T.-H. Wu, Fiber Network Service Survivability. Artech House, 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....in a WDM network may affect upwards of a Terabit of traffic per second, motivates the study of WDM network survivability and reliability. The concept of survivable optical networks has been discussed extensively in [13 19] In addition, Path and link recovery schemes have also been researched in [20 22]. These studies have shown that path protection provides a better spare capacity utilization than link protection, but suffers from longer recovery times. We assume that the network is survivable or protected against any single link failure at the optical layer. In our work, such protection is ....

T. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

....INTRODUCTION N ETWORK survivability techniques have been proposed to guarantee the seamless communication services in the face of network failures. Most techniques use centralized planning and are developed for circuit switched networks such as public switched telephone networks [1] SONET SDH [2], 3] 4] ATM [5] 6] 7] WDM networks [8] 9] However, circuitswitched backbone networks are being replaced or overlapped with packet switched networks which provide better manageability of bandwidth granularity and connection types. This architecture migration has been significantly ....

....noted otherwise. The network redundancy is measured by the ratio of the total spare capacity over the total working capacity. It depends highly on the network topology as well as the spare capacity allocation algorithms used. For example, a self healing ring (SHR) topology has 100 redundancy [2], 3] In mesh type networks, when working paths are the shortest hop paths, more than 100 redundancy is needed in reserving backup paths. However, the redundancy can be reduced by sharing spare capacity reservations and this reduction is feasible only when failure scenarios are non overlapping ....

Tsong-Ho Wu, Fiber Network Service Survivability, Artech House, 1992.

....optical networks has been discussed extensively in [ 1 3,11,12] In addition, in [4,5] the authors compared path and link protection restoration strategies by formulating their capacity requirements as an Integer Linear Program. Path and link recovery schemes have also been researched in [13 15]. These studies have shown that path protection provides a better spare capacity utilization than link protection, but suffers from longer recovery times. In [6] the authors proposed analytical methods to estimate capacity utilization in optical networks that are resilient to single link ....

T. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

....is prepared to recover from failures but encounters instead an attack, it may malfunction and cause failures. A common recovery scheme is based on rings. We consider the two types of network restoration used for SONET SDH, the most common standards in use for highspeed optical communications [55]. Note that SONET SDH are not all optical standards, but the rates they support make their need for rapid service restoration commensurate with that of AONs. Speed of recovery with opto mechanical switches is in the tens of milliseconds and nanoseconds for acousto optical switches. SONET SDH allow ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, 1992.

....algorithm has the potential of minimizing network cost both in terms of efficient use of fiber and reducing use of electronics. 5) Protection and Restoration: Various failures, such as fiber cuts, line card and switch failures, and software failures, can occur that disrupt network services [58]. Protection and restoration are two methods networks used to recover from these failures. Protection refers to hardware based, preplanned, fast failure recovery. Restoration refers to software based, dynamic, slower recovery. Protection is generally limited to simple topologies like rings or the ....

T.-H. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

....of the failure and restoration reconfiguration. The generic term demand refers to a working unit of aggregated traffic to be transported between origin destination (O D) nodes of the network. The term follows Wu s distinction between traffic itself and the demand units required to transport it [15]. For example, traffic is the individual IP packet and or STS level tributary flows exchanged between O D pairs. But demand expresses the aggregate requirement of all traffic types for lightpaths between a given O D pair. One unit of demand consumes one working wavelength on each span traversed ....

T. S. Wu, Fiber Network Service Survivability, Artech House, 1992.

....The nodal elements of rings are relatively low cost add drop multiplexers (ADMs) An ADM has two optical line (e.g. OC 24, or OC 48 say) terminations and can originate (add) or terminate (drop) any of the tributary payload signals (e.g. STS 1 or DS3) from the line signal passing through it. See [2] for more on rings. The important point is that rings use a simple switching mechanism which permits restoration in about 50 60 ms, but they require at least 100 redundancy. In complete multi ring network designs the working fiber or channel groups themselves are usually not fully utilizable, so ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, Boston, Mass.

....through pre planned cycles ( GS98] The most direct approach is to design the network in term of rings. The building blocks of SONET networks are generally self healing rings (SHRs) and diversity protection (DP) WCB91, Was91, WB90, SWC93, SGM93, SF96, STW95, GHS 94, WW92, TYKK94, Wu94, Wu92, WKC89, HT92] SHRs are unidirectional path switched rings (UPSRs) or bi directional line switched rings (BLSRs) while DP refers to physical redundancy where a spare link (node) is assigned to one or several links (nodes) Wu92] pp. 315 32) In rings, such as BLSR, link or node restoration is ....

