A hybrid networking architecture

businessmakeshiftNetworking and Communications

Oct 29, 2013 (4 years and 14 days ago)

43 views

1


A h
ybrid network
ing

architecture

Malathi Veeraraghavan

and
Admela Jukan

University of Virginia

mvee@virginia.edu

Feb. 28, 2010

1

Introduction

A recent funding opportunity announcement
1

defines hybrid networking as follows:
A hybrid
networking paradigm combines traditional packet and circuit switching concepts over a single integrated
backbone network to provide differentiated network services to high
-
end science applications with
differ
ent end
-
to
-
end networking performance requirements.

Further, it lists key networking challenges of hybrid networks as:
dynamic allocation of resources
across multiple networking modes, hybrid networking traffic engineering services and inter
-
domain
peering

services, and protection and recovery mechanisms for hybrid networks
.

The purpose of this document is to
define a hybrid networking architecture to meet these networking
challenges
.

2

Background: Current ESnet deployment and services

Figure
1

shows the ESnet deployment as of Summer 2009. It consists of two nodes at each PoP, a core
IP router and an Science Data Network (SDN)
MPLS
switch
, which are interconnected by one o
r more
10Gbps links
.
There are
multiple

inter
-
PoP links,
some interconnecting

core IP routers and
others

interconnecting

SDN switches.
There are two primary

types of connectivity services offered by ESnet
2
:
IP
-
routed services
and
virtual circuit

services.

The IP
-
routed services are supported by the core IP routers,
and the
virtual circuit

services are supported by the SDN switches. The latter also requires
an
OSCARS
(
On
-
demand Secure Circuits and Advance Reservation System
) InterDomain Controller (IDC
)
3
, w
hich
is
a circuit scheduler

through which users and applications can
request

circuits of known durations and rates
for immediate or future use.

In addition

to the router/switch equipment at the PoPs
, ESnet deploys its own routers in many of the
site

networ
ks
a
, referred to as Provider Edge (PE) routers. Customer Edge (CE) routers owned and
operated by the sites connect to these PE route
rs within the sites.

PE routers typically connect to the
core
IP routers at the PoPs, though some site routers connect to th
e core SDN switches directly as well, e.g.,
Fermilab.

Packet
filters and route filters are

executed on these site PE routers
.
It is prefe
rable to execute
these filters at the site PE routers than at core routers because core routers

handle traffic from
mul
tiple

sites, which would make the aggregate size of the filter files
unmanageably large

(per
-
site

inbound and
outbound filters
often

exceed 10K lines or more
4
)
.

ESnet also peers with commercial networks and other research
-
and
-
education networks (RENs).




a

The term “site” is used to refer to national laboratories and other organizations connected to ESnet.

2



Figure
1
:
Summer

09
deployment [Source:
http://www.es.net/pub/maps/current.pdf
]

3

Integrated
network

The first step in
designing

a hybrid network, as per the definition stated in Section
1
, is to
determine
equipment suitable as integrated nodes.
The next step is to determine how these integrated nodes, located
at PoPs and possibly some sites
, are interconnected.

3.1

Integrated node

For this contex
t,
a
n integrated node

is
defined as one

that supports both (i) IP packet forwarding, and
(ii) virtual circuit switching.

Given
the ubiquity of

IP
-
routed service
s
,
IP
packet forwarding

capability

is a must in any integrated
node.

For
virtual
circuit
switching
, there are a number of technology choices: SONET/SDH, WDM, MPLS
variants, and Ethernet VLANs/
carrier Ethernet. Circuit switches, such as SONET/SDH switches and
WDM switches, are one potential choice. MultiService Provisioning Platforms (MSPPs), s
uch as Ciena’s
Core Director, integrate Ethernet VLAN capability with SONET/SDH switching.
These MSPPs are used
in
Internet2’s Dynamic
-
Circuit Service (DCS) deployment. However, t
hey do not support IP packet
forwarding

capability
. MPLS is built into IP rou
ters, and is the curren
t solution used for the virtual
circuit
services provided by ESnet. Equipment such as Juniper’s M, MX and T series
systems
,
and
Cisco’s
Catalyst 6500 series,

among others,

support IP
packet forwarding
, MPLS switching and Ethernet VLA
N
switching. VLAN switching is made more scalable with new standards defined under the umbrella term
“Carrier Ethernet.”


