Jose Rafael Ballesteros Hernandez - Academia.edu (original) (raw)

Papers by Jose Rafael Ballesteros Hernandez

Photonic Network Communications, 2008

The in-advance reservation of bandwidth capacity philosophy of Optical Burst Switching architectu... more The in-advance reservation of bandwidth capacity philosophy of Optical Burst Switching architectures via Burst-Control Packets brings high flexibility in the separation of network resources for services with different qualityof-service requirements. In this light, real-time applications can periodically be guaranteed a certain amount of bandwidth reservation for the transmission of traffic with Constant Bit Rate requirements (for instance IP television, VoIP, etc), whilst the remaining capacity may be used for transmission of best-effort traffic of the so-called elastic applications (e-mailing, web browsing, etc). The Polymorphous, Agile and Transparent Optical Networks (PATON) architecture (Qiao et al. IEEE Commu Mag 44(12):104-114 2006) proposes periodic reservation of time-slots over one or several wavelengths of an optical fibre, yet remaining gaps in between them for transmission of best-effort traffic. This work presents a novel analysis of the performance perceived by best-effort traffic which are given full access to optical switching only during a portion of the total time. The following analyses the nonblocking probability among best-effort data bursts that share such available gaps in between the periods of CBR traffic. An exact expression of the non-blocking probability is derived when a single wavelength is used for CBR traffic, along with a lower bound for the case when CBR traffic is transmitted using multiple wavelengths. These results can be of further interest in the optimal design of OBS architectures where the transmission of high-priority real-time traffic and best-effort data coexist over the same wavelength.

2007 10th Ifip/Ieee International Symposium on Integrated Network Management, 2007

The Optical Burst Switching (OBS) paradigm proposes a new set of transmission protocols and netwo... more The Optical Burst Switching (OBS) paradigm proposes a new set of transmission protocols and network architectures that permits the high-utilization of the raw bandwidth available by Dense Wavelength Division Multiplexing at a moderate computational cost. Accordingly, it is necessary to extend the management plane of such networks to include the particular aspects of OBS, in order to guarantee the appropriate network operation. This paper analyzes the information required for the management of such OBS networks and proposes a new information model based on observed management use-cases. A simple data model is also specified to reduce the computational burden, but compliant with the modeled information.

Encyclopedia of Internet Technologies and Applications

Switching in core optical networks is currently being performed using high-speed electronic or al... more Switching in core optical networks is currently being performed using high-speed electronic or all-optical circuit switches. Switching with high-speed electronics requires optical-to-electronic (O/E) conversion of the data stream, making the switch a potential bottleneck of the network: any effort (including parallelization) for electronics to approach the optical speeds seems to be already reaching its practical limits. Furthermore, the store-and-forward approach of packet-switching does not seem suitable for all-optical implementation due to the lack of practical optical Random-Access-Memories to buffer and resolve contentions. Circuit switching on the other hand, involves a pre-transmission delay for call setup and requires the aggregation of microflows into circuits, sacrificing the granularity and the control over individual flows, and is inefficient for bursty traffic. Optical burst switching (OBS) has been proposed by Qiao, C., ?[1] to combine the advantages of both packet an...

Optical Code Division Multiple Access (OCDMA) techniques have shown outstanding capabilities in t... more Optical Code Division Multiple Access (OCDMA) techniques have shown outstanding capabilities in the sharing of optical media, in particular in access networks. However, OCDMA systems may suffer from Multiple Access Interference (MAI) and other kinds of noise when many users access the shared media simultaneously, increasing the BER (Binary Error Rate) to unacceptable levels, that is, a situation at which all combined signals interfere and are lost. This work proposes a mixed OCDMA and Tunable Transmitter-Fixed Receiver (TT-FR) WDM and ring architecture at which the ring is split into small-size segments to limit the probability of MAI. Essentially, every segment in the ring has got two hub nodes (on the segment's head and tail) which forwards inter-segment traffic to other hub nodes on dedicated home wavelengths, thus making use of WDM. The access media inside the segment is shared between the nodes by means of OCDMA, and code reuse is possible on different segments. Our performance analysis shows how to split a given ring into segments in order to minimise the BER due to multiple users accessing the network and allow for high bit-rates for a given traffic load. In addition, we analyse the possibility of introducing Forward Error Correction (FEC) at a moderate overhead cost to improve performance.

The long list of benefits (especially cost and capacity) of Ethernet LANs has made the IEEE, the ... more The long list of benefits (especially cost and capacity) of Ethernet LANs has made the IEEE, the ITU-T, and the Metro Ethernet Forum define the requirements for taking Ethernet beyond the local area, toward the metropolitan region. In addition, the ever-increasing traffic demands of new applications and users can only be met by the huge bandwidth capacity provided by optical fibers. This work studies how to provide metro Ethernet services over transparent tunable-transmitter fixed-receiver WDM optical ring networks. A new adaptation layer of ME to WDM is proposed, and its benefits and drawbacks are studied. It is shown that such a transparent WDM ring network can be seen as a logical full-mesh topology by the upper ME layer, thus reducing to one the number of optical-electronic-optical conversions per unicast frame. Additionally, two different approaches are proposed in the case of broadcast/multicast traffic, since this may bring scalability difficulties in ring topologies.

