Reliability Issues in IP over WDM Networks€¦ · Several Views for IP over WDM Networks SONET ATM...
Transcript of Reliability Issues in IP over WDM Networks€¦ · Several Views for IP over WDM Networks SONET ATM...
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Reliability Issues inReliability Issues inIP over WDM NetworksIP over WDM Networks
Masayuki MurataGraduate School of Engineering ScienceOsaka Universitye-mail: [email protected]://www-ana.ics.es.osaka-u.ac.jp/~murata/
M. Murata 2
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Past Researches in the AreaoRouting and Wavelength Assignment (RWA)
Problem7 Static assignment
4Optimization problem
7 Dynamic assignment4Natural extension of call routing4Call blocking is primary concern4No wavelength conversion makes the problem difficult
oOptical Packet Switches for ATM7 Fixed packets and synchronous transmission
XX
XX
XX
Optical Cross-Connect
Router
M. Murata 3
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Several Views for IP over WDM Networks
SONETATM
WDM
IP
oIP over ATM over SONET over WDMoIP over SONET over WDMoIP over (PPP or HDLC) over WDM
M. Murata 4
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
oFour Kinds of Architecture1. WDM link network
4Connects adjacent routers by WDM (multiple wavelengths)
2. WDM path network 4Logical topology is built
by wavelength routing
Photonic Internet Architecture
Router
Optical Crossconnect
Router
XX
XX
XX
M. Murata 5
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
3. WDM Path Network4Lambda switching by
MPLS technology
4. WDM Packet-switched Network
4E.g., burst switching by routing and wavelength assignment on demand basis
Photonic Internet Architecture (Cont’d)
XX
XX
XX
Optical Cross-Connect
Router
XX
XX
XX
burst
M. Murata 6
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearchWavelength Router
in WDM Path Network
OpticalSwitchOpticalSwitch
ElectronicRouter
ElectronicRouter
Wavelength Demux Wavelength Mux
Wavelength Router
OpticalSwitchOpticalSwitch
λ2
λ1
λ1
λ1
λ1
λ2λ2
λ2
λ2
λ2
λ1
λ1
λ2
λ1
Local Access
M. Murata 7
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Logical Topology by Wavelength Routing
oPhysical Topology oLogical Topology
Router
WDM Node
Wavelength
λ2 λ2λ1 λ1λ2
λ1
N3N2
N4N1
N5
λ2 λ2λ1 λ1λ2
λ1
N3N2
N4N1
N5λ1
M. Murata 8
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Logical View provided to IP
oRedundant Network with Large Degrees
åSmaller number of hop-counts between end-nodes
åDecrease load for packet forwarding at the router
åRelief bottleneck at the router
λ2λ1 λ1
λ1
λ1
λ2
N 3N2
N 4N1
N5
M. Murata 9
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
How should IP over WDM be Established?
oWDM network itself has network control capabilities7 Routing function
4IP also has it!7 Congestion control function
4TCP also has it!4TCP over ATM (ABR service class) is difficult to work well
Parameter tuning of control parameters in ABR is not easy7 Connection establishment
4IP is connectionless4Multimedia application does not require 10Gbps channel
å Functional partitioning vs. Multi-layered Functionalities?
o Important is reliability
M. Murata 10
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Functional Partitioning between IP and WDM?
