Search

In this article, we share our experience of a trial that attempted to gain practical experience in migrating telephony services from the public service telephone network (PSTN) to the IP multimedia system (IMS) domain. We point out some key challenges on the migration path to IMS and identify many issues for successful service deployment in an IMS-based next generation network. Some regulatory concerns and non-technical issues also are addressed.

In this paper, we propose a framework for real-time multimedia transmission in asynchronous transfer mode (ATM) networks using an efficient traffic scheduling scheme called multilayer gated frame queueing (MGFQ). MGFQ employs only one set of FIFO queues to provide a wide range of QoS for real-time applications. We also propose special cell formats for real-time multimedia transport and a hybrid design to allow MGFQ to combine its scheduling scheme with Age Priority Packet Discarding scheme. For this hybrid design, the cell level performance as well as the packet level QoS can be improved at the same time, Simulation results show that this hybrid design will be useful for packetized voice and progressive layer-compressed video transmission across the backbone networks. With the presented framework and the MGFQ algorithm, real-time multimedia traffic streams can be much better supported in terms of cell/packet delay and jitter.

As the growth of applications and services over the Internet keeps increasing, the deployment of layer-3 switching using ATM approach in wide area broadband Internet backbones has been a major solution to meet the traffic demand. Although the performance degradation for TCP/IP over ATM during congestion can be reduced if switch buffer management techniques such as early packet discarding (EPD) and partial packet discarding (PPD) scheme are employed, the improvement are often not significant. We introduce the use of an ACK spacing scheme to further improved the performance of TCP/IP over ATM WANs. The simulation shows that ACK spacing is dominant in the improvement, comparing with the EPD or PPD.

In the current ATM AAL5 implementation, even a single cell loss event can lead to the corruption of one whole packet. Hence, it has been observed that the throughput of the upper layer protocol may easily collapse on a congested ATM network. We propose a buffer management method called age priority packet discarding (APPD) scheme to be used along with two other schemes: the early packet discarding (EPD) and the partial packet discarding (PPD) schemes. After describing the operations and the pseudo code of the proposed APPD scheme and how it operates with the EPD/PPD schemes, the packet level QoS of APPD and its extended versions are derived analytically under homogeneous on-off source model. Numerical results obtained via, analytical approach suggest that the proposed APPD scheme can more effectively and fairly reduce the packet loss probability than other schemes.

We propose a new traffic scheduling scheme, called differentiated multi-layer gated frame queueing (DMGFQ), to provide users with differentiated QoS, better jitter control and fair bandwidth sharing simultaneously. We show that the DMGFQ scheme can achieve excellent performance for well-behaved flows, including delay, jitter and cell discarding ratio, under the presence of misbehaved flows. The residual bandwidths released from other terminated sessions are also fairly distributed among backlogged flows. As a result, the DMGFQ scheme not only supports a wide range of QoS for real-time multimedia, but also achieves the goal of protecting the users conforming to their service level agreements. In addition, DMGFQ also accommodates many flexible realization approaches without sacrificing its performance.

The generalized wireless differentiated fair queueing (GWDFQ) algorithm is proposed to accommodate delay/jitter controls, and fair residual bandwidth sharing for real-time and non-real-time traffic streams simultaneously. The location-dependent channel error property, as appeared in most wireless networks, are considered in the algorithm and the temporary short error burst are compensated by the design of credits. The simulation results show that GWDFQ can achieve excellent performance, including timely delivery of real-time traffic, virtually loss-free transmission of non-real-time traffic, and fair usage of channel bandwidth among remote stations.

We propose a novel and efficient traffic scheduling scheme called multi-layer gated frame queueing (MGFQ) to support real-time multimedia services in the ATM networks. MGFQ employs only one set of FIFO queues to provide a wide range of QoS for real-time applications over ATM networks. We also propose a hybrid design to allow MGFQ to combine its scheduling scheme with age priority packet discarding (APPD) scheme. For this hybrid design, the cell level performance as well as the packet level QoS can be improved at the same time. Simulation results show that this hybrid design will be useful for packetized voice and progressive layer-compressed video transmission across the backbone networks. With MGFQ, a receiver can allocate less resources to compensate the disturbed cell arrivals.

We proposed an improved hierarchical packet pair queueing (H-PFQ) mechanism, using ACK Spacing, for effective bandwidth management of TCP traffic over ATM networks. According to the pre-determined bandwidth sharing and the class hierarchy of all TCP sessions, we design on algorithm to calculate the required time intervals between consecutive ACK packets of each TCP session to avoid packet drops due to buffer overflow. We demonstrated via computer simulations that the proposed improvement techniques may result in much better performance than the original H-PFQ mechanism used in the forward direction in the sense that not only the effective throughput of the bottleneck link is improved but also the fairness among TCP sessions can be maintained.

In this paper, we propose an efficient scheduling scheme called multi-layer gated frame queueing (MGFQ) for real-time traffic over ATM networks. ATM switches equipped with the function of MGFQ which employs only one set of FIFO queues can provide real-time multimedia communication with a wide range of QoS requirements. In addition, a hybrid design which combines MGFQ scheme with an age priority packet discarding (APPD) scheme is proposed to enhance packet level QoS. The simulation results show that the cell level performance as well as the packet level QoS can be improved simultaneously when applying this hybrid design.