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Contention resolution for optical burst switching networks using alternative routing

Authors:
Sungchang Kim at Electronics and Telecommunications Research Institute
Sungchang Kim
Namook Kim
Namook Kim
Namook Kim
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Minho Kang at Korea Advanced Institute of Science and Technology
Minho Kang
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Abstract

Optical burst switching (OBS) is an approach to building very high capacity routing switches based on optical data paths and electronic control. Therefore, OBS is considered as a viable solution in the high-speed optical Internet backbone. In this paper, we propose an intra-class contention resolution scheme in optical burst switching networks by the enhanced alternative routing algorithm. The blocking probability of the proposed scheme is significantly reduced as compared with the general OBS while the additional delay due to the alternative path is smaller than 10% of the basic offset time.
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1
NGI seminar 1
Contention Resolution for Optical
Burst Switching Networks Using
Alternative Routing
(Mar. 11, 2003)
Yonsei Univ.
Computer Communication Lab.
Kim Hyo Jin
NGI seminar 2
Contents
Abstract & INTRODUCTION
OPTICAL BURST SWITCHING
ALTERNATIVE ROUTING IN OBS
NETWORKS
SIMULATION AND RESULTS
CONCLUSION
2
NGI seminar 3
Abstract & INTRODUCTION
Dense Wavelength Division Multiplexing(DWDM)
technology
9Exploit the huge potential bandwidth
9Without any opto-electro-optic(O/E/O) conversions.
Optical Burst Switching(OBS)
9To build very high capacity routing switches.
9Good solution in high-speed optical Internet
backbone.
9Eliminate the electronic bottleneck
9at switching node without O/E/O conversion
9Guarantee the Class of Service(CoS)
9without any buffering.
NGI seminar 4
Propose :
Propose :
9
9Alternative routing based intra
Alternative routing based intra-
-contention
contention
resolution scheme by suggesting a control
resolution scheme by suggesting a control
header packet format
header packet format
9The blocking probability is significantly reduced.
Additional delay
for the alternative path Basic offset time< 10% x
3
NGI seminar 5
OPTICAL BURST SWITCHING
OBS composition
9OBS network
9Optical core routers and electronic edge routers
9Each burst
9Control header packet and a data burst
9Control header contains
9Information of the data burst length and offset time
Packets are
9Assembled into bursts at the network ingress.
9Disassembled back into packets at the network
egress.
NGI seminar 6
Two coupled overlay networks
9A pure optical network transferring data bursts
and a hybrid control network transferring control
header packets.
9Control network
9A packet switched network
9Controls the routing and scheduling of data bursts in the
all optical network
9based on the control header packet’s information
9Advantages
9Mature electronic control technologies
9Promising optical transport technologies
4
NGI seminar 7
Fig. 1 : three burst switching techniques
9A burst can cut through intermediate routers.
NGI seminar 8
(a) In-Band Terminator(IBT) based
burst switching
9Bandwidth is reserved
9As soon as IBT
9Followed end of the data burst
9Limitation
9Be processed all optically
9Not support optical processing
5
NGI seminar 9
(b) Tell-And-Go(TAG) based burst switching
9Operating steps
①Source node sends a control packet over the control
channel to reserve a bandwidth.
②Corresponding data burst is transmitted without waiting
for the acknowledgement.
③The source node sends a release packet to the
destination.
9Ex) Just-In-Time(JIT) protocol
9Disadvantage
9Large signaling overhead
NGI seminar 10
(c) Reserve-Fixed-Duration(RFD) based
burst switching
9Bandwidth is reserved
9fixed time duration at each router
9Information of reservation time
9Carried by control packet
9Ex) Just-Enough-Time(JET) protocol
9Eliminates the signaling overhead
9Improve the resource utilization
9Disadvantage
9Complexity increased.