.... WB90, SWC93, SGM93, SF96, STW95, GHS 94, WW92, TYKK94, Wu94, Wu92, WKC89, HT92] SHRs are unidirectional path switched rings (UPSRs) or bi directional line switched rings (BLSRs) while DP refers to physical redundancy where a spare link (node) is assigned to one or several links (nodes) Wu92] pp. 315 32) In rings, such as BLSR, link or node restoration is simply implemented using loop back. The waste of bandwidth due to back hauling may be remedied by looping back at points other than the failure location ( Mag97, KTK94] Using only DP and SHRs is a constraint which has cost ....

[Article contains additional citation context not shown here]

T.H. Wu. Fiber Network Service Survivability. Artech House, 1992.

....INTRODUCTION N ETWORK survivability techniques have been proposed to guarantee the seamless communications services in the face of network failures. Most techniques use centralized planning and are developed for circuit switched networks such as public switched telephone networks [1] SONET SDH [2], 3] 4] ATM [5] 6] 7] WDM networks [8] 9] However, circuit switched backbone networks are being replaced or overlapped with packet switched networks which provide better manageability of bandwidth granularity and connection types. This architecture migration has been significantly ....

....noted otherwise. The network redundancy is measured by the ratio of the total spare capacity over the total working capacity. It depends highly on the network topology as well as the spare capacity allocation algorithms used. For example, a self healing ring (SHR) topology has 100 redundancy [2], 3] In mesh type networks, when working paths are the shortest hop paths, more than 100 redundancy is needed in reserving backup paths. However, the redundancy can be reduced by sharing spare capacity reservations and this reduction is feasible only when failure scenarios are non overlapping ....

Tsong-Ho Wu, Fiber Network Service Survivability, Artech House, 1992.

....(SCA) problem is to decide how much spare capacity should be reserved on network links for given traffic flows and their working paths on two connected mesh networks. It is part of survivable network design and is NP complete [1] Many research efforts on this issue has been done on SONET SDH [2], 3] 4] 5] ATM [6] 7] 8] 9] WDM networks [10] 11] 12] Recent issue on IP and MPLS networks are also given in [13] 14] 15] A detailed literature review on different spare capacity allocation algorithms and restoration schemes is given in [16] 1] In this paper, we first ....

Tsong-Ho Wu, Fiber Network Service Survivability, Artech House, 1992.

....are multiplexed and transported on a relatively sparse backbone of high capacity fiber optic transmission links. The impact of failure can be drastic [1] 2] There are currently two main approaches to provide a selfhealing capability for these networks. These are, generically, the ring [3] [11] and mesh [12] 20] restoration strategies. In a self healing mesh, demand flows are restored by agile re routing through the relatively small allocations of spare capacity on other spans of the network. Control of the process may be distributed [12] 14] 16] 18] or centralized [12] ....

....to offset the cost of the digital cross connect systems they use, making them effective in long haul networks. In comparison, rings require greater total capacity but reconfigure independently in a much simpler switching reaction and are based on less expensive add drop multiplexer (ADM) equipment [3] [7] Rings consequently Manuscript received June 6, 1996; revised February 1, 1998; approved by IEEE ACM TRANSACTIONS ON NETWORKING Editor K. S. Vastola. The author is with TRLabs, Edmonton, AB, Canada T5K 2P7 (e mail: grover edm.trlabs.ca) Publisher Item Identifier S 1063 6692(99)06391 8. ....

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T. H. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

....two seconds of outage, at which time switched and private line connections in progress are dropped by the circuit switches [1] Two seconds is therefore widely recognized as one significant real time target for restoration. Dedicated diverse routed fiber systems and protection switching rings [9] can restore service in 50 150 ms but represent an essentially fixed transport configuration to which the selforganizing methods that follow do not apply. In span restoration, signal replacement paths are formed between the end nodes of the span failure. The restoration path set is formed ....

T. H. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

....20, 1999. The authors are with TRLabs and the Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB T5K 2P7, Canada (e mail: dstamate edm.trlabs.ca; grover edm.trlabs.ca) Publisher Item Identifier S 0090 6778(00)07098 7. 1 Bidirectional line switched ring (see [2]) set of experimental design trials were presented which showed, at least empirically, that optimized sets of p cycles could support 100 span restorability with very little or no spare capacity requirements beyond that of a theoretically minimal span restorable mesh network. The significance of ....

