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1
OpMiGua, a Circuit/packet hybrid optical network enabling absolute service guarantees and high throughput
Steinar Bjørnstad Norwegian University of Science and
Technology (NTNU) Institute of Telematics
OpMiGua homepage: www.opmigua.com
2
Challenge: Migration from circuitto packet networks• Candidate: Optical packet/circuit hybrid
networks that brings together the best from two worlds– QoS and cost efficiency
3
Outline• Background• Motivation• QoS demands in broadcast and mobile networks• Introduction to the OpMiGua hybrid principle• Node and network architecture• Performance simulations• Experimental results• Further work• Summary
4
OpMiGua
• Optical Packet Switched Migration capable Network with Guaranteed service– Project proposed by S. Bjørnstad 2003, ended 2006
• Explore the packet/circuit hybrid network• Funded by Norwegian research council• Participants
– Telenor, Norwegian Univ. Science and Technology, Network Electronics
• Homepage: www.opmigua.com
5
Motivation• Network capacity needs increases• Packet based transport replaces circuit based
transport– Not straight forward: Added latency, jitter– Potentially higher power consumption and cost.
• Desire for a converged network serving multiple services – Telephony, file transfer, IP-TV, TV-broadcast,….
• Converged network requirements– Efficiency of packet switching (statistical multiplexing)– QoS of circuit switching (high reliability and performance)
6
TV-broadcast network structure
Distributionnetwork
Operator distributionnetwork
Distributionnetwork
Head-End
Distributionnetwork
Head-End
Head-End
Broadcastercontributionnetwork
7
QoS demands in TV-broadcasting• Contribution
– Between production facilities– A single packet loss affects all viewers– Packet loss or any type of interruption should not occur
• Primary distribution– From broadcaster to TV-transmitters or IP-TV head-ends– Information loss affects all viewers in a segment
• Secondary distribution– From IP-TV head-end or TV-transmitter to the individual viewers. – Information loss typically affects a high number of viewers
8
Broadcast performance requirements• Viewers call customer support when artifacts occur in
the picture– Especially during films and sports events like e.g. Olympic games– Expensive!– PLR demand < 10-8
• Pictures must not be skipped or repeated at receiver side– Synchronization between transmitter and receiver needed– Difficult in asynchronous IP-networks, GPS needed
9
Mobile backhaul QoS requirements
• Migration from circuit (PDH) to packet (Ethernet)– Mobile data-traffic drives the demand
• Voice traffic demands low packet loss and low delay• Handover between base-stations demands predictive
delays and synchronization– Low or no delay jitter, alternatively GPS
10
The OpMiGua hybrid network• Packet based transport but circuit/packet switched• ORION (Ghent univ. and part of STOLAS proj.)
Related principle and project• Time multiplexed packet and circuit switched network
– Some packets follow wavelength paths (circuits) – Some packets are switched by packet switches
• Packets are tagged to decide: Wavelength path or packet switching– OpMiGua uses polarizations state as tag
11
GST lightpath from A→D
A DCB
D
D
D
D
Pure Circuit switched system
Incoming GST packets destined for node D
- Traffic is routed according to circuit e.g. wavelength → minimal delay ☺- Traffic to different destinations must use different circuits or wavelengths
– Ensures no collisions between the two traffic streams ☺
– Requires one wavelength per stream
–Streams may e.g. be one circuit and one packet: Classic hybrid
C
C
C
C
12
Pure packet switched system
Ingr
ess
queu
e
Ingr
ess
queu
e
Ingr
ess
queu
e
Egr
ess
queu
e
Egr
ess
queu
e
Egr
ess
queu
e
Transit queue Transit queueTransit queue
A B C
•Single circuit (may be several wavelengths) for transmission•All packets are processed electronically: Header address lookup, queuing, forwarding•Packets from Ingress queue and Transit queue are statistically multiplexed
13
Pure packet switched system
A B C
•Packets from A and B are destined to C•Different streams have different color•Interleaving of simultaneously arriving packets gives variable packet delays
C
C
C C
C
14
Pure packet switched system
A B C
•Packets from A and B are destined to C•Different streams have different color•Interleaving of simultaneously arriving packets gives variable packet delays
CCCCC
C
15
Pure packet switched system
A B C
•New arrivals at B destined for C•Transmit queue is full => packet drop in ingress node B !
CCCCC C
C
C
C
C
16
Pure packet switched system
•Packets arrive reordered at output •Packets may be dropped •Efficient utilization of transmission wavelength ☺
C
C
C
CC CC
C
C
C
A B C
17
DB
GST lightpath from A→D
Underutilized circuit (wavelength)
Incoming GST packets destined for node D
Transit traffic is not being processed in B and C
Time between packets is unused
– Pure WDM system (circuit) gives low channel utilization
– For 270 Mb/s video on a 1 Gbps, 70 % of capacity is wasted
OpMiGua switch will insert lower quality (Internet) traffic in voids
B
C
C
Packet Switch
D
Input Queue Output Queue
A C
D
CD
D
D
C
18
Two basic QoS classes
• Guaranteed Service Class (GST)– No logical packet loss, fixed delay, no packet jitter– Fixed delay allows synchronous transfer if desirable– Suitable for broadcast-TV and mobile backhaul
• Statistical Multiplexed (SM)– Statistical multiplexed packet switched– Suitable for less demanding services, e.g. file transfer
19
OpMiGua network nodes• Packets are detected at input SM or GST• SM packets are only scheduled if no GST packet is
detected at input. – A delay through the node ensures that preemption of packets at the
output does not occur.
