Internetting LAN's and MAN's to B-ISDN's for connectionless trafficsupport

One of the challenges in the interconnection of LANs and MANs to asynchronous transfer mode (ATM) networks is the support of connectionless traffic in the ATM network. A commonly proposed strategy consists of maintaining a thin, low bandwidth virtual path (VP) between each pair of gateways and requesting more bandwidth whenever a burst comes in from the LAN or MAN. Unfortunately, this strategy places a heavy burden on the ATM control processors; furthermore, it is overly conservative in the use of bandwidth. An alternative solution is proposed: on the-fly tranmission of bursts without prior bandwidth reservation. The key conditions for this scheme to work are the use of the cell loss priority (CLP) bit in the ATM cell header and the knowledge of available bandwidth on the path through bandwidth advertising. An on-the-fly strategy for connectionless traffic is described and is compared with a bandwidth renegotiation strategy     

Designing a practical ATM LAN

The adaptor cards and driver software for workstations and local asynchronous transfer mode (ATM) switches and switch control software used in an ATM local area network (LAN) system are discussed. It is shown that the ATM hardware and software components together provide services that are essential for ATM to be considered a realistic alternative to current shared-media LANs. These services include: completely transparent support for the TCP/IP protocol suite, an application programming interface for full access to the underlying ATM capabilities, support for AAL5, AAL3/4, and the null AAL, both connection-oriented and connectionless service, dynamic connection establishment or switched virtual circuits, resource reservation of guaranteed bandwidth and quality of service, full-bandwidth multicast and broadcast, virtual path and channel routing among multiple switches, automatic configuration and failure recovery, dynamic address assignment and internetwork address resolution, and network management via the simple network management protocol (SNMP)     

Cells-In-Frames: a system overview

Cells-In-Frames provides an efficient mechanism for integrating both voice and data traffic on an existing campus network that is currently supporting legacy LAN workstations. The solution suggested by this article is to export ATM services within standard LAN frames. Each frame will carry the traffic from one or more ATM cells, but any given LAN frame is associated with only one ATM virtual circuit. The widely different qualities of service required for voice and data traffic is achieved rough the use of AAL1 and AAL5 services. The AAL functions are split appropriately between the workstation and the LAN switch that interfaces to an ATM backbone network. With the use of the Q.2931 signalling protocols defined for ATM, Cells-in-Frames achieves a long-sought-after goal of providing switched networking services to LAN-attached workstations     

Data communications using ATM: architectures, protocols, andresource management

The introduction of ATM is being propelled by the need for fast data communications in public and private networks. What is needed is a clear picture of protocol architectures and traffic characteristics of the various applications to be supported both now and in the future. The authors discuss ATM network architectures with special focus on the support of connectionless LAN interconnection and show which benefits can be obtained from the introduction of a connectionless server in an ATM network. They outline issues related to the use of existing protocols when ATM networks are introduced and show which protocol complexities have to be handled by gateways and servers, again using the example of connectionless LAN interconnection. Having presented network and protocol architectures the issue of data communication in ATM, resource allocation, is treated     

Performance management issues of currently operated ATM enterprisenetworks

The author proposes a solution for the allocation and balancing of resources to maximize available bandwidth shared among corporate users. Currently established broadband virtual private networks (BVPNs) based on asynchronous transfer mode (ATM) technology comprise ATM cross-connects (ATM-CCs) and a lot of intelligent customer premises equipment (CPE). The CPE, an intelligent ATM service switcher or ATM multiplexer, enables the corporate user to connect routers, private branch exchanges (PBXs), or codecs onto the ATM network. One fundamental characteristic of CPE is that it is capable of accumulating asynchronous and synchronous traffic which may belong to different corporate users' sites. A typical example given of a BVPN configuration serving two corporate network users with four user sites each. In general, each user site needs to exchange asynchronous (connectionless) data streams for the inter-local area network (LAN) communication and synchronous (connection-oriented) data streams with constant bit rates for video/voice communication. The configuration and the performance aspects of inter-LAN communications employing a connectionless server (CLS) are discussed. The bandwidth allocation aspects of the BVPN having to convey synchronous and asynchronous traffic in an ATM environment without a CLS are discussed, including the bandwidth allocation algorithm. The important characteristics of the proposed algorithm is also summarised     