The InterDomain Controller Protocol (IDCP)
5

has been defined to offer
users

inter
-
domain

virtual
circuits.
R
ecalling Metcalfe’s law th
at value grows exponentially with th
e number of connected
endpoints, this extension of virtual circuit services to inter
-
domain usage is highly important.

SONET/SDH, WDM, and MPLS technologies have no data
-
plane constraints for scaling to inter
-
domain
3


usa
ge. However, for Ethernet VLANs,
C
arrier Ethernet
standards,

s
uch as IEEE 802.3ad and 802.3ah, are
required to
overcome scalability problems with the
basic
12
-
bit VLAN identifier
6
.


In summary, the key requirements
for

an integrated node
are

that it supports: (i) IP packet forwarding,
and (ii) a virtual circuit switching technology that scales for interdomain usage.

3.2

Integrated links


Figure
2
: Integrated node and links

Figure
2

depicts an integrated node that meets the high
-
level requirements specified in Section
3.1

in
that

it supports both IP packet
-
forwarding capability and a scalable virtual circuit switching capability. In
this section, we focus on how the links can be shared between IP
-
routed and
virtual circuit

services.

Shown in
Figure
2

are access links to sites and peers and inter
-
PoP links, on both of which static circuits
(shown in blue)
and

dynamic circuits
b

(shown in red) can be provisioned. IP addresses will be assigned to
t
he static circuits causing packets arriving on these to be handled by IP packet forwarding. Frames
arriving on the dynamic circuits will be handled by the virtual circuit switch.

Figure
3

shows an illustrative example of how integrated nodes can be deployed using a part of the
ESnet topology. Five PoPs, PNWG, DENV, ALBU, ELPA and SUNN, and three sites, PNNL, LBL and
LANL, are shown.
Since some sites may just have IP rou
ters while others may have these integrated
nodes
,
as
an example
Figure
3

shows just an IP router in the
PNNL
site (which could be a PE or CE
router) and integrated no
des at the

LBL and LANL
sites
. Links between PoPs are shown to be 100GbE.
Blue dashed lines are used to depict static circuits provisioned via a network management system, such as
the Spectrum NMS currently used by ESnet
2
. A red dashed line is used to depict a dynamic circuit set up
between LBL and LANL, which is created by the OSCARS IDC.

Projects such as Terapaths
7
, StorNet
8
,
and ESCPS
9

will increase the number of end applications that request the use of virtual circuits.




b

The term “dynamic circuit” is assumed to be a generic term including both circuits and virtual circuits, depending
on the technology used. ESnet refers

to this service in [
2
] as just “virtual circuit” service. Hence these terms are
used interchangeably in this document.

4



Figure
3
: An example integrated (hybrid) network deployment for a part of the ESnet topology

Such an integrated use of
links for both IP
-
routed traffic and dynamic virtual circuit traffic requires the
support of additional network functionality, which is described in the next section.

4

Additional functionality in hybrid networks

As stated in Section
1
, three networking challenges are iden
ti
fied
for hybrid networks
in [
1
]
.

These
include:
dyn
amic allocation of resources across multiple networking modes, hybrid networking traffic
engineering services and inter
-
domain peering services, and protection and recovery mechanisms for
hybrid networks
.

4.1

Dynamic allocation of resources
between IP
-
routed s
ervice and dynamic circuit service

Capacity of all inter
-
PoP links and site/peer access links needs to be divided
for IP
-
routed services
managed by

the Spectrum NMS and
virtual circuit services controlled by
OSCARS IDC. For example,
each 100GbE link
between PoPs may be divided into a 10Gb/s allocation for static circuits between PoPs
to carry IP
-
routed traffic, and the remaining 90Gb/s allocated for dynamic circuit service.

