topology, MPLS assures that locations on the network
can exchange data with one another (think video conferencing and VoIP).
Disadvantages
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An additional layer is added
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The router has to understand MPLS
Evolution of MPLS
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Because of its key features MPLS has been widely adopted
by enterprises for their WANs, as the most recent data from
Nemertes Research (2009) indicates that around 84% of
companies are now using MPLS for their WANs.
IETF has been working on a number of different
improvements to MPLS that allows it to be applied to transport
architecture, IPv6.
Perhaps the most important MPLS evolution will be MPLS
Transport Profile (MPLS-TP), that can take advantage of
features such as Quality of Service and fast reroute and put
that into optical and transport networks
Evolution of MPLS
References
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RFC 3031 - Multiprotocol Label Switching Architecture
Introduction to MPLS http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/p
s6557/prod_presentation0900aecd8031205f.pdf
http://www.cisco.com/en/US/docs/ios/12_1/switch/configuratio
n/guide/xcdtagov.html
http://www.javvin.com/protocolLDP.html
http://www.ciscopress.com/articles/article.asp?p=361409
Understanding High Availability of IP and MPLS Networks
http://en.wikipedia.org/wiki/Multiprotocol_Label_Switching
http://www.networkworld.com/news/2009/122109-mplsfuture.html
Thank You!