Unicast Connections Research Articles

P2P vs. IP multicast: Comparing approaches to IPTV streaming based on TV channel popularity

Already a popular application in the Internet, IPTV is becoming, among the service providers, a preferred alternative to conventional broadcasting technologies. Since many of the existing deployments have been done within the safe harbor of telco-owned networks, IP multicast has been the desired streaming solution. However, previous studies showed that the popularity of the TV channels follows the Pareto principle, with the bulk of TV channels being watched only by a small fraction of viewers. Recognizing the potential scalability issues, we believe that multicast streaming approach may not be desirable for unpopular TV channels, especially when there are many such channels in the provider’s service package. For this reason, the peer-to-peer content distribution paradigm is seen as an alternative, in particular for non-popular content. In order to analyse its viability, in this paper we perform a comparative analysis between IP multicast and a peer-to-peer overlay using unicast connections as streaming approaches, in the context of channels with different degrees of popularity. The analysis targets the bandwidth utilization, video quality and scalability issues, and our findings show that while multicast is always more efficient, peer-to-peer has a comparable performance for unpopular channels with a low number of viewers.

Adaptive Routing Strategy for Large Scale Rearrangeable Symmetric Networks

This paper proposes an adaptive unicast routing algorithm for large scale symmetric networks comprising 2 × 2 switch elements such as Bene?s networks. This algorithm trades off the probability of blocking against algorithm execution time. Deterministic algorithms exploit the rearrangeability property of Bene?s networks to ensure a zero blocking probability for unicast connections, at the expense of extensive computation. The authors’ algorithm makes its routing decisions depending on the status of each switching element at every stage of the network, hence the name adaptive routing. This method provides a low complexity solution, but with much better blocking performance than random routing algorithms. This paper presents simulation results for various input loads, demonstrating the tradeoffs involved.

Anycasting in connection-oriented computer networks: Models, algorithms and results

Anycasting in connection-oriented computer networks: Models, algorithms and resultsOur discussion in this article centers around various issues related to the use of anycasting in connection-oriented computer networks. Anycast is defined as aone-to-one-of-manytransmission to deliver a packet to one of many hosts. Anycasting can be applied if the same content is replicated over many locations in the network. Examples of network techniques that apply anycasting are Content Delivery Networks (CDNs), Domain Name Service (DNS), Peer-to-Peer (P2P) systems. The role of anycasting is growing concurrently with the popularity of electronic music, movies, and other content required by Internet users. In this work we focus on the optimization of anycast flows in connection-oriented networks. We formulate a model of anycast connections and next propose a heuristic algorithm based on the Lagrangean relaxation aimed to optimize jointly routes for anycast and unicast connections. Results of numerical experiments are presented and evaluated. Finally, we analyze briefly problems related to anycasting in dynamic routing and multi-layer networks.

A new stage in mathematical teletraffic theory

History of the development of theory of queues and mathematical teletraffic theory achieved at the MSU and PFUR are outlined. Basic theorems and algorithms for calculation of probability measures for multiservice loss networks with unicast connections, multicast connections, as well as with both types of connections are presented. A Triple Play network analysis is determined to be the key task for the future.

Island Multicast: Combining IP Multicast With Overlay Data Distribution

Traditional overlay protocols use unicast connections to form delivery trees. While it can achieve global multicast across the Internet, it is not as efficient as IP multicast. In this paper, we integrate IP multicast into overlay data distribution to improve delivery efficiency. We investigate island multicast where unicast connections are used to connect multicast domains and IP multicast is used within multicast domains. We first explore a centralized island multicast protocol (termed CIM), which relies on a central server to construct a delivery tree. We then study a distributed protocol (termed DIM), where hosts can distributedly join islands and form a delivery tree. We study the key issues in both protocols. We also discuss how to apply these protocols to media streaming applications. We have evaluated both protocols on Internet-like topologies. We have also implemented a prototype for CIM and tested it on PlanetLab. The results show that our approaches can significantly im prove network performance as compared to pure overlay protocols. Our study shows that it is important to consider local multicast capability when designing overlay protocols.

Experimental demonstration of layer-1 multicast for WDM networks using reconfigurable OADM

The feasibility of multicast-capable-reconfigurable optical add/drop multiplexer (MC-ROADM) based on broadcast-and-select switch is experimentally demonstrated. The MC-ROADM can support unicast connection as well as multicast connection, and can provide directionless switching and low insertion loss in path-through channel. We implement fully-reconfigurable multi-degree MC-ROADM based on wavelength selective switch, and evaluate multicasting performances by fully loading 40 × 10 Gbit/s wavelength division multiplexed (WDM) signals. For unicast and multicast operation, measured spectrum and bit-error-rate (BER) show good uniformity and no power penalty. After 1040 km transmission with 25 dB span loss, the measured BER is higher than forward-error-correction (FEC) limit for BER of 10 −15.