T. S. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

....a (multiple of) four fiber system in the remainder of the paper. III. BACKGROUND For link restoration, the main approaches are through the use of rings and, more recently, through generalized loopback in mesh networks [3] The most direct approach is to design the network in term of rings [4] [5], 6] or partially using rings [7] 8] Such architectures allow distributed recovery from link failures. However, rings are not necessary to construct survivable networks; mesh based topologies can also provide redundancy [9] Ring based architectures may be more expensive than meshes [8] and ....

....[8] and as nodes are added, or networks are interconnected, ring based structure may cease to be maintained, thus limiting the scalability of the approach. Even if we constrain ourselves to always use ring based architectures, such architectures may not be easily scalable as the network grows [5], 10] making mesh based architectures a more promising candidate for future networks. In general, ring based techniques do not scale well, as small changes to a network can result in major restructuring of the desired set of rings. As a network grows, small localized changes can require global ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, 1992.

....logical rings. Trac is restored after a link failure byswitching the working VP trac onto a backup VP that is routed along the arc of the circle with no failure. SHR s are widely used at the physical layer where optical ber length and link interfaces must be minimized due to the high costs [13]. On the ATM layer, however the cost of logical links and extra entries in routing tables are small giving no clear bene ts of ATM SHRs over APS systems or distributed dynamic schemes. ### ########### ########## ## ########### During the design of the VP network topology the working trac VPs are ....

T. H. Wu, Fiber Network Service Survivability, Artech House Publishers, Boston, 1992.

....of future networks. Moreover, one of the important objectives of this article is to clarify the remaining problems that must be solved by future studies. These problems will be discussed subsequently. Reliable networking techniques in SDH SONET networks are already very well compiled in Wu s book [1] and papers [2] Therefore, this article focuses to new reliable networking techniques for ATM. To provide background, restoration characteristics of SDH SONET are briefly compared to those of ATM in the section Different Characteristics Between SDH and ATM Layer Restoration. In particular, this ....

....path (STM) Virtual path (ATM) IEEE Communications Surveys . http: www.comsoc.org pubs surveys . Fourth Quarter 1998 . Vol. 1 No. 1 4 case by case according to the local conditions (e.g. network topology, scale, etc. Most schemes evolved from those of conventional networks (e.g. SDH) [1]. Existing and prototype schemes for ATM networks include centralized control switching, SHN, APS, and SHR. Compared to these schemes, FRVP realizes failure restoration with no service interruption. This result is reasonable because the restoration time, which is a measure of reliability, must be ....

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T.-H. Wu, "Fiber Network Service Survivability," Artech House, 1992

....except the ls on each fiber are divided into working and protection groups. To avoid the need for l conversion at the nodes for loop back purposes, the working and protection l groups on each fibre are transposed. Further description of optical rings can be found in [4] and previous SONET rings in [7]. 3 THE MULTI RING NETWORK DESIGN PROBLEM Although the operation of a single ring is simple, the optimization of fully restorable networks employing multiple rings is an extremely complex problem. This section describes the main aspects of the multi ring network design problem. Problem inputs ....

T.-H. Wu, Fiber Network Service Survivability, Artech House Inc., Boston, Mass., 1992.

....that any (unspecified) pattern or combination of protection structures can provide per spare link consumed. We then consider the same figure of merit for pcycles, trees, and linear segments and show that only p cycles match the generalized upper bound. 1. Bi directional line switched ring. See [2]. 2. This is also just the reciprocal of the network redundancy. Theory for Efficiency of Restorable Networks using p cycles Dec. 1999 (TComm 99 013) Stamatelakis, Grover 3 12 99 3 11 Third we show that a p cycle network is in the same class as a span restorable mesh network in the sense that ....

T.S. Wu, Fiber Network Service Survivability, Artech House, 1992.

....of spare capacity required to protect working demands, relative to selfhealing rings or 1:1 protection switching [3, 4, 8, 9, 11, 12, 13, 14] Mesh restoration algorithms should restore network failures within two seconds using a minimum amount of spare capacity. Of all restoration architectures [21], mesh restorable networks employing distributed path restoration have the greatest potential to satisfy this goal. The main contribution of the present research is a distributed dynamic path restoration algorithm, named OPRA (Optimized Path Restoration Algorithm) which largely satisfies this ....

Wu, T., Fiber Network Service Survivability, Norwood, MA: Artech House Inc., 1992.