In practice, the
OSCARS IDC could manage the creation/deletion of both dynamic

circuits and static circuits, with the
Spectrum NMS used for monitoring and other functions. Even in this scenario, capacity should
still
be
divided between static circuits and dynamic circuits
to prevent starvation of either of these two service
types
.


For an optimal computation of capacity allocations for the two types of services,
IP
-
routed

and
dynamic circuit services, network management systems that have a complete view of the current routing
and traffic conditions are required. These consist of:



5


H
ybrid
r
oute

monitoring
servers


Basic route monitoring servers

have been implemented to

listen
to
but not actively participate in the
distributed
routing protocol
s

executed by the route processors of
IP routers
. Special monitoring
systems

such as the OSPF
Monitor
10

have been successfully deployed in large ISP networks and have been
integrated within the monitoring and management systems successfully in order to identify faults in IP
networks
11
.

Similar systems can be implemented for ISIS and BGP, and other r
outing protocols
, if any,

deployed by ESnet. New hyb
r
id route monitoring servers
,

which are
required to support
hybrid

capacity
allocation
servers (see below)
,

could build on these systems, and add functionality, such as determining

the cause of routing changes and the effect
s
of these changes on routing in the network
.

Hybrid t
raffic monitoring
servers


Basic traffic monitoring servers
are
deployed in ISPs

to
periodically read out link loads measured by
SNMP agents
running

within

IP

routers
.
Averaging is done on the order of 10
-
30sec. Traffic matrices
(showing
traffic
levels
between each pair of PoPs
)

can be estimated from these link
-
level measurements
using t
echn
iques such as the Gravity model
12
. Other techniques used to determine tr
affic matrices is to
deploy a full mesh of
MPLS
LSPs between PoPs

with no rate policing/limiting
, and
then
obtain SNMP

traffic measurements on these
LSPs
13
.

Some such mechanism is required

to determine traffic matrices for
both the IP
-
routed and dynamic cir
cuit service in order to then use the optimization tools to compute new
capacity allocations.

Hybrid capacity allocation servers

Using information from the hybrid route monitoring and traffic monitoring servers, forecasting can be
done to project expected
traffic for a time interval into the future. Optimization algorithms can then be
executed to determine the ideal capacity divisions between IP
-
routed and dynamic circuit services. The
allocations determined for IP
-
routed service can be implemented with rat
e policing on the static circuits
establis
hed between the integrated nodes
. The allocations determined for the dynamic circuit service
would need to be communicated to the OSCARS IDC for its use as it accepts/rejects requests for circuit
reservations.

This

functionality of dynamic capacity allocation
is

important if
a service provider chooses to operate
the network at high levels of
link
utilization.

However, service providers typically operate their links at
less than 50% utilization both to absorb sudden surges, as in the REN community (e.g., Internet2 has a
stated “headroom practice” of operating links at a maximum of 25
-
30% utilization to “
enable

researchers
to engage in unpredictable large
-
bandwidth

applications

14
), and for handling
additional traffic loads
caused by rerouting if and when
failures

occur

(an often cited reason by commercial providers for

maintaining

low link utilization
).

In other

words, service providers typically overprovision their link
capacities by adding new links as traffic loads increase.

Furthermore, d
ynamic capacity allocation for the IP
-
routed service could r
equire rerouting of some of
the static

circuits

and/or reroutin
g of IP
-
layer traffic
. O
perations divisions of service providers typically
have strong resistance to change the network topology because of the potential for “route flaps” and
drastic changes in the end
-
end packet latency (e.g., greater than 10ms). For the
se reasons,
the frequency
with which dynamic capacity reallocations
will be required is likely to be

small.

