The document provides an overview of MPLS for traffic management. It discusses how MPLS improves on conventional IP networks and ATM by allowing traffic engineering through label switching. Key topics covered include MPLS components, terminology, dynamic LSP setup using RSVP signaling, traffic trunks, and deployment strategies. The goal of MPLS traffic engineering is to increase resource utilization and speed up network convergence.

1. Presentation
MPLS FOR TRAFFIC MANAGEMENT
S.T.RAJAN
CJB0912010, FT12
M. Sc. (Engg.) in Computer Science &
Networking
Module Leader : Narasimha Murthy K.R
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2. Session Topics
• Convention IP Datagram & ATM
• MPLS by Definition
• Traffic Management
• Terminology & Components
• Primary Protocols for Qos & Cos
• Working Mechanism
• Implementation
• Deployment Strategy
• Summary
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3. Conventional IP Networks &ATM
IP Routing Disadvantages:
•It is based on connectionless so no QOS.
• Each router has to make independent forwarding decisions based on the IP-
address.
• Large IP Header - At least 20 bytes
• Routing in Network Layer - Slower than Switching
• Usually designed to obtain shortest path- Do not take into account additional
metrics .where it was not competent
Overall it is Based on the Metric Optimisation .so the link constraints not taken
into consideration.
ATM Principle :.
• It overlays network solution.
– fast packet switching with fixed length packets (cells)
– integration of different traffic types (voice, data, video)
Drawbacks Of ATM:
• Not well integrated for engineering traffic flows
• Wastage of bandwidth .
• Complex & Expensive.
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4. Evolution of MPLS
It stands for “Multi Protocol Label Switching”.
Control:
Control: Control:
ATM Forum
IP Router Software Software
IP Router Software
Forwarding: Forwarding: Forwarding:
Longest-match
Lookup Label Swapping Label Swapping
• Figures Represent protocol used in layer 2 & 3 in TCP/IP Stack
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5. Need for MPLS
MPLS Functions
•Uses Control-driven model.
•MPLS simplifies forwarding function by taking a totally different
approach by introducing a connection oriented mechanism inside the
connectionless IP networks
•Initially Designed for Enhancing Look up Speed for Routers but
essentially used for traffic engineering.
• IETF creates MPLS working group to create unified standard (Frame
Relay, PPP, SONET), not just ATM.
MPLS Characteristics
– Mechanisms to manage traffic flows of various granularities (Flow
Management) by using single forwarding algorithm .
– Is independent of Layer-2 and Layer-3 protocols
– Maps IP-addresses to fixed length labels
– Interfaces to existing routing protocols (RSVP, OSPF)&futuristic
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6. MPLS-TE Example
• Buses run with Route Number which is indication of route from
start point .
• Similarly in MPLS each LSR will label the packets with the route
label or swaps label and sends to the end Router
• Traffic management is done by signaling protocol with dedicated
path called Trunk Tunneling .
LSP
Trunk Tunneling
Router B Router B
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7. Need For Traffic Management
Traffic Management
•The task of mapping traffic flows onto an existing physical
topology to facilitate efficient and reliable network operations
• traffic oriented e.g. minimization of packet loss
•resource oriented - optimization of resource utilization e.g.
efficient management of bandwidth
Performance Objective
Minimizing congestion is a major traffic and resource oriented
performance objective
Congestion manifest under two scenarios
-network resources are insufficient or inadequate can be solved
by capacity expansion or classical congestion control
techniques
-traffic streams are inefficiently mapped onto available
resources can be reduced by adopting load balancing policies
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8. Advantages of TM & Working
• Variously divisible traffic aggregation and disaggregation
Maneuvering load distribution
• Stand-by secondary paths and precomputed detouring paths
Strongly unified measurement and control for each “traffic-
engineered path”
Explanation :If network core runs conventional longest-match IP forwarding:
–Data from Host A and B follow path 1 since it is the shortest-path
computed.
–With MPLS, network administrator could split traffic:
•Host A traffic over path 1 & Host B traffic over path 2
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9. Terminology
• FEC (Forwarding Equivalence Class)-Group of packets sharing
the same type of transport.
