Wireless ATM layouts for chain networks

In this paper we consider the problem of constructing ATM layouts for wireless networks in which mobile users can move along a chain of base stations. We first show that deciding the existence of a layout with maximum hop count h, load l and channel distance d is NP-complete for every fixed value of d greater or equal to 1. We then provide optimal layout constructions for the case d less than or equal to 2. Finally, optimal layout constructions are obtained also for any d within the class of the so-called canonic layouts, that so far have always been shown to be the optimal ones

Virtual path bandwidth distribution and capacity allocation with bandwidth sharing

Broadband high-speed networks, such as B-ISDN, are expected to play a dominant role in the future of networking due to their capability to service a variety of traffic types with very different bandwidth requirements such as video, voice and data. to increase network efficiency in B-ISDN and other such connection oriented networks, the concept of a virtual path (VP) has been proposed and studied in the literature. A VP is a permanent or semi-permanent reservation of capacity between two nodes. Using VPs can potentially reduce call setup delays, simplify hardware, provide quality of service performance guarantees, and reduce disruption in the event of link or node failure.;In order to use VPs efficiently, two problems must be solved. With the objective of optimizing network performance, (1) the VPs must be placed within the network, and (2) network link capacity must be divided among the VPs. Most previous work aimed at solving these problems has focused on one problem in isolation of the other. at the same time, previous research efforts that have considered the joint solution of these problems have considered only restricted cases. In addition, these efforts have not explicitly considered the benefits of sharing bandwidth among VPs in the network.;We present a heuristic solution method for the joint problem of virtual path distribution and capacity allocation without many of the limitations found in previous studies. Our solution method considers the joint bandwidth allocation and VP placement problem and explicitly considers the benefits of shared bandwidth. We demonstrate that our algorithm out-performs previous algorithms in cases where network resources are limited. Because our algorithm provides shared bandwidth, solutions found by our algorithm will have a lower setup probability than a network that does not use VPs as well as a lower loss probability than provided by VPDBA solutions produced by previous algorithms. In addition, our algorithm provides fairness not found in solutions produced by other algorithms by guaranteeing that some service will be provided to each source-destination pair within the network

The Optimal Virtual Path Design of ATM Networks

This paper studies the optimal configuration of virtual paths in ATM networks. A linear model that minimizes the maximum flow density of links is proposed for the optimal virtual path configuration. The advantage of the modeling is that traffic loads are distributed evenly over entire network. An algorithm based on the multi-commodity approach is proposed to solve the problem. Examples are given to show that this algorithm solves the optimal VP assignment problem very quickly and efficiently. Since only single source-destination linear programming subproblems need to be solved in our approach, this algorithm can be applied to large-scale networks.published_or_final_versio

Virtual network embedding in the cycle

AbstractWe consider a problem motivated by the design of Asynchronous transfer mode (ATM) networks. Given a physical network and an all-to-all traffic, the problem consists in designing a virtual network with a given diameter, which can be embedded in the physical one with a minimum congestion (the congestion is the maximum load of a physical link). Here we solve the problem when the physical network is a ring. We give an almost optimal solution for diameter 2 and bounds for large diameters

DIGRAF EKSENTRIK DARI GRAF BUKU

Diberikan G suatu graf dengan himpunan berhingga vertex V(G) dan himpunan edge E(G). Jarak dari vertex u ke vertex v di G, dinotasikan d(u,v), adalah panjang dari path terpendek dari vertex u ke v. Eksentrisitas vertex u dalam graf G adalah jarak maksimum dari vertex u ke sebarang vertex yang lain di G, dinotasikan e(u). Vertex v disebut vertex eksentrik dari u jika d(u,v) = e(u). Digraf eksentrik ED(G) dari suatu graf G adalah suatu graf yang mempunyai himpunan vertex yang sama dengan himpunan vertex G, dan terdapat suatu arc (edge berarah) yang menghubungkan vertex u ke v jika v adalah suatu vertex eksentrik dari u. Dalam makalah ini diselidiki digraf eksentrik pada graf buku yang merupakan salah satu kelas graf. Kata kunci: eksentrisitas, digraf eksentrik, graf buk

Applications of satellite technology to broadband ISDN networks

Two satellite architectures for delivering broadband integrated services digital network (B-ISDN) service are evaluated. The first is assumed integral to an existing terrestrial network, and provides complementary services such as interconnects to remote nodes as well as high-rate multicast and broadcast service. The interconnects are at a 155 Mbs rate and are shown as being met with a nonregenerative multibeam satellite having 10-1.5 degree spots. The second satellite architecture focuses on providing private B-ISDN networks as well as acting as a gateway to the public network. This is conceived as being provided by a regenerative multibeam satellite with on-board ATM (asynchronous transfer mode) processing payload. With up to 800 Mbs offered, higher satellite EIRP is required. This is accomplished with 12-0.4 degree hopping beams, covering a total of 110 dwell positions. It is estimated the space segment capital cost for architecture one would be about $190M whereas the second architecture would be about$250M. The net user cost is given for a variety of scenarios, but the cost for 155 Mbs services is shown to be about $15-22/minute for 25 percent system utilization