4.2

H
ybrid network

traffic engineering services

The ESnet services document [
2
] explains
the
traffic
-
engineering services
deployed on today’s ESnet
as follows: “ESnet employs a variety of techniques to make the best use of the resources deployed, these
include:
scavenger service
, and
site specific traffic engin
eering

to support programmatic needs such as
6


LHC Tier1 to Tier2 support at FNAL.” The
scavenger service

is implemented to be “consistent with
Internet2’s QBone Scavenger Service (QBSS)” and is done by “done by allocating a separate queue
within each router

in ESnet and configuring it with an aggressive drop profile and minimal service quota”
so that large bulk transfers do not impact day
-
to
-
day traffic. The
site
-
specific traffic engineering

is
implemented with Policy
-
Based Routing (PBR) to map specific traf
fic flows on to virtual circuits
established through the dynamic circuit service (using OSCARS IDC).

The integrated (hybrid) network architecture, described in Section
3
, should build on these deployed
traffic engineering services
.
There are two approaches
, both of which can be viewed as
hybrid element
management systems
: LambdaStation
15

and HNT
ES
16
. In the
Lambdastation

approach, end
applications, such as dCache/SRM, signal LambdaStation servers associated with IP routers that a
particular flow being generated by the application would prefer the use of virtual circuits. The
LambdaStation server communicates with the OSCA
RS IDC to dynamically create the circuit, and then
configures the IP router using PBR to redirect packets corresponding to that flow to the newly established
circuit.

By deploying such Lambdastation servers, a better use of the two services types is accomp
lished
with the help of end user applications.

In the
Hybrid
Network Traffic Engineering Software (H
N
T
ES)

approach, Netflow data collected
by routers (which is currently enabled in ESnet routers) is analyzed offline using an Offline Flow
Analysis Tool (OFA
T). Unlike on the Internet, where P2P flows that i
mplement port masquerading make

5
-
tuple iden
ti
fication of long flows challenging, in the ESnet context, it is easier to detect long flows
generated by scientific applications. For example, the Unidata LDM a
pplication used by Climate
scientists runs on a well
-
known TCP port, 388. An analysis of Internet2 Netflow data has already shown
that many flows generated by this application are indeed of long durations (running tens of minutes to
hours). When long flows

are identified by OFAT, flow identifiers (wh
ich is a subset of the 5 tuple:

source IP address, destination IP address, source port number, destination po
rt number and IP protocol
number
) of long flows are placed in a monitored flow database (MFDB). The a
ssociated IP router is
configured to mirror pa
ckets from these flows to the H
N
T
ES system. A flow monitoring software module
is executed
within

the H
N
T
ES system, capturing these packets, and then communicating with the
OSCARS IDC to create a dynamic circuit

for a particular flow. Again PBR is used to redirect packets
within the IP router to the newly established circuit.

These two hybrid network traffic engineering schemes ensure a more
-
effective usage of the capacity
allocations that are determined by the h
ybrid capacity allocation servers described in Section

4.1
. The
hybrid capacity allocation algorithms cannot be executed too often as it could cause instabilities.
Therefore, these hybrid network traffic engineering servers ensure that traffic is more effectively spread
between these two allocations. Even as user application
s initiate

flows directed to the IP
-
routed service,
these traffic engineering servers redirect

some of these flow
s

selectively to the virtual circuit service to
improve overall performance.

4.3

Protection and recovery mechanisms for hybrid networks

The ESnet services document [
2
] notes that “ESnet’s multiple ring backbone topology insures that no
single backbone circuit failure will cause an outage to a site. The internal routing protocols are configured
to switch to

a backup path within 2
seconds

upon determining a backbone link has failed.” The topology
in
Figure
1

shows these rings.

For example, if there is a failure on the li
nk between DENV and KANS,
the ring passing through HOUS, ELPA and ALBU can be used to reroute IP
-
routed traffic.

This means
restoration is occurring at the IP
-
routed layer (Layer 3).

