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RSVP-TE Extensions forLSP Rerouting in NS2
D. Adami, C. Callegari, S. Giordano, M. PaganoDepartment of Information Engineering - University of Pisa
6-7 December 2007IST Congress Center, Lisbon, Portugal
Workshop on IP QoS and Traffic Control
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Outline
• Introduction
• MPLS-based Recovery
• RSVP-TE Reservation Styles
• NS2 Software Modules
• Simulations Results
• Conclusions
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Introduction
• Multiprotocol Label Switching (MPLS) provides:Traffic Engineering capabilitiesVirtual Private Networks supportNetwork Survivability
172.16.0.0/16
In Lab-
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Address Prefix
172.16...
OutI/F1...
Out Lab30...
In I/F3...
In Lab40...
Address Prefix
172.16...
OutI/F1...
Out Lab-
...
In I/F3...
LSRCLSRC
LSR BLSR B
LSR ALSR Adata172.16.1.230
data172.16.1.240
data172.16.1.2
data172.16.1.2172.58.0.0/16
Transit LSRTransit LSR (Label swapping)(Label swapping)In
Lab30...
Address Prefix
172.16...
OutI/F1...
Out Lab40...
In I/F3...
Ingress LSR Ingress LSR (Label pushing)(Label pushing)Egress LSREgress LSR (Label popping)(Label popping)
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R8R1
R2
R3
R4
R5LSR8
R7 R6
IP Routing
R9
ShortestPath
High Convergence Time!
IssuesIssuesHighly reliable services require very low recovery times (tenths of ms)IP routing does not assure QoS recovery
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IngressLER
Working LSP
Backup Path
EgressLERLSR1
LSR2
LSR3
LSR4
LSR5LSR8
LSR7 LSR6
MPLS Recovery: Path Protection
MPLS-based Recovery aims at reducing the recovery timeswhen a failure occurs and dynamic routing protocols are used!
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MPLS Recovery: Path Restoration
IngressLER
EgressLERLSR1
LSR2
LSR3
LSR4
LSR5LSR8
LSR7 LSR6
Working LSP
Backup Path
MPLSMPLS--basedbased RecoveryRecovery ObjectivesObjectivesOptimal use of network resourcesTraffic protection with different granularityMinimization of unprotected traffic degradation
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The Recovery Cycle
IngressLER
EgressLERLSR1
LSR2
LSR3
LSR4
LSR5LSR8
LSR7 LSR6
PathTear
PathErr
Path
Resv
PathTraffic
Recovered
RecoveryOperationComplete
Start ofRecoveryOperation
Start ofNotification
FaultDetected
NetworkImpairment
Fault Detection Fault Detection TimeTime
Fault Fault HoldHold--offoffTimeTime
TrafficTraffic RecoveryRecoveryTimeTime
Fault Fault NotificationNotificationTimeTime
RecoveryRecoveryOperationOperation
TimeTime
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RSVP-TE Reservation Styles
Wildcard-Filter(WF) style
Wildcard Sender Selection
Shared-Explicit(SE) style
Fixed-Filter(FF) style
Explicit Sender Selection
Shared ReservationDistinct Reservation
• A reservation style indicates whether senders in the RSVP session have distinct or shared resource reservation and whether they are selected according to an explicit list
• RSVP defines three different Reservation Styles– the FF style creates a distinct reservation for each sender– the SE style allows a receiver to make a single reservation shared by a set of
senders explicitly specified in the reservation message– the WF style creates a single reservation that is shared by all senders in the
session
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RSVP-TE Reservation Styles: Application Scenario
(1,50)(2,100)
(1,100)
(1,100)
(1,50)
(5,100)
(2,100)
(1,100)
(1,50)
A
B C
D E
FLSP (A_B_C_F)
40 Mbps
Bandwidth70 Mbps
New PathA_D_B_C_F
Without SE Reservation Style, it isnecessary to tear down the old LSP and
to set-up a new LSP
(Metric, Bandwidth)
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Motivations and targets
• Since planning MPLS-based recovery strategies involves trade-offs based on several factors
End-user applications requirementsNetwork efficiencyComplexityRevenues
our goal was to develop a powerful and flexible simulation tool to help network designers and administrators in their work
• An MPLS Network Simulator (MNS) was available for the Network Simulator 2 (NS2)
developed at Chungnam National University, Koreabased on the Constrained Routing – Label Distribution Protocol (CR-LDP)
but…a full open-source MPLS networks simulation tool had not been realized yet!!
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NS2 Software Modules
MNS - MPLS Network SimulatorOld Modules
New Modules
RSVP-TE\ns with Reservation Styles
OSPF-TE\ns
MPLS Recovery Strategies
QoS Routing
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New MPLS Node Architecture in NS2
OSPF-TE module
OSPF-TE module
RSVP-TE module
RSVP-TE module
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LSP Recovery in NS2
• LSP Protection<Ingress-LSR> protection-ff <Source> <Egress> <Dest> <OldSID> <SessionID> <FlowID> <TunnelID> <Rate> <Buffer> <Er>
<Ingress-LSR> protection-se <Source> <Egress> <Dest> <OldSID> <SessionID> <FlowID> <TunnelID> <Rate> <Buffer> <Er>
• LSP Rerouting with Path Precomputation<Ingress-LSR> fastrerouting-ff <Source> <Egress> <Dest> <OldSID> <FlowID> <TunnelID> <Rate> <Buffer> <Er>
<Ingress-LSR> fastrerouting-se <Source> <Egress> <Dest> <OldSID> <FlowID> <TunnelID> <Rate> <Buffer> <Er>
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Simulation Scenario
GÉANT
• Pan-European multi-gigabitdata communications network specifically reserved forresearch and education use
• The GÉANT project was a collaboration between 26 National Research and Education Networksrepresenting 30 countries
• The network connects a total of 34 countries
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Simulation Scenario
Simulation Scenario
• Available Bandwidth = 1 Mb/s• CBR Sources at 400 Kb/s• Link cost = 1
• A failure on the link 7_22 of the primary LSP is forced
• Fault Hold-off Time = 0
TargetTarget
• To highlight the advantages of using SE Reservation Styles
CBR TrafficDestination
CBR TrafficSource
PrimaryPrimaryLSPsLSPs
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LSP Rerouting with FF Reservation StyleDestinations
CBR TrafficSources
ReservedLSP
Back-Up LSPs
PRIMARY LSPs
IP Shortest Path
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Recovery Time for FF Reservation Style
620
640
660
680
700
720
740
760
780
1 2 3 4 5 6 7 8 9 10
Simulation
ms
LSP 1 LSP 2
Link status is checked by a polling mechanism, simulated as a randomvariable uniformely distributed within [0, 100 ms]
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LSP Rerouting with SE Reservation StyleDestinations
CBR TrafficSources
ReservedLSP
Back-Up LSP
PRIMARY LSP
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0
20
40
60
80
100
120
140
160
180
1 2 3 4 5 6 7 8 9 10
Simulation
ms
Recovery Time for SE Reservation Style
Avg. Recovery Time: 126 ms vs. 736 ms
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Conclusions
• Design and development of a new NS2 software module which enhances RSVP-TE\ns with the reservation styles supported by RSVP-TE
• The availability of reservation styles allows MPLS network designers to plan complex scenarios with heterogeneous recovery strategies
• The new NS2 module may help a network designer to choose the most suitable MPLS-based recovery strategy
• Reservation styles are also essential to set-up Point-to-Multipoint and Multipoint-to-Multipoint LSPs
• The software is available on the TlcNetGroup software repository at the site:
http://netgroup-serv.iet.unipi.it