Minimum Cell Rate Research Articles

ATM 망에서 인터넷 서비스를 위한 셀 스케줄링 알고리즘

최근 ATM 포럼에서 승인한 GFR(Guaranteed Frame Rate) 서비스는 ATM 망에서 TCP/IP 트래픽을 효율적으로 서비스하는 중요한 서비스가 될 것으로 기대된다. GFR 서비스는 프레임 단계에서 최소 대역 서비스를 보장할 뿐 아니라 가용 대역을 공평하게 사용하도록 지원한다. 본 논문에서는 GFR 서비스를 위한 새로운 셀 스케쥴링 알고리즘을 제안한다. 제안된 알고리즘은 VC에 우선순위를 제공하고 버퍼에 있는 좀더 서비스를 받지 못한 셀에 좀더 높은 우선순위를 부여한다. 높은 우선순위의 VC들은 낮은 우선순위의 VC들 보다 더 많은 서비스를 받는다. 제안된 알고리즘은 GFR VC에 MCR 보장과 공평 대역 공유를 제공할 수 있다. 시뮬레이션 결과는 제안된 셀 스케줄링 알고리즘이 TCP 출력과 공평성 면에서 기존의 알고리즘 보다 우수한 성능을 제공함을 보여주고 있다. Guaranteed Frame Rate(GFR), recently approved by the ATM Forum, expects to become an important service category to efficiently support TCP/IP traffic in ATM networks. The GFR service not only guarantees a minimum service rate at the frame level, but also supports a fair share of available bandwidth. We proposed new scheduling scheme for the GFR service. Proposed scheme provides priority to VCs and high priority to a VC which have more untagged cells in buffer. High priority VCs have much more serviced than low priority. Proposed scheme can provide MCR(minimum cell rate) guarantee and fair sharing to GFR VCs. Computer simulation results show that proposed scheduling scheme provide a much better performance in TCP goodput and fairness than previous scheme.

ATM-GFR 서비스를 위한 F-GCRA 알고리즘 개선

ATM 포럼은 ATM 네트워크에서 인터넷 트래픽을 효과적으로 서비스하기 위해 guaranteed frame rate (GFR) 서비스를 정의하였다. GFR 서비스는 가상 연결에게 minimum cell rate (MCR) 을 보장하고, 여분의 대역폭을 공평하게 공유하도록 한다 또한, 보장된 대역폭을 사용하기에 적합한 ATM 셀을 프레임 단위로 판별하는 프레임 분류기로 frame-based generic cell rate algerian (F-GCRA)을 사용하도록 ATM 포럼은 권고하고 있다. ATM 스위치는 현재 버퍼의 사용량을 고려하여 셀을 프레임 단위로 버퍼에 저장하거나 폐기한다. FIFO 공유 버퍼는 단순한 구조로 인해 스위치에 구현하는데 용이하지만, 가상 연결 별 버퍼 사용량에 따른 버퍼 관리 없이는 각 가상 연결의 MCR를 보장할 수 없었다. 본 논문은 가상 연결 별 버퍼 사용량 관리 없이 각 가상 연결의 MCR을 보장할 수 있도록 F-GCRA 프레임 분류기를 개선한다. 개선된 프레임 분류기는 혼잡 제어로 인한 TCP 트래픽의 burst 특성을 고려하여, 각 가상 연결이 예약한 대역폭을 충분히 사용할 수 있도록 한다. 이러한 개선된 프렌임 분류기의 기능은 여분의 대역폭 사용의 불공정성 문제 역시 완화시키는 효과를 갖는다. 모의실험을 통해 개선된 프레임 분류 알고리즘이 TCP 트래픽에게 GFR 서비스에 대한 만족스런 GoS를 제공함을 보인다. ATM Forum has defined a guaranteed frame rate (GFR) service to serve Internet traffic efficiently. The GFR service provides virtual connections (VCs) for minimum cell rate (MCR) guarantees and allows them to fairly share the residual bandwidth. And ATM Forum has recommended a frame-based generic cell rate algorithm (F-GCRA) as a frame classifier, which determines whether an Am cell is eligible to use the guaranteed bandwidth in a frame level. An ATM switch accommodates cells in its buffer or drops them in a frame level according to current buffer occupancy. A FIFO shared buffer has so simple structure as to be feasibly implemented in switches, but has not been able to provide an MCR guarantee for each VC without buffer management based on per-VC accounting. In this paper, we enhance the F-GCRA frame classifier to guarantee an MCR of each VC without buffer management based on per-VC accounting. The enhanced frame classifier considers burstness of TCP traffic caused by congestion control algorithm so as to enable each VC to use its reserved bandwidth sufficiently. In addition, it is able to alleviate the unfairness problem in usage of the residual bandwidth. Simulation results show that the enhanced frame classifier satisfies quality of services (QoSs) of the GFR service for the TCP traffic.

