Internet DRAFT - draft-choi-ccamp-e2e-restoration-srlg
draft-choi-ccamp-e2e-restoration-srlg
CCAMP Working Group Jun Kyun Choi(ICU)
Document : Hee Jung Goh(ICU)
<draft-choi-ccamp-e2e-restoration-srlg-01.txt> Tai Won Um(ICU)
Expiration Date: August 2004 Mi-Sun Ryu(ICU)
Tae Gon Noh(Samsung AIT)
June Koo Rhee(Samsung AIT)
Hyeong Ho Lee(ETRI)
Jea Hoon Yu(ETRI)
February 2004
Signaling Extension for the End-to-End Restoration with SRLG
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC-2026.
Internet-Drafts are working documents of the Internet Engineering
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The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at
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Abstract
This draft describes the concept of the SRLG-based logical ring
configuration and recovery method using the ring-SRLG for the purpose of
restoration in mesh networks. In this restoration architecture, backup
paths can be easily established through the end-to-end path, which
follows the logical ring configuration. It guarantees the establishment
of backup path disjointed from the working path. We also propose the
GMPLS signaling extension for the end-to-end restoration based on the
SRLG-based logical ring configuration.
Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119.
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Table of Contents
1. Introduction.....................................................2
2. Logical ring configuration in the mesh networks..................3
2.1 Cycle based recovery mechanisms.................................3
2.2 Segment-wised logical ring......................................5
3. Logical ring configuration based on SRLG information.............6
3.1 Logical ring with SRLG..........................................6
3.2 Resource allocation with SRLG in logical ring configuration.....7
3.3 Signaling for restoration of logical ring configuration.........8
4. Signaling extension for restoration with SRLG....................9
BACKUP Ring Object (BRO)............................................9
5.Conclusion........................................................10
References..........................................................11
Acknowledgement.....................................................12
Author's Addresses..................................................12
Full Copyright Statement............................................13
1. Introduction
With the rapid growth of the Internet, the advance of wavelength
division multiplexing (WDM) technology, and the integration of
various communication technologies, the communication network is
evolving to include huge bandwidth-intensive network applications.
Survivability refers to the ability of the network to transfer the
interrupted service onto spare network capacity to circumvent a point
of failure in the network and it is a critical requirement for IP
over WDM networks. In a WDM network, a link failure, fiber cut, node
down may be due to human error or natural disasters leading to the
loss of large amount of data and multiple failures of all the optical
paths that traverse the fiber. So, we have to develop appropriate
recovery architecture and strategies which minimizes the data loss
when a failure on a path occurs in WDM based GMPLS (Generalized Multi-
Protocol Label Switching) networks that will offer fast recovery,
comparable speed to SONET, and versatile survivable functions.
Recovery techniques are broadly classified by computation timing as
pre-computed and dynamic and by their type of rerouting as link-based,
partial path-based and path-based. In dynamic techniques, a search
for backup path is initiated upon occurrence of a failure. A backup
path is computed based on availability of resource at that time of
failure. While dynamic techniques provide better resource utilization,
they suffer from long delays to search and reroute the traffic on to
the backup path and there is no guarantee that the connection can be
restored upon failure. Dynamic techniques provide a best-effort type
of service. In protection techniques the primary and backup routes
are computed and resources are reserved for backup paths before the
connection is established. Upon occurrence of a failure the backup
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path is established and traffic is immediately routed on to the
backup path. A pre-computed method avoids long delays in setting up
backup paths upon failure. The pre-computed techniques also provide
guarantee that a connection can be restored in the event of failure.
According to range of rerouting, the recovery techniques are
classified into link-based, segment-wised based and path-based
recovery. Link-based techniques reroute disrupted traffic around the
failed link. This approach requires the ability to identify a failed
link at both ends. It also makes recovery more difficult in the event
of a node failure. Furthermore, it limits the choice of backup path
and thus may use more capacity, while path-base techniques replace
the whole path between the two endpoints of a demand. The path-based
techniques have better resource utilization while span-based
techniques have shorter recovery time. Therefore, we may focus on the
path-based recovery, called end-to-end recovery.
