Jan 13, 2006 Lahore University of Management Sciences 1 Protection Routing in an MPLS Network using Bandwidth Sharing with Primary Paths Zartash Afzal Uzmi Computer Science and Engineering Lahore University of Management Sciences (LUMS) Visiting Professor – Chonbuk National University
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Protection Routing in an MPLS Network using Bandwidth Sharing with Primary Paths
Protection Routing in an MPLS Network using Bandwidth Sharing with Primary Paths. Zartash Afzal Uzmi Computer Science and Engineering Lahore University of Management Sciences (LUMS) Visiting Professor – Chonbuk National University. Outline. Background Network Services and QoS Requirements - PowerPoint PPT Presentation
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Jan 13, 2006 Lahore University of Management Sciences 1
Protection Routing in an MPLS Network
usingBandwidth Sharing with Primary
Paths
Zartash Afzal UzmiComputer Science and Engineering
Lahore University of Management Sciences (LUMS)
Visiting Professor – Chonbuk National University
Jan 13, 2006 Lahore University of Management Sciences 2
Outline Background
Network Services and QoS Requirements Protection Routing in MPLS Backup Bandwidth Sharing Sharing with Primary Paths
Simulation Results Evaluation and Experimentation Simulation Parameters Comparative Results
Jan 13, 2006 Lahore University of Management Sciences 4
IP versus MPLS
In IP Routing, each router makes its own routing and forwarding decisions
In MPLS: Only one router (source) 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)
Jan 13, 2006 Lahore University of Management Sciences 5
Bandwidth Guaranteed Backup Paths BW remains provisioned in case of network failure
Minimal “Recovery Latency” Recovery latency is the time that elapses between:
“the occurrence of a failure”, and “the diversion of network traffic on a new path”
Preset backup paths needed for minimal latency
Jan 13, 2006 Lahore University of Management Sciences 6
Types of Backup Paths
Primary PathBackup Path
All links and all nodes are protected!
A B C D E
PLRPLR: Point of Local Repair: Point of Local Repair
nnhop
nhop
LOCAL PROTECTION (showing one LSP only)
Jan 13, 2006 Lahore University of Management Sciences 7
Opportunity cost of backup paths
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?
YES: Try to share the bandwidth along backup paths
Jan 13, 2006 Lahore University of Management Sciences 8
BW Sharing in backup Paths
Example:
max(X, Y)
BW: Y
A B
C D
E F G
LSP1LSP1
LSP2LSP2
BW: XBW: X
Primary PathBackup Path
XX XXXX
YY YYX+Y
Sharing is possible
IF
Links (A,B) and (C,D) do not simultaneously fail!
Jan 13, 2006 Lahore University of Management Sciences 9
Sharing with Primary Paths
Can we do any sharing with primary paths? Normally, the answer is NO because… Traffic is always flowing on the primary paths BUT…
Backup paths protecting a node N may share bandwidth with primary paths that originate or terminate at node N because… Such backup will be active when:
node N fails, and in that condition… No primary originates or terminates at node N
Sharing with (some) primary paths is possible
Jan 13, 2006 Lahore University of Management Sciences 10
Outline Background
Network Services and QoS Requirements Protection Routing in MPLS Backup Bandwidth Sharing Sharing with Primary Paths
Jan 13, 2006 Lahore University of Management Sciences 12
1.Scalable routing overhead
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 Rij: Bandwidth remaining on link (i, j)
Extended NPP (NPP++) relies on AIS Low routing overhead
More Information propagated More potential for BW sharing
Jan 13, 2006 Lahore University of Management Sciences 13
2.Optimal backup paths Backup path computation is moved to a node that has
maximal information about the activation set of protected element
Node that computes backup paths maintains two local maps: BFTLIM
How much backup bandwidth will fall on a given link (u,v) if this element fails
PFTLIM How much primary bandwidth will be available on a given link
(u,v) if this element fails FTLIMs keep historical information about bandwidth
reserved for protecting an element Leads to the computation of backup paths that are optimal
Jan 13, 2006 Lahore University of Management Sciences 14
Path Computation in NPP++
R1
R2
R3
R4
R5
The backup paths protecting The backup paths protecting against the failure of R2 against the failure of R2 cannot share bandwidth on cannot share bandwidth on any link.any link.
R2 Contains:R2 Contains:
a) BFTLIMa) BFTLIM
b) PFTLIMb) PFTLIM
Path computation is shifted to R2 because…Path computation is shifted to R2 because…
Only R2 has full knowledge of its own Activation setOnly R2 has full knowledge of its own Activation set
But such backup paths But such backup paths may share bandwidth may share bandwidth with primary paths with primary paths originating or originating or terminating at R2.terminating at R2.
Jan 13, 2006 Lahore University of Management Sciences 15
3.Maximum Bandwidth Sharing Optimal path is signaled with requirements
for FULL bandwidth All nodes (along the backup path) maintain
two local data structures: BLTFIM
How much backup bandwidth will fall on this link if a given element fails
PLTFIM How much primary bandwidth will be released on
this link if a given element fails LTFIMs help nodes reserve only what is
needed Leading to maximum sharing along backup paths
Jan 13, 2006 Lahore University of Management Sciences 16
NPP++ Summary
Primary PathBackup Path
R1
R2
R3
R4
(2) Path computation is shifted to special (2) Path computation is shifted to special nodesnodes(3) Nodes in primary path maintain “local data (3) Nodes in primary path maintain “local data structures” called BFTLIM/PFTLIMstructures” called BFTLIM/PFTLIM
(4) Nodes in backup paths maintain “local data (4) Nodes in backup paths maintain “local data structures” called BLTFIM/PLTFIMstructures” called BLTFIM/PLTFIM
(1) Advertise aggregate link usage information (1) Advertise aggregate link usage information onlyonly
Results:Results:
•Path computation is Path computation is optimaloptimal
•Bandwidth sharing on backup paths is Bandwidth sharing on backup paths is maximummaximum..
•Advertisement overhead is minimumAdvertisement overhead is minimum
FTLIMsFTLIMs
LTFIMsLTFIMsFTLIMsFTLIMs
FTLIMsFTLIMs
LTFIMsLTFIMs
LTFIMsLTFIMs
Protecting R2
Jan 13, 2006 Lahore University of Management Sciences 17
Outline Background
Network Services and QoS Requirements Protection Routing in MPLS Backup Bandwidth Sharing Sharing with Primary Paths