Separated Unicast/Multicast Splitter-and-Delivery Switch and Its Use in Multicasting-Capable Optical Cross-Connect

We propose a novel separated unicast/multicast splitter-and-delivery (SUM-SaD) switch for mixed unicast and multicast traffic. Only multicast connections undergo extra splitting loss but are compensated by incorporated optical amplifiers. A typical multicasting-capable optical cross-connect is constructed by using the proposed SUM-SaDs. Theoretically, we prove that it is strictly nonblocking for both unicast and multicast connections if d=N/2, where N and d are the dimension of SUM-SaD and the number of SaD input ports, respectively. Therefore, d means the maximum accommodated trees in the SUM-SaD. To save cost, d can be less than N/2 , and the throughput performance is investigated by simulation. The results show that the throughput is improved when d increases. In the experiment, we construct a 4 times 4 SUM-SaD prototype and measure the bit-error rate (BER) of unicast connection, multicast connection with or without optical amplifier. There is no clear BER difference between them for the small dimensional SUM-SaD switch.

P2Cast: peer-to-peer patching for video on demand service

Providing video on demand (VoD) service over the Internet in a scalable way is a challenging problem. In this paper, we propose P2Cast—an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques, while only relying on unicast connections among peers. We address the following two key technical issues in P2Cast: (1) constructing an application overlay appropriate for streaming; and (2) providing continuous stream playback (without glitches) in the face of disruption from an early departing client. Our simulation experiments show that P2Cast can serve many more clients than traditional client-server unicast service, and that it generally out-performs multicast-based patching if clients can cache more than 10% of a stream’s initial portion. We handle disruptions by delaying the start of playback and applying the shifted forwarding technique. The threshold in P2Cast, i.e., the length of time during which arriving clients form a single session, can serve as a “knob” to adjust the balance between the scalability and the clients’ viewing quality.

Dynamic provisioning of low-speed unicast/multicast traffic demands in mesh-based WDM optical networks

This paper addresses the problem of dynamically provisioning both low-speed unicast and multicast connection requests in mesh-based wavelength division multiplexing (WDM) optical networks. Several routing/provisioning schemes to dynamically provision both unicast and multicast connection requests are presented. In addition, a constraint-based grooming strategy is devised to utilize the overall network resources as efficiently as possible. Based on this strategy, several different sequential multicast grooming heuristics are first presented. Then, we devise a hybrid grooming approach and combine it with sequential approaches to achieve a grooming scheme that is biased toward serving multicast traffic demands in comparison with all other sequential grooming approaches. To achieve our objective, we decompose the problem into four subproblems: 1) routing problem; 2) light-tree-based logical-topology-design problem; 3) provisioning problem; and 4) traffic-grooming problem. The simulation results of the proposed schemes are compared with each other and with those of conventional nongrooming approaches. To the best of our knowledge, this is the first detailed paper to address and examine the problem of grooming dynamic multicast traffic demands.

OPQR-G: algorithm for efficient QoS partition and routing in multiservice IP networks

This paper considers the combined problem of optimal QoS partition and routing (problem QPQR-G) for a QoS framework in which a performance dependent cost function is associated with each network element and the QoS metric is additive (e.g. delay, jitter). This problem has been addressed in the context of unicast connections and multicast trees only. Here we consider the problem for a more general case of a multicommodity flow network. Also, it is assumed that the performance dependent cost functions are non-increasing and are of general integer type. The goal is to determine primary paths between the origin and destination (OD) pairs and QoS partitions on the links so that the overall cost in the network is minimised while all OD pair QoS requirements are satisfied. As the problem is NP-complete, we concentrate on the development of an efficient heuristic algorithm. In addition, two LP-based algorithms were developed, that use the optimisation tool ILOG™ CPLEX 7.1 LP for solving the problem OPQR-G. The numerical results obtained for various test network scenarios are very close to the optimal. The problem addressed in this paper provides the basis for the solution of many interesting and practical engineering problems, such as dimensioning and admission control/resource reservation in IP networks that support service differentiation.