Most backbone networks have a mesh physical topology. However, the
mesh-based schemes have some shortcomings. They are not as fast in
failure recovery as ring-based scheme and complicated working path
and backup path routing arrangements are used to achieve optimality,
and also the optimization procedures used for mesh-based schemes are
very computationally intensive, virtually impossible to solve for
very large networks.[12] SONET networks are, for the most part,
protected in the form of rings. The rings are interconnected in order
to provide overall network connectivity and protection. It is
possible to design a fast and simple recovery strategy for ring
network so ring protection switching is well established and robust
in these days. Therefore, we need the ring concept in the mesh
optical network.
This draft describes the Ring configuration based on SRLG information
and signaling extension to support end-to-end restoration from a
source to a destination in pre-OTN network. The restoration scheme
should be timely recovery from failures and also be resource
efficient and flexible to meet requirements. It represents the
protocol specific procedures for GMPLS RSVP-TE (Resource Reservation
Protocol-Traffic Engineering) signaling to support end-to-end
restoration with SRLG based ring architecture which support entire
LSP from the source to the destination. For the disjointness of
end-to-end restoration path from failed working path, we extend the
RSVP-TE signaling message to support SRLG through logical ring.
2. Logical Ring configuration in the mesh networks
Recovery mechanism having advantages both ring and mesh, namely
having speed like ring and efficiency like mesh has been investigated
in recent years as new recovery mechanism.
2.1 Cycle based recovery mechanisms
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In this part, we describe the history of the logical ring
configuration method for the optical networks. Ring-based schemes are
essentially some extensions of self-healing ring in the mesh
topology, and the study of logical ring in mesh network has been
developed. [9],[10],[11],[13]
The optical protection ring has two types.[12],[13] These are the
path-protection and the shared-protection optical ring. In a path
protection optical ring, the forward and return signals of each
lightpath are transmitted in the same direction around the ring from
a source to a destination on a working fiber. Because each wavelength is
protected independently, the service is assured even for failures
that impact a single wavelength. Each connection takes up the entire
ring capacity for one wavelength, however, so the maximum number of
optical paths that can be supported by a ring is equal to the total
number of wavelength channels available. In a shared optical ring
with 2-fiber and 4-fiber, the forward and return signals in a
lightpath do not circumnavigate the entire ring. Once the forward and
returned signals reach their end nodes, the wavelengths used to carry
these signals may be reused by other lightpaths on the remaining
spans of the ring.
P-cycle based on closed cycle routes is the one of the recovery
mechanisms using logical ring in mesh networks.[9] P-cycle adopted
the preconfiguration method to reduce the total connection time would
be to reduce the number of active switch. If the present routes are
to be useful towards the overall recovery of the network, they must
be set with consideration of the restoration of all possible failures
as it is not possible to predict. This preconfigured method made ring
architecture to support fast recovery. Additionally, because P-
cycle can recover not only an on-cycle span failure but also a
straddling span failure it has three to six times greater demanding-
carrying capacity than rings for a given transmission capacity
because p-cycle can recover not only an on-cycle span failure but
also a straddling span failure.
Determining patterns in p-cycle cannot be calculated at once. So it
separately carries out two steps to find optimal p-cycle patterns.
However, this procedure also has some serious problems. First problem
generates large file that is a database file related to ring patterns
which are embedded the network, primarily because of the size of the
set of candidate cycles to consider. Second problem is that it is
also difficult to solve optimality because of large file handled.
If an applied pattern is a cycle traversing all the nodes in the
network exactly once, this pattern can provide one more than spare
routes for any span failure. This cycle is so called Hamiltonian
cycle and can provide maximum restorability with minimum spare
links.[10] Namely, the Hamiltonian cycle of the working network can
provide recovery routes against a single link failure with the
minimal spare links.
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Restricted P-cycle (RPC) has the algorithm to search the min coast
pattern shaped only as the HPC a closed cycle that traverses all the
nodes in the network exactly once.[11] Determining patterns in p-
cycle cannot be calculated it at once. So it carries out two steps to
find optical p-cycle patterns. However, this procedure also has some
serious problems. First problem generates large file that is a
database file related to ring patterns which are embedded the network,
primarily because of the size of the set of candidate cycles to
consider. Second problem is that it is also difficult to solve
optimality because of large files handled. RPC is modified and enhanced
Hamiltonian cycle to reduce the complexity of the existing method for
the recovery of the span failure in mesh networks by using limited
pattern.
