Girish Chiruvolu

Issues and approaches on extending Ethernet beyond LANs

Currently, LAN technology is predominantly Ethernet-based and offers packet-optimized switched technology. With more than 90 percent of Internet traffic originating from Ethernet-based LANs, efforts are underway to extend Ethernet beyond LANs into MANs and further into WANs. However, native Ethernet protocols need extensions or support from other technologies in order to succeed as MAN technology in terms of scalability, QoS, resiliency, OAM, and so on. The two emerging trends to carry Ethernet traffic across the MAN can be classified into native Ethernet (IEEE) protocol extensions, and encapsulation by another transportation technology such as MPLS networks. The goal is to offer new and challenging services such as virtual private LAN service, also known as transparent LAN service (TLS). This article presents a comprehensive overview of the required extensions/support of the Ethernet with an emphasis on the emerging provider bridge technology.

Traffic engineering in metro Ethernet

Traffic engineering is a critical issue that has to be addressed in metro Ethernet networks for proper and efficient resource utilization as well as facilitating quality of service. This article aims at understanding the relevant issues and outlines novel algorithms for multipoint-TE in the metro Ethernet. We first propose a grouping scheme that extends the current label space in the provider domain and allows for a large number of VLANs to be provisioned efficiently. Next, the issues of load balancing, multiple spanning trees, and interaction between grouping and bandwidth provisioning are discussed, and solutions are provided. Finally, we address differentiated survivability in next-generation Ethernet and provide a novel scheme based on multiple spanning trees. The schemes proposed in this article are shown to be scalable, bandwidth-efficient, and practical for both the customer and the provider.

Mobility and QoS support for IPv6-based real-time wireless Internet traffic

IPv6 (ipng) is expected to replace the current Internet protocol (IPv4) in the near future and it is most likely that mobile communications shall be supported by the IPv6 at the network layer. Mobile-IPv6 is currently in the standardization process. In addition to network mobility, real-time applications that run on mobile nodes have certain quality of service (QoS) requirements such as constraints on packet loss, delay and jitter. Prior bandwidth reservations at intermediate nodes along a path are required to guarantee the QoS; RSVP would most likely be employed for this purpose. IPv6 supports mobility to some extent. However, novel mechanisms are necessary to enable RSVP-based services to support real-time wireless Internet traffic. The mobility and hence the associated break-and-make of the routes from a correspondent to a mobile node makes the dynamic reservations on-the-fly very critical to the QoS sensitive real-time traffic. A number of issues related to maintaining QoS support for real-time wireless traffic are discussed. Further, an integrated approach (scheme) and its implementation addressing the issues for a better network mobility management and QoS for IPv6-based real-time wireless Internet traffic is proposed. The scheme is developed over the existing RSVP messages with slight extensions/modifications. The proposed scheme intelligently reduces the volume of signaling messages that have to be transmitted by the wireless mobile node leading to reduction in power consumption.

Bandwidth sensitive fast failure recovery scheme for Metro Ethernet

Restoration in Ethernet has evolved over the years as specified in various standards: first the classical reconstruction of spanning trees was proposed in 802.1d; later 802.w specified RSTP to reduce the convergence time required in the STP protocol. Recently, the use of multiple spanning tree was suggested in 802.1s standard. In addition, there have been several proposals to implement multiple tree based restoration. Even though the results are promising they fall short of elevating Ethernet to a carrier grade technology. In this paper, we develop a distributed fast failure recovery spanning tree scheme, which restores lost facilities within tens of milliseconds. Recovery algorithm is localized around the point of failure on the spanning tree, thus avoiding disruption of the entire network. Failures are repaired using pre-configured sub spanning trees which are computed based on traffic requirements and resource availability. This paper also proposes possible enhancements to the failure recovery method using IEEE link aggregation standard to further reduce restoration time and provide differentiated survivability.

Adaptive VBR video traffic management for higher utilization of ATM networks

The VBR video traffic exhibits high burstiness and correlation properties that are quite complex to be captured by a single traffic model. Efficient resource management based on few parameters of the source traffic is highly desirable. The real-time VBR video traffic has stringent quality of service (QoS) requirements such as delay (few milliseconds) and cell loss (1 in 10 -5) that are difficult to achieve with good utilization (> 0.6) by static bandwidth allocation schemes. In order to satisfy such QoS constraints with good utilization, proper adaptive mechanisms have to be devised. This paper presents a dynamic bandwidth allocation scheme for VBR video traffic based on buffer monitoring and a simple LMS (least mean square) traffic prediction system. The goal is to reduce the frequency of the bandwidth reallocations and at the same time reduce the Cell-loss Ratio (CLR) with increased utilization. Simulation results indicate that utilization up to 0.8 can be achieved by the proposed scheme even under high source alignment [26] for bursty VBR video traffic. It is found that the proposed adaptive scheme outperforms the static FCFS allocation scheme with lower buffer requirements and fewer (< 5%) bandwidth reallocations.