....than the UPSR. The nodal elements of rings are add drop multiplexers (ADMs) An ADM has two optical line (e.g. OC 24, or OC 48 say) terminations and can originate (add) or terminate (drop) any of the tributary payload signals (e.g. STS 1 or DS3) from the line signal passing through it. See [1] for more on rings. Mesh survivability is typically based on the use of digital cross connect systems (DCS) embedded in a mesh like set of point to point transmission systems, under centralized or distributed control. Signals that traverse a failed span spread out as individuals or subgroups and ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, Boston, Mass. 1992, pp. 123-134 and 439-441.

....to the ring working capacity. However for determining the appropriate ring capacity for a given set of demands, SHRs are classified as belonging to one of two categories depending on the way the working 3 traffic may be routed on them under normal conditions (see Baudron, Khadr and Kocsis [4] Wu [35]) C A B C D E F A NORMAL MODE A C Protection line Working line C A B C D E F A FAILURE MODE A C X Projection line Working line Figure 1: Unidirectional or Dedicated Protection SHR. In the first type, called unidirectional SHR, all traffic is routed in the same direction along ....

Wu, T.H. (1992). Fiber Network Service Survivability. Artech House, Boston, MA. 27

....for this, about which nothing much is known. Operation Research (OR) techniques are also applied to the RAIN problem. Most often, a fixed number of shortest paths for each demand are precomputed, and the problem is solved using linear programming with very large constraint systems of equations [1,5,16,33]. However, because only a given number of routes are considered, these techniques are not guaranteed to find a solution if one exists. Moreover, OR techniques are not as flexible as CSP based methods (see Section 8) Mann and Smith [22] search for routing strategies that attempt to ensure that no ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, 1992.

....Drop Multiplexers and telephone central offices are connected into a ring topology. Offices can communicate with one another along both clockwise and counter clockwise directions on the ring. Consequently, any single failure in transmission systems can be circumvented and no one will be affected (Wu, 1992). This two phased process can also be found in the provision of Integrated Services Digital Network (ISDN) service. In phase 1, the service can be offered through Centrex stations, which is not an option for most consumers. By replacing analog lines and switches with digital ones, a phone company ....

Wu, T.-H., 1992, Fiber Network Service Survivability, (Artech House).

....if there is no such route. Operations Research (OR) techniques are also applied to the RAIN problem. Most often, a fixed number of shortest paths for each demand are pre computed, and the problem is solved using linear programming with very large constraint systems of equations [6] 7] 8] [9]. However, because only a given number of routes are considered, these techniques are not guaranteed to find a solution if one exists. Moreover, OR techniques are not as flexible as CSP based methods (see Section VIII) Mann and Smith [10] search for routing strategies that attempt to ensure that ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, Boston - London, 1992.

....dynamic call routing network (see, for example, 3] 4] 5] 6] Network survivability and restoration have been gaining attention in recent years. Designing for survivability has been addressed by several researchers for various networks (for example, see, 7] 8] 9] 10] 11] 12] [13], 14] 15] Results on network performance under a failure for wide area circuit switched networks have been presented in ( 2] 12] 16] 17] 18] and for wide area packet networks in [19] Network restoration has also been addressed by several researchers; e.g. Coan et al. [20] have ....

....Due to this aggregation, for our purpose here, transmission link is synonymous with physical link. Due to this aggregation and also since our primary interest is on the impact in the traffic network, we do not take into consideration the role of automatic protection switching or self healing ring [13], 28] For the trunks required for the traffic network, a circuit layout procedure [29] is used to determine the transmission path on which various trunk demands (and how much) should be routed between cross connect nodes. This routing is called circuit routing, not to be confused with 3 call ....

T.-H. Wu, Fiber Network Service Survivability , Artech House, Boston, Mass., 1992.

....the network is to be designed for survivability, i.e. so that a certain acceptable percentage of the traffic can still be carried immediately after a failure. Recently, several researchers have addressed the issue of designing various networks for survivability [3] 6] 8] 13] 19] 26] [27]. These studies address the design in terms of either the traffic network or the facility network. However, since the traffic network exists purely at the logical level, design of a survivable traffic network may not be adequately addressed without incorporating the connectivity aspect of the ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, Boston, Mass., 1992.

.... end users by autonomously switching affected virtual paths (VP s) to alternate routes [4] 5] 10] 12] Depending on the location where traffic rerouting is performed, the proposed self healing strategies can be categorized into two classes: line restoration and end to end restoration (Figure 1) [16]. When a link failure occurs, the line restoration scheme dispatches alternate routes between the two end nodes of the failed link and reroutes all affected traffic around the link. On the other hand, the end to end restoration scheme switches failed VP s to alternate routes established between ....