2.2 Segment-wised Logical Ring
As a network became large, the possibility of the size of the ring
pattern also became large. So, applying ring does not promote
efficiency in terms of end-to-end delay and recovery time. In this
section we propose the method, called segment-wised ring, that can be
effectively applied to real networks without those problems.
Additionally, it can support fast recovery and can care for partially
multiple simultaneous failures.
The main concept of segment-wised ring are to partition a large network
into several small networks to configure ring to each small network.
The method to divide the large network is out of scope in this article.
Sub-networks can be chosen according to circumstance of a network such
as physical layer, call demands or QoS demands. In this article, network
is divided by based on physical layer.
In the segmented network, sub-RPC can recover failures in each sub-network.
Subnetwork 1 Subnetwork 2 Subnetwork 3
+-----------------+--------------+------------------+
| +--+ | +--+ | +--+ |
| | | | | | | | | |
| //+--+\\ | /+--+\ | //+--+\\ |
| // \\ | / \ | // \\ |
| // \\ | / \ | // \\ |
| +--+ +---+ +---+ +--+ |
| | | | | | | | | |
| +--+ +---+ +---+ +--+ |
| \ / | \\ // | \ / |
| \ / | \\ // | \ / |
| \ / | \\ // | \ / |
| +--+ | +--+ | +--+ |
| | | | | | | | | |
| +--+ | +--+ | +--+ |
+-----------------+--------------+------------------+
// : Working path
/ : backup path
Figure 1. Segment-wise ring architecture
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3. Logical Ring Configuration based on SRLG information
3.1 Logical Ring with SRLG
Shared Risk Link Groups (SRLGs) allow the definition of resources or
groups of resources that share the same risk of failure.[7] The
knowledge of SRLGs may be used to compute diverse paths that can be
used for protection in optical network. The concept of the SRLG has been
used for computing a path that is disjoint from a set of links sharing
the same risk. When tow or more links share the same risk, it means
that when a link failed, the others can fail at the same time. Network
can be planned to recover from failures due to a single risk
(represented by an SRLG) using different mechanism. The SRLG concept
generates another dimension to the existing constraint-based path
computation methods traditionally used in hierarchical networks
Existing logical ring architectures for recovery do not consider the
SRLG information for survivability of working paths and backup paths
and has just been configured based on topology information and
characteristics of network such as P-cycle or the RPC. For example,
the RPC mechanism provides protection switching at a fiber
granularity but there is a lack of true diverse fiber routes. If the
link from start node is broken, the network can not provide the
disjointness because of the SRLG property. This is very fatal
restriction to support survivability of connection with different
bandwidth requirements and QoS constraints. Existing logical ring
configuration does not take account into the probability of resource
failure and risk of the link. Therefore, the disjoint path may find
hardly and the probability of backup path failure increases although
the backup path may exist. We need to considier the possiblity of
failure of the logical ring configuration at the connection setup
stage.
We propose the network architecture as the concept of the logical ring
with the SRLG for reliable transmission in preconfiguration stage. The
network with ring-SRLG which is the set of SRLGs with contribution
weight per each link to avoid the danger of backup path failure and
guarantees the survivability of traffic. We describe the proposed network
architecture as the concept of the logical ring configuration with
SRLG for the purpose of restoration in mesh networks. In this
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restoration architecture, backup paths can be easily established
through the end-to-end path, which follows the logical ring
configuration. It guarantees the establishment of backup path
disjointed from the working path. There are many algorithms to
generate logical rings in mesh network but we will use the similar
concept of p-cycle to make the logical ring pattern. The logical ring
with ring-SRLG has both a working path and a backup path in same ring with
one ring-SRLG and the connection in ring-SRLG must be two-connectivity,
which support logical ring in OXC based mesh network. In a network
which has a SRLG contribution weight associated with each network link
failure, a maximum weight spanning ring is a ring for which the sum of
the contribution weights of the SRLG per link is a maximum. The reason
of finding the maximized SRLG contribution weight ring is that is most
utilized the network resource of backup path and can reduce the
contention probability and be good resource efficiency. We repeatedly
find the logical ring pattern for the newly obtained maximum-weight
logical cycle in links and allocate the unique ring-SRLG ID in each
logical ring. We may consider various optimal ring selection
algorithms. Based on a given SRLG table, which is configured at each
node, one can make rings between a source node and a destination node.
