Master’s Thesis

Title

Performance Evaluation of Optical Packet / Path Integrated
Architecture for WDM-based Networks

Supervisor
Professor Masayuki Murata

AuthorMasatoshi Ohashi

February 13th, 2008

Department of Informaiton Networking
Graduate School of Information Science and Technology
Osaka University

Master’s Thesis

Performance Evaluation of Optical Packet / Path Integrated Architecture for WDM-based
Networks
Masatoshi Ohashi

Abstract
Wavelength Division Multiplexing (WDM) technology, which carries multiple wavelength
channels on a single fiber, is expected to accommodate the traffic volume for the current and future Internet. One approach for accommodating IP traffic on the wavelength division multiplexing(WDM) network is to construct a logical topology by establishing a set of lightpaths between
nodes. The lightpath carries IP traffic and does not require any electronic packets processing at
intermediate nodes, which reduces the load of packet processing at those nodes. Another approachis to utilize WDM networks as path switched networks. This approach can support applications
that require high reliability and large bandwidth by establishing wavelength channels (called lightpath) between source and destination nodes on-demand basis. Applications requiring high reliability and large bandwidth such as grid computing services or digital cinemas become available
recently. If we accommodate such applications using IP network, unexpected packet loss or packet
delay may occur because of collision with other traffic. To prevent this, integration of packet andpath switched networks is key to achieve high reliable and high bandwidth services in the Internet. In this thesis, we investigate the performance of optical packet / path integrated architecture
in WDM-based networks. For this purpose, we develop an approximation analysis method to reveal how path network achieve effective network utilization and relax the load of packet switched
network. Our method is based on M/M/1/K queuing system and iterative calculation. We verify
the accuracy of our approximation analysis method and evaluate the throughput and packet loss
rates of the integrated architecture by comparing with results of computer simulations. Our results
indicate that the throughput of integrated architecture increases as the number of wavelengths
assigned to path network increases, but throughput of integrated architecture decreases when all
wavelengths are assigned to the path network.
1Keywords
Wavelength Division Multiplexing, IP over WDM, Dynamic Path Setup, Reduced load approximation, queuing system, approximation analysis

2

Contents
1 Introduction

6

2 Packet / Path Integrated Architecture

9

2.1

IP over WDM Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

2.2

Dynamic Lightpath Setup Architecture . . . . . . . . . . . . . . . . . . . . . . .

11

2.3

Models of Packet / Path Integrated Architecture . . . . . . . . . . . . . . . . . .

13

3 Analysis Method

14

3.1

Network Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14

3.2

Analysis Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15

3.3

Analysis Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17

3.3.1

Analysis Method for Path network . . . . . . . . . . . . . . . . . . . . .

17

3.3.2

Analysis Method for Packet Network with UDP Connections . . . . . . .

20

3.3.3

Analysis Method for Packet Network with TCP Connections . . . . . . .

21

4 Results and Discussions

24

4.1

Parameter Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24

4.2

Performance of Integrated Network with UDP connections . . . . . . . . . . . .

27

4.3

Performance of Integrated Network with TCP connections . . . . . . . . . . . .

27

4.4

Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

5 Conclusion

35

Acknowledgements

36

References

38

3

List of Figures
1

A model of packet/path integrated network . . . . . . . . . . . . . . . . . . . . .

82

IP over Point-to-Point WDM . . . . . . . . . . . . . . . . . . . . . . . . . . . .

93

IP over WDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10

4

Dynamic Lightpath Setup Architecture . . . . . . . . . . . . . . . . . . . . . . .

115

Backward signaling for lightpath establishment . . . . . . . . . . . . . . . . . .

12

6

The flowchart of data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14

7

The analysis model for integrated network . . . . . . . . . . . . . . . . . . . . .

16

8

NSFNET topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24

9European Optical Network (EON) topology . . . . . . . . . . . . . . . . . . . .

25

10Throughput and loss rate of integrated networks; The case for UDP connections .

26

11

Throughput and loss rate of integrated networks; The case for TCP connections .

28

12

Throughput and loss rate of integrated networks ( Request arrival rate: 200 request/ sec, OXC configuration delay: 20 ms, holding time: 0.1 sec) . . . . . . . . . . .

13Throughput and loss rate of integrated networks ( Request arrival rate: 400 request/sec, OXC configuration delay: 20 ms, holding time: 100 ms) . . . . . . . .

14

31

Throughput and loss rate of integrated networks ( Request arrival rate: 200 request/sec, OXC configuration delay: 200 ms, holding time: 100 ms) . . . . . . .

15

30

33

Throughput and loss rate of integrated networks ( Request arrival rate: 200 request/sec, OXC configuration delay: 20 ms, holding time: 50 ms . . . . . . . . .

4

34

List of Tables
1

The traffic demand matrix for NSFNET topology . . . . . . . . . . . . . . . . .

