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Restoration Routing in MPLS Networks

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Background. Network Services and QoS. Architectural Requirements. IP and MPLS ... Remote collaboration (e.g., remote desktop) Many new applications are real-time ... – PowerPoint PPT presentation

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Title: Restoration Routing in MPLS Networks


1
Restoration Routing in MPLS Networks
  • Zartash Afzal Uzmi
  • Computer Science and Engineering
  • Lahore University of Management Sciences

2
Outline
  • Background
  • Network Services and QoS
  • Architectural Requirements
  • IP and MPLS
  • Introduction to restoration routing
  • Local Restoration Types of Backup Paths
  • Local Restoration Fault Models
  • Backup Bandwidth Sharing
  • Activation sets
  • Restoration routing framework
  • Components
  • Typical example
  • Evaluation and Experimentation

3
Outline
  • Background
  • Network Services and QoS
  • Architectural Requirements
  • IP and MPLS
  • Introduction to restoration routing
  • Local Restoration Types of Backup Paths
  • Local Restoration Fault Models
  • Backup Bandwidth Sharing
  • Activation sets
  • Restoration routing framework
  • Components
  • Typical example
  • Evaluation and Experimentation

4
Network Traffic and Services
  • Network Traffic today
  • Not what it was 10 years ago
  • Multimedia intensive
  • New and interactive applications are emerging
  • Internet telephony
  • Videoconferencing
  • Streaming media (voice and video)
  • Remote collaboration (e.g., remote desktop)
  • Many new applications are real-time
  • More and more users of these applications

Burstiness behavior has changed over the years!
5
Current Network Architecture
  • Internet is popular because
  • It is inexpensive
  • Internet is inexpensive because
  • It uses resource sharing
  • by means of statistical multiplexing
  • Current Internet architecture
  • Uses packet switches with buffers
  • Required buffer size is primarily determined by a
    random traffic pattern
  • Buffer size optimization
  • Too low ? High drop rate
  • Too high ? High delay

6
Architectural Requirements
  • Emerging applications
  • Two-way interactive communications
  • One-way streaming media type applications
  • Under normal conditions
  • We are worried about the two-way interactive
    applications
  • When resources fail
  • We are also worried about the one-way
    applications
  • Current Internet architecture is not suitable for
    new and emerging applications
  • New architectures are being researched

7
Architectural Requirements
  • New network architectures
  • All circuit-switched?
  • Mix of packet-switch and circuit-switch-like
  • Experience with networks
  • Bigger buffers are required when there is more
    randomness and more aggregation
  • Should use circuits at places where we see more
    randomness
  • Example 100x100 project
  • Edge network is packet-switched
  • Core network is virtual-circuits

8
IP versus MPLS
  • In IP Routing, each router makes its own routing
    and forwarding decisions
  • In MPLS
  • source router makes the routing decision
  • Intermediate routers make forwarding decisions
  • A path is computed and a virtual circuit is
    established from ingress router to egress router
  • An MPLS path or virtual circuit from source to
    destination is called an LSP (label switched path)

9
Outline
  • Background
  • Network Services and QoS
  • Architectural Requirements
  • IP and MPLS
  • Introduction to restoration routing
  • Local Restoration Types of Backup Paths
  • Local Restoration Fault Models
  • Backup Bandwidth Sharing
  • Activation sets
  • Restoration routing framework
  • Components
  • Typical example
  • Evaluation and Experimentation

10
Restoration in IP network
  • In traditional IP, what happens when a link or
    node fails?
  • Information needs to be disseminated in the
    network
  • During this time, packets may go in loops
  • Restoration latency is in the order of seconds
  • We look for restoration possibilities in an MPLS
    network

11
QoS Requirements
  • Bandwidth Guaranteed Primary Paths
  • Bandwidth Guaranteed Backup Paths
  • BW remains provisioned in case of network failure
  • Minimal Restoration Latency
  • Restoration latency is the time that elapses
    between the occurrence of a failure and the
    diversion of network traffic on a new path

Path Restoration ? More Latency Local Restoration
? Less Latency
12
Restoration in MPLS
Path Protection
S
1
2
3
D
This type of path Protection still takes 100s
of ms.
We may explore Local Protection to quickly
switch onto backup paths!
Primary Path
Backup Path
13
Local Restoration Fault Models
Link Protection
Node Protection
A
B
C
D
Element Protection
A
B
C
D
14
nhop and nnhop paths
nnhop
A
B
D
C
E
nhop
PLR Point of Local Repair
All links and all nodes are protected!
15
Opportunity cost of backup paths
  • Local Protection requires that backup paths are
    setup in advance
  • Upon failure, traffic is promptly switched onto
    preset backup paths
  • Bandwidth must be reserved for all backup paths
  • This results in a reduction in the number of
    Primary LSPs that can otherwise be placed on the
    network
  • Can we reduce the amount of backup bandwidth
    but still provide guaranteed backups?