There may be a number of rings, which include the source and the
destination. For the purpose of restoration, we have to select an
optimal ring among the rings list. The selection algorithm should be
restricted by a certain factors such as delay, link costs, and so on.
The ring with SRLG is preconfigured but resources are not allocated.
Therefore, the signaling is applied to the ring architecture for
backup resources after failures on working paths. In our mechanism,
signaling for restoration is needed along the primary route and the
restoration route at the time of initial connection setup. GMPLS
mechanism is similar to those used for setting up the primary path
and also be used to set up the restoration path. In shared-
restoration related signaling, which we suggest, the signaling is
activated only in the case of failure. During restoration, affected
connections are rerouted along their alternate path and this
signaling can be used to reserve sufficient resources. To extend
network scale, the distributed system must be used than centralized
system. In order to configure the SRLG-based logical ring, we may use
a control unit handling the algorithm to set up the SRLG-based
logical ring as well as the GMPLS signaling. Our restoration
signaling on the SRLG-based logical ring can allow dynamic network
configuration instead of static configuration by operators or
management systems. The use of signaling with SRLG may reduce the
complexity of network configuration.
3.2 Resource allocation with SRLG in Logical Ring configuration
Backup resources should be allocated to the logical ring
configuration based on SRLG information in each node. Traditional
concept of SRLG is based on link. But we need the SRLG concept for the
end users. We can easily show the relationship between SRLG per link
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and ring-SRLG for end-to-end connection. The source node can
precompute the ring configuration based on SRLG information during
the primary path setup. The network architecture with the concept of
the logical ring with SRLG for reliable transmission is established
in preconfiguration stage.
As a matter of fact, each SRLG information per link is used to
alternate the failed link. In this case, the SRLG information can be
collected to a ring shape by the topology information. This network
is called as ring-SRLG, which is the set of SRLGs with contribution
weight per each link avoids the danger of backup path failure and
guarantees the survivability of traffic. The logical ring with ring-
SRLG has both working path and backup path in same ring with one ring-
SRLG and the connection in ring-SRLG must be two-connectivity, which
support logical ring in OXC based mesh network. In a network which has
a SRLG contribution weight associated with each network link failure,
a maximum weight spanning ring is a ring for which the sum of the
contribution weights of the SRLG per link is a maximum.
To discuss about the survivability of logical topology, we mean that
the logical topology is redundant (two-connectivity), that is the
logical topology remains connected when a physical link down. The
ingress nodes should have the SRLG history and ring-SRLG combined
with logical ring. The ingress node can precompute the ring
architecture before failure by using the network topology information and
the SRLG contribution weight factors and also configures the ring
architecture after failure by allocating resources by signaling for
backup resources.
3.3 Signaling for restoration of Logical Ring Configuration
We need the signaling to set up path reservation and confirmation
after failures. The ring with SRLG is preconfigured but resources are
not allocated. Therefore, the signaling is applied to the ring
architecture for backup resources after failures on working paths.
In our mechanism, signaling for restoration is needed along the
primary route and the restoration route at the time of initial
connection setup. GMPLS mechanism is similar to those used for
setting up the primary path and also be used to set up the
restoration path. In shared-restoration related signaling, which we
suggest, the signaling is activated only in the case of failure.
During restoration, affected connections are rerouted along their
alternate path and this signaling can be used to reserve sufficient
resources. To extend network scale, the distributed system must be
used than centralized system. In order to configure the SRLG-based
logical ring, we may use a control unit handling the algorithm to set
up the SRLG-based logical ring as well as the GMPLS signaling. Our
restoration signaling on the SRLG-based logical ring can allow
dynamic network configuration instead of static configuration by
operators or management systems. The use of signaling with SRLG may
reduce the complexity of network configuration.
