CCAMP Working Group Jun Kyun Choi(ICU) Document : Hee Jung Goh(ICU) 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 Task Force (IETF), its areas, and its working groups. Note that other groups MAY also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and MAY be updated, replaced, or obsolete by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 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. Choi et al Expires -- August 2004 [Page 1] End-to-End restoration with SRLG February 2004 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 Choi et al Expires -- August 2004 [Page 2] End-to-End restoration with SRLG February 2004 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 Choi et al Expires -- August 2004 [Page 3] End-to-End restoration with SRLG February 2004 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. Choi et al Expires -- August 2004 [Page 4] End-to-End restoration with SRLG February 2004 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 Choi et al Expires -- August 2004 [Page 5] End-to-End restoration with SRLG February 2004 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 Choi et al Expires -- August 2004 [Page 6] End-to-End restoration with SRLG February 2004 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 Choi et al Expires -- August 2004 [Page 7] End-to-End restoration with SRLG February 2004 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. Choi et al Expires -- August 2004 [Page 8] End-to-End restoration with SRLG February 2004 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. Choi et al Expires -- August 2004 [Page 9] End-to-End restoration with SRLG February 2004 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 Choi et al Expires -- August 2004 [Page 10] End-to-End restoration with SRLG February 2004 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. Choi et al Expires -- August 2004 [Page 11] End-to-End restoration with SRLG February 2004 [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 Choi et al Expires -- August 2004 [Page 12] End-to-End restoration with SRLG February 2004 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 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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