ATM local area networks

LAN emulation offers a best-effort, connectionless, packet transfer service at the MAC sublayer, implemented on top of a connection-oriented ATM network LAN emulation using switched virtual connections requires address resolution to locate the destination end station followed by connection establishment to the resulting ATM address. Address resolution may be implemented by a broadcast technique or by an address server. The broadcast method is the simplest for small networks but a combination of both is probably better. The use of the MAC address to identify an end station, with dynamic binding to its current physical location in the ATM network, allows the ATM LAN segment to be viewed as a virtual LAN. The virtual LAN model permits end stations to move and change physical location while maintaining connection to the same ATM LAN segment. This greatly simplifies the management of large data networks     

Multicast forwarding over ATM: Native approaches

Multicasting is growing in importance as new multimedia applications are devised. Throughout this article, multicasting is understood as the efficient multipoint-to-multipoint transmission of information (in terms of network resource consumption) between the members of a group. Most multicast services have been designed up to now to work over connectionless environments. The approach adopted by connection-oriented networks has been to try to imitate these connectionless multicast schemes with the aim of supporting IP multicast or network-layer broadcast. However, these solutions present drawbacks in terms of delay or signaling overhead. The goal of native ATM multicasting is to provide multicast communications support by taking into account the characteristics of ATM. Therefore, the design philosophy of multicast must be rethought by making it more suitable for connection-oriented networks. Native ATM multicasting is based on mechanisms implemented at the switches to allow the correct ATM-layer multicast forwarding of information. These mechanisms seek to avoid the delay and signaling problems of current solutions, e.g., LAN emulation and IP multicast over ATM. This article provides a survey of the literature on the strategies that offer multicast communications in ATM environments, with special stress on native ATM multicast forwarding mechanisms. Other aspects, such as signaling, quality of service, traffic control, and routing, are not addressed in detail in this article.     

IP switching-ATM under IP

Internet protocol (IP) traffic on the Internet and private enterprise networks has been growing exponentially for some time. This growth is beginning to stress the traditional processor-based design of current-day routers. Switching technology offers much higher aggregate bandwidth, but presently only offers a layer-2 bridging solution. Various proposals are under way to support IP routing over an asynchronous transfer mode (ATM) network. However, these proposals hide the real network topology from the IP layer by treating the data-link layer as a large opaque network cloud. We argue that this leads to complexity, inefficiency, and duplication of functionality in the resulting network. We propose an alternative in which we discard the end-to-end ATM connection and integrate fast ATM hardware directly with IP, preserving the connectionless nature of IP. We use the soft-state in the ATM hardware to cache the IP forwarding decision. This enables further traffic on the same IP flow to be switched by the ATM hardware rather than forwarded by IP software. We claim that this approach combines the simplicity, scalability, and robustness of IP, with the speed, capacity, and multiservice traffic capabilities of ATM     

Efficient support for client/server applications over heterogeneousATM networks

We present a new network design problem that is applicable for designing virtual paths (VPs) in an asynchronous transfer mode (ATM) network to efficiently support client/server applications. We present several alternatives for the solution, compare their properties, and focus on a novel “greedy” solution, which we prove to optimize certain important criteria (namely, the network overhead for a request/response and the utilization of bandwidth and routing table resources). We also present simulation results that demonstrate the performance and scalability of our solution. In addition, we propose a new efficient bandwidth allocation scheme which is tailored for client/server applications over ATM networks     

Data communication in ATM networks

An increasing number of customers require LAN access with high bandwidth and low delay over long distances. To satisfy these needs, several high-speed network techniques have been developed. Asynchronous transfer mode (ATM) is superior compared to other networking technologies, as it offers high bandwidth and is scalable in the sense that the bandwidth capacity of an ATM system is not fundamentally limited to the technology itself. Initial ATM installations will operate as subnetworks of existing networks and MAC layer protocols. One of the main challenges in ATM is the transparent support of existing connectionless LAN services. Several activities have been launched within international standard bodies and forums to specify ways of providing data communication services over ATM. Most notable examples are Switched Multimegabit Data Service (SMDS) and the similar Connectionless Broadband Data Service (CBDS) supported mostly by public network service providers. But also other approaches such as IP over ATM, and LAN emulation that show more adherence to the existing local and campus area networking paradigms. The article presents the requirements and architecture of the LAN emulation service. It describes the alternative methods for carrying IP packets over ATM, a public broadband service architecture and CBDS. The traffic management aspects of the data communication services are also discussed     