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If there is just one ring pattern between a source and a destination,
the working path and the backup path would be configured via the ring.
In this case, the backup path will follow opposite direction on the
ring. It will simply guarantee the disjoint path between the working
and backup paths. We also need to consider that there is a segment-
wised ring from the source to the destination, and then the working
and backup path will pass several sub-rings. It may cause confliction
between the working and backup paths at the cross point between rings
when the backup path follows the same route on the ring of next sub-
networks. In order to guarantee to establish the backup path through
the different route with working path, it requires a rule which the
signaling is delivered a certain direction. For example, if the
working path is established through clock-wise direction on rings
from the source to the destination, the backup path should be set up
via counter clock-wise direction.
4. Signaling Extension for Restoration with SRLG
In this section, we describe the signaling extension to support the
ring architecture with SRLG for backup path. Also we can show the
message format and its definition. The ring has unique ID. With the
ring ID we should consider the signaling for backup ring setup.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length |Ckass-Num | C-Type(1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved |P-Type(TBD)| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed LSP ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Backup Ring ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG Type | SRLG Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// . . . //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
BACKUP Ring Object (BRO)
The BACKUP ROUTE Object (BRO)is defined to indicate that the backup
resources should be allocated on ring architecture. The BRO can be
presented in path messages and handles the backup ring corresponding
the failed working LSP and its SRLGs for physical/logical disjointess
between working LSP and backup LSP. The BRO has the following format.
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Secondary (S): 1 bit
When set to 1, this bit indicates that the requested LSP is a ring
for secondary path, it indicates that the requested LSP is a
primary LSP.
Protection (P) Type : 6 bits
Indicates desired resource protection type. A value of 0 implies
that LSP recovery type is left unspecified. Only one bit can be
set at a time. The following values are defined. All other values
are reserved and must be sent as Zero and ignored on receipt.
0x00 Unspecified
0x01 End-to-End protection available
0x02 End-to-End protection in use
0x04 Bandwidth protection
0x08 Node protection
TBD SRLG protection
Failed LSP ID : 16 bits
Identifies the LSP affected by the failure. If unknown, this
values by default set to 0.
Ring ID for backup LSP : 16 bits
Identifies the backup LSP for restoration. If unknown, this values
by default set to 0
SRLG Type, Weight, Identifier is described in[7]
Identifiers the SRLG affected by the failure. In other words, the
SRLG Identifier in PROTECTION object represents the failed SRLG ID.
5. Conclusion
Network survivability is a critical requirement in the high-speed
network. So, recovery mechanisms that can provide fast recovery and
efficient capacity are needed. We proposed the new network restoration
architecture called ring-SRLG that has grouped traffic shaped logical
ring by considering of SRLG and sharing resources in GMPLS based networks.
Ring-SRLG can guarantee the survivability of backup path with
constraint to the other logical ring configurations. Our proposed
backup paths can be easily established through the end-to-end path,
which follows the logical ring configuration. It guarantees the
establishment of backup path disjointed from the working path. We
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also propose the GMPLS signaling extension for the end-to-end
restoration based on the SRLG-based logical ring configuration. In
order to configure the SRLG-based logical ring, we may use a control
unit handling the algorithm to set up the SRLG-based logical ring as
well as the GMPLS signaling. Our restoration signaling on the SRLG-
based logical ring can allow dynamic network configuration. The use
of logical ring configuration and signaling with SRLG may provide
efficient network resources and disjointness.
References
[1] Papadimitriou, D. and E.Mannie, "Analysis of Generalized MPLS-
based Recovery Mechanisms (Including Protection and Restoration)",
Internet Draft, work in progress, draft-ietf-ccamp-gmpls-recovery-
analysis-01.txt, November 2003.
[2] Eric Mannie. , "Recovery (Protection and Restoration) Terminology
for Generalized Multi-Protocol Label Switching (GMPLS)", Internet
Draft, work in progress, draft-ietf-ccamp-gmpls-recovery-terminology-
02.txt, November 2003.