525

1 Introduction
The increase in the number of Internet users and the appearance of multimedia services suchas video streaming have led to the rapid growth in Internet traffic. Until now, Internet traffic
doubles each year [1]. New services such as grid computing, P2P will drive the traffic growth andbandwidth demands in the future. The answer to meet the bandwidth demand is centered on a
new emerging technology, WDM (Wavelength Division Multiplexing). WDM technology allows
transmitting multiple optical signals on different wavelengths on a single fiber, which dramaticallyincreases the link bandwidth. There are several approaches to utilize WDM networks effectively.
One approach is to utilize WDM networks as packet switched networks, called IP over WDM[2–4]. In this method, wavelength channels, also known as lightpaths, are configured between
each node and packets are transmitted on the lightpaths. The nodes consist of IP router and OXC(Optical Cross Connect) that bind an input wavelength channel to a specified output wavelength
channel. Lightpaths are established by OXC in the first place and packets routing by IP router
are transfered through the lightpaths. Photonic network works as layer 2 (data link layer) on OSI
Reference Model and IP works as layer 3 (network layer) in this method. Therefore, IP over
WDM has good compatibility with the Internet. However, applications requiring high reliability
and large bandwidth such as grid services or digital cinemas become available recently. If you use
such applications using IP network, it has possibilities to occur drop or delay of packets because ofcollision with other traffic. Hence, it is eligible way to divide traffic which requires high reliability
and large bandwidth from other traffic. One possible approach to fulfill this is to use WDM
technology where it can split wavelengths and assign different architecture to each wavelength.
Another approach to utilize WDM networks is to establish lightpaths [5–8]. The source nodecommunicates with a destination node by signaling messages to configure OXCs along the route
when a data transfer request arises at the source node. A lightpath is established when all OXCs
along the route between a source node and a destination node. Then, the source node starts datatransfer to the destination node through the established lightpath. In this case, there is no congestion and packet drop because only one flow can appropriate the large bandwidth lightpath. Furthermore, any transport mechanism can be applied to this method. So, it can support applications
that require high reliability and large bandwidth. The drawbacks of this approach are lightpath
setup delay. There is lightpath setup delay from time when data transfer request arises to time6

when data transfer can start.
Theses two approaches have advantages and drawbacks. Therefore, some integrated mechanisms such as TCP Switching have been researched [9–11]. TCP Switching is a network architecture that creates a separate circuit for each IP flow. It lets IP directly controls the creation or
destruction of circuits. Integration of packet and path switched networks is key to achieve high reliable and high bandwidth services in the Internet. It is easy to integrate packet and path switched
networks by using WDM technology. Wavelength channels can be dealt each other since eachwavelength is independent from other wavelengths. Thus, it is feasible that packet switched architecture uses some wavelengths, while path switched architecture uses the remaining wavelengths.
Figure 1 shows a packet / path integrated network model we consider. The source node in the
integrated network can select which network it uses. In order to utilize the integrated networks
effectively, we must investigate the performance of integrated architecture. Therefore, it is necessary to reveal how path network achieve effective network utilization and relay the load of packet
switched network. Especially, it is important to share wavelengths to packet and path networks
optimally because wavelengths on fibers are limited.
In this thesis, we develop an approximation analysis method to reveal the throughputs and thedata loss rates of integrated networks. Using our analysis method we reveal the optimal proportion of wavelength assignment to packet and path networks. We develop an approximation analysis
method for packet network with UDP and TCP connections. The method is based on M/M/1/K
queuing system and iterative calculation. It reveals the throughput and loss rate of each connectionin the path network. Additionally, by combining it with the approximation analysis method forpath network introduced in [14], the total throughput and data loss rate of integrated network are
obtained. Furthermore, we verify the results of analysis by comparing with those of computer
simulation. Then, we evaluate the throughputs and the drop rates of the integrated network by ourapproximation analysis method. As a result, the throughputs and loss rates obtained by our approximation analysis method are close to that of computer simulation. Moreover, our results showthat the total throughputs of integrated networks increase, as the number of wavelength assigned
to path network increase. However, the total throughputs decrease when all of wavelengths are
assigned to path network because there is no support of packet network. It is also revealed that thethroughputs of packet networks are not so high when the data transfer requests arrival rate is high.
Because the path network works as a buffer agent.
7

Figure 1: A model of packet/path integrated network
This thesis is organized as follows. In Section 2, we show attributes of IP over WDM architecture as packet network and distributed dynamic lightpath setup architecture as path network.
After that, we explain integrated packet and path architectures. In Section 3, we show our analysis
method for integrated networks. We explain both path network part and packet network part, andeach case applied UDP and TCP to packet network part. Section 4 describes results of analysis
and computer simulation. Comparing results of analysis and simulation, we verify our analysis
method leads the throughput and data loss rate near by that of computer simulation. Finally wesummarize our thesis in Section 5.

8

Figure 2: IP over Point-to-Point WDM

2 Packet / Path Integrated Architecture
There are mainly two types of architecture to utilize WDM network effectively. One is packet
networks and another is path networks. In this section, we first describe two architectures on
WDM networks. After that, we explain packet/path integrated architectures.