• LSR (Label Switched Router)-Swaps labels on packets in core of
network.
• LER (Label Edge Router)-Attach Labels to packets based on a
FEC.
• LSP (Label Switch Path)-Path through network based on a FEC
(simplex in nature). The “traffic-engineered path”
• LIB (Label Information Base)- MPLS equivalent to IP routing
table, contains FEC-to-Label bindings
• Traffic Trunk (TT)
-Traffic Trunk - aggregation of traffic flows of the same class
which are placed inside a Label Switched Path
-forwarded through a common path with common TE
requirements characterized by its ingress and egress
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10. Positions In MPLS
LER (Label Edge Router ) or Penultimate Router
LSR (Label Switch Router) or Transit Router
LSP:Label Switch Path
Mumbai is Ingress Router & Kolkata is Egress Router
Mumbai Kolkata
Pune Secunderbad Vijayawada Bhuvaneshwar
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11. LSP & Graphs
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 LSR 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!.Two types Static or dynamic.
Induced MPLS Graph
•analogous to a virtual topology in an overlay model
•logically mapped onto the physical network through the selections
o LSPs for traffic trunk
•comprises a set of LSRs which act as nodes of the graph and a set
of LSPs which provide logical point to point connectivity between
LSRs and thus act as edges of the graph Advanced Studies
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12. Components MPLS-TE
• Packet Forwarding Component
MPLS, label switching itself
• Information Distribution Component
IGP (OSPF/IS-IS) extension
• Path Selection Component
Constrained Shortest Path First (CSPF) algorithm or BGP
• Signaling Component
LDP, CR-LDP, and RSVP-TE
-In MPLS, traffic engineering is inherently provided using
explicitly routed paths.
• The LSPs are created independently, specifying different paths
that are based on user-defined policies. However, this may
require extensive operator intervention.
• RSVP-TE and LDP are two possible approaches to supply
dynamic traffic engineering and QoS in MPLS.
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13. Dynamic LSP using RSVP
• Dynamic LSP Created without user intervention
• User control used by two protocol RSVP or LDP
RSVP (Resource Reservation Protocol)
• Signaling Protocol designed by IETF
• Application to request & reserves resources hop by hop
• Request bandwidth and traffic conditions on a defined path.
• Using “Path” message from source to destination
• Reply message “Resv” From destination to source by updating “softstate”which is
database for reservation .
• Establishes the LSP.
• LSP is operation as long as soft state
• QOS and COS
• The generic protocol is extension of MPLS implementation R8
R3 R4
R2
Setup: Path (R2->R6->R7->R4) R5
Pop
Labels Established on Resv R1 R6 R7
message
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22

14. LDP
Label Distribution Protocol designed specifically for MPLS
Four message classes
1. Discovery-Announce and
maintain presence of an
LSR.
2. Session-establish, maintain,
terminate sessions b/w LDP
peers.
3. Advertisement-create,
change, delete label
mappings.
4. Notification-advisory and
error info. •Discovery: Runs over UDP
Multicast’s “Hello” •All others run over TCP
message is by LSR
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15. CBR-LDP
• Enables a demand driven, resource reservation aware, routing
paradigm to co-exist with current topology driven protocols
uses the following inputs
traffic trunk attributes
resource attributes
other topology state information
• Basic features
prune the resources that do not meet the requirements of the
traffic trunk attribute
run a shortest path algorithm on the residual graph
Advantages of traffic trunks
•No. of trunks dependent only on the topology
•Forwarding table does not grow with the traffic
•Rerouting RSVP, CR-LDP, or IGP
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16. Working Mechanism -TE
Steps For TE Establishment
• LSP Tunnels which are Signaled to RSVP which are unidirectional
•Link State IGP for global flooding of resource Information & automatic
routing of traffic .
•MPLS traffic engineering module for path calculation which path to be
used LSP tunnel.