In the integrated (hybrid) network described in Section
3
,
since ESnet would has its own capability to
provision circuits via its virtual circuit switching engines, instead of establishing single static circuits
between PoPs
for the IP
-
r
outed service
as shown in
Figure
3
, two path
-
disjoint circuits could be
7


established for IP
-
routed service, with one circuit being the working path and the second, a p
rotection
path. This would consume
more
bandwidth but offer a faster restoration than the IP layer restoration
implemented
today. It however requires the virtual circuit switching technology implemented within the
integrated nodes, as shown in
Figure
2
, to support automated protection switching schemes as offered by
SONET or fast reroute of MPLS.

Whether Carrier Ethernet supports such automated protection should be
con
sidered while choosing the integrated node equipment.


Alternate schemes are possible in which IP routing tables could list routes via the backup virtual
circuits, but then set the backup virtual circuits to a “down” state until failures occur on the prima
ry
virtual circuits. When a fault management NMS sees an

alarm indicating a failure of
a primary
virtual
circuit
, it could signal the router to make the backup virtual circuit interface functional, allowing for
the
IP packet forwarding engine

to immediatel
y find reachability for addresses via the backup virtual circuits.
This form of restoration would be faster than IP (Lay
er 3) restoration, such as the ring

based solution used
in ESnet today, since the latter requires IGP routing protocol messages to be ex
changed before new
reachability information is stable for addresses than become unreachable when a link fails.

In addition to an immediate protection switch to a backup circuit, commercial service providers such
as AT&T
17

implement a two
-
phase approach leveraging the hybrid nature of these integrated networks.
Phase 1 is the immediate protection switch to the backup circuit. Phase 2 consists of a
hybrid fault
-
management NMS

computing an alternate set of two paths (working
and protection), and then
communicating with either the OSCARS IDC or the Spectrum NMS to establish these circuits, based on
whichever of these two
software systems
handle
s

the static circuits
required
for
the
IP
-
routed

service
.

5

Literature review on hybri
d networks

Urushidani et al.
18

use
s

the term hybrid netwo
rks in the following manner: “s
ome academic backbone
networks [Internet2 and GEANT2 are cited] focus on providing layer
-
1 circuit services as well as packet
services by using hybrid network architect
ures composed of IP routers and next
-
generation SDH/SONET
devices”.

Effectively, this definition does not require an integrated network deployment in order to
support the two types of service
s as in the definition provided in [
1
].

Gauger et al
.
19

defines a hybrid n
etwork as follows
:

an optical network architecture is called hybrid if
it combines two or more basic network t
echnologies at the same time.”
Three optica
l network
technologies are named: optical packet switching (OPS),
e.g.,

Nejabati
20
, optical burst switching (OBS),
e.g.,
Qiao
21

, and optical circuit switching (OCS) technologies operating on wavelengths, wavebands or
fiber. Optical hybrid networks are then
classified
as
: (a) c
lient
-
s
erver
, (b) p
arallel
, and (c) i
ntegrated
.

The
IP
-
routed services layer is not considered as part of this definition of “hybrid” networks. In all three cases
of “optical hybrid networks,” IP routers are considered the endpoints of the hybrid optical network.

In client
-
server networks, OPS and OBS

form “client layers”
that use wavelength
-
,

waveband
-

or
fiber
-
based circuits established through the “OCS server layer.” IP packets from IP routers are carried
within optical packets through an OPS network, or in bursts through an OBS network. These optic
al
packet switches or optical burst switches are interconnected via optical circuits established a priori
through the OCS network. In the
parallel
optical
hybrid network,
IP routers can feed packets directly into
both the (i) OPS/OBS network, and (ii) OCS
network. An example o
f a parallel hybrid network is
a

polymorphic
multiservice optical network (PMON)
proposed
by de Miguel et al.
22

The third class of
hybrid architectures is the integrated hybrid network, where the
optical
circuit

switching capability is
integrated with an optical packet or burst switch
.
The hy
b
r
id optical switch (HOS) proposed
work by Xin,
et
al.
23

combines an OBS with an OCS.
Another such integrated OBS/OCS hybrid node was proposed by

Lee et al.
24


8


Recently, Grid and cloud computing comm
unities have used the term

hybrid networking


in the
context of connectivity services for scientific communities, such as in
a
paper by de Laat
et al
.
25

A p
aper
by Yeh et al
.
26

discusses the

important issue of alarm correlation in combined optical/IP networks.