.... Nodes 1 and 6 for the VP #A and between Nodes 4 and 3 for the VP #B in the example of Figure 1 b) Despite the high complexity of its rerouting decision process, an end to end restoration scheme has been widely cited to be more advantageous than a line restoration scheme [5] 7] 8] 12] 15] [16]. The former scheme could effectively use the spare bandwidth, and thus less redundant capacity would be necessary to construct a fully restorable network. In addition, a VP may suffer backhauling [5] after restoration with line restoration. A VP relayed at a node adjacent to a failed link could ....

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T-H.Wu, "Fiber network service survivability," Artech House, Norwood, M.A., 1992.

....Optical Network) rings. For example, if a network is equipped with fast automated digital cross connect system and or SONET self healing ring capability at the transmission network, the network where the services are provided may not perceive any failure because of fast automated restoration [15, 33]. At the same time, the transmission network level restoration schemes do not address failures such as a line card failure, or a switch or router failure; thus, restoration at the logical network level also needs to be triggered; this may include rerouting and automatic reconnection of affected ....

T.-H. Wu, Fiber Network Service Survivability, Norton, MA: Artech House, 1992. d.medhi 10

....communication service has led to a growing interest in the design of survivable networks as well as studies of fault recovery techniques to be employed in the event of a network outage (e.g. cable cut, switch failure, line card failure, etc. Several survivability techniques have been proposed [1,2] to minimize the effect of failures, common ones being multiple homing nodes and users, trunk diversity, digital cross connect systems and self healing ring architectures. The topic of fault recovery in virtual circuit (VC) based packet networks such as ATM networks has received special attention ....

T.H.Wu, Fiber Network Service Survivability. Artech House, Boston, Mass., 1992.

....networks. With the widespread deployment of fiber optic transmission systems and the alarming rate of outages due to fiber cuts [WROB90] there is great interest in strategies for improving the process of restoring disrupted traffic from minutes to sub seconds following a fiber cut [WU92] Automatic protection switching probably is the fastest technique and can switch the disrupted traffic to dedicated spare links in under 50 milliseconds. However, it requires high dedicated spare capacity. With recent advances in digital cross connect systems, DCS, there is increasing interest ....

T.-H. Wu, Fiber Network Service Survivability, Artech House, 1992.

....has become increasingly important. This has lead to a growing interest in the design of survivable networks as well as studies of fault recovery techniques to be employed in the event of a network outage (such as a cable cut, node failure or line card failure) Several survivability techniques [6, 21] have been discussed in the literature to minimize the effect of failures, common ones being multiple homing nodes and users, trunk diversity, digital cross connect systems, and self healing ring architectures. The topic of fault recovery in the event of a network outage in ATM networks has ....

....to minimize the effect of failures, common ones being multiple homing nodes and users, trunk diversity, digital cross connect systems, and self healing ring architectures. The topic of fault recovery in the event of a network outage in ATM networks has received special attention recently [1, 3, 11, 13, 12, 21] . This work focuses primarily on facility (transmission) level restoration or virtual path layer restoration, and primarily for a link failure (such as a fiber cable cut) At the facility layer most of the work has been on the provisioning of spare network capacity in the form of SONET rings and ....

T.H.Wu, Fiber Network Service Survivability. Artech House, Boston, Mass., 1992.

....functions are controlled by an external CPU. To increase the processing speed, most of the OAM function processing is being done without intervention of the CPU. The interface function also has the redundancy for automatic switching in case of system or line fault, service degradation in quality[5][6] 7] 8] The automatic protection switching (APS) was implemented in this interface function for the ring topology of the DANS. In this paper, the general structure of the DANS and its line interface functions are described, the implemented APS is briefly explained using several fault ....

.... as DANS reduces the transmission costs due to sharing the medium link of the ring and increases robustness and survivability owing to self healing ring with unidirectional line protection switching (USHR L) in the sense of automatically detouring traffic on working ring into protection ring[5][6] 7] 8] logically occurring from line level in the sense of gathering information of the switching triggering, although switching function is physically implemented in the interface between ATM layer and upper layer. In the DANS, the ULIF plays a role of configuring ring topology, accommodating ....