•Link Management Module link admission and book keeping of resource
information to be flooded
•Label Switching Forwarding based on Resource based Routing
Algorithm
Mapping into Tunnel
•IGP uses Dijkstra's shortest path first (SPF) algorithm.
Routing Tables are Derived from Shortest Path Tree.
•Another Algorithm calculates explicit route from one or more nodes
based on LSP and TE Tunnels
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17. SFP Computation
Determination of first Hop Information
•When Path is found for new node it moves new node from tentative list
to path lists
•Based on TE Tunnel the tail end is First Hop Information updated
•Without TE Tunnel the uses First Hop Information from adjacent of
just connected node.
•When both Cases fail ,it copies the information from parent node to new
node.
Advantages
If there is more than one TE tunnel to different intermediate nodes on the
path to destination
node X, traffic flows over the TE tunnel whose tailend node is closest to
node X.
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18. TE-Tunneling Mesh Network
R-B R-C
R-A
R-D R-E
Assume
Tunneling
present from A
to D and Same
cost Network.
Then SFP
implements to The diagram shows Mesh Topology with dedicated
do load sharing trunks
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19. Signaling Protocols
•Implicit routing- labels are set-up and torn-down (like
telephone calls), also known as hard state.
•Explicit routing- allows for better traffic engineering, traffic
tunnels are created based on overall view of topology. More
dynamic.
Protocol Routing Traffic engineering
LDP Implicit NO
BGP Implicit NO
IS-IS Implicit NO
CR-LPD Explicit YES
RSVP-TE Explicit YES
OSPF-
Explicit YES
TE
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20. Implementation Consideration
Management Interface
Constraint Based Conventional
MPLS
Routing Process IGP Process
Resource Attribute Link State
Availability Database Database
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21. Deployment Strategy-1
Congestion Free Network :
1) Configure your IGP, RSVP
2) Configure TE tunnels around congested links
- one IGP tunnel, one or more explicit-path tunnels.
3) Turn up tunnels one at a time via ‘autoroute announce’
4) Add BW requirements to tunnels
Tunnel BW ratio is important.
Link Protection:
Step1: link failure detection
O(depends on L2/L1)
Step2: IGP reaction (ISIS case)
Either via Step1 or via IGP hello expiration (30s by default for
ISIS) .5s (default) must occur by default before the generation of
a new LSP
Step3: RSVP signalization
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22. Deployment Strategy-2
Step4: Either stepA or stepB alarms the head-end
Step35: Re-optimization
dijkstra computation: O(0.5)ms per node (rule of thumb)
RSVP signalisation time to install re-routed tunnel
⇒convergence in the order of several seconds (at least).
⇒This includes fast switch over into secondary TE tunnel Path.
Backup Tunnel to the next-hop of the
LSPs next-hopR3 R4
R2
R1 R5
R7
R6
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23. MPLS-TE Deployment Issues
MPLS is proposed as a standard TE solution by IETF, BUT
• Vendor Interoperability problem
• Limitation in online path calculation
• Problems on Traffic Trunks
• Measurement and Control Issues
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24. Summary
Based On MPLS
•Improves packet-forwarding performance in the network
•Supports QoS and CoS for service differentiation
•Supports network scalability
•Integrates IP and ATM in the network
•Builds interoperable networks
Based on MPLS TE:
•MPLS supports tunneling, which breaks the transparency paradigm.
•MPLS supports sessions, it breaks the datagram model.
•TE Done by SFP based on different Protocols.
•Higher return on network backbone infrastructure investment.
•Reduction in operating costs
•To increase the resource utilization
MPLS Traffic Engineering
•To speed up convergence upon link or node failure
MPLS TE and Link/Node protection
•To ease capacity planning -Aggregate Admission Control
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25. References
• Sreekanth P V, Digital Transmission Hierarchies, Universities
Press ,2010,p209-225.
• Ramaswami .R and Sivarajan. K. N. , Optical Networks: A
Practical Perspective ,Morgan Kaufmann Publishers, 2nd .
• Cisco IOS Release 11.3 Network Protocols Configuration Guide,
Part 1, “Multiple Label Switching Traffic” chapter.
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26. Thank You
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