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Path Protection in MPLS Networks

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Short Intro to MPLS. Introduction to Our work Protection and the segment ... A visualization system developed based on POLKA an algorithm animation toolkit ... – PowerPoint PPT presentation

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Title: Path Protection in MPLS Networks


1
Path Protection in MPLS Networks
  • Using Segment Based Approach

2
Overview
  • Short Intro to MPLS
  • Introduction to Our work Protection and the
    segment Based approach
  • Algorithms for QoS constraints
  • Switch Over time Algorithm
  • Greedy Approach
  • Consideration of Backup Paths
  • Conserving protection resources sharing bw
  • End-to-End delay and Jitter
  • Combining the above constraints
  • Reliability
  • Visualization System
  • Experimental Results
  • Conclusion and work done

3
Introduction to MPLS
1
47.1
3
3
1
2
1
2
47.3
3
47.2
2
4
Label Switched Path (LSP)
1
47.1
3
3
1
2
1
2
47.3
3
47.2
2
5
MPLS ROUTE AT EDGE, SWITCH IN CORE
IP
IP
IP Forwarding
IP Forwarding
LABEL SWITCHING
  • Applies concept of VC routing
  • Packet forwarding is done based on Label
    Switching
  • FEC Destination address prefix, Traffic
    Engineering tunnel, Class of Service.

6
Introduction to Path Protection
1
47.1
3
3
1
2
1
2
47.3
3
47.2
2
7
Introduction to Path Protection
1
47.1
3
3
1
2
1
2
47.3
3
47.2
2
8
Requirements of Path Protection
  • Should Reroute the traffic satisfying certain QoS
    constraints
  • Should aim to conserve the amount of protection
    resources reserved

9
Global Path Protection
Backup Path
10
Local Path Protection
11
Segment Based Path Protection
  • Look at the path as a group of segments
    protect each segment separately
  • Results in fewer backup paths conserves
    resources
  • Meets QoS constraints in a tight manner
  • Gives flexibility

Issue How to segment the path ?
12
Algorithms for QoS constraints
13
QoS Constraints
  • Important parameters
  • Switch-Over Time
  • End-to-End Delay
  • Jitter
  • Reliability
  • Combination of above
  • Have to conserve protection resources

14
Bounded Switch Over Time
  • Definition of Switch Over Time

15
An expression for switch over time
  • Analysis for switch over time

RTT( Ri , Rj ) Ttest lt ?
16
Example for Segment Based Approach
17
Example for Segment Based Approach
Here we are able to meet the Switch Over time
constraint with 3 backup paths as compared to 7
backup paths in LPP
A simple algorithm for segmentation Greedy
Approach
18
The Resource advantage
19
Problem with Greedy Approach
Need to consider the topology of the network as
well
20
An adaptive Algorithm for segmentation
Start from the egress and look for longest
possible segment
21
End-to-End Delay
  • An important parameter

22
Analysis
Max (T ( t2 t1 ) ) lt EED Bound
23
Algorithm for end-to-end delay
  • For each backup path, we need to make sure that
    the end-to-end constraint is satisfied
  • Use shortest path approach for finding a backup
    path minimizes end-to-end delay

24
Algorithm for end-to-end delay
Searching for a backup path
25
Jitter
  • Jitter can be treated as a link property
  • Path Jitter S Link Jitter
  • Algorithm similar to end-to-end delay

26
Combination of above constraints
A combined Algorithm for
Switch Over Time End-to-End Delay Jitter
  • Approach
  • Dynamic Programming

27
Algorithm based on Dynamic Programming
Ri
Rk
Rj
Artificial Node
28
Reliability
  • An important QoS parameter in Computer Networks.
  • Path Reliability Probability of a path to be in
    a working state at some instant of time.
  • Link Reliability (p) Probability of a link to
    be in working state at some instant of time.

29
Reliability - Objectives
  • Effect of Path Protection on Reliability
  • Effect of Segment Size on Reliability
  • An O(No. of Links (No. of Segments)2 )
    Algorithm to find exact path reliability !
  • Algorithm for Finding most reliable Backup Path
  • Heuristics for SBPP with reliability bounds

30
Effect of Path Protection on Reliability
n links
B
A
  • Total number of links in primary path n
  • Reliability of a link p
  • Path Reliability from A to B pn

Path Reliability from A to B with backup path
2pn p2n
31
Effect of Path Protection on Reliability
32
Effect of Segment Size on Reliability
  • Total number of links in primary path n
  • Reliability of a link p
  • Size of Segments k
  • Number of Segments n/k
  • Size of Backup Path Size of Segment
  • Reliability of the path (2pk p2k)n/k

33
Effect of Segment Size on Reliability
34
Algorithm to find path reliability
Theoretically a path exists between ingress and
egress nodes R1 -gt R2 -gt R4 -gt R5 -gt R6 -gt
R7 No path between ingress and egress nodes in
our path switching approach !
35
Algorithm to find path reliability
36
Algorithm for Finding most reliable Backup Path
Ri
Rj
Artificial Node
37
Heuristics for SBPP with reliability bounds
  • Find the Segmentation with least number of
    segments
  • Divide any segment into two till the reliability
    bound is met

38
Visualization System
39
Visualization of Algorithms
  • A visualization system developed based on POLKA
    an algorithm animation toolkit
  • Closely Integrated with the simulator
  • Aids in understanding how the algorithms work
  • Assists in establishing correctness of algorithms
    and simulations
  • Dynamic Nature of Visualizations

40
Visualization
  • Two categories of Visualization
  • Animation for Adaptive Bounded Switch Over Time
    Algorithm
  • Rerouting of packets by SSR in case of failure
    (packet flow animation) demonstrates various
    cases

41
Topology for Visualization
42
Visualization Demo
43
Experimental Results
44
Implementation
  • Simulator developed in C for implemented some
    algorithms
  • Size of model graph 100 nodes , 1000 edges
  • RTT of each link 10 ms
  • BW 50 to 100
  • Generated large number of random LSP requests and
    observed various parameters
  • Results indicate advantages of SBPP

45
Segment Size vs BW reserved
46
Segment Size vs Rejection Rate ( for 250 LSPs )
47
No. of Requested LSPs vs Rejection Rate
48
Effect of Backup Path Sharing
49
Crossover - Effects of backup path sharing
50
Effect of additional constraint
51
Effect of additional constraint
52
Bandwidth Reserved vs Density
53
Detection and Notification
54
A Mechanism for Notification
  • After a fault is detected, notification needs to
    be sent to the SSR for switching the traffic
  • Some nodes will participate in notification and
    the SSR will switch the route
  • What information will be passed after a fault
    occurs ?
  • What changes do we need in the LSR tables for
    switching?
  • Case of Multiple LSPs All LSPs using that
    segment may not pass through the faulty node/link
    Only concerned LSPs should be switched

55
A Mechanism for Notification
56
Conclusions
  • Fault Tolerance can now be assured to satisfy
    various QoS constraints
  • Segment Based Algorithms show significant
    improvement in terms of protection resources used

57
Work Done
  • Mechanisms for Detection , Notification
  • Algorithms for various QoS constraints
  • Bounded Switch over time
  • End-to-End delay
  • Jitter
  • Combination of above
  • Reliability
  • Issues relating to backup path - sharing
  • Simulator developed for above
  • Visualization System
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