2.1 IP over WDM Architecture
Because of the majority of the Internet traffic is IP, it is an important task to develop networkarchitectures which transport IP traffic on the WDM network. There are several alternatives for
IP over WDM networks, IP over point-to-point WDM, IP over reconfigurable WDM, and IP overswitched WDM [2]. Under the IP over point-to-point WDM architecture (Figure 2), the WDM ison each optical fiber link. That is, each wavelength on the fiber is treated as a physical link between
conventional IP routers. The VNT is same as the physical fiber topology. Thus, multiple links ofwavelength are provided between IP routers. In this case, the bandwidth of optical fiber links is
actually increased by the WDM technology. However, it is insufficient to deal with increasing
traffic demand because the bottle neck of the network shifts to electronic routers.

9

Figure 3: IP over WDM
In the IP over reconfigurable WDM architecture and IP over switched WDM (Figure 3), wavelength channels are configured in the WDM layer, and IP packets are transfered by the channels.
Each intermediate node of the network has OXC and IP packets are transfered without any processing at each nodes. In this way, lightpaths reduce the load of IP routers. Reconfigurable WDM
means VNT is configured as network state. On the other hand, switched WDM means VNT is
pre-configured and it is static.
We consider IP over WDM as point-to-point WDM architectures in this thesis because wewould like to know the performance of integrated networks with simple architecture at first.
Thus, the VNT equals topology of physical fiber in this thesis. When data transfer request
arises at a source node, the data is packetization and the packets are transfered by IP like theInternet. Therefore IP over WDM has compatibility with the Internet.
However, normal IP cannot provides high reliability and large bandwidth to a connection.
Because there are congestion, packets collision, forwarding processing delay and packet drop atrouters and sharing bandwidth with many other connections Therefore, the flows which require
high reliability and large bandwidth like digital cinema are unstable to transfer on IP network.

10Figure 4: Dynamic Lightpath Setup Architecture

2.2 Dynamic Lightpath Setup Architecture
One approach to effectively utilize WDM networks is to transfer the data on-demand basis throughwavelength reservation based on RSVP signaling (Figure 4). That is, when a data request arises
at a source node, a wavelength is dynamically reserved between the source and destination nodes,
and a lightpath is configured. The overview of dynamic lightpath setup with backward reservation
method is as follows.
In backward reservation, the reservation of the network resource is performed more accurately.
That is, the source node sends a PROBE packet before a wavelength reservation. A PROBE
packet collects the information on usage of wavelength along the forward path, but no wavelength
is reserved at this time. Along the forward path, the source node checks which wavelength isavailable in the next link and writes the information of available wavelength on a PROBE packet
as available-list and sends the packet toward destination node. Every intermediate node which
receives a PROBE packet examines that each wavelengths written in a PROBE packet is available
or unavailable in the next link. If a wavelength is unavailable or in-use, the wavelength is removed
from the available-list in a PROBE packet. When the destination node receives a PROBE packet, it

11Request

EstablishedSource

Intermediate Destination
Source
Intermediate Destination
Request
PROBE
PROBE
PROBE
PROBE
Failure
RESV
RESV
RESV
NACK
RLS
Request drop
FailureRequestData transfer
PROBE
Request
drop
NACK
RLS
RLS
(a)Successful case(b)Failure case

Figure 5: Backward signaling for lightpath establishment
will know that which wavelength is now available on the path between the source and destination.
Based on this information, the destination node determines a wavelength for reservation, and thensends a RESV packet toward the source node. Figure 5(a) shows this successful case.
Although the reservation in backward scheme is more precisely due to PROBE-based reservation policy, the reservation failure is still unavoidable. There are two cases where the reservation
failure occurs in backward scheme. The first one is the PROBE-failure. If there is no wavelength
which is available through the entire path, an intermediate node is aware of it because there is
no wavelength in a PROBE packet. In this case, the node returns a NACK packet and the source
node notice the failure of lightpath establishment. The wavelength converter will be a powerfulsolution of this problem. But, applying the wavelength converters will produce another issue, i.e.,
facility cost. Note that, in this paper, we do not consider the wavelength conversion facilities. Thatis, a lightpath uses the same wavelength along the entire path, which is known as the wavelength
continuity constraint. The second one is the congestion between RESV packets. Because of the
propagation delay or OXC configuration delay, the information collected by a PROBE packet may
be different from the current actual link state. There is no guarantee that a wavelength which wasfree until a few seconds ago is still available. In dynamic WDM networks, the link state changes
from moment to moment. It is impossible for edge nodes to know the current actual link state
exactly. If the destination node sends a RESV packet based on the outdated information, the reservation may be failure because the wavelength has been already reserved by the other lightpath
establishment request. Figure 5(b) shows this case of reservation failure.
12

If it succeed to establish a lightpath, there are no congestion and packet drop because a established lightpath is leased for the connection which establishes the lightpath. This method provide
high reliable and large bandwidth, dedicated channel for each connection.
But there are some disadvantages. First, data transfer cannot start immediately when the request arises because there is lightpath setup delay such as RSVP signaling and OXC configuration.
If the data size is small, the influence of lightpath setup delay is large. Second, it cannot utilize thelarge bandwidth effectively, because a wavelength with large bandwidth is occupied by only one
flow. Furthermore, the large bandwidth is cannot utilized while lightpath setup phase.