Architectural issues of ATM based connectionless overlay network

Connectionless service such as SMDS, or its European equivalent CBDS, can be provided by an ATM network by building a separate connectionless overlay network (CLON) on top of the ATM bearer service. A CLON is composed of a number of connectionless servers, CLSs, which provide the routing function, connected by semipermanent virtual paths (VPs). In this paper, architectural issues related to the design of a CLON are studied. In particular, we address the question of the optimal number of CLSs and their interconnection topology, assuming the underlying ATM network and the mean connectionless traffic load are known. The objective of the design process is to meet given design criteria with minimum costs. The QoS requirements of the SMDS/CBDS service are briefly reviewed and a simple cost model for the CLON network is given. The dimensioning of the logical links is also considered. Then the design process to find the optimal solution for the whole network is outlined. A simplified procedure was applied in numerical studies of the topological optimization. In order to find the general dependence of the optimal number of CLSs on the size of the network and other network parameters, the optimization procedure was applied to a large number of sample ATM networks, generated by an algorithm which is briefly described. Results from these studies are presented and discussed.     

The UniMIN switch architecture for large-scale ATM switches

A general expansion architecture is proposed that can be used in building large-scale switches using any type of asynchronous transfer mode (ATM) switch. The proposed universal multistage interconnection network (UniMIN) switch is composed of a buffered distribution network (DN) and a column of output switch modules (OSMs), which can be any type of ATM switch. ATM cells are routed to their destination using a two-level routing strategy. The DN provides each incoming cell with a self-routing path to the destined OSM, which is the switch module containing the destination output port. Further routing to the destined output port is performed by the destination OSM. Use of the channel grouping technique yields excellent delay/throughput performance in the DN, and the virtual FIFO concept is used for implementing the output buffers of the distribution module without internal speedup. We also propose a “fair virtual FIFO” to provide fairness between input links while preserving cell sequence. The distribution network is composed of one kind of distribution module which has the same size as the OSM, regardless of the overall switch size N. This gives good modular scalability in the UniMIN switch. Performance analysis for uniform traffic and hot-spot traffic shows that a negligible delay and cell loss ratio in the DN can be achieved with a small buffer size, and that DN yields robust performance even with hot-spot traffic. In addition, a fairness property of the proposed fair virtual FIFO is shown by a simulation study     

Mobility and connection management in a wireless ATM LAN

This paper proposes algorithms for handoff, location, and connection management in a wireless asynchronous transfer mode (ATM) local-area network (LAN). Fast handoffs while maintaining cell sequence and quality-of-service (QoS) guarantees are achieved by distributing switching functionality to base stations, and using a networking scheme based on provisioned virtual trees. A new distributed location management scheme using a minimal registration procedure and broadcasts on wired links is proposed for this LAN. The detailed signaling procedures that support the algorithms for mobility and connection management are described. Finally, an implementation of these procedures and an analysis of the measured data is presented. Measurements of service times obtained from this implementation indicate that over 100 calls/s. can be handled by each node in 50-node network with a high-percentage of mobiles (75%) relative to fixed endpoints. This is comparable to current wired ATM switch call handling throughputs, in spite of the fact that these nodes perform additional handoff and location management functions. The data also indicates handoff latency times of 1.3 ms. This validates our proposal for maintaining cell sequence while performing handoffs     

A simple adaptive routing scheme for congestion control inShuffleNet multihop lightwave networks

The authors describe a simple adaptive routing scheme for datagram (connectionless) and virtual circuit (connection-oriented) transmission that relieves congestion resulting from nonuniform traffic patterns and network failures. The authors describe a fixed-routing algorithm for dedicated channel ShuffleNets. Based on the fixed routing algorithm, an adaptive routing scheme for datagram transmission is presented followed by performance results for uniform and nonuniform traffic patterns and fault tolerance. The adaptive routing of datagrams uses only the local queue size information available at the network interface units (NIUs) and redistributes the load as congestion develops. Since datagrams are individually routed through the network, they may not arrive at their destination in the order they were generated and may need to be resequenced. The authors compute an upper estimate on the resequencing buffer size for stream traffic. A virtual circuit version of the adaptive routing algorithm eliminates the need for resequencing buffers     

无线ATM局域网的移动和连接管理

提出了在无线ＡＴＭ局域网中的越区切换、定位和连接管理的方法。通过把交换功能建立在基站上,并且使用一种建立在虚拟树上的网络连接方案,可以在保持码元序列和服务质量的同时,实现快速越区切换。     