Performance analysis of congestion avoidance algorithms with non‐zero MCR guarantee for ABR service in ATM networks

AbstractThis paper proposes a novel explicit rate allocation algorithm called Fast Rate Allocation Congestion Avoidance (FRACA) algorithm supporting non‐zero minimum cell rate (MCR). The non‐zero MCR guarantee strategy for ABR service in ATM networks focused in this paper is MCR plus equal share (The ATM Forum Traffic Management Specification, version 4.0. April 1996). The main goals for designing the algorithm are the fast convergence according to the max–min fairness criteria, fairness among all sessions, maximum network utilization while the switch queue length is properly controlled. At the same time, it should work well under a wide range of network conditions without the need for adjusting the algorithm parameters. The performance of the proposed algorithm is evaluated and compared with the Generic Weighted Fairness (GWF) ERICA + (J Comput Comm 2000; 149). Simulation results show that the proposed algorithm achieves the design goals in the evaluated scenarios. Copyright © 2004 John Wiley & Sons, Ltd.

On the performance analysis of ABR in ATM LANs with Stochastic Petri Nets

In this paper we use Generalized Stochastic Petri Nets (GSPNs) and Stochastic Well-formed Nets (SWNs) for the performance analysis of Asynchronous Transfer Mode (ATM) Local Area Networks (LANs) that adopt the Available Bit Rate (ABR) service category in its Relative Rate Marking (RRM) version. We also consider a peculiar version of RRM ABR called Stop & Go ABR; this is a simplified ABR algorithm designed for the provision of best-effort services in low-cost ATM LANs, according to which sources can transmit only at two different cell rates, the Peak Cell Rate (PCR) and Minimum Cell Rate (MCR). Results obtained from the solution of GSPN models of simple ATM LAN setups comprising RRM or Stop & Go ABR users, as well as Unspecified Bit Rate (UBR) users, are first validated through detailed simulations, and then used to show that Stop & Go ABR is capable of providing good performance and fairness in a number of different LAN configurations. We also develop SWN models of homogeneous ABR LANs, that efficiently and automatically exploit system symmetries allowing the investigation of larger LAN configurations.

SWFA: a new buffer management mechanism for TCP over ATM-GFR

We investigate packet discarding schemes for transport control protocol (TCP) over asynchronous transfer mode with guaranteed frame rate service. In this letter, we propose the selective weighted fair allocation (SWFA) scheme, which discards packets from selected sessions. 15 TCP connections with equal minimum cell rate (MCR) and unequal MCRs are simulated. The SWFA scheme with per-virtual connection (VC) queuing is compared with early packet discard (EPD) with first-in, first-out queuing, EPD with per-VC queuing, and differential fair buffer allocation with per-VC queuing. Our results show that SWFA with per-VC queuing achieves significant enhancement on throughputs, goodputs, and fairness.

GFR 서비스의 성능 향상을 위한 새로운 스케줄링 알고리즘

CFR 서비스는 가장 최근에 제안된 ATM 서비스 범주의 하나이다. GFR 서비스는 ATM 네트워크에서 TCP/IP 트래픽을 효율적으로 지원하기 위해 ATM 포럼에 의해 최근 제안되었다. GFR 스위치 구현시, 효율적인 스케줄링 알고리즘은 최소 전송율 보장과 공평성 향상이 중요하다. 본 논문에서는 GFR 서비스를 위한 새로운 스케줄링 알고리즘을 제안한다. 제안된 스케줄링 알고리즘은 VC에 우선 순위를 제공한다. 버퍼에 태깅이 안된 셀 수가 적은 VC에 높은 우선 순위를 두어 낮은 우선 순위의 VC보다 우선적으로 서비스를 제공하여 VC의 MCR을 보장하고 공평성을 향상한다. 컴퓨터 시뮬레이션을 통해 TCP 수율과 공평성 지표에서 기존 스케줄링 방식보다 성능이 우수함을 보여주었다. Guaranteed Frame Rate (GFR) service category is one of the most recent ATM service categories. The GFR specification was recently finalized by the ATM Forum and is expected to become an important service category which can efficiently support TCP/IP traffic in ATM network. In GFR switch implementation, it is important to guarantee MCR (minimum cell rate) and improve fairness. In this paper, we propose a new scheduling algorithm for the GFR service. Proposed algorithm provides priority to VC (virtual circuit)s and high Priority given to a VC which has fewer untagged cells in buffer. High priority VCs are serviced before low priority VCs. Proposed algorithm can guarantee MCR and improve fair sharing of the remaining bandwidth between GFR VCs. From computer simulation results, we demonstrate the proposed scheduling algorithm provide much better performance in TCP goodput and fairness than previous schemes.

