W. D. Grover, "Self-organizing Broad-band Transport Networks", Proc. of the IEEE: Special Issue on Communications in the 21st Century, vol. 85, no.10, pp. 1582-1611, October 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....by optimization of spare capacity to support 100 percent restorability with minimum total spare capacity. Restoration occurs via k shortest paths, e.g. re routing between the end nodes of the failure span. A dynamic restoration mechanism can adaptively construct the replacement paths on demand [5], or the switching arrangements can be preplanned within the same spare capacity (in which case this scheme is often called link protection. Span Restoration Joint Capacity Assignment (JCA) Here the choice of route taken by each working demand is optimally coordinated with the spare ....

W.D. Grover, "Self-organizing Broadband Transport Networks," Proc. IEEE, vol. 85, no. 10, Oct. 1997, pp. 1582--611.

....should be shortened. To solve this issue a planning tool should incorporate unified network models such as the layered network approach proposed in [3] One important issue that the designers of a network planning tool should consider is the concept of self organizing (self configurable) networks [2]. For example a network topology of IP routers overlaid over ATM (SDH, WDM) can be easily configured and modified according to the traffic demands through network management systems either automatically or manually. The reconfiguration of networks can be initiated at specific time periods. ....

W. D. Grover, "Self-Organizing Broadband Transport Networks", Proceedings of the IEEE, October 1997, pp. 1582-1611

....real time restoration protocols work the same way. For instance a distributed span restoration protocol may actually find all paths at once without iteration and be equivalent in terms of path number and path length total to algorithmic ksp, without being based on a direct iterative ksp approach [12]. Capacity design for span restoration: A span restorable mesh network is one in which the spare capacity allocation across the network is sufficient to allow this type of rerouting behavior to provide 100 restoration of any single span cut. An input parameter when we design the spare capacity ....

W.D. Grover, "Self-organizing Broad-band Transport Networks", Proceedings of the IEEE: Special Issue on Communications in the 21st Century, vol. 85, no.10, October 1997, pp. 1582-1611.

....technically, however, there is now a considerable literature on mesh restorable network design, distributed restoration, service provisioning, restorability audit, reversion after failure, automatic integration of new service paths into the restorability plan, and so on. See for instance [1] [2], 3] 10] and references therein. In further support of the viability of mesh based survivable networking, half a dozen optical networking start ups have made the technical and business judgements that there is enough accumulated knowledge to now proceed with optical mesh restorable networks and ....

....are then sought, completing the restoration reaction to the failure. Figure 1 details the overall algorithm for calculating the risk field. The procedure in (iii) is a functional approximation for the effects of a distributed restoration protocol that is self updating, an example of which is in [2]. Such a protocol immediately gives working status to any spare channel it uses in a restoration path or as a maintenance replacement path. This inherently updates itself should it be triggered to act again to protect either new capacity or maintenance replacement paths in the event of a failure ....

W. D. Grover, "Self-organizing Broadband Transport Networks", Proc. of the IEEE Special Issue on Communications in the 21st Century, vol. 85, no.10, pp. 1582-1611, October 1997.

....finely resolved patterns of rerouting are permitted, resulting in greater sharing of spare capacity. At a threshold value of H, the theoretical minimum of spare capacity is reached [11] Real time mechanisms for distributed adaptive span restoration were initially developed in the Sonet era [12] [16] and are being considered for adaptation to WDM transport applications. The optimal spare capacity design of span restorable mesh networks is also well understood today [11] 17] 18] 19] It is important to note that historically some authors refer to mesh networks without implying ....

....required paths are found, or no more can be found. This is known to be extremely close to maximum flow in typical transport networks [30] and can be computed in ( log ) O nntime [31] ksp is also an accurate functional model for the self organized restoration path sets formed by the SHN protocol [16]. We now look at three levels of adaptability in restoration that can be modelled with ksp to determine R 2 by exhaustion of all f = 2 experimental trials. In all cases the number of needed but infeasible restoration paths is denoted N(i,j) for the (i,j) failure pair. a) Static restoration ....

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W. D. Grover, "Self-organizing Broad-band Transport Networks", Proc. of the IEEE: Special Issue on Communications in the 21st Century, vol. 85, no.10, pp. 1582-1611, October 1997.