T. H. Wu, "Fiber Network Service Survivability", Artech House, Boston London, 1992. pp. 123~144.

....to problems in case of failure, as the amount of bandwidth lost by a component or cable failure is now much larger than what would have been lost in a traditional network. This is why extra effort must be spent in analyzing optical WDM networks and in finding ways to protect them against failures [6, 7, 8]. 1.1 Definitions We consider a backbone WDM photonic network consisting of optical crossconnect nodes (or simply nodes) interconnected by optical bidirectional links (see bottom of Figure 1) Each link actually consists of a pair of unidirectional fibres and is capable of transporting a limited ....

....objective of ensuring that a bidirectional communication channel between two network ports will remain operational in the event of a component or an optical link failure. This protection is performed at the physical level. It can react very rapidly to such failure, but requires hardware redundancy [8, 14]. In general, physical protection also includes the ability to re route clear channels after a failure, without the higher level switches being aware of it [6] There is a price to pay for Physical Protection, namely that of optical hardware duplication. In many situations it may not be ....

T.-H. Wu, Fiber Network Service Survivability. Artech House, 1992.

....in this paper that a link is unidirectional, and therefore, a link failure is a unidirectional link failure. FAULT TOLERANT DESIGN OF WAVELENGTH ROUTED OPTICAL NETWORKS 3 such a failure can lead to a severe disruption in the network. There are several approaches to ensure network survivability [3]. The approach we consider here is that of restoration, where lightpaths affected by a component failure are rerouted around the failure, by reconfiguring network components such as wavelength routing switches, transmitters, receivers, etc. Higher protocol layers (such as ATM or IP) operating on ....

....utilizing multiplexed spare capacity, for protection against link failure in an optical networks, and in this manner is different from previous work. Network survivability, restoration schemes, and optimal spare capacity design have been studied extensively in circuit switched transport networks [3, 12, 13, 14]. 1.2. Outline of remaining sections. In Section 2, we develop the Integer Linear Programming (ILP) formulations of the one on one and multiplexed sparecapacity protection problems. A solution approach for the ILP formulation, and the complexity of the solution procedure is considered in Section ....

T. Wu, Fiber Network Service Survivability, Artech House, 1992.

....different failure conditions. Section 2 proposes and analyzes different recovery schemes. In Section 3, we discuss fault management aspects of these solutions, and conclude in Section 4. 1. 1 Related Work Extensive work has been performed on fault tolerant network architectures in general (e.g. [3]) and selfhealing rings in particular (e.g. 4, 5] However, most networks that have such fault tolerant mechanisms built into them use time division multiplexing on their fibers (SONET, ATM, FDDI are a few of the many examples) and thus can perform the recovery in the time domain. In contrast, ....

T. Wu, Fiber Network Service Survivability. Artech House, 1992.

....grant NCR 9506652 On Fault Recovery Priority in ATM Networks, B. Jager 2 I Introduction A basic challenge in ATM networking is meeting user demand for reliability and fault tolerance in a cost effective manner. The topic of fault recovery in ATM networks has received special attention recently [1, 2, 3, 4, 5, 6, 7]. This work focuses primarily on facility (i.e. physical) layer restoration or logical layer layer (i.e. virtual path (VP) layer in ATM) restoration and mainly for a single link failure. At the facility layer most of the work has been on provisioning spare network capacity in the form of SONET ....

T.H.Wu, Fiber Network Service Survivability. Artech House, Boston, Mass., 1992.

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T.-H. Wu, Fiber Network Service Survivability. Artech House, 1992.

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T-H. Wu. Fiber Network Service Survivability. Artech House, Inc., Norwood, MA, 1992.

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T.H. Wu, "Fiber Network Service Survivability", 1992, Artech House, ISBN 0-89006-469-5

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T. H. Wu, Fiber Network Service Survivability, Artech House.

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T. Wu, Fiber Network Service Survivability, Artech House, 1992.

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T.-H. Wu. Fiber Network Service Survivability. Artech House, 1992.

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Tsong-Ho Wu. Fiber Network Service Survivability. Artech House, Inc., Norwood, MA, USA, 1992.

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T. Wu, Fiber Network Service Survivability, Norwood, MA: Artech House, 1992.

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T. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

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T. Wu, Fiber Network Service Survivability, Norwood, MA: Artech House, 1992.

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Tsong-Ho Wu, Fiber Network Service Survivability, Artech House, Norwood, MA, 1992.

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T.-H. Wu (1992). Fiber Network Service Survivability. Artech House.

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T.-H. Wu, Fiber Network Service Survivability. Norwood, MA: Artech House, 1992.

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T.-H. Wu, "Fiber Network Service Survivability," Artech House, New York, 1992.

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