A Presentation about Traffic engineering fault tolerance using MPLS routing protocol.

1. MPLS-TE FaultTolerance
MPLS- TE PROTECTION OR FAST REROUTE (FRR)
Sakkhor Chowdhury

2. What is MPLS?
From MPLS Resource center:
“MPLS stands for "Multiprotocol Label Switching". In an MPLS network, incoming packets are assigned a
"label" by a "label edge router (LER)". Packets are forwarded along a "label switch path (LSP)" where each
"label switch router (LSR)" makes forwarding decisions based solely on the contents of the label. At each
hop, the LSR strips off the existing label and applies a new label which tells the next hop how to forward
the packet.
Label Switch Paths (LSPs) are established by network operators for a variety of purposes, such as to
guarantee a certain level of performance, to route around network congestion, or to create IP tunnels for
network-based virtual private networks. In many ways, LSPs are no different than circuit-switched paths in
ATM or Frame Relay networks, except that they are not dependent on a particular Layer 2 technology.
An LSP can be established that crosses multiple Layer 2 transports such as ATM, Frame Relay or
Ethernet. Thus, one of the true promises of MPLS is the ability to create end-to-end circuits, with specific
performance characteristics, across any type of transport medium, eliminating the need for overlay
networks or Layer 2 only control mechanisms.”

3. MPLS process
Label removal
Classification
Label assignment
Routing Protocol
Label Switch Path
LFIB
Layer 2
Layer 1
Layer 2
Layer 1
Layer 2
Layer 1
LFIB
Layer 2
Layer 1
Layer 2
Layer 1
FEC FEC FEC
LFIB
Label Swapping

4. Traffic Engineering
• Traffic engineering allows a network administrator to make the path deterministic and bypass
the normal routed hop-by-hop paths. An administrator may elect to explicitly define the path
between stations to ensure QoS or have the traffic follow a specified path to reduce traffic
loading across certain hops.
• The network administrator can reduce congestion by forcing the frame to travel around the
overloaded segments. Traffic engineering, then, enables an administrator to define a policy
for forwarding frames rather than depending upon dynamic routing protocols.
• Traffic engineering is similar to source-routing in that an explicit path is defined for the frame
to travel. However, unlike source-routing, the hop-by-hop definition is not carried with every
frame. Rather, the hops are configured in the LSRs ahead of time along with the appropriate
label values.

5. MPLS – Traffic Engineering
 End-to-End forwarding decision determined by ingress node.
 Enables Traffic Engineering
LER
1
LSR
2
LSR
3
LER
4
LIP
Forward
to
LSR 2
LSR 3
LSR 4
LSR X
Overload
!!
Overload
!!
IP
IP
LIP
LIP

6. NetworkFailures
• Node failures
Hardware Failures
Maintenance
Electrical Problems
• Link failures
Loose Cables
Fiber Cuts
ADM Problems
PacketLost

7. PossibleSolutions
• Interior GatewayProtocol(IGP)
• OSPF
• IS-IS
Convergence/Rapid Convergence
Congestion
SPF
• SONETAutomatic Protection Switching
(APS)
• Active Link
• Passive/Standby Link
~50msDelaybetween link
changes
IGPConvergence
ADM Required
Insufficient FaultTolerance

8. Background
• RFC2702 “Requirementsfor TrafficEngineeringOverMPLS”
• LSP reroute/Headendreroute
New TELSP(RSVP)Signaling
SFP
Substantial TrafficLost
PacketLost
MPLS-TEProtection
or
FastReroute (FRR)

9. Protection
• Procedures
• Resources
• Physical
• Links
• Nodes
• Logical
• LSP
Minimal TrafficLost
• Protection
 Preset LSPBackup
 Pre-computed
 Pre-signaled

10. ProtectionSchemes
• Path Protection
• End-to-End Protection
• LocalProtection
• Link Protection
• Node Protection

11. PathProtection
• Backup/SecondaryLSP
• Parallel to Primary LSP
• Distinct route
• Pre-signaled
• BWproperties similar to primary LSP
 Better Convergencevs.IGP& TELSPreroute
1:1
Bit Scalable

12. LocalProtection
• BackupLSPfor asegment of the primary
LSP
• Pre-signaled
• Around the affected link (link protection)
• Around the affected node (node protection)
• Encapsulatesprimary LSP
 FastFailure Recovery
 1:N
 High Scalability

13. LabelStacking
•12008a – 12008c link failure
•12008a switch traffic to backup LSP
•12008a stack label 38 to 33, {38,33}
•12008a switch to 12008b {38,33}
•12008b relieve {38,33} & switch to 12008d based on high
level label (38), replacing 38 by 35, {35,33}
•12008d receive {35,33}, performs PHPremoving 35 & switch
to 12008c,{33}
•12008c receive {33}, performs PHP& resend to7200c• Required
• Label Stacking
• Global Label Space

14. LinkProtection
• BackupTunnel or LSP
• Avoids "protected link"
 Protects against linkfailures.
Vulnerable against node failures
• NHopTunnels
• From PLRto NHopNode
• PLRknows MPexpectedlabel

15. Node Protection
• BackupTunnel or LSP
• Avoids "protected node"
• NNHopTunnels
• From PLRto NNHop
• Label Recording required
 Protects against link and nodefailures

16. Advanced Methods ofProtection
• Multiple backuptunnels
• BackupBWReservation
• Promotion

17. Conclusions
Slow andInsufficient
• Real-timeApplications
• VoIP
• Live Meeting
• etc.
• IGP
• MPLS-TEheadend
reroute
• FRR
• Local Protection