oReliability functionalities offered by two layers7 IP Layer: Routing7 WDM Layer: Path Protection and Restoration
oWDM should provide its high-reliability mechanism to IP7 Protection mechanism
4link protection4dedicated-path protection4shared-path protection
7 Network dimensioning is important to properly acquire the required capacity of IP paths (traffic glooming)
4Reconfiguration mechanism of logical topology by wavelength routing
M. Murata 11
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
WDM Protectiono Immediately switch to backup path on failure of nodes/links
7 In the order of 10mso 1:1 Protection vs. Many:1 Protection
o Protection technique suitable to IP over WDM network?7 IP has its own protection mechanism (i.e., routing) while it
is slow7 We want an effective usage of wavelengths7 Many:1 protection is reasonable
1:1 Protection
Primary Path
Backup Path
Many:1 Protection
Primary Path
M. Murata 12
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearchFormulation of Reliability Design
Problem for Many-to-1 Path Protection
oObjective7 Minimize the utilized wavelengths in total
oGiven Conditions7 The number of wavelengths on the fiber7 Physical topology and logical topology7 Primary routes
oApplication to 5-node network
N0
N3
N2N1
N4
N0
N3
N2N1
N4
Sharing of wavelengths
M. Murata 13
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Application to Large-Scaled Network
oPrevious formulation is MILP (Mixed Integer Linear Problem); difficult to be applied to the large-scaled network
oMin-hop-first approach7 It is rare that lightpaths with a small number of hop counts
contend the backup lightpaths7 First protect the lightpaths with small hop-counts, and
then protect lightpaths with large hop-counts using the remaining wavelengths
oLargest-traffic-first approach7 Assign the paths in a descending order of the traffic loads
oRandom approach7 For only reference purpose
M. Murata 14
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Network Model
oNSFNET; 7 14 node7 20 physical links
oLogical topology is first determined by MLDA7 First set up the lightpaths
between adjacent nodes7 Set up the lightpaths for the
path in a descending order of traffic volume NSFNET
M. Murata 15
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Effect of Min-Hop-First Approach
oThe required number of wavelengths to protect all lighpaths with 7 Random-selection
method?7 Traffic-large-first
method?7 Min-hop-first method?
0
5
10
15
20
25
30
0 2 4 6 8 10 12 14
requ
ired
# o
f wav
elen
gths
# of primary wavelengths
min-hop-firsttraffic -first
random
M. Murata 16
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearchEffect of Min-Hop-First Approach
(Cont’d)
oFix the wavelength on the fiber to be 16oChange the number of wavelengths dedicated to
primary lightpaths to compare the number of protected lightpaths
0
0.2
0.4
0.6
0.8
1
2 4 6 8 10 12 14
perc
enta
ge o
f pro
tect
ed li
ghtp
ath
# of backup wavelengths
min-hop-firsttraffic -large-first
random
10
20
30
40
50
60
70
80
90
2 4 6 8 10 12 14
# o
f pro
tect
ed li
ghtp
ath
# of backup wavelengths
min-hop-firsttraffic -large-first
random
M. Murata 17
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Effect on IP Routerso A increased amount of traffic load at the IP router after the
failure?7 We choose the largest traffic increase among all possible cases
for failureso Primary wavelengths; 12, Backup wavelengths; 4o Largest-traffic -first approach can decrease the traffic
handled by the IP router[Mpps]
0
0 . 5
1
1 . 5
2
2 . 5
3
3 . 5
4
4 . 5
5
N 0 N 1 N 2 N 3 N 4 N 5 N 6 N 7 N 8 N 9 N 1 0 N 1 1 N 1 2 N 1 3
R a n d o m
M i n - h o p
L a r g e s t - t r a f f i c
M. Murata 18
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Functional Partitioning in IP over WDMo Total volume of the traffic protected/non-protected by
backup lightpaths before routing table upgradeo Sum of total traffic volume for each fiber failure scenarioo Largest-traffic -first approach provides better performance
7 Lots of traffic is protected by a lower number of backup wavelengths
0
50
100
150
200
250
300
2 4 6 8 10 12 14 16
Traf
fic V
olum
e [
Mpp
s]
# of primary wavelengths
largest-trafficmin-hop
random-restoration
50
100
150
200
250
300
350
2 4 6 8 10 12 14 16
Traf
fic V
olum
e [
Mpp
s]
# of primary wavelengths
largest-trafficmin-hoprandom
M. Murata 19
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Effect of IP Routing Table Updateo traffic volume of non-protected lightpath before/afterbefore/after routing table
upgrade o Largest-traffic-first approach also provides good performanceo Traffic volume increase after routing tables are updated
7 Another path is selected after update
0
50
100
150
200
250
300
2 4 6 8 10 12 14 16
Traf
fic V
olum
e [
Mpp
s]
# of primary wavelengths
largest-trafficmin-hop
random-restoration
before upgrade
0
50
100
150
200
250
300
2 4 6 8 10 12 14 16
Traf
fic V
olum
e [
Mpp
s]
# of primary wavelengths
largest-trafficmin-hoprandom
after upgrade
M. Murata 20
AdvancedNetworkArchitectureResearch
AdvancedNetworkArchitectureResearch
Concluding RemarksoWDM Protection is useful to increase
reliability of IP over WDM networksoA cost effective way must exist by
partially protecting lightpaths by WDM protection
oSeveral backup paths (8/182) are not used IP after IP updates its routing table.