The document discusses traffic engineering in networks using MPLS. It begins by defining traffic engineering and explaining how shortest path routing can lead to link congestion and underutilized paths. It then describes MPLS, constraint-based routing, and enhanced interior gateway protocols. Constraint-based routing computes paths subject to constraints like bandwidth and policies. MPLS extends routing to control packet forwarding and paths. The document outlines the basic components and functioning of an MPLS system for traffic engineering, including setting up label switched paths (LSPs) with attributes like bandwidth, priority, affinity and establishing multiple LSPs between endpoints to distribute load.

1. Network Traffic
Engineering using MPLS
T h e P A C K E Ts s t a r t m o v i n g . . . . . . .

2. Catalogue
▪ The Sketch of Traffic Engineering
▪ Basic Terms
– Multi Protocol Label Switching (MPLS)
– Constraint Based Routing
– Enhanced Link State Interior Gateway Protocols (IGP)
▪ Rough Sketch of ISPs Network
▪ Issues in Designing an MPLS System for Traffic Engineering
▪ Basic steps for deploying an MPLS System for Traffic Engineering
▪ Conclusion & References
-Jay Patel (UDIT, University Of Mumbai)
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3. The Sketch of
Traffic Engineering
▪ Traffic Engineering – Defined:
– Traffic engineering is a process of optimizing the performance of
a telecommunications network by dynamically analyzing, predicting and regulating
the behaviour of data transmitted over that network.
▪ Data Traffic – Cause:
– The IGPs (Interior Gateway Protocols) always use the shortest possible path which
leads to:
▪ Overlapping some links, causing congestions on those links.
▪ The shortest path exceeds the capacity and the longer paths remain under-utilized.
-Jay Patel (UDIT, University Of Mumbai)
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4. Basic Terms
▪ Multi Protocol Label Switching:
– It’s an advanced forwarding scheme.
– It extends routing with respect to packet forwarding and path controlling.
▪ Constraint Based Routing:
– Computes routes that are subject to constraints such as bandwidth and
administrative policy.
– As Constraint-based Routing considers more than network topology in computing
routes, it may find a longer but lightly loaded path better than the heavily loaded
shortest path. Network traffic is hence distributed more evenly.
-Jay Patel (UDIT, University Of Mumbai)
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5. Basic Terms
(Cont.)
▪ Enhanced Link State Interior Gateway Protocols:
– In order for Constraint-based Routing to compute LSP paths subject to constraints,
an enhanced link state IGP must be used to propagate link attributes in addition to
normal link state information. Common link attributes include:
▪ Reservable Bandwidth.
▪ Link Affinity – An administratively specified property of the link.
-Jay Patel (UDIT, University Of Mumbai)
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6. MPLS –
In Brief:
▪ Multi Protocol Label Switching:
– It’s an advanced forwarding scheme.
– It extends routing with respect to packet forwarding and path controlling.
▪ MPLS Header:
– In non-ATM Environment:
▪ Contains a 20-bit label, a 3-bit Experimental field (formerly known as Class of Service,
or CoS, field), a 1-bit label stack indicator and an 8-bit TTL field.
– In ATM Environment:
▪ Contains only a label encoded in the VCI/VPI field.
▪ An MPLS capable router, termed Label Switching Router (LSR), examines the label
and possibly the experimental field in forwarding the packet.
-Jay Patel (UDIT, University Of Mumbai)
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7. MPLS –
Working
-Jay Patel (UDIT, University Of Mumbai)
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8. LSP –
Attributes
Attribute Name
Meaning of the Attribute
Bandwidth
The minimum requirement on the reservable bandwidth of a path for the LSP to be set
up along that path.
Path Attribute
An attribute that decides whether the path of the LSP should be manually specified or
dynamically computed by Constraint-based Routing.
Setup Priority
The attribute that decides which LSP will get the resource when multiple LSPs
compete for it.
Holding Priority
The attribute that decides whether an established LSP should be pre-emptied the
resource it holds by a new LSP.
Affinity (Color)
An administratively specified property of an LSP.
Adaptability
Whether to switch the LSP to a more optimal path when one becomes available.
Resilience
The attribute that decides whether to reroute the LSP when the current path is
affected by failure.
-Jay Patel (UDIT, University Of Mumbai)
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9. Constraint Based Routing –
In Brief
▪ Constraint Based Routing:
– Computes routes that are subject to constraints such as bandwidth and
administrative policy.
– As Constraint-based Routing considers more than network topology in computing
routes, it may find a longer but lightly loaded path better than the heavily loaded
shortest path. Network traffic is hence distributed more evenly.
-Jay Patel (UDIT, University Of Mumbai)
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10. Constraint Based Routing
-Jay Patel (UDIT, University Of Mumbai)
– Working
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11. Putting All Together
– MPLS + CBR + Enhanced IGPs
▪ With MPLS, Constraint-based Routing and an enhanced IGP, Traffic
Engineering can be done much more effectively.
▪ The two problems discussed here are:
– Congestion Avoidance
– Load Sharing
-Jay Patel (UDIT, University Of Mumbai)
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12. Congestion Avoidance
▪ By setting the maximum reservable bandwidth of each link (e.g., to the
physical bandwidth of the link), and by setting the bandwidth
requirement for each LSP, Constraint-based Routing will automatically
avoid placing too many LSPs on any link.
-Jay Patel (UDIT, University Of Mumbai)
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13. Load Sharing
▪ If traffic from router C1 to router B1 exceeds the capacity of any single
path from C1 to B1, then multiple LSPs can be configured from C1 to B1,
and load ratio of these two LSPs can be specified as desired, so that
load can be distributed optimally.
-Jay Patel (UDIT, University Of Mumbai)
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14. Rough Sketch of
ISPs Network
# AR – Access Router
# BR – Border Router
# HR – Hosting Router
# CR – Core Router
*Usually Ring Topology is used
by ISPs to maintain symmetry.
*A large ISP can have more
than 30 POP’s
-Jay Patel (UDIT, University Of Mumbai)
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15. Issues in Designing an MPLS System
▪ The geographical scope of the MPLS System.
▪ The Participating Routers.
▪ The Hierarchy of MPLS System.
▪ The Bandwidth requirement of LSP.
▪ The Path Attribute of LSP.
▪ The priority of LSPs.
▪ The number of parallel LSPs between each end-point pair.
▪ The affinity of the LSPs and links.
▪ The adaptability and the resilience attributes of LSPs.
-Jay Patel (UDIT, University Of Mumbai)
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16. Basic Steps to Deploy MPLS Syetem:
I.
Statistics collecting using MPLS
II. Deploy LSPs with Bandwidth Constraints
III. Periodic update of LSP Bandwidth
IV. Offline Constraint-Based Routing
-Jay Patel (UDIT, University Of Mumbai)
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17. Example of
MPLS System Design:
-Jay Patel (UDIT, University Of Mumbai)
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18. References:
▪ Research Paper: “Traffic Engineering with MPLS in the Internet” –
Michigan State University.
▪ http://searchtelecom.techtarget.com/feature/Traffic-engineeringthe-service-provider-network?offer=briefcase#projiCopy
▪ http://en.wikipedia.org/wiki/Multiprotocol_Label_Switching
▪ http://en.wikipedia.org/wiki/Internet_traffic_engineering
-Jay Patel (UDIT, University Of Mumbai)
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19. Thank You
- Jay J. Patel
(University Department of IT,
University of Mumbai)
-Jay Patel (UDIT, University Of Mumbai)
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