Enterprise Network Design and Simulation - Cisco Virtual Lab

Tématem této diplomové práce (dále jen DP) je návrh rozsáhlých podnikových sítí podle doporučení stanovených společností Cisco. Dále je realizována simulace navržené topologie prostřednictvím programů s otevřeným zdrojovým kódem a dohled nad sítí prostřednictvím programu Nagios. Úvodní část obsahuje stručné seznámení se základním rozdělením sítě do jednotlivých funkčních bloků. Druhá část se zabývá popisem jednotlivých funkčních bloků a jejich rolí v rámci celé síťové topologie. Bloky jsou dále rozděleny na jednotlivá zařízení a jsou popsány služby, které tato zařízení musí poskytovat. Třetí část DP se snaží zmapovat základní požadavky na služby, které jsou kladeny na dnešní síťové infrastruktury. Hlavní důraz je kladen na dostupnost všech nabízených služeb sítě. Jsou vyjmenovány jednotlivé protokoly druhé až třetí vrstvy OSI modelu, které zabezpečují stálou dostupnost sítě v případě selhání aktivních prvků. Čtvrtá část DP se věnuje popisu návrhu síťové topologie WAN. Pátá část obsahuje popis bezpečnostních rizik, která ohrožují dostupnost sítě, tak i popis útoků, které mají za cíl krádež identity uživatele. V šesté části DP jsou popsány programové nástroje pro zprávu sítí (Nagios, Cisco Security Device Manager) a programy, které simulují Cisco přepínače, směrovače (Dynamips & Dynagen, GNS3) a Cisco PIX firewall (PEMU). Sedmá kapitola se zabývá konkrétním návrhem rozsáhlé sítě s použitím principů, které byly zmíněny v předcházejících kapitolách. Navržená infrastruktura je dále realizována pomocí simulačních programů a tato virtuální síť dovoluje demonstrovat nastavení a chování všech popsaných protokolů a zařízení. V závěrečném shrnutí je nejdůležitější poznatek, že návrh a konfigurace rozsáhlé sítě a její realizace ve virtuálním prostředí je funkční a použitelná pro pokusné účely i pro studijní účely.This Master's Thesis (further only MT) deals with subject of enterprise network design according to recommendations of Cisco company. As part of the thesis is developed simulation of enterprise network, according to created concept. The virtual lab is realized by open-source programs and monitored by Nagios software. The first part contains brief introduction to network designs and description of hierarchical network design. The second part describes building blocks of the network design and their role in hierarchical network. Each block is further divided into specific network devices and then there are described services that have to be provided by them. The third part of MT deals with basic service demands which are expected from today’s network infrastructures. The main focus is on availability of network services. There are specified information about second and third layer protocols of OSI model which are securing availability of all services provided by the network infrastructure in case of failure. The following fourth part contains information about WAN design. The fifth part describes security risks which can jeopardize network availability. It also contains description of attacks on network users. The sixth part of MT contains brief description of software tools for network management and monitoring (Nagios, Cisco Security Device Manager) and programs for simulating Cisco routes and switches (Dynamips & Dynagen, GNS3) and Cisco PIX firewall simulation program (PEMU). The seventh chapter deals with developed network design concept. The concept is deployed as virtual lab running under simulation programs. The virtual infrastructure allows demonstration of settings and behavior of all protocols and equipments described before. In conclusion is the most important recognition that the network concept and its simulation as virtual lab is functional and it can be used for tests or educational purposes.

Fault Tolerant Rerouting in Broadband Multiclass Networks

Modern broadband integrated service digital networks (B-ISDN) must handle multiclass traffic with diverse quality of service (QOS) requirements. The main purpose of our research is to design call rerouting mechanisms which provide rapid restoration of network services in case of link failures. We suggest two approaches: Virtual circuit (VC) and virtual path (VP) reroutings. The first approach is more reactive while the latter is more proactive. The applicability conditions for the first approach include the availability of a layered network structure similar to VC/VP architecture which is widely accepted in asynchronous transfer mode (ATM) networks. Another applicability condition is the extent of network failure: VP level restoration is designed for single link failures - the most common in the telecommunication networks. On the other hand, in case of less predictable multiple link failures, VC-level rerouting is appropriate. These two rerouting approaches vary in the amount of time required to carry them out. Though both schemes are designed to work in real time, VP-level rerouting tends to be faster and can be performed in an on-line mode using pre-computed paths. VC- level rerouting requires real-time computation of routes which may result in a noticeable impact on some services. On the other hand, VP-level rerouting requires a substantial amount of off- line computation to design the VP layout and the backup routes.In this dissertation we propose a new model and associated algorithms to solve a VC-rerouting problem in real time. This model takes advantage of the distributed network data and computational resources by decomposing the problem at an early stage and then performing the computations in a decentralized mode.In order to solve the fault tolerant VP layout problem, we formulate a bi-criteria optimization model reflecting the tradeoff between throughput and certain QOS requirements. The model involves a piece-wise linear approximation to the capacity allocation rule for variable bit rate connections statistically multiplexed over a VP.Both models are formulated as integer programs. The solution method developed employ relaxation and aggregation of variables, feasible solution heuristics and valid inequalities. The results of the computational experiments presented indicate that the methods developed are efficient and produce accurate solutions