2.3 Models of Packet / Path Integrated Architecture
There are some related researches about packet / path integrated networks [10, 11, 13].
There are many types of packet / path integrated architectures because
One type is the network used for transfering data is determined by some policy and informationsuch as the data size. In [11], a source node in the network can choice either packet network orpath network. If the data size is larger than threshold, the data is transfered through path network.
Otherwise, the data is transfered through packet network. This usage may be hold promise because
path networks is superior for transfering large data and packet networks is superior for transfering
small data. But in such network, it is difficult to determine the policy which network is used fordata transfer because the network cannot know much information such as how the data size islarge.
Another type of the integrated network is used preferentially for transfering data first and theother network is used for retrial as subsidiary. Furthermore, how the data transfer retry gives
variety to types of integrated network usage.
In this thesis, we apply the type of sending data in the order corresponding to path network
first and packet network second because of the simplicity and therefore, we can investigate therelationship between packet network and path network in the integrated network. In the network
which a source node can choice either packet network or path network by some criteria, the criteria
dominates the performance of the network. So it is difficult to investigate pure performance of
these networks. Additionally, if it sends data through packet network first, it is unclear that how
dropped packets are resend through path network.

13

Figure 6: The flowchart of data transfer

3 Analysis Method
In this section, we explain our analysis method for packet / path integrated networks. At first, weshow the network model we consider in this thesis. Then, we explain our analysis method. Our
analysis method consists of two sub method for getting the throughputs and data loss rates of eachpath and packet networks. We consider both UDP and TCP connections. We show details of each
sub method in Section 3.2.

3.1 Network Model
The networks we consider consist of nodes and optical fibers. The nodes consist of a IP router,a OXC and its controller because there are a packet network and a path network on a integrated
network. The nodes are connected by optical fibers. The nodes have no wavelength conversion
device. Therefore, a lightpath consists of same wavelength on all path along the route. One
wavelength in the fibers is used to exchange control packets and other wavelengths are assigned to14either packet or path network. A packet network and a path network have each own wavelengths
and run independently. The switching architecture is based on that of introduced in [10].
In packet network on the integrated network, static lightpaths are configured on each fiber atthe beginning. The VNT consists of these static lightpaths and the VNT equals physical fiber
topology in this case. Data packets are transfered on this VNT. In path network, on the other hand,a lightpath is configured between source and destination nodes on demand by RSVP signaling and
OXCs. The wavelength reservation method is backward reservation.
Our simple network model shows as figure 6. When data transfer request arises at a source
node, the source node try to send the data through path network. If the source node succeeds toestablish a lightpath between the source and the destination nodes, the data is transfered throughthe lightpath. Because of occupancy of the lightpath, the source node sends the data with all of
bandwidth.
By contrast, if the source node fails to establish a lightpath because of collision of signaling
messages or lack of utilizable wavelength, the source node sends the data through packet network
like traditional packet networks.

3.2 Analysis Model
The network topology has J links and traffic demand are given. Each link has W + 1 wavelengths,
and one wavelength is assigned control plane. WA wavelengths of remaining wavelengths are
assigned to path network and WP wavelengths are assigned to packet network. Thus, W =WA + WP . The set of All source and destination nodes pair is A Data transfer requests to eachpair a ∈ A of source and destination nodes arrive at the arrival rate of Ea . The requests arrive inaccordance with the Poisson process. The bandwidth of a wavelength is b and propagation delay
The data size is set to follow an exponential distributed with mean b/µ because lightpath holding
time is set to follow an exponential distributed with mean 1/µ. The data is transfered along thepredefined route Ra and the number of hops is ha And we call each link on Ra as a1 , a2 , ..., aha
by turns from upper reaches.
When a data transfer request is arrives on a source and destination pair a, the source node try
to send the data through path network. So, we have beginning of analysis from path network. The
analysis method for path network is based on [14]. In [14], the approximation analysis method for
distributed dynamic lightpath setup network based on various reservation methods.
15

Figure 7: The analysis model for integrated network16

We apply the approximation analysis method in [14] to analysis of path network. As a resultof path network analysis, throughputs Ha and request drop rates La of each connection a. When alightpath setup request is dropped in path network, the source node sends the data through packet
network. Thus, we consider that data transfer requests arrive at each connection a according to a
Poisson process with rate Ea La .
We consider both case all packets in packet network are transfered with UDP connection or
TCP connection. In the case with UDP connections, we regards packets arrival to each link as
according to a Poisson process and we consider each link as M/M/1/K queuing system. Thereby,
packet drop rates of each link and each connection are revealed at given some condition about
packet arrival rate at each link. But, to give the suitable condition is so difficult. So, we apply
iterative calculation to the condition settings. If the given condition is not suitable, it updates
the condition and recalculates. Thus, the results of calculation converge to that of static state.
Consequently, we can get the throughputs and the drop rates each of path and packet networks. The
total throughput of the integrated network is sum of the throughputs of path and packet networks.