....In environments of rapid growth and shifting demand patterns, the greater efficiency and flexibility of a mesh network can also help the operator keep pace with the growth. Indeed mesh networks lend themselves rather gracefully to the vision of a completely self organizing transport layer [2]. An aspect of mesh networks that is less widely understood, however, is the behaviour and characteristics of the restoration path sets. In contrast to rings, the restoration routes are much more adaptive and potentially exploit spare capacity anywhere in the network. It has been shown that for ....

W. D. Grover, "Self-Organizing Broad-Band Transport Networks", Proceedings of the IEEE, vol. 85, no. 10, pp. 1582-1611 (1997).

.... A dynamic span restoration mechanism (i.e. a distributed restoration algorithm (DRA) can also be used to conduct the pre failure dress rehearsals that prepare a network to act in a pre planned link protected mode adaptively tracking the demand pattern under distributed pre planning (DPP) [10]. And as Medard et. al [11] point out, such span protected networks have the desirable properties of very high speed and since [protection arrangements are] not dependent upon specific traffic patterns, the network] can be pre planned once and for all. We would only refine Medard s statement to ....

....of OXC layer, not the router layer. An optical network layer using Digital Wrapper on each lightwave channel is ideally suited to support span restoration with very simple robust protocols, not requiring explicit dissemination and maintenance of an entire network topology and capacity database [10]. Span restoration (or closely related link protection via DPP) schemes offer a set of design properties and operational aspects that may be preferable to an operator that wishes to refer protection into the optical networking layer rather than positioning it as a function of the service ....

W. D. Grover, "Self-Organizing Broad-Band Transport Networks," Proceedings of the IEEE, vol. 85, no. 10, pp. 1582-1611, October 1997.

.... Refinements have included aspects such as modularity [10] hybridization with rings [23] nodal bypass effects [22] various heuristics and relaxations [20,25,32,52] for the working and or restoration capacity design problems and self organizing or other forms of distributed restoration [7,19,21]. In virtually all of the optimization problems so far posed on mesh restorable networks, however, the graph of the physical facility routes is a given. In practice most facilities based network operators entered the current era with a legacy topology or a pre determined topology arising from a ....

W.D. Grover, Self-organizing broad-band transport networks, Proceedings of the IEEE 85(10) (1997) 1582--1611.

....in 10. One way to simulate alarm scenarios would be to define a test AIS byte in the SONET overhead. preprint of paper to appear in IEEE Journal on Selected Areas in Communications, Special Issue on Recent Advances in Network Management and Operations scheduled to appear in 2nd Quarter, 2000 [40] and, to a lesser extent, in [14] Both of those discussions are based on a span DRA, but many of the operational ideas are easily transferred or adapted to a path DRA based network. B. Staggered failures Another operational consideration is dealing with time staggered failure sequences; the ....

W.D. Grover, "Self-organizing Broad-band Transport Networks", Proc. of the IEEE: Special Issue on Communication in the 21st Century, vol. 85, no.10, Oct. 1997, pp. 15821611.

....replacement paths between the immediate end nodes of the failure span. The replacement paths can be pre computed prior to the span failure, either centrally, or via distributed pre planning (DPP) using the same embedded restoration protocol that can operate adaptively in real time if needed [18]. The operational principles and the capacity design models of a span restorable network have been well studied in sources such as [1] 5] The Shared Backup Path Protection (SBPP) scheme provides a single fully disjoint end to end backup path for each demand pair in the event of a span ....

W.D. Grover, "Self-organizing broadband transport networks," IEEE Proceedings: Special Issue on Communications in the 21st Century. vol.85, no.10, October 1997, pp.1582-1611.

.... Refinements have included aspects such as modularity [20] hybridization with rings [53] nodal bypass effects [26] various heuristics and relaxations [42,43,50,46] for the working and or restoration capacity design problems and self organizing or other forms of distributed restoration [41,25,49]. In virtually all of the optimization problems so far posed on mesh restorable networks, however, the graph of the physical facility routes is a given. In practice most facilities based network operators entered the current era with a legacy topology or a pre determined topology arising from a ....

W.D. Grover, "Self-organizing Broad-band Transport Networks", Proceedings of the IEEE Special Issue on Communications in the 21st Century, vol. 85, no.10, October 1997, pp. 1582-1611.

