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“ Rate and distance fairness in OBS networks ”
Tananun Orawiwattanakul, Yusheng Ji
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Topics
• Optical Burst Switching (OBS) Networks
• Rate and Distance Fairness Preemption (RDFP)
• Simulation results
• Future works
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First OBS commercial product (2006)
Matisse Networks' EtherBurst™ is the world's first optical burst switch, purpose-build for scaling metro and campus networks from 10 to 640 gigabits-per-second (Gbps).
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Optical Burst Switching (OBS)
OEO
OOO
OEO
OOO
OEO
OOOData Burst (DB)
BCP
Offset = T Offset = T-D Offset = T-2D
Ingress edge
switch
Egress edge
switch
IP/ATM/GbE IP/ATM/GbE
OBS core network
Control channel
Data channelBurst
AssemblyBurst
De-assembly
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DB4
Data ChannelsDB1
DB3
DB2
Time
Control Channels
C1 C2
C3
C4
T1 T2 T3 T4 T5
Offset Time1
Offset Time4
Offset Time1
Offset Time3
Offset Time2
C5DB5
Offset Time5
No Buffer -> High LossesVoid ->Network cannot be fully utilized
Challenge of OBS
DB
C
Data Burst
Burst Control Packet
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Rate Fairness
E1E1
C1C1
E2E2
Flow1 – 8 Gbps
Flow2 – 4 Gbps
E3E310 Gbps
‘Rate fairness’ refers to the fair bandwidth allocation (FBA) for each connection according to its offered rate and available bandwidth in the network.
The fair rate of flow 1 and flow 2 is 5 Gbps. It’s NOT FAIR!!! for me.
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Distance fairness
S4 S5S3
S1 S6
S7 S8S2
Path of Flow 1
Path of Flow 2
‘Distance fairness’ refers to the fair performance in terms of loss which respects to hop counts between the source and destination.
The loss probability of long-path flow tends to be higher than that of short path flow.It’s NOT FAIR!!! for me.
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Rate and Distance Fairness Preemption (RDFP)
Provide both “Rate and Distance fairness” in OBS networks.
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Rate and Distance Fairness Preemption (RDFP)
1. Allocate bandwidth to each flow according to the max-min fairness.
2. If any of the connections send the input traffic higher than their optimum fairly allocated bandwidth, the RDFP scheme can protect and prevent well-behaved connections from being degraded by misbehavior of other flows (rate fairness).
3. In the meantime, RDFP also balances the loss probability of bursts with different number of hops between the source and destination (distance fairness) for transmitted traffic amounts under the max-min rate.
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IngressEdge Switch
EgressEdge Switch
Core Switch 1
Core Switch 2
Core Switch N
Flow id
OriginalArrival Rate
Optimal Fairly
Allocated Bandwidth
i Ai Ti
RDFP: Control Plane
FBCP FBCPAi
BBCPBBCPTi
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Rate Fairness Preemption (RFP)
RDFP: Burst Marking
Time
Input RateIngress
Edge Switch
Flow id
OriginalArrival Rate
Optimal Fairly
Allocated Bandwidth
i Ai Ti
when Ai ≤ Ti, all bursts are marked as “Under-rate bursts (HIGH PRIORITY)”
Ti
Ai
Under-rate bursts (HIGH PRIORITY)
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Rate Fairness Preemption (RFP)
RDFP: Burst Marking
Time
Input RateIngress
Edge Switch
Flow id
OriginalArrival Rate
Optimal Fairly
Allocated Bandwidth
i Ai Ti
Ti
Ai
when Ai > Ti bursts are marked as
“Over-rate bursts (LOW PRIORITY)” with probability Pi-O = (Ai – Ti)/ Ai“Unver-rate bursts (HIGH PRIORITY)” with probability Pi-U = 1- Pi-O
Over-rate bursts (LOW PRIORITY)
Under-rate bursts (HIGH PRIORITY)
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When contention occurs in core networks, the “Under-rate (HIGH PRIORITY)” bursts can preempt an original scheduled channel
from “Over-rate (LOW PRIORITY)” bursts with different flow ids.
DB4
Data ChannelsDB3
DB2
Time
Control Channels
C2
C3
C4
T2 T3 T4 T5
Offset Time1
Offset Time1
Offset Time1
C5DB5
Offset Time5 Under-rate Burst
DB5DB1
C1
T1
Offset Time1
Over-rate Burst
RDFP: Rate fairness preemption policy
If no original scheduled over-rate burst -> determine the DISTANCE FAIRNESS preemption policy.
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When contention occurs in core networks, the “Under-rate (HIGH PRIORITY)” bursts can preempt an original scheduled
channel from bursts with lower of I.
DB4
Data ChannelsDB3
DB2
Time
Control Channels
C2
C3
C4
T2 T3 T4 T5
Offset Time1
Offset Time1
Offset Time1
C5DB5
Offset Time5 Under-rate Burst
DB5DB1
C1
T1
Offset Time1
Under-rate Burst with Lower I
RDFP: Distance fairness preemption policy
I = No of sucessful hops – Weight * (No. of remaining hops)
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Simulation networks
CoreSwitch 1
CoreSwitch 1
CoreSwitch 2
CoreSwitch 2
CoreSwitch 3
CoreSwitch 3
CoreSwitch 4
CoreSwitch 4
CoreSwitch 5
CoreSwitch 5
CoreSwitch 6
CoreSwitch 6
CoreSwitch 7
CoreSwitch 7 Edge
Switch 2Edge
Switch 2
EdgeSwitch 3
EdgeSwitch 3
EdgeSwitch 4
EdgeSwitch 4
EdgeSwitch 5
EdgeSwitch 5
EdgeSwitch 6
EdgeSwitch 6
EdgeSwitch 7
EdgeSwitch 7
EdgeSwitch 1
EdgeSwitch 1
The network consists of 42 flows: 3-hop flows = 14 flows, 4-hop flows = 14 flows, and 5-hop flows = 15 flows.
No. of data wavelength = 16
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RDFP: simulation results
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.05 0.06 0.07 0.08
The normalized sending rate of each 5-hop flow
Bur
st lo
ss p
roba
bilit
y 3-HOP4-HOP5-HOP
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.05 0.06 0.07 0.08The normalized sending rate of each 5-hop flow
Bu
rst
loss
pro
bab
ility 3-HOP
4-HOP5-HOP
Normalized rate 1 = 16 Gbps.
Input rate of each 3-hop and 4-hop flow = 0.05.
Input rate of each 5-hop = 0.05-0.08.
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Future works
• Extensively study the performance of TCP in RDFP-OBS based network.
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Q & A
Thank you