Fast, Fair and Frugal Bandwidth Allocation in ATM Networks

Abstract. ATM networks are used to carry a variety of types of traffic. For some types of traffic, in particular Available Bit Rate (ABR) traffic, the bandwidth of a network is typically insufficient to satisfy the requests of all the sessions, and so some fair allocation scheme must be devised. The ATM Forum, the standards setting body for ATM networks, has specified that the fairness criterion for ABR traffic should be Max-Min Fairness , which intuitively means that raising the bandwidth of any session comes at the expense of some other session of no greater bandwidth. Protocols to allocate bandwidth to sessions in a max-min fair manner are an important part of a network design. For a protocol to be realistic, it must conform to the Resource Management (RM) cell mechanism specified by the ATM Forum. Such RM cells get sent as a constant fraction of all cells sent by the source; however, they have only a few fields. RM cells are the only means of communication allowed from link to link so any reasonable protocol is totally distributed and asynchronous, since the RM cell mechanism does not easily lend itself to synchronization. Finally, RM Cells must be handled very quickly at each link. We call a protocol frugal if at each link it performs O(1) computation per RM cell and uses O(1) space per session. Recently, several frugal RM cell protocols have been proposed for ABR traffic, but none have been shown to converge to the max-min fair state. Protocols that are known to converge in a linear number of maximum round-trip times require RM cell processing that is linear in the number of sessions that go through a link. In this paper we give a frugal RM cell protocol for ABR that matches the convergence time of the fastest known non-frugal protocol. A second type of ABR traffic is the Minimum Cell Rate (MCR) type, where every session can specify a minimum amount of bandwidth. The max-min fair allocation should then respect these MCR requests. We extend our results to give the first frugal RM cell protocol for MCR and achieve a quadratic convergence rate.

Design of a new globally stable explicit rate controller for ABR service with saturation

In this paper, we consider the closed-loop rate-based flow control for available bit rate (ABR) service in asynchronous transfer mode (ATM) networks, where the ABR sources adjust their transmission rates in response to feedback explicit rates (ER) from the network switches. The feedback ER may be saturated due to the peak cell rate (PCR) and the minimum cell rate (MCR). The buffer occupancy state of the network switch can also be saturated due to the buffer occupancy. To solve saturation nonlinearity problem and analyze the stability globally, a new ER controller is designed, which is composed of a nonlinear controller and a linear controller. The nonlinear controller is employed to bring buffer occupancy state inside the buffer saturation limits and ensure ER value between PCR and MCR. The linear controller is used to ensure that the buffer occupancy state converges to the desired buffer state. Finally, we demonstrate that good transient and steady-state performances can be achieved through a numerical example.

Interoperability of EFCI and ERICA ATM switches for ABR services with VS/VD enhancements

To improve network bandwidth utilization, the asynchronous transfer mode (ATM) forum has standardized available bit rate (ABR) service which requires a number of parameters to be negotiated during connection setup. MCR is the minimum cell rate guaranteed by the network and can be used to provide an acceptable quality of service for applications. In this study, explicit forward congestion indication (EFCI) and explicit rate indication for congestion avoidance (ERICA) switches were adopted in a current transitional ATM network. First, we transfer traffic with ABR service to realize the interoperability of EFCI and ERICA switches. Second, we implemented the virtual source/virtual destination (VS/VD) feature into a homo or heterogeneous EFCI and ERICA switch environment in order to observe the performance. From the simulation results, a smaller queue length was obtained after the VS/VD was introduced into the EFCI and ERICA switches. The high link data transfer utilization with ABR service was also obtained.

Picture quality optimization in ABR video services

In transmission of bursty traffic such as video and data, a network with a fixed capacity may have some unused bandwidth. The available bit-rate (ABR) scheme in ATM networks can make use of this spare channel capacity as a lower priority service. ABR has been developed initially for delay-tolerant services such as data. In this paper we demonstrate how with the help of a video transcoder delay-sensitive services such as video may be transmitted over ABR networks. The transcoder further compresses the video bit stream according to the rates dictated by the network with minimum degradation to the picture quality. We have optimised the video quality by combining the classical minimum cell rate (MCR) with the subjectively acceptable minimum quality (SAMQ). The performance of two different coding formats for ABR sources, namely the constant bit-rate (CBR) and variable bit-rate (VBR) video input to the transcoder are compared. We also present techniques for further reduction of congestion at the multiplexing switches to improve video quality and report on the impact of the forward and backward link delays on the ABR performance with a video transcoder.