In summary, most of existing
literature

uses the concept of “optical
hybrid
networking” to r
efer to
network technologies that combine
different
optical
switching mechanisms (
such as opt
ical
circuit

switching
,
optical
burst

switching
,
and optical
packet

switching
).
Unlike the architecture described in this
current paper,
IP

packet forwarding

capability

is not part of these “optical hybrid
nodes
.” In all cases, IP
routers are edge devices
that connect to these optical hybrid networks. In addition to these publications on
“optical hybrid networking”
,
there is a
significant amount of
literature on integrating the design of IP
routed networks with Routing and Wavelength Assignment (RWA) algori
thms in optical circuit switched
networks, such as SONET/SDH and WDM networks
. T
hese papers are not
cited here as they are
essentially separate networks with the
optical
circuit
-
switched networks serving the IP
-
routed networks
by providing point
-
to
-
point c
onnectivity between IP routers

(e.g., Gauger et al.’s client
-
server
architecture)
.

6

Summary

There are several advantages to creating an integrated network, consisting of integrated nodes that
support both IP packet forwarding and
virtual circuit

switching,
and one set of shared inter
-
PoP and
site/peer access links, on which t
wo distinct types of services,
IP
-
routed and dynamic
virtual circuit

services are supported. Equipment maintenance costs, col
l
ocation service costs and costs of wide
-
area
link leases, wi
ll all be lower than in a solution where separate network

equipment

and separate links are
deployed to offer customers these two types of services.

Three networking functions are identified to
enable the support of these dual services on this integrated single network. These include: (i) dynamic
link capacity allocation
s

for these two services, (ii) hybrid network traffic
-
engineering services to
effe
ctively use both capacity partitions, and (iii)

hybrid fault management systems for improved
protection and recovery capabilities.




1

Office of Science, Financial Assist
ance, Funding Opportunity Announcement DE
-
FOA
-
0000264, "High
-
Capacity
Optical Networking and Deeply Integrated Middleware Services for Distributed Petascale Science,"
http://www.science.doe.gov/grants/FOA
-
10
-
0000264.ht ml

2

Joseph Burrescia, Michael Collins
, William Johnston, “ESnet Services and Service Level Descriptions Version
4.0,” July 17, 2009, http://www.es.net/hypertext/ESnetServiceLevels
-
V4.0.pdf

3

https://oscars.es.net/OSCARS/

4

Conversation with Chin Guok, ESnet, October 2009.

5

Dante, Internet2,
Canarie and ESNet (DICE), “Inter
-
domain Controller (IDC) Protocol Specification.” [Online].
http://www.controlplane.net/idcp
-
v1.1/idc
-
protocol
-
specification
-
v1.1
-
feb092010.pdf
, Feb. 9, 2010
.

6

Samer Salam and Ali Sajassi, “Provider Backbone Bridging and MPLS:Complementary Technologies for Next
-

Generation Carrier Ethernet Transport,” IEEE Communications Magazine, March 2008

7

TeraPaths
: Configuring End
-
to
-
End Virtual Network Paths with QoS Guarantees,
https://www.racf.bnl.gov/terapaths/

8

StorNet,
http://indico.fnal.gov/conferenceOtherViews.py?view=standard&confId=2970

9

End Site Control Plane System (ESCPS),
http://indico.fnal.gov/conf
erenceOtherViews.py?view=standard&confId=2970

10

A. Shaikh and A. Greenberg, “OSPF monitoring: Architecture, design, and deployment experience,” in Proc.
Networked Systems Design and Implementation, March 2004.