3.3 Analysis Method
3.3.1 Analysis Method for Path network
We introduce the approximation analysis method for path network proposed in [14]The overview of the method is follows.
(A)(1) The request drop rates La(A)of each connection a are initialized as La= 0(a ∈ A),(A)
and the probability qj of some wavelength on the link j is not free are initialized as(A)
qj = 0(j = 1, ..., J).
(A)(2) We calculate a arrival rate Λjof signal for wavelength reservation at each wavelength on

the link j.
(3) We calculate a wavelength utilization time Tj which is from the time when the wavelength
is reserved at link j to the time when the wavelength is released at link j for all links.
0(A)(4) We calculate the new probability qj

of some wavelength on the link j is not free in staticstate for all links.

17

0(A)

(5) We calculate the new request drop rate La

for all connections. If the request drop rates

(A)
0(A)
converge as La ≈ La , iteration phase is finished and go to next step.

Otherwise, the(A)(A)
request drop rates La and qj are updated and return to step 2.

(6) We obtain the request drop rates of each connections.
The details are as follows.
Derivation of Λj and Tj(A)

We focus a connection a. γai means the request arrival rate of the ith link of the connection a.
Similarly, αai means the request arrival rate which succeed to establish lightpath finally, and βaimeans the request arrival rate which fail to establish lightpath finally. Thus,γa(A)= αai + βaii(1)

The probability of a wavelength is free on all links between the source and destination nodes
is

ha
∏
)
(1 − qa(A)
i

(2)

i=1

The arrival rate at which a PROBE message received by destination node σa0 is
(
(
))
ha
∏
)
σa0 = Ea 1 − 1 − (1 − qa(A)
i

(3)

i=1

Because we consider a wavelength selects randomly, the arrival rate of a RESERVE signal at thelink aha isγa(A)= σa0 σ 0select
aha

(4)

0
0
σselect
means the probability which a free wavelength is selected. So, σselectis inverse of expecta-tion of the number of free wavelengths.
0

σ select =(h)k ()(WA −k−1)
ha
a
∏
∏
(A)
(A)
(k + 1)WA −1 Ck(1 − qai )1 − (1 − qai )

W∑
A −1
k=0

i=1

(5)

i=1

A RESERVE signal succeeds to reserve a wavelength if a RESERVE signal of the other connection is not received by the node. Thus,
αaah = γa(A)hah∏a −1 ((A)−Λha (ha −k+ 21 )D

e

k=1

18

h

)
(6)

βaah = γa(A)− αahaha(7)

Similarly, about each link along the route ai ,(A)i−Λa +1 (ha −(i+1)+ 12 )D

(8)

i−1 (
)
∏
(A)
1
e−λak (ha −k+ 2 )D

(9)

γa(A)
e
= γa(A)
a
a +1
i

i

αai = γa(A)ik=1

βai = γa(A)
− αai
i

(10)

sj means the time from when a wavelength is reserved to when the wavelength is released insuccess case for lightpath establish. On the other hand, tj means the time from when a wavelength
is reserved to when the wavelength is released in failure case for lightpath establish.

sai = iD −

D
1
+
2
µ

(11)

D
2

(12)

tai = iD −(A)

Thereby, the request signaling arrival rate Λjtime Tj is calculated as,
(A)

Λj
1
=
Tj

∑

=

at each wavelength on link j and link utilization

∑

γa(A)
i

(13)

ai =j
ai =j (αai sai + βai tai )∑(A)
ai =j γai

(14)

(A)

Derivation of La(A)

The request drop rate qj

at link j is described as,
(A)

(A)
qj =

Λj
(A)

Λj

(15)
+ Tj

Sa means the probability that the PROBE signal sended by the source node returns as NACK
signal.

(
Sa =

1−

ha
∏

)WA
i = 1(1 − qa(A)
)
i

19

(16)

(A)

Consequently, the request drop rate La(of connection a is calculated as
(
))
ha
∏
(A)
1
(1 − Sa ) 1 −e−Λak (ha −k− 2 )D

L(A)= Sa +
a

(17)

k=1

3.3.2 Analysis Method for Packet Network with UDP Connections
We explain our approximation analysis method for packet network with UDP connections. We
consider packet arrival rate and processing time at each link is according to a Poisson process andmodel each link as M/M/1/K queuing system. K means buffer size at each link.
The overview of the method is as follows.
(P )(1) We calculates data transfer request arrival rates Ea(P )to each connection a by Ea(P )the result of path network analysis. And we initialize packet drop rates La(P )nection a as La(P )= 0 and packet drop rates qj(P )(2) We calculates packet arrival rates Λj(P )of each link j as qj= Ea La ,of each con-= 0.

at each link j.
0(P )(3) We calculates new packet drop rates qj

at each link j by analysis of M/M/1/K queuingsystem.
0(P )(4) We calculate new packet drop rates La(P )of each connections converge as Laof each connection a. If the packet drop rates
0(P )

≈ La

, iterative phase is finished and go to next
(P )step. Otherwise, packet drop rates at each link is updated as qj

0(P )