Buffer management and scheduling schemes for TCP/IP over ATM‐GFR

AbstractToday ATM technology is facing challenges from integrated service IP, IP switching, gigabit IP router and gigabit ethernet. Although ATM is approved by ITU‐T as the standard technology in B‐ISDN, its survivability is still in question. Since ATM‐UBR (unspecified bit rate) provides no service guarantee and ATM‐ABR (available bit rate) is still unattainable for most users, many existing users have little or no incentives to migrate to ATM technology. The guaranteed frame rate (GFR) service is introduced to deal with this dilemma. The GFR can guarantee the minimum cell rate (MCR) with fair access to excess bandwidth. This paper studies various schemes to support the GFR. We have studied different discarding and scheduling schemes, and compared their throughput and fairness when TCP/IP traffic is carried. Through simulations, it is shown that only per‐VC queueing with weighted round robin (WRR) can guarantee minimum cell rate. Among all the schemes that have been explored, we recommend dynamic threshold–early packet discard (DT–EPD) integrated with MCR+ (a WRR variant) to support the GFR service. Copyright © 2001 John Wiley & Sons, Ltd.

Generalized max-min rate allocation: Theory and a simple implementation

An important concept in the available bit rate (ABR) service model is the minimum cell rate (MCR) guarantee as well as the peak cell rate (PCR) constraint for each flow. Due to the MCR and PCR requirements, the well-known max-min rate allocation policy no longer suffices to determine the rate allocation for each flow since it does not support either MCR or PCR. In this paper, we present a generalized max-min (GMM) rate allocation policy, which supports both the MCR and PCR requirements for each flow. Furthermore, a simple distributed algorithm using the ABR flow control protocol is developed to achieve the GMM rate allocation in a distributed network environment. The effectiveness of this distributed algorithm is demonstrated by simulation results.

A simple and efficient ABR control algorithm for large-scale networks

A simple and efficient available-bit-rate (ABR) control algorithm is described that fairly allocates bandwidth to each virtual channel (VC) in large-scale networks. In ABR control, the peak cell rate (PCR) and minimum cell rate (MCR) are specified at call set-up, and the cell-emission rate of each VC is controlled between them based on the explicit rate (ER) calculated from the traffic conditions at the ATM switches. Conventional control algorithms that do not use per-VC accounting allocate the same ER to all VCs. Therefore, if there is a VC with a PCR lower than the allocated ER, the control algorithm may not utilize the bandwidth effectively. A VC with an MCR higher than the allocated ER may suffer persistent congestion. Furthermore, algorithms that do not use per-VC accounting cannot achieve weighted bandwidth allocation. However, it is hard to implement algorithms that do use per-VC accounting in large-scale networks. The described ABR control algorithm makes it possible to maintain high throughput under PCR/MCR constraints and to achieve weighted bandwidth allocation based on the traffic conditions, without using per-VC accounting. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(9): 44–56, 2000

An MCR-weighted protocol for multipoint-to-point communication over ABR service

In this paper, we propose an available bit rate (ABR) algorithm which can work with multipoint-to-point (mpt-to-pt) as well as with point-to-point (pt-to-pt) connections. The algorithm is an extension to the MCR-weighted max–min algorithm [Y. Hou, H. Tzeng, S. Panwar, IEEE GLOBCOM, 1997, pp. 492–497], which allocates rates to users in proportion to their MCR requirements. This paper shows how source-level information can be compensated for in order to achieve a performance comparable to that of the pt-to-pt algorithm. This is achieved by combining the current cell rate (CCR) and minimum cell rate (MCR) values of all merged connections hierarchically at each merging point and inserting the aggregate values in the outgoing FRM cells. However, we propose to combine the bottlenecked information only in order to avoid mixing the rates of bottlenecked and non-bottlenecked sources. The same switch algorithm used for the pt-to-pt case can therefore still run on the VC level. A simulation study is conducted under different network configurations. Results show that the algorithm produces an oscillation-free allocation vector with almost the same convergence time of the pt-to-pt algorithm. The results also indicate that the additional buffer requirements due to packet level service is minimal.