6
NGI seminar 11
Many challenges to implement the
OBS network
9Edge router
9Burst offset time management, burstification
and burst assembly mechanism
9Core router
9Data burst and control header packet
scheduling, protection and restoration
mechanism and contention resolution scheme
NGI seminar 12
We focused
We focused…
…
9Contention resolution
9The core router has no fiber delay line(FDL) and the
offset time is fixed at the ingress router.
9Classify the contention in intermediate core
routers.
9The inter-class contention caused by different class
bursts.
9The intra-class contention caused by same class bursts.
9To prevent the inter-class contention
9Additional QoS offset time can be used and high priority
bursts can avoid blocking caused by low priority bursts.
9No published result yet.
7
NGI seminar 13
ALTERNATIVE ROUTING IN
OBS NETWORKS
Our three methods for solving the
intra-contention problem in core
routers
①The wavelength converter
②FDL
③The deflection routing
We proposed..
9
9An alternative routing scheme
An alternative routing scheme
9
9Combines wavelength converters and the enhanced
Combines wavelength converters and the enhanced
deflection routing algorithm.
deflection routing algorithm.
NGI seminar 14
If contention occurs at intermediate
core routers, the data burst is blocked.
9Because it can’t change its path.
In our algorithm
In our algorithm
9
9Every core router has hop by hop routing
Every core router has hop by hop routing
functions.
functions.
9
9The routing table has two different paths
The routing table has two different paths
for each destination.
for each destination.
8
NGI seminar 15
NGI seminar 16
Operating steps
9If contention occurs at certain intermediate core router,
the hop by hop routing functions are performed.
9One is routed through the short path and the other is routed
through the alternative path obeying certain policy(time
critical burst, number of hops, etc.)
9If next node does not encounter any contention, the
rerouted data burst will be routed through the shortest
path.
9The control packets contain the number of rerouting times
9Thus if the number of rerouting is over the threshold value,
the rerouted bursts are just drop to prevent looping and early
arrival of data bursts.
Better than deflection routing
9
NGI seminar 17
“Routing offset time”
9The additional offset time
9to make up the time by alternative routing.
9Depends on
9the network size and the header processing
time
9Ingress edge routers decide the offset time
9Prevents the data burst surpasses the
control header.
NGI seminar 18
10
NGI seminar 19
Message type
9The header packet type
9Uniquely determines the exact layout of the message.
QoS
9Following data burst’s priority.
Input port
and
Input wavelength identifier
9Indicate the incoming data burst’s port and wavelength.
Offset time
9The separation time between control header and data burst
9Consists of the basic offset time and routing offset time.
Burst length
9Length of data burst
Hop count
9Prevent bursts not to lose their destination router or the looping
environment.
Source address and Destination address
9Addresses of the source and the destination.
NGI seminar 20
SIMULATION AND RESULTS
Java language
9To evaluate the performance of blocking probability
9in the slotted 4x4 Manhattan Street network.
In fig. 2
9Assumed
9Nodes
90,3,12,15 nodes –edge routers
9Others –core routers
9The bursts arrive synchronously.
9Each time slot is equal to the burst duration.
9Available wavelength at each node is one.
9For simplify the simulation
9Input traffic
9Exponential distribution and Pareto distribution with Hurst parameter
H=0.9.
11
NGI seminar 21
Fig. 5 and Fig. 6
9Blocking probability is reduced by 10 and 2 times
9When offered load is 0.1 and 0.9.
9Self-similar traffic with H=0.9,
9The proposed alternative routing scheme performs very well.
NGI seminar 22
Fig. 7
9Alternative Path makes the additional delay(additional hop
counts) performance.
12
NGI seminar 23
CONCLUSION
An intra-contention resolution
scheme
9By introducing additional routing offset
time in bufferless intermediate core
routers in the OBS network.
9Using “Routing offset time”
9Effective to significantly reduce the blocking
probability for the exponential
... Regardless of the limitations of switching speed of the switching technology (OPS or OBS), our attention moves towards the buffering part. So far, FDL has been used for optical buffering [2][3][4]. A microsecond of delay requires about 200 m of fiber. ...