= qj

and next iterative

calculation starts from step 2.
(P )(5) we calculate throughputs Ha(P )of each connection a with resulting packet drop rate La(P )(6) we calculate H (P ) as sum of Ha .
The details of the method is as follows. We attention to a connection a. We caclurate The
packet arrival rate γai of the ith link ai as)b ∏(1 − qa(Pl )µiγai = Ea(P )

(18)

l=1

qai is packet drop rate of the link ai and b/µ is data size. There are some flows on a connectionand each flow continue to send packets until all packets are transfered. So, the source node sends(P )packets to the connection at rate Ea b/µ on static state.
20

(P )

The packet arrival rate Λj

at link j is
(P )

Λj

∑

=

γ ai

(19)

ai =j
0(P )

Then, we calculate new packet drop rate qj
0(P )
qj =

by M/M/1/K queuing system as(P )1 − Λj dj

(P )

(P )
1 − (Λj dj )K+1

(Λj dj )K(20)

dj is processing or propagation delay. If processing delay Dp is longer than propagation delay
D,
0(P )

Consequently, new packet drop rate Laof the connection a is
ha (
∏

)
L0(P
=1−
a

1 − qa(Pi )

)
(21)

i=1
(P )

Then, if La(P )Otherwise, qj≈ L0 (P )a about all a, La

(P )

(P )

= qj

is packet drop rate of connection a in static state.

for each link j and next iterative calculation starts.

Finally, the throughput of the connection a isHa(P ) = Ea(P )

)
bs (
)
1 − L(Paµ(22)

s means packet size. And Total throughput H (P ) of packet network is
H (P ) =∑Ha(P )(23)

a∈A

3.3.3 Analysis Method for Packet Network with TCP Connections
We explain analysis method for packet network with TCP connections. We apply relational expressions between throughput and packet loss rate under TCP Reno congestion control and iterative
calculation with analysis of UDP. The overview is follows.
(1) The packet sending rate is initialized as r = 1(P )(2) We calculates data transfer request arrival rates Ea(P )to each connection a by Ea(P )the result of path network analysis. And we initialize packet drop rates La(P )nection a as La(P )= 0 and packet drop rates qj
21

(P )

of each link j as qj= 0.

= Ea La ,of each con-

(P )(3) We calculates packet arrival rates Λj

at each link j.
0(P )(4) We calculates new packet drop rates qj

at each link j by analysis of M/M/1/K queuingsystem.
0(P )(5) We calculate new packet drop rates La(P )of each connections converge as Laof each connection a. If the packet drop rates
0(P )

≈ La

, iterative phase is finished and go to next
(P )step. Otherwise, packet drop rates at each link is updated as qj

0(P )

= qj

and next iterative

calculation starts from step 2.
(P )(6) We calculate throughputs Ha(P )of each connection a with resulting packet drop rate La .
0(P )Besides, we calculate TCP throughputs Haof each connection a by relational expression

between throughput and packet loss rate under TCP congestion control introduced in [15].
(P )If the throughputs converge as Ha

0(P )

≈ Ha

, iterative phase is finished and go to next step.

Otherwise, packet sending rate is updated as rnext = r + 1 and next iterative calculation
starts.
(P )(7) we calculate H (P ) as sum of Ha .
The details are as follows.
In this method, two methods for getting throughputs are applied. One is approximation analysis with UDP connections we described, and another is relational expression between throughput
and packet loss rate under TCP congestion control introduced in [15]. If the results of the two
methods is same, it is performance of static state.
First of all, packet sending rate is set as 1. Although there are parallel flows on a connection,
we consider these flows is one flow. In the UDP approximation analysis with packet sending rate(P )r, b/µ is replaced by r. Then, the throughputs Ha(P )and packet loss rates Laof each connection

is found in UDP connections sending packets at rate r.
On the other side, we calculate the throughputs of each connection under TCP congestion(P )control by packet loss rate La

it can be calculated by following expression introduced in [15]
√
3
2s
0(P )
√
(24)
Ha =
(P )
ha D La

22

(P )Finally, the total throughput is calculated by convergent throughput Ha
H (P ) =

∑
a∈A

23

Ha(P )

as(25)

Figure 8: NSFNET topology

4 Results and Discussions
4.1 Parameter Settings
We evaluate the performance of the proposed approximation analysis method in Section 4 on the
NSFNET (Figure 8) that has 14 nodes and 21 bidirectional links. A bidirectional link has an unidirectional optical fiber that multiplexes 16 + 1 wavelengths in each direction and one wavelength
is assigned to control channel. The transmission capacity of each wavelength is set to 10 Gbps.
The link propagation delay is 10 ms per a link and OXC configuration delay is 20 ms per a link.
The processing capacity of IP router is set to 40 Gbps, and data size is exponentially distributedwith a mean value of 1 Gbyte. Thus, the holding time of path network is exponentially distributedwith a mean value of 0.1 second. The size of packets is 1500 byte, and each link has queue which
length is 10 packets. IP traffic flows between each node pair a arrive according to Poisson processwith the average rate ² × ma , where M = ma is traffic demand matrix and ² is scale factor of
the traffic demand matrix. We use the traffic demand matrix shown in the reference [4]. In Table
1, we show this traffic demand matrix. The route of each connection is static minimum hop path,and VNT in packet network is same as physical fiber topology.
In the computer simulation with UDP connection, the UDP packets sending rate is 100 Mbps.