QoS routing in ad hoc wireless networks

The emergence of nomadic applications have generated much interest in wireless network infrastructures that support real-time communications. We propose a bandwidth routing protocol for quality-of-service (QoS) support in a multihop mobile network. The QoS routing feature is important for a mobile network to interconnect wired networks with QoS support (e.g., ATM, Internet, etc.). The QoS routing protocol can also work in a stand-alone multihop mobile network for real-time applications. This QoS routing protocol contains end-to-end bandwidth calculation and bandwidth allocation. Under such a routing protocol, the source (or the ATM gateway) is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real-time applications. In addition, it enables more efficient call admission control. In the case of ATM interconnection, the bandwidth information can be used to carry out intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit (VC) service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine the system performance in various QoS traffic flows and mobility environments via simulation. Simulation results suggest distinct performance advantages of our protocol that calculates the bandwidth information. It is particularly useful in call admission control. Furthermore, “standby” routing enhances the performance in the mobile environment. Simulation experiments show this improvement     

Effective control of traffic flow in ATM networks using fuzzyexplicit rate marking (FERM)

We describe the fuzzy explicit fate marking (FERM) traffic flow control algorithm for a class of best effort service, known as available bit rate (ABR), proposed by the ATM Forum. FERM is an explicit rate marking scheme in which an explicit rate is calculated at the asynchronous transfer mode (ATM) switch and sent back to the ABR traffic sources encapsulated within resource management (RM) cells. The flow rate is calculated by the fuzzy congestion control (FCC) module by monitoring the average ABR queue length and its rate of change, then by using a set of linguistic rules. We use simulation to compare the steady-state and transient performance of FERM with EPRCA (a current favourite by the ATM Forum) in the presence of high priority variable bit rate (VBR) video and constant bit rate (CBR) in both a local-area network (LAN) and a wide-area network (WAN) environment. Our experiments show that FERM exhibits a robust behavior, even under extreme network loading conditions, and ensures fair share of the bandwidth for all virtual channels (VCs) regardless of the number of hops they traverse. Additionally, FERM controls congestion substantially better than EPRCA, offers faster transient response, leads to lower end-to-end delay and better network utilization     

Internetworking connectionless and connection oriented networks

The use of connection-oriented (CO) networks for the transport of IP traffic is seen to have value to both users and service providers. Given the expectation that most endpoint-generated traffic will be in the form of connectionless (CL) IP datagrams, we address the problem of how to internetwork a CL (IP) network with a CO network. CO networks can be packet-switched or circuit-switched. Examples of packet-switched CO networks include ATM and MPLS networks, in which resource reservations are made at the ATM or shim layer, and IP-switch-based networks, in which resource reservations are made at the IP layer. Examples of circuit-switched networks include SONET/SDH and WDM networks that consist of programmable optical crossconnects. We consider the internetworking problem for two modes of operation of CO networks: provisioned, in which connections are set up a priori, and switched, in which connections are set up on demand. The main focus of this article is on the more complex problem: the internetworking of CL IP networks with CO networks operated in a switched mode. Our solution consists of (i) interworking user plane protocols with protocol conversion in some cases instead of always using protocol encapsulation, (ii) interworking routing protocols by either simply having gateways know routing information of both networks or having all nodes know routing information of both networks, and (iii) interworking signaling protocols by using application- or transport-layer end-to-end handshakes to trigger connection setups through the CO network. We demonstrate throughput improvements with our integrated routing interworking scheme over the MPOA IP-ATM internetworking solution for two example networks     

A simple and efficient routing protocol for the UMTSA Access network

This paper presents a simple network layer protocol that integrates routing and connectionless transfer of data in a wireless environment. The protocol is specifically geared towards supporting transfer of signalling in mobile networks based on a rooted tree topology. Exploiting the special characteristics of such a topology allows the specification of a very simple and processing efficient routing function. Using the routing function, a connectionless message transport service is implemented. The connectionless transport service is comparable to that of typical network layer protocols of existing data networks. The protocol has originally been specified to carry signalling messages in the control plane of mobile, cellular systems but has the potential to be used also in other environments.     

B-ISDN中的无连接业务

以ATM交换为基础的B-ISDN提供高速、面向连接、分组长度固定的信元交换.当代PC和高速LAN的发展需要面向连接的ATM网络传输无连接业务.本文重点介绍ATM网络中无连接业务的分类、协议结构和具体实现形式.