A Modular Approach to Mobile QoS Signaling— Motivation, Design & Implementation

In order to support mobile multimedia applications in next generation wireless IP-based networks, it is necessary to deliver seamless voice, video and data at high quality. Therefore, session mobility and Quality of Service (QoS) for mobile end systems are required. Within this article, the authors point out a new way to approach the problem. Instead of tightly coupling a modified QoS signaling mechanism with a certain mobility mechanism, a more generic and long-term solution is proposed and exemplified on the basis of existing IETF protocols. The connection-less IP network layer is enhanced by a lightweight and truly optional connection-oriented mobile network service, which offers the possibility to establish soft state unicast connections at the network layer. Hence, a connection-oriented network service is available within a radio access network (RAN) architecture to all end systems—mobile or fixed—independent of the application. Thereby, it is possible to integrate QoS and connectivity signaling for mobile end systems, as well as other connection-oriented services like explicit routing or load balancing.

Comprehensive performance modeling and analysis of multicasting in optical networks

Multicasting is becoming increasingly important in today's networks. In optical networks, optical splitters facilitate the multicasting of optical signals. By eliminating the transmission of redundant traffic over certain links, multicasting can improve network performance. However, in a wavelength-division multiplexed (WDM) optical network, the lack of wavelength conversion necessitates the establishment of a single multicast circuit (light-tree) on a single wavelength. On the other hand, establishing several unicast connections (lightpaths) to satisfy a multicast request, while requiring more capacity, is less constrained in terms of wavelength assignment. The objective of the paper is to evaluate the tradeoff between capacity and wavelength continuity in the context of optical multicasting. To this end, we develop accurate analytical models with moderate complexity for computing the blocking probability of multicast requests realized using light-trees, lightpaths, and combinations of light-trees and lightpaths. Numerical results indicate that a suitable combination of light-trees and lightpaths performs best when no wavelength conversion is present.

Jumpstart just-in-time signaling protocol: a formal description using extended finite state machines

We present a formal protocol description for a just-in-time (JIT) signaling scheme running over a core dense wavelength division multiplexing (DWDM) network that utilizes optical burst switches (OBSs). We apply an eight-tuple extended finite state machine (EFSM) model to formally specify the protocol. Using the EFSM model, we define the communication between a source client node and a destination client node through an ingress and one or multiple intermediate switches. We work on on-the-fly and persistent unicast connections. The communication between the EFSMs is handled through messages.

Application-layer multicasting with Delaunay triangulation overlays

Application-layer multicast supports group applications without the need for a network-layer multicast protocol. Here, applications arrange themselves in a logical overlay network and transfer data within the overlay. We present an application-layer multicast solution that uses a Delaunay triangulation as an overlay network topology. An advantage of using a Delaunay triangulation is that it allows each application to locally derive next-hop routing information without requiring a routing protocol in the overlay. A disadvantage of using a Delaunay triangulation is that the mapping of the overlay to the network topology at the network and data link layer may be suboptimal. We present a protocol, called Delaunay triangulation (DT protocol), which constructs Delaunay triangulation overlay networks. We present measurement experiments of the DT protocol for overlay networks with up to 10 000 members, that are running on a local PC cluster with 100 Linux PCs. The results show that the protocol stabilizes quickly, e.g., an overlay network with 10 000 nodes can be built in just over 30 s. The traffic measurements indicate that the average overhead of a node is only a few kilobits per second if the overlay network is in a steady state. Results of throughput experiments of multicast transmissions (using TCP unicast connections between neighbors in the overlay network) show an achievable throughput of approximately 15 Mb/s in an overlay with 100 nodes and 2 Mb/s in an overlay with 1000 nodes.

Caching and Scheduling for Broadcast Disk Systems

Unicast connections lead to performance and scalability problems when a large client population attempts to access the same data. Broadcast push and broadcast disk technology address the problem by broadcasting data items from a server to a large number of clients. Broadcast disk performance depends mainly on caching strategies at the client site and on how the broadcast is scheduled at the server site. An on-line broadcast disk paging strategy makes caching decisions without knowing future page requests or access probabilities. This paper gives new implementations of existing on-line algorithms and reports on extensive empirical investigations. The gray algorithm [Khanna and Liberatore 2000] always outperformed other on-line strategies on both synthetic and Web traces. Moreover, caching limited the skewness of broadcast schedules, and led to favor efficient caching algorithms over refined scheduling strategies when the cache was large.