24Figure 9: European Optical Network (EON) topology

Table 1: The traffic demand matrix for NSFNET topology

25

1.1e+11
1e+11
9e+10
Throughput [bps]8e+10
total (ana)total (sim)path (ana)path (sim)packet (ana)packet (sim)

7e+10
6e+10
5e+10
4e+10
3e+10
2e+10
1e+10
0
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(a) Throughput

1

Path request/Packet loss rate

0.01
path (ana)path (sim)packet (ana)packet (sim)0.0001
1e-06
1e-08
1e-10
1e-12
1e-14
1e-16
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(b) Loss rate

Figure 10: Throughput and loss rate of integrated networks; The case for UDP connections26

4.2 Performance of Integrated Network with UDP connections
Figure 10(a) shows the each throughput of the path and the packet networks and total throughput
with UDP connections in approximation analysis and computer simulation at data transfer request
rate of 100 requests per second.
As a result, the results of approximation analysis come near that of computer simulation. All
differences of results are within small range. Thus, our approximation analysis method is effective
to deal with integrated networks.
At the number of wavelength assigned to path network is 0, it is the case of only packet
network and at the number of wavelength assigned to path network is 16, it is the case of only
path network. As a result, the total throughputs of two case are inferior to integrated network.
Therefore, the integrated networks are effective to increase total throughput.
As the number of wavelength assigned to path network, the throughput of path network increase and that of packet network decrease. The difference of the increase and the decrease degree
influences to the total throughput. In this case, the total throughput increase gradually as increasing the number of wavelength assigned to path network, and it is achieved full throughput at thecase the wavelength assigned to path network is in the range from 8 to 14.
Figure 10(b) shows the loss rate of path request and packet.
In the case only packet network, the packet loss rate is about 0.04 and it is high rate. However,in the case few wavelengths are assigned to path network, the loss rate decrease near 0.
In this case, the performance of path network is high compared to packet network because
processing capacity of IP routers is low. Similarly, the performance of path network is dominatedby OXC configuration delay.

4.3 Performance of Integrated Network with TCP connections
Figure 11 shows the throughputs and the loss rates of approximation analysis and computer simulation. The differences of results are within small range. The throughputs and packet loss rate ofpacket network are low because of congestion control mechanism. The throughputs of approximation analysis of each network are lower side of that of computer simulation. Thus, the differenceof the total throughput is a little bit large. However, it is not a important problem because the total
throughput of analysis is safety side, which is lower side of computer simulation too.

27

1e+119e+10

Throughput [bps]8e+10
total(sim)total(ana)path(sim)path(ana)
packet(sim)packet(ana)

7e+10
6e+10
5e+10
4e+10
3e+10
2e+10
1e+10
0
0

2
4
6
8
10
12
14
Number of Wavelength Assigned to Path Network

16(a) Throughput

Path Request / Packet drop rate

1
0.01
0.0001path(sim)path(ana)
packet(ana)packet(sim)

1e-06
1e-08
1e-10
1e-12
1e-14
0

2
4
6
8
10
12
14
Number of Wavelength Assigned to Path Network

16(b) Loss rate

Figure 11: Throughput and loss rate of integrated networks; The case for TCP connections28

4.4 Discussions
We investigate the effects of each parameter such as request arrival rate, OXC configuration delay
and data size (holding time) on integrated networks with UDP and TCP connections with EON
Topology. For EON topology, we randomly generate a traffic matrix according to exponential
distribution.
In Figure 12, the throughputs and the loss rates of integrated networks with settings as follows.
The request arrival rate is 200 requests per second, the OXC configuration delay is set to 20 ms andthe average data size is 1 Gbytes. Thus, the average holding time of a lightpath in path network is
100 ms.
In Figure 12(a) shows the throughputs in the standard case. The throughput of the networkwith TCP connections inferior to that of the network with UDP connections because of congestion
control mechanism. Therefore, the packet loss rate is under 1e-06 in all area shown by Figure12(b). The packet loss rate of the network with UDP connections is high under 0 or 2 wavelengths
are assigned to path network because the traffic through bottleneck links exceeds the capacity andthere is no congestion control mechanism. At the view of the time require for transmission of alldata, low throughput and high loss rate with re-transmission lead to lengthen the time.
In Figure 13, the request arrival rate increased to 400 requests per second from standard case.
Thus, Figure 13 shows us the results of high arrival rate case. In this case, the loss rate of UDP
network keeps high rate over all range because path network drops much of traffic, and the arrival
rate for packet networks is also high. On the other hand, the loss rate of TCP network keeps low
level because of congestion control mechanism. Therefore, compared with the throughput of UDP
network, that of TCP network is stable against difference of number of wavelength. That means
it is ineffective to assign many wavelengths to a packet network with TCP connections in higharrival rate case.
Compaired with the case the request arrival rate is 200 the throughtputs of path network areinfluenced by the change of the request arrival rate. However, the throughputs of packet networks
are not so high because the path network works as a buffer agent.
The performance of path network is dominated by OXC configuration delay. Figure 14 shows
the a high OXC configuration delay case which set to 200ms. The other parameters are same withstandard case. In this case, the performance of path network is low, and hence, the request arrival29