11

Us e of OSPFMON in TSO Diagnos tics tools us ed

by
Cisco,

http://www.cisco.com/en/US/docs/ios/sw_upgrades/interlink/r2_0/sysmgmt/smtools.html#wp878634

12

A. Medina, N. Taft, K. Salamatian, S
. Bhattacharyya, and C. Diot, “Traffic matrix estimation: Existing techniques
and new directions,” in Proc. of ACM SIGCOMM, Aug. 2002.

13

X. Xiao, A. Hannan, B. Bailey, and L. Ni, “Traffic engineering with MPLS in the Internet,” IEEE Network, no. 2,
pp. 28
-
33, Mar/Apr 2000.

9









14

R. P. Vietzke, “Internet2 Headroom Practice,” Aug. 15, 2008,
https://wiki.internet2.edu/confluence/download/attachments/17383/Internet2+Headroom+Practice+8
-
14
-
08.pdf?version=1

15

The Lambda Station Project. [Online]. Available: http://w
ww.lambdas tation.org/

16

Hybrid Network
Traffic Engineering Software (H
N
T
ES) Software,
http://www.ece.virginia.edu/mv/res earch/DOE09/documents/deliverables/
feb
2010/mv
-
hyntes.pdf.

17

A. Chiu, G. L. Choudhury, G. Clapp, R. Dovers pike, J. W. Gannett, J. G. Klin
cewicz, G. Li, R. A. Skoog, J. L.
Strand, A. C. Von Lehmen, and D. Xu, "Network Des ign and Architectures for Highly Dynamic Next
-
Generation
IP
-
Over
-
Optical Long Distance Networks," Journal of Lightwave Technology, vol. 27, no. 12, pp. 1878
-
1890, June
2009.

18

Urus hidani, S.; Abe, S.; Yus heng Ji; Fukuda, K.; Koibuchi, M.; Nakamura, M.; Yamada, S.; Shimizu, K.;
Hayas hi, R.; Inoue, I.; Shiomoto, K.; , "Des ign of vers atile academic infras tructure for multilayer network s ervices,"
Selected Areas in Communications
, IEEE Journal on

, vol.27, no.3, pp.253
-
267, April 2009

19

C. M. Gauger, et al., “Hybrid Optical Network Architectures: Bringing Packets and Circuits Together”,

IEEE Communications Magazine, August 2006

20

Nejabati, R.; Zervas, G.; Simeonidou, D.; O'Mahony, M.J.; Klonidis, D.; , "The “OPORON” Project:
Demonstration of a Fully Functional End
-
to
-
End Asynchronous Optical Packet
-
Switched Network,"
Lightwave
Technology, Journal of

, vol.25, no.11, pp.3495
-
3510,
Nov. 2007

21

C. Qiao, M. Yoo, “Optical burst switching (OBS)
-

a new paradigm for an optical Internet,

Journal of High Speed Networks, 8(1), 1999

22

Ignacio de Miguel, et al., “Polymorphic Architectures for Optical Networks and their Seamless Evolution towar
ds
Next Generation Networks,” Photonic Network Communications, Volume 8, Number 2, September 2004

23

C. Xin, C. Qiao, Y. Ye, S. Dixit, “A Hybrid Optical Switching Approach,” IEEE GLOBECOM 2003

24

Gyu Myoung Lee, Bartek Wydrows ki, Mos he Zukerman,Jun Kyun Choi

and Chuan Heng Foh, “Performance
Evaluation of an Optical Hybrid Switching System,” IEEE Globecom 2003.

25

C. de Laat, et al., “A distributed topology information system for optical networks based on the semantic web,”
Optical Switching and Networking
,
Volume 5, Issues 2
-
3
, June 2008, Pages 85
-
93.

26

E. Yeh., et al, Des ign of Alarm Management Sys tem in Hybrid IP/Optical Networks, International Conference on
Advanced Information Networki
ng and Applications Works hop, 2009.