16
BW Sharing in backup Paths
  • Example

L1
BW X
A
B
X
X
max(X, Y)
X
E
G
F
XY
Y
Y
C
D
BW Y
L2
17
Activation Sets
A
A
E
E
B
B
C
C
D
D
Activation set for node B
Activation set for link (A,B)
18
Outline
  • Background
  • Network Services and QoS
  • Architectural Requirements
  • IP and MPLS
  • Introduction to restoration routing
  • Local Restoration Types of Backup Paths
  • Local Restoration Fault Models
  • Backup Bandwidth Sharing
  • Activation sets
  • Restoration routing framework
  • Components
  • Typical example
  • Evaluation and Experimentation

19
Restoration Routing Frameworks
  • We look to answer the following questions?
  • Who computes the primary path?
  • What is the fault model (link, node, or element
    protection)?
  • Where do the backup paths originate?
  • Who computes the backup path?
  • At what point do the backup paths merge back with
    the primary path
  • What information is stored locally in the
    nodes/routers
  • What information is propagated through routing
    protocols
  • What if a primary path can not be fully protected
  • The goal is almost always to maximize bandwidth
    sharing
  • Performance criteria is almost always the maximum
    number of LSPs that can be placed on the network

20
Evaluation Experimentation
  • Traffic Generation
  • Use existing or emerging traffic models
  • Consider call holding times and multi-service
    traffic
  • Rejected Requests Experiments
  • Measure the number of rejected requests
  • Simulate on various topologies
  • Network Loading Experiments
  • Set link capacities to infinity
  • Measure the total bandwidth required to service a
    given set of requests
  • Simulate on various topologies

21
Recent Trends
  • Preemption of lower class traffic
  • Multilayer recovery
  • We can almost deal with recovery at a single
    protocol layer
  • What if we intend to provide recovery at multiple
    protocol layers?
  • For multilayer recovery, we need to consider
    these additional issues
  • Interworking of layers
  • Local information stored at each node of each
    layer
  • Recovery provided by each individual layer
  • Signaling mechanism from one layer to another
  • Effects on bandwidth sharing (if sharing is used)

22
  • Thank You!
  • Questions Answers

23
  • Extra Stuff!

24
Extent of BW Sharing oAIS
More Information propagated ? More potential for
BW sharing
  • Aggregate Information Scenario (AIS)
  • Fij Bandwidth reserved on link (i, j) for all
    primary LSPs
  • Gij Bandwidth reserved on link (i, j) for all
    backup LSPs
  • Optimized AIS (oAIS) (Hij instead of Fij)
  • Hij Maximum bandwidth reserved on any one link
    by all backup paths spanning link (i, j)

25
oAIS versus AIS Example
  • LSP Request-1 (src, dst, bw) (A, C, 4)

D
E
F
GAF4
FAB4
A
B
C
HAB4
G
26
oAIS Example
LSP Request-2 (src, dst, bw) (A, C, 5)
D
E
F
GAF4
FAB9
FAB4
A
B
C
HAB5
HAB4
GAG5
G
27
oAIS Example
LSP Request-3 (src, dst, bw) (D, E, 7)
FDE7
D
E
F
GAF4
GAF7
FAB9
A
B
C
HAB5
GAG5
G
28
oAIS Example
LSP Request-4 (src, dst, bw) (A, C, 6)
Need to Evaluate cost of all possible backup
paths?
FDE7
How much BW is shareable on (A, F)?
D
E
AIS Shareable max(0, GAF - FAB)
GAF - min(GAF, FAB) 0 Additional resv 6
F
GAF7
oAIS (HAB FAB) Shareable GAF - min(GAF, HAB)
2 Additional resv 6 - 2 4
FAB9
A
B
C
HAB5
CIS (link (A,B) knows BWred) Shareable GAF -
BWred 7 - 4 3 Additional resv 6 - 3 3
GAG5
G
29
Single Link Protection Network 1
30
Single Link Protection Network 1
31
Single Link Protection Network 2
32
Single Link Protection Network 2
33
Single Node Protection Network 1
34
Single Element Protection Network 1
35
A Bandwidth Sharing Model
(Simplified for the Link Protection Fault
Model) Recall the definition of nhop paths
Link Protection
All links and all nodes are protected!
36
Bandwidth Sharing Model
  • Previous
  • Aij Set of all primaries traversing through (i,
    j)
  • Buv Set of all backups traversing through (u,
    v)
  • New definition (specialized for link protection
    case)
  • Aij Set of all primaries traversing through (i,
    j)
  • Buv Set of all nhop paths traversing through
    (u, v)
  • µij Set of all nhop paths that span (i, j)
  • ?ijuv Buv n µij (set of paths falling on (u,v)
    if (i,j) fails)

37
Bandwidth Sharing Model
RED7 BLU2
u
v
GRN3 (New Request) Guv 10
3
k
i
j
NEW MODEL Aij R, B Buv nhijr, nhijb,
(nhops through (u, v)) µij nhijr, nhijb,
(nhops spanning (i, j)) ?ijuv µij n Buv
nhijr, nhijb ?ijuv 2 7
9 (Un-shareable) Shareable Guv - ?ijuv
10 - 9 1
OLD MODEL Aij R, B Buv R, B, Aij n
Buv R, B Aij n Buv 27
9 Un-shareable 9 Shareable 10 - 9 1
38
Bandwidth Sharing Model
RED7 BLU2
u
v
GRN3 (New Request) Guv 10
3
k
i
j
OLD MODEL Aij R, B Buv R, B, Aij n
Buv R, B Aij n Buv 27
9 Un-shareable 9 Shareable 10 - 9 1
NEW MODEL Aij R, B Buv nhijr, nhjkb,
(nhops through (u, v)) µij nhijr, nhijb,
(nhops spanning (i, j)) ?ijuv µij n Buv
nhijr ?ijuv 7 (Un-shareable) Shareable
Guv - ?ijuv 10 - 7 3
39
Restoration in MPLS
Path Protection
A
B
C
D
E
MPLS path Protection may take 100s of ms, whereas
MPLS Local protection takes less than 10 ms.
Primary Path
Backup Path
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