2e+111.8e+11

Throughput [bps]1.6e+11
total(UDP)
total(TCP)
path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

1.4e+111.2e+11
1e+11
8e+10
6e+10
4e+10
2e+10
0
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(a) Throughput

1

Path request/Packet loss rate

0.01
path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

0.0001
1e-06
1e-08
1e-10
1e-12
1e-14
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(b) Loss rate

Figure 12: Throughput and loss rate of integrated networks ( Request arrival rate: 200 request /sec, OXC configuration delay: 20 ms, holding time: 0.1 sec)30

4e+11
3.5e+11

Throughput [bps]3e+11
2.5e+11
total(UDP)
total(TCP)
path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

2e+11
1.5e+11
1e+11
5e+10
0
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(a) Throughput

Path request/Packet loss rate

1

0.1

0.01

0.001

path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

0.0001

1e-05

1e-06
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(b) Loss rate

Figure 13: Throughput and loss rate of integrated networks ( Request arrival rate: 400 request/sec,
OXC configuration delay: 20 ms, holding time: 100 ms)
31

rate to packet network is high.
The path network cannot bring out the merits with transfering small data because the loss
with lightpath setup delay become larger than the case transfering large data relatively. Figure 15
shows the performance of each network in the case which the data size is small which set to half ofstandard case. In this case, the performance of path network is lower than standard case and thatof packet networks crossly increase. However, the step of increasing or decreasing throughput aswavelength is almost same as that in the standard case. Therefore, the pattern of results is steady.

32

2e+11
total(UDP)
total(TCP)
path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

1.8e+11

Throughput [bps]1.6e+11
1.4e+111.2e+11
1e+11
8e+10
6e+10
4e+10
2e+10
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(a) Throughput

Path request/Packet loss rate

1

0.1

0.01

0.001

path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

0.0001

1e-05

1e-06
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(b) Loss rate

Figure 14: Throughput and loss rate of integrated networks ( Request arrival rate: 200 request/sec,
OXC configuration delay: 200 ms, holding time: 100 ms)
33

2e+111.8e+11

Throughput [bps]1.6e+11
total(UDP)
total(TCP)
path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

1.4e+111.2e+11
1e+11
8e+10
6e+10
4e+10
2e+10
0
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(a) Throughput

Path request/Packet loss rate1

0.01
path(UDP)
path(TCP)
packet(UDP)
packet(TCP)

0.0001

1e-06

1e-08

1e-10

1e-12
0

2
4
6
8
10
12
14
Number of wavelength assigned to path network

16(b) Loss rate

Figure 15: Throughput and loss rate of integrated networks ( Request arrival rate: 200 request/sec,
OXC configuration delay: 20 ms, holding time: 50 ms
34

5 Conclusion
One approach to utilize WDM networks effectively is to utilize WDM networks as packet switched
networks because IP over WDM has good compatibility with the Internet. However, applications
requiring high reliability and large bandwidth such as grid services or digital cinemas become
available recently. On the other hand, path network can fulfill this. Though the drawbacks of thisapproach is lightpath setup delay. To correspond to diversity of traffic pattern in recent years, it isa solution to integrate packet networks and path networks. It is easy to integrate packet and pathswitched networks by using WDM technology.
We have developed an approximation analysis method for optical packet / path integrated
networks. We consider the network as first transmission tried through path network and sends data
through packet network if the first trial is failed. Our approximation analysis method is consists ofapproximation analysis of path network and that of packet network. The approximation analysis
method of path network is the method introduced in [14]. The approximation analysis method ofpacket network is based on M/M/1/K queuing system and iterative calculation.
We evaluate the accuracy of our approximation analysis method by comparing with computer
simulations. As a result, the difference between the results of our approximation analysis and thatof computer simulation is small.
We then evaluate the throughputs and data loss rates of packet / path integrated network by ourapproximation analysis method. The results show that the greater the wavelengths assigned to path
network, the greater the total throughputs of integrated networks. However, the total throughputsof integrated networks decrease when all wavelengths are assigned to path networks because there
is no support of packet networks. It is also revealed that the throughputs of packet networks are
not so high when the data transfer request arrival rate is high, because the path network works asa buffer agent.

35

Acknowledgements
I would like to express my sincere appreciation and great respect to Professor Masayuki Murata
of Osaka University, who was my supervisor and has given me tremendous advice and inspiration
throughout my studies and in the preparation of this thesis.
All works of this thesis would not have been possible without the support of Assistant Professor Shin’ichi Arakawa of Osaka University. He has always provided me with appropriate guidance
and invaluable advice. I am also indebted to Associate Professor Naoki Wakamiya who have given
me helpful advice and support.
Finally, I thank Yuki Koizumi, Yuichi Kiri, Yusuke Sakumoto and many other friends andcolleagues in the Department of Information Science and Technology of Osaka University for
their support.

36

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38