Scheduling multicast traffic in input-buffered ATM switch

Performance of an input-buffered ATM switch is limited by the head-of-line (HOL) blocking problem. HOL blocking is even more pronounced in multicast switch where cells compete for multiple outputs simultaneously. Previous studies in input-buffered unicast switch have shown that HOL blocking can only be eliminated by using per-output queuing and sophisticated scheduling methods, such as the maximal weight matching (MWM) or the parallel iterative matching (PIM) methods. The MWM or PIM types of scheduling algorithm cannot be applied to multicast switch because of the high computation complexity. In this paper, we present a reservation based scheduling algorithm, which employs per-VC queuing for multicast connections and per-output queuing for unicast connections. Instead of the input ports sending a huge amount of state information to the output ports for processing, we circulate reservation vectors amongst the input ports. Each input port will then make reservation based on its local state and the availability of the output ports. The scheduling is done on a frame by frame basis. While the input ports are transmitting cells according to the schedule of the current frame, the next frame schedule is computed. Simulations reveal that our method substantially outperforms the methods that employ FIFO queuing discipline.

Power-efficient design of multicast wavelength-routed networks

In this paper, we introduce the power-efficient design space for multicast wavelength-routed networks. The power-efficient design space is based on the impact of power on the overall design of wavelength-routed networks. Two cross-connect architectures on this design concept are investigated. One is an existing architecture called splitter-and-delivery (SaD). The other is a new architecture called multicast-only splitter-and-delivery (MOSaD). The MOSaD architecture uses power splitters for multicast connections only, allowing unicast connections to pass without enduring unnecessary power losses. Our cross-connect design provides a strictly nonblocking service for unicast connections while eliminating unnecessary power loss of the SaD cross-connect. Experimental results demonstrate that the MOSaD architecture provides substantial savings in cost and reduction in signal power loss with minimal effects on the blocking performance of the network.

On the Internet-Mediated TV-Like Distance Learning Services

The Internet-mediated distance learning has received a lot of attention in both universities and corporations in the past few years. With the proliferation of new network and multimedia technologies, there is an increasing need for delivering TV-like video lectures. The Cisco IP/TV system has been widely used as an efficient platform in supporting TV-like lectures in MPEG-1 format. However, since it relies on Microsoft multimedia technology, IP/TV cannot be architecture-neutral. Further, in spite that a Web interface to IP/TV is provided, it lacks in application program interfaces to endorse the development of interaction applications between instructors and students. Both limitations can be relieved by appealing to the emerging Java technology. However, playing RTP/MPEG objects using JMF (Java Media Framework) is a non-trivial task. This paper presents a novel Java-based TV-like distance learning system by integrating Cisco IP/TV and Java JMF technology so that the superiority of both models can be complemented. In particular, we enhance the JMF engine to make playing RTP/MPEG media objects over the Internet possible. This system offers two learning modes, namely on-demand learning via unicast connection and scheduled learning via multicast connection. A course sample and its performance evaluation are illustrated to validate the effectiveness and efficiency of delivering TV-like courseware. Furthermore, synchronous distance learning services can be implemented at less cost.

Small group multicast: a new solution for multicasting on the Internet

The Internet's global ubiquity has fostered numerous applications that use many different communications models. Applications like FTP Web browsing, and e-mail employ a unicast model where two parties exchange data over logical point-to-point connections. In other applications, such as multiparty audio/video conferencing and collaborative gaming, a source sends data to multiple parties. One way to support multiparty communications is with unicast connections between the source and all of the receivers. If a group has N parties, then a source must set up N-1 unicast connections and transmit the data N times over the network. When N is large, scalability becomes an issue for the source and the network. IP multicast solves this problem by sending a single copy of the data over a distribution tree that is rooted at the source and that branches out to the various destinations. Because the source transmits a single copy of the data, only one copy of the data appears on the branches in the distribution tree.

Mobile multicasting in wireless ATM networks

Multicasting is a desired function in both wired and wireless networks. Currently, multicasting‐based applications have pervasive presence and influence in our Internet. Wireless ATM aims to support different traffic types over a high speed wireless network. In particular, traditional approaches towards multicasting in wired networks cannot be directly applied to mobile ATM networks. This includes the mechanism proposed to handle mobility in wired networks. In this paper, we address the issues behind multicasting in wireless ATM networks and the underlying mechanisms to support handoffs of both unicast and multicast connections. Through simulation, we evaluated the performance of optimal core‐based tree (CBT), late‐joined CBT, optimal source‐based tree (SBT), and late‐joined SBT during changing multicast host membership conditions. In addition, we evaluated the impact of multicast receivers' migration on the total link cost of the resultant multicast tree. Simulation results revealed that source‐based trees incur more total link costs under both dynamic host membership and receivers' migration scenarios. However, it generates less control messages than the distributed CBT and SBT approaches.