An intelligent buffer management approach for GFR services in IP/ATM internetworks

In ATM networks, the Guaranteed Frame Rate (GFR) service has been proposed to accommodate non-real-time traffic with packet size not exceeding a maximum length, such as TCP/IP based traffic. The GFR service not only guarantees a minimum throughput at the frame level, but also supports a fair share of available resources. In this article, we propose a buffering strategy called Intelligent Fair Buffer Allocation (IFBA) that provides minimum cell rate (MCR) guarantees and fair sharing to GFR virtual circuits (VCs). From the simulation results, we demonstrate that IFBA fulfills the requirements of GFR service as well as improves the TCP throughput using the FIFO scheduling.

Fair intelligent bandwidth allocation for rate-adaptive video traffic

This paper presents an algorithm for network bandwidth sharing using explicit rate feedback, the Fair Intelligent Bandwidth Allocation (FIBA) for transporting rate-adaptive video traffic. We show that the FIBA algorithm is capable of allocating bandwidth fairly for a given fairness criteria, among competitive, rate-adaptive video sources. The algorithm is able to reallocate smoothly when a new connection is admitted or when there is renegotiation of the minimum guaranteed cell rate by some connections, or when a connection is throttled somewhere earlier along the connection path. Furthermore, it can prevent congestion, especially during the initial periods when buffer queues can build up significantly.

Weighted fairness with MCR guarantee and a general-purpose explicit rate allocation algorithm for ATM ABR service

In this paper, weighted fair rate allocation for ATM available bit rate (ABR) service is discussed with the concern of the minimum cell rate (MCR). Weighted fairness with MCR guarantee has been discussed recently in the literature. In those studies, each ABR virtual connection (VC) is first allocated its MCR, then the remaining available bandwidth is further shared among ABR VCs according to their weights. For the weighted fairness defined in this paper, the bandwidth is first allocated according to each VC's weight; if a VC's weighted share is less than its MCR, it should be allocated its MCR instead of the weighted share. This weighted fairness with MCR guarantee is referred to as extended weighted (EXW) fairness. Certain theoretical issues related to EXW, such as its global solution and bottleneck structure, are first discussed in the paper. A distributed explicit rate allocation algorithm is then proposed to achieve EXW fairness in ATM networks. The algorithm is a general-purpose explicit rate algorithm in the sense that it can realise almost all the fairness principles proposed for ABR so far whilst only minor modifications may be needed.

Congestion reduction in transmission of video over ABR networks

In transmission of bursty traffic such as video and data, a network with a fixed capacity may have some unused bandwidth. The available bit rate (ABR) scheme in ATM networks can make use of this spare channel capacity as a lower priority service. ABR has been developed initially for delay-tolerant services such as data. The authors demonstrate how, with the help of a video transcoder, delay-sensitive services such as video may be transmitted over ABR. The transcoder further compresses the video bit stream according to the rates dictated by the network with minimum degradation to the picture quality. The video quality has been optimised by combining the classical minimum cell rate (MCR) with the subjectively acceptable minimum quality (SAMQ). The performance of two different coding formats for ABR sources, namely the constant bit rate (CBR) and variable bit rate (VBR) video input to the transcoder are compared. The authors also present techniques for further reduction of congestion at the multiplexing switches and report on the impact of the forward and backward link delays on the ABR performance with a video transcoder.

A generic weight-proportional bandwidth sharing policy for ATM ABR service

A generic weight-proportional max–min (WPMM) policy has been proposed for the ATM available bit rate (ABR) service. This policy generalizes the classical max–min policy by supporting the minimum cell rate (MCR) requirement, the peak cell rate (PCR) constraint, and a generic weight for each connection. This paper presents a distributed ABR flow control algorithm for the the WPMM policy and gives a formal proof of the distributed algorithm’s convergence to the WPMM policy under any network configuration and any set of link distances. Simulation results on various network configurations demonstrate that the distributed algorithm has a very fast convergence property.

Congestion control with a new fairness criterion for multicast ABR service in ATM networks

The authors present an explicit-rate (ER) based congestion control scheme for multicast available-bit-rate (ABR) service in asynchronous-transfer-mode (ATM) networks which support bandwidth allocation with a new fairness criterion, and analyse the stability of the network for both the unicast connections case and the unicast-plus-multicast connections case. Specifically, under the new fairness criterion, allowed-cell-rate (ACR) for a connection is proportional to the difference between peak-cell-rate (PCR) and minimum-cell-rate (MCR) of the connection. The effectiveness of the proposed control scheme is confirmed by computer simulations.