DelayGST λ1
Sense SM add
Delay
SM drop/GST sense SM add
DelayGST λ2
SM drop
GST λ2
GST λ1
Ingress node Core node Egress node
Aggregation interfaces Aggregation interfaces
20
Node architecture• Optical cross connect• Optical or electronic packet switch• SM packet scheduling always finishes
– GST packets delayed in FDL corresponding to SM MTU
Packet switch
Cross coupling matrix1
s
s X PBS
1
s
1
s
1
s
s X PM
1
s
1
s
Packet/Circuitinput
Packet/CircuitoutputControl unit
GSTpackets
HCT/NCTpackets
FDL
FDL
SM
Inputs Outputs
21 Performance of SM class(Bjornstad et.al. ICTON 2004, JSAC 2006)
• GST packets introduce contention for SM packets, but…• High GST share implies fewer SM packets to be switched and buffered
– Lower SM PLR– Higher SM Delay
Performance varying GST traffic share
0,0E+00
1,0E-03
2,0E-03
3,0E-03
4,0E-03
5,0E-03
6,0E-03
0 20 40 60 80 100
GST traffic share (%)
PLR
0
0,5
1
1,5
2
2,5
Del
ay
PLRDelay
22 Performance and cost savings(Bjornstad et.al. ICTON 2004, JSAC 2006)
• GST performance (circuit)– No packet loss– Fixed delay (transmission delay + # nodes X FDL
• GST traffic not processed in intermediate packet switches– Transit traffic may follow the wavelength path if vacant capacity available– Transit traffic through the node does not need processing
• Less powerful packet switch required – Potential cost savings– Quantified in the ORION project
23
Experimental resultsFrom the OpMiGua testbed
24 OpMiGua testbedIngress
CorePolarisationcontrol
Fibre
25
Ingress
CorePolarisationcontrol
Fibre
OpMiGua testbed
Delay line
26
Experiments
• Polarization control experiments• Measuring packet loss of the SM class• Transferring video in GST or SM class
27
Polarization labeling (Tuft et.al. ICTON 2005 )
• Different from polarization multiplexing– Not simultaneous signals in SOPs
• Less sensitive to pol. Misalignment– Avoids inter-channel interference– 4.5 dB less power penalty @16 degrees
misalignment
• Experiments– Polarization misalignment sensitivity– Polarization control
SOP axesChannel 1 packets
Channel 2 packets
SOP axesChannel 1 packets
Channel 2 packets
PolMUX PolTDM
PolTDM
PolMUX
28
Measuring packet loss in OpMiGua
• Three node experimental network• GST class confirmed to have no packet loss
DelayGST λ1
GST detect
SM insert
Delay
SM insert
Delay
GST λ2
GST λ2
GST λ1
Ingress node
Corenode
Egressnode
SM dropSM drop /GST detect
gaps
29
SM PLR (ECOC 2006)
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80SM load
Pack
et L
oss
Rat
io (P
LR)
GST load 0.29
GST load 0.39
GST load 0.49
GST load 0.58
SM PLR vs SM loads
SM Buffer overflowcauses steep risein SM PLR. Due to the CBR type of traffic, one or more packets are lost in each SM burst
For SM PLRs below 4x10-5, the total load (GST load + SM load) should be below 0.8. Total load 0.96 achieved in later exp. M. Nord et. al. PTL 2006
(Minimum SM PLR on the order of 10-6 due to error floor in PC generators. No error floor in PTL 2006 when using instrumental generators.)
30 Experimental setup video• Packet sources
– Uncompressed 270 Mb/s video-streaming over RTP/UDP/IP/Ethernet
– Packet generator and monitor
E/O GST interface
Logiccircuit
E/O SM interface
PBC
100 km SSMF
SOPSM
1550.5nm
PolTDM scheme SOPGST
SOPSM
Ingress
PBSFDL
(3.5 km) EDFA
SOPSM
PCSOPGST
power tap
Packet detector
PBC
SOPGST
1550.5 nm SOPSM
PC
PCSOPSM
O/E O/ECore Egress
25 km SSMF
Gigabit Ethernet packet generator
SOPGST
EDFA
PBS
SM interface
VideoEncoder
Logic/
Video monitorand recorder
packet counter
VideoDecoder
31
Two experiments on Gigabit Ethernet link• Experiment 1: Verify video transmission in GST class
without packet loss– Video quality should not be affected by SM packets
• Experiment 2: Video transmission in SM class.– Find how GST load degrades uncompressed video signals.
32
Experimental results, video in GST• GST always error free, independent of SM load
– Total load < 0.5 => SM PLR < 1 x 10-4 – Total load = 0.5 = saturation => SM PLR increases steeply to 2.3
%, 29 % @ load = 0.6
33Experimental results, video in SM• High error rate for total load >=0.5• Low error rate on SM for low GST loads• Error rate 5x10-4 gives visible errors in video!
0.5/5X10-4 0.7/1X10-3
0.8/4X10-1 0.9/8X10-1 1/~1
34
Further work
• Control and management of the OpMiGua hybrid network
• GMPLS compatible node and network design• Demonstration closer to a commercial product
35
Summary and conclusion• Migration from circuit to packet is a great challenge
– Applications like TV-broadcast and mobile puts very high demands on QoS– At its best: Low fixed delay for synchronization and a PLR < 10-8
– High cost efficiency
• OpMiGua hybrid circuit/packet network – GST packet transmission without packet loss, optionally with
synchronization– Processing of node transit traffic not required => Cost efficiency
• Experiments– Error free streaming of broadcast video in network with high total load– Load > 0.9 demonstrated with moderate SM PLR– Polarization labeling successfully demonstrated
• Further work– Management and control