....of these WDM networking elements is that they provide the reconfigurability to adapt the logical wavelength connectivity layer to match changing demand patterns in the service layers, enabling the concept of an automatically switched (a.k.a. self organizing ) transport network (ASTN) 2] [3]. But another advantage, and the topic of our present interest, is that OADM and OCX elements enable mesh restoration schemes for the optical networking layer. One driver for optical layer mesh restoration over the ring protection schemes of SONET is the greater capacity efficiency that can be ....

W. D. Grover, "Self-organizing Broad-band Transport Networks," Proceedings of the IEEE, vol. 85, no.10, pp. 1582-1611, October 1997.

....based network. But a selforganizing strategy for the autonomous deployment and continual adaptation of a network p cycle state also seems possible. The Distributed Cycle PreConfiguration (DCPC) protocol is an adaptation of the statelet processing rules of the Selfhealing Network (SHN) protocol [13]. A statelet is embedded on each spare link and contains a number of semi static information fields (like the K1 K2 bytes in the Sonet APS protocol) Each logical link (any managed capacity unit) as viewed by a node attached to it, has an incoming statelet and outgoing statelet. An incoming ....

W.D. Grover, "Self-organizing Broad-band Transport Networks ", Proc. of the IEEE: Special Issue on Communications in the 21st Century, vol. 85, no.10, October 1997, pp. 1582-1611.

....In environments of rapid growth and shifting demand patterns, the greater efficiency and flexibility of a mesh network can also help the operator keep pace with the growth. Indeed mesh networks lend themselves rather gracefully to the vision of a completely self organizing transport layer [2]. An aspect of mesh networks that is less widely understood, however, is the behaviour and characteristics of the restoration path sets. In contrast to rings, the restoration routes are much more adaptive and potentially exploit spare capacity anywhere in the network. It has been shown that for ....

W. D. Grover, "Self-Organizing Broad-Band Transport Networks", Proceedings of the IEEE, vol. 85, no. 10, pp. 1582-1611 (1997).

....the first failure that were severed by the second. N a,b is the sum of non restored units for both failed spans after the second searches. This is a very close functional models behavior of the SHN protocol, which immediately gives working status to any spare links it uses in restoration paths [10]. With programs that implement each of these restoration routing models we conducted all possible IEEE VDE Design of Reliable Communication Networks (DRCN 2000) Munich, April 2000, pp. 181 186. ordered 4 dual failure experiments and recorded the number of un restorable working links N a,b ....

W.D. Grover, "Self-organizing Broad-band Transport Networks", Proc. of the IEEE: Special Issue on Communications in the 21st Century, vol. 85, no.10, October 1997, pp. 1582-1611.

....followed by optimization of spare capacity to support 100 restorabilty with minimum total spare capacity. Restoration occurs via k shortest paths like re routing between the end nodes of the failure span. A dynamic restoration mechanism can adaptively construct the replacement paths on demand [5]or the switching arrangements can be preplanned within the same spare capacity (in which case this scheme is often called link protection. c) Span Restoration Joint Capacity Assignment (JCA) Here, the choice of route taken by each working demand is optimally co ordinated with the spare ....

W.D. Grover, "Self-organizing Broad-band Transport Networks", Proceedings of the IEEE, vol. 85, no. 10, October 1997, pp. 1582-1611.

....state Here we give an overview of a self organizing strategy for the autonomous deployment and continual adaptation of the network p cycle state. The Distributed Cycle PreConfiguration (DCPC) protocol is an adaptation of the statelet processing rules of the Selfhealing Network (SHN) protocol [10,11]. A statelet is embedded on each spare link and contains a number of state fields. Each logical link, as viewed by a node attached to it, has an incoming statelet and outgoing statelet. An incoming statelet arrives at a node on a link, and originates from the adjacent node connected through the ....

....is the data of Table 4. Table 4 indicates that even in the worst of these tests against a most stringent theoretical benchmark, one could obtain ring like restoration speed for 83.75 or more of affected demands. By then triggering a follow up real time restoration protocol such as the SHN [10,11], a final restorability level of 95 to 100 would be reached. This 2 step restorability is the result when, after first exploiting all useful p cycles, one follows up with conventional execution of a suitable distributed or centralized restoration protocol on demand for the remaining ....

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W.D. Grover, "Self-organizing Broad-band Transport Networks", Proceedings of the IEEE: Special Issue on Communications in the 21st Century, vol. 85, no.10, October 1997, pp. 1582-1611.

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