[3] Jonathan P. Lang., "Generalized MPLS Recovery Functional
Specification", Internet Draft, work in progress, draft-ietf-ccamp-
gmpls-recovery-functional-00.txt, July 2003.
[4] Berger, L. "Generalized MPLS Signlaing-RSVP-TE Extension",
RFC3473,January 2003
[5] Mannie, E., et. al., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture," draft-ietf-ccamp-gmpls-architecture-07.txt,
November 2003.
[6] Papadimitriou, D. et al., "Shared Risk Link Groups Encoding and
Processing", Internet Draft, draft-papadimitriou-ccamp-srlg-
processing-01.txt, May 2003
[7] P. Czezowski., "Optical Network Failure Recovery Requirements",
Internet Draft, draft-czezowski-optical-recovery-reqs-00.txt, April
2003.
[8] J.P. Lang, et.al., "RSVP-TE Extensions in support of End-to-End
GMPLS-based Recovery", Internet Draft, work in Progress, draft-lang-
ccamp-gmpls-recovery-e2e-signlaing-00.txt, August 2003.
[9] W.D.Grober, "Cycle-Oriented Distributed Preconfiguration: Ring-
link Speed with Mesh-link Capacity for Self-planning Network
Restoration", Communications, 1998.ICC 98. Conference Record.1998
IEEE International Conference on. Volume:1,7-11June 1998,
Page:537~543 vol1.
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[10] Hong Huang, "Hamiltonian Cycle Protection: A Novel Approach to
Mesh WDM Optical Network Protection", High Performance Switching and
Routing, 2001 IEEE Workshop on, 29~31 May 2001, Page(s): 31~35
[11] MiSun Rye, "Survivable Network design using Restricted P-cycle,"
ICOIN 2003, pp25~34, Jan/Feb. 2003
[12] Morley, G.D.and Grover, W.D., "Current approaches in the design
of ring-based optical networks," Electrical and Computer Engineering,
1999 IEEE Canadian Conference on , Volume: 1, pp.:220 - 225 vol.1, 9-
12 May 1999
[13] T.Shiragaki, S.Nakanura, M.Shinta, N. Nenmi, and S,Hasegawa
"Protection architecture and applications of Och Shared protection
Ring," Optical networks magazine, Vol.2, No4, pp.48~58, July/August
2001
Acknowledgement
This work was supported in part by the Korean Science and Engineering
Foundation (KOSEF) through OIRC project
Author's Addresses
Jun Kyun Choi
Information and Communications University (ICU)
58-4 Hwa Ahm Dong, Yusong, Daejon
Korea 305-732
Phone: +82-42-866-6122
Email: jkchoi@icu.ac.kr
Hee Jung Goh
Information and Communications University (ICU)
58-4 Hwa Ahm Dong, Yusong, Daejon
Korea 305-732
Phone: +82-42-866-6282
Email: kaumi@icu.ac.kr
Tai Won Um
Information and Communications University (ICU)
58-4 Hwa Ahm Dong, Yusong, Daejon
Korea 305-732
Phone: +82-42-866-6231
Email: twum@icu.ac.kr
Tae Gon Noh
Samsung Advanced Institute of Technology (Samsung AIT)
P.O. Box 111, Suwon, Kyoungki
Korea 440-600
Phone: +82-31-280-9621
Email: tgnoh@samsung.com
June-Koo Rhee
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Samsung Advanced Institute of Technology (Samsung AIT)
P.O. Box 111, Suwon, Kyoungki
Korea 440-600
Phone: +82-31-280-8193
Email: jk.rhee@samsung.com
Hyeong Ho Lee
ETRI (Electronics and Telecommunications Research Institute)
161 KaJong-Dong, Yusong-Gu, Daejeon
Korea 305-309
Phone: +82-42-860-6130
Email: holee@etri.re.kr
Jea Hoon Yu
ETRI (Electronics and Telecommunications Research Institute)
161 KaJong-Dong, Yusong-Gu, Daejeon
Korea 305-309
Phone: +82-42-860-1602
Email: jh-yoo@etri.re.kr
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Choi et al Expires -- August 2004 [Page 13]