Physiologia plantarum, 2002

In pea (Pisum sativum L.) plants the effect of short-term salt stress and recovery on growth, wat... more In pea (Pisum sativum L.) plants the effect of short-term salt stress and recovery on growth, water relations and the activity of some antioxidant enzymes was studied. Leaf growth was interrupted by salt addition. However, during recovery, growth was restored, although there was a delay in returning to control levels. Salt stress brought about a decrease in osmotic potential and in stomatal conductance, but at 48 h and 24 h post-stress, respectively, both parameters recovered control values. In pea leaves, a linear increase in the Na + concentration was observed in salt treated plants. In the recovered plants, a slight reduction in the Na + concentration was observed, probably due to a dilution effect since the plant growth was restored and the total Na + content was maintined in leaves after the stress period. A significant increase of SOD activity occurred after 48 h of stress and after 8h of the recovery period (53% and 42%, respectively), and it reached control values at 24 h post-stress. APX activity did not change during the stress period, and after only 8h post-stress it was increased by 48% with respect to control leaves. GR showed a 71% increase after 24h of salt stress and also a significant increase was observed in the recovered plants. A strong increase of TBARS was observed after 8h of stress (180% increase), but then a rapid decrease was observed during the stress period. Surprisingly, TBARS again increased at 8h post-stress (78% increase), suggesting that plants could perceive the elimination of NaCl from the hydroponic cultures as another stress during the first hours of recovery. These results suggest that short-term NaCl stress produces reversible effects on growth, leaf water relations and on SOD and APX activities. This work also suggests that both during the first hours of imposition of stress and during the first hours of recovery an oxidative stress was produced.

Computer Networks, 2008

Typically, core networks are provided with both optical and electronic physical layers. However, ... more Typically, core networks are provided with both optical and electronic physical layers. However, the interaction between the two layers is at present limited, since most of the traditional transport functionalities, such as traffic engineering, switching and restoration, are carried in the IP/MPLS layer. In the light of this, the research community has paid little attention to the potential benefits of the interaction between layers, multilayer capabilities, on attempts to improve quality of service control. This paper shows when to move incoming label switched paths (LSPs) between layers based on a multilayer mechanism that trades off a QoS metric, such as end-to-end delay, and techno-economic aspects. Such a mechanism follows the Bayesian decision theory, and is tested with a set of representative case scenarios.

… Conference, 2007. GLOBECOM'07. …, Nov 26, 2007

In this paper we investigate the potentialities offered by IEEE 802.15. 3 framework for supportin... more In this paper we investigate the potentialities offered by IEEE 802.15. 3 framework for supporting multimedia services. More specifically, we analyze the performance of some classical scheduling policies in presence of intensive heterogeneous realtime and multimedia traffic, in order to identify the most effective strategy for the considered scenarios. The analysis has been performed by using a complete 802.15. 3 C++ simulator, where we have realized the different scheduling strategies upon an entirely standard-compliant ...

Journal of Networks, 2010

Next generation networks are required to provide bandwidth on-demand for fine granularity session... more Next generation networks are required to provide bandwidth on-demand for fine granularity sessions. In this sense, centralized CAC (connection admission control) approaches could suffer from scalability problems if the number of requests for connections were very high. In this paper we investigate local CAC schemes where the decisions are performed at the network edges, based on pre-calculated admission quotas.

Photonic Network Communications, 2007

In Optical Burst-Switched (OBS) networks, the limitation of optical buffering devices make it imp... more In Optical Burst-Switched (OBS) networks, the limitation of optical buffering devices make it impractical to deploy conventional delay-based differentiation algorithms such as Active Queue Management, Weighted Fair Queuing, etc. Furthermore, since only the delay that appears due to the burst-assembly process constitutes a variable quantity (all the other sources of delay are mostly fixed), it is then reasonable to make use of the burst-assembly algorithm to provide class-based delay differentiation. The aim of the following study is twofold: first it defines an average assembly delay metric, which represents the assembly delay experienced by a random arrival at the burst assembler of an edge OBS node; and secondly, this metric is used to define and configure a two-class burst-assembly policy which gives preference to high-priority traffic over low-priority packet arrivals. The results show that, (1) tuning the parameters of the two-class assembly algorithm, the two classes of traffic exhibit different burst-assembly delay; and, (2) such parameters can be adjusted to provide a given differentiation ratio in the light of the proportional QoS differentiation approach proposed in the literature. A detailed analysis of the two-class assembly algorithm is given, along with an exhaustive set of experiments and numerical examples that validate the equations derived.