Traffic engineering in enterprise ethernet with multiple spanning tree regions

IEEE 802.1s multiple spanning tree protocol (MSTP) is part of a family of standards for local and metropolitan area networks based on Ethernet protocol. MSTP allows a set of regions to be defined whose logical union spans the entire network, which in turn defines the association between VLANs and Spanning Tree Instances. In this paper we propose an algorithmic approach for constructing multiple spanning tree regions in the enterprise network domain which will provide better convergence time, reusability of VLAN tags, protection from failures, and optimal broadcast domain size.

An efficient edge-based congestion management for a differentiated services domain

A novel efficient and low-complexity congestion management method in a differentiated service (DiffServ) domain, so-called edge-based congestion management (ECM), to improve network resource utilization, is proposed. Based on a pro-active congestion control and a dynamic rate regulation, the core nodes and the edge nodes cooperate to respond early to the onset of congestion and to quickly recover from the congestion. This cooperative ECM is implemented using a modRED and a token bucket filter (TBF) rate regulator. Based on early local congestion notification, the ingress nodes adjust their traffic rates via a state-dependent token consumption of the outgoing packets at the TBF. It regulates traffic, avoiding loss during congestion period, and takes advantage of transient available bandwidth quickly by exploiting the lower round trip times between a given pair of ingress and egress nodes. The ECM scheme does not require a per-flow state maintenance hence it is scalable, in addition to its low complexity that is comparable to that of the RED and the token bucket. The simulation study shows that packet loss in the domain can be substantially improved with ECM by at least 30% over a non-feedback scheme especially at high utilization factors. It is also able to maintain the DiffServ domain in a congestion-free state thereby improving overall resource utilization. Finally, the ECM is robust under the presence of unresponsive, aggressive applications in that the packet loss is localized at the ingress TBF with more traffic than that can be accommodated at the core of a DiffServ domain.

A scene-based generalized Markov chain model for VBR video traffic

The efficient transportation of real-time variable bit rate (VBR) video traffic in high-speed networks has been an area of active research. The VBR video traffic characteristics having heavy tail distribution, high variance and correlation properties are quite complex. These characteristics of VBR video (MPEG) traces are studied and a new traffic model for VBR video is proposed. A modulating Markov chain model is employed in which each state represents the I, B, P frames (pictures) of a group of pictures (GOP). From the video traces, we classify the scenes (collection of GOPs) into high- and low-activity scenes, based on the average number of bits generated during the scenes. The scene activity is modeled by an auxiliary Markov chain wherein each state represents the degree of activity (high/low). The transitions of the auxiliary Markov chain represent scene changes of a video sequence. The bit generation during a low-activity scene is modeled by independent AR processes for I, P, B frames. The cross-correlation with the I frames is taken into account by the AR(1) processes for the P and B frames during the high-activity scenes. The traffic thus generated by the model is analyzed and its characteristics are found to be in close agreement with those exhibited by the real traces. The proposed model is quite flexible in order to model scene changes and the autocorrelation characteristics that are common to all packetized broadcast video sequences. The parameters of the scene changes in the proposed traffic model can be appropriately tuned, so that, even the teleconferencing video traffic that involves few scene changes, can be modeled.

An approach towards resource management and transportation of VBR video traffic

This paper investigates the predictability of VBR video traffic which exhibits long-range dependence (LRD) based on the fractional ARIMA (1,d,0) model. We consider a novel predictor based dynamic bandwidth allocation for the short term resource management and study its queueing performance. This method is simple to implement and is demonstrated to provide superior performance over some existing methods. The performance results are presented.

QoS-based routing in optical networks

In this paper two aspects of optical quality of service (QoS), namely the quantitative measures of the optical signal and the functional requirements such as routing stability and protection were discussed. Transmission impairments-based routing of 40 Gb/s connections was investigated and substantial improvement in bandwidth utilization was demonstrated when traffic was split at the source into 10 and 40 Gb/s connections, that were routed separately based on the quality of the available transmission links. The feasibility of differentiation based on routing stability in integrated traffic engineering was demonstrated using the RITE scheme with the preliminary results indicating substantial potential for better utilization of existing lightpaths. Class-based protection and restoration has been investigated and numerical examples were provided that show how different classes of traffic could be routed in a cost-effective way requiring less protection bandwidth.