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... Output port contention can occur due to unavailability of a wavelength at the desired output port for an incoming burst. Several techniques exist in the literature to avoid contention such as FDLs[43,44], Deflection Routing[45,46], Wavelength Conversion[47] and Segmentation Based Dropping[48,49] but none of them can guarantee zero burst loss. OBS with a two-way reservation scheme ensures zero burst loss in which a control packet reserves resources across all intermediate nodes from the source to the destination and is sent back to the source as an acknowledgement. ...
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... The handle packet includes the amount of deflections and the bursts are simply dropped, whether that number has ended the limit worth. An added routing cancel delay of 10% leads to more than 50% decrease in competition [25]. ...
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... Researcher proposed an intra-class contention resolution scheme in optical burst switching networks by the enhanced alternative routing algorithm. The blocking probability of the proposed scheme is significantly reduced as compared with the general OBS while the additional delay due to the alternative path is smaller than 10% of the basic offset time [1]. The first optical switching paradigm that has been proposed in the literature is the Optical Burst Switching with burst drop. ...
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Optical burst switching is a promising solution for terabit transmission of IP data bursts over WDM networks. Optical Burst Switching (OBS) is a promising paradigm for the next-generation Internet. In this paper, we propose a random algorithm, first-fit wavelength algorithm and wavelength reservation algorithm. The blocking probability of the Optical Burst Switch will be analyzed depending upon the number of channels, loads and the number of links. The number of wavelengths on all the links will be kept constant. The blocking probability of the proposed scheme is significantly reduced as compare with general OBS.
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With the propelling high capacity demands, passive optical networks (PONs) are getting extra consideration nowadays. Problem: Burst blocking in wavelength division multiplexed (WDM) PON system increase with the contention period > burst time. Motivation: In the absence of optical random memory in optical communication networks, contention resolution using temporal delays is prominent work and can be accomplished using Fiber temporal delay paths. Burst blocking becomes high in the network at larger contention period such as time between two bursts is larger. Methods: Therefore, in this work, a 40 Gbps × 10 WDM channels based PON system with 50 GHz channel spacing over 20 km is investigated by incorporating switches, switch controller, buffers and Fiber temporal delay paths to decrease the bursts blocking in the system. In order to assign delay to bursts, an algorithm is proposed and calculated amount of delay are assigned to demanding wavelengths for bursts which inturn decrease the blocking. Analysis: Proposed WDM-PON system is simulated in the simulation tool and investigated for different FTD delays, burst loss probability, burst arrival rate, buffering delay and performance is also analyzed in terms of log BER. Results: Bursts blocking probability increases with the increase in burst arrival rate, lesser buffering delays, and more no. of input ports. Further investigation reveals that higher extinction ratios can provide better log BER.
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Optical Burst Switching (OBS) [1][2][3][4] has been proposed for the next generation Internet based on the Wavelength Division Multiplexing (WDM) [5] network technologies. In the OBS, the serious problem is the burst loss due to the burst contention. There have been a number of traffic control methods [6][7] for solving the burst contention problem. The Internet has two traffic classes, i.e. real-time bursts and reliable bursts. However, most of the conventional traffic controls aren’t suitable for the real-time bursts. In this paper, we propose a new effective traffic control method named a Leaky Bucket Burst Window (LB-BW). The proposed method is composed of the three algorithms, a Leaky Bucket algorithm, a Burst Window algorithm and a determining network state algorithm. Only in a Leaky Bucket algorithm, both real-time bursts and reliable bursts would be delayed under high load. It is possible to reduce the burst loss probability, but real-time bursts are weak in the delay. Therefore by integrating a Burst Window algorithm and a determining network state algorithm, the edge node can transmit real-time burst priority under high load. We show the effectiveness of the proposed method through computer simulations.
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  • M Yoo
  • C Qiao