Synchronization of a WDM Packet-Switched Slotted Ring

In this paper, we present two different strategies of slot synchronization in wavelength-division-multiplexing (WDM) packet-switched slotted-ring networks. Emphasis is given to the architecture behind the WDM Optical Network Demonstrator over Rings (WONDER) project, which is based on tunable transmitters and fixed receivers. The WONDER experimental prototype is currently being developed at the laboratories of Politecnico di Torino. In the former strategy, a slotsynchronization signal is transmitted by the master station on a dedicated control wavelength; in the latter, slave nodes achieve slot synchronization aligning on data packets that are received from the master. The performance of both synchronization strategies, particularly in terms of packet-collision probability, was evaluated by simulation. The technique based on transmitting a timing signal on a dedicated control wavelength achieves better performance, although it is more expensive due to the need for an additional wavelength. However, the technique based on aligning data packets that are received from the master, despite attaining lower timing stability, still deserves further study, particularly if limiting the number of wavelengths and receivers is a major requirement. Some experimental results, which were measured on the WONDER prototype, are also shown. Measurement results, together with theoretical findings, demonstrate the good synchronization performance of the prototype

Energy Efficient Virtual Machines Placement Over Cloud-Fog Network Architecture

Fog computing is an emerging paradigm that aims to improve the efficiency and QoS of cloud computing by extending the cloud to the edge of the network. This paper develops a comprehensive energy efficiency analysis framework based on mathematical modeling and heuristics to study the offloading of virtual machine (VM) services from the cloud to the fog. The analysis addresses the impact of different factors including the traffic between the VM and its users, the VM workload, the workload versus number of users profile and the proximity of fog nodes to users. Overall, the power consumption can be reduced if the VM users’ traffic is high and/or the VMs have a linear power profile. In such a linear profile case, the creation of multiple VM replicas does not increase the computing power consumption significantly (there may be a slight increase due to idle / baseline power consumption) if the number of users remains constant, however the VM replicas can be brought closer to the end users, thus reducing the transport network power consumption. In our scenario, the optimum placement of VMs over a cloud-fog architecture significantly decreased the total power consumption by 56% and 64% under high user data rates compared to optimized distributed clouds placement and placement in the existing AT&T network cloud locations, respectively

Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results

Fixed and mobile telecom operators, enterprise network operators and cloud providers strive to face the challenging demands coming from the evolution of IP networks (e.g. huge bandwidth requirements, integration of billions of devices and millions of services in the cloud). Proposed in the early 2010s, Segment Routing (SR) architecture helps face these challenging demands, and it is currently being adopted and deployed. SR architecture is based on the concept of source routing and has interesting scalability properties, as it dramatically reduces the amount of state information to be configured in the core nodes to support complex services. SR architecture was first implemented with the MPLS dataplane and then, quite recently, with the IPv6 dataplane (SRv6). IPv6 SR architecture (SRv6) has been extended from the simple steering of packets across nodes to a general network programming approach, making it very suitable for use cases such as Service Function Chaining and Network Function Virtualization. In this paper we present a tutorial and a comprehensive survey on SR technology, analyzing standardization efforts, patents, research activities and implementation results. We start with an introduction on the motivations for Segment Routing and an overview of its evolution and standardization. Then, we provide a tutorial on Segment Routing technology, with a focus on the novel SRv6 solution. We discuss the standardization efforts and the patents providing details on the most important documents and mentioning other ongoing activities. We then thoroughly analyze research activities according to a taxonomy. We have identified 8 main categories during our analysis of the current state of play: Monitoring, Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path Encoding, Network Programming, Performance Evaluation and Miscellaneous...Comment: SUBMITTED TO IEEE COMMUNICATIONS SURVEYS & TUTORIAL

L3 Latency in Regional Networks : Preparing 5G launch

The purpose of the research was to measure the two-way L3 latency in Telia Finland’s regional MPLS networks. The subject was topical, as 5G networks require a significantly smaller amount of delay compared to the existing 4G mobile networks. The primary objective was to produce a baseline for the network delay to be used in planning and development of the regional networks to prepare for the introduction of 5G. An additional objective was to compare two measurement methods to determine their suitability for conducting measurements in the production network. Eventually ping was selected as a measurement method while TWAMP implementation was limited solely to Telia’s laboratory environment. However, the results gained from TWAMP testing were used as a reference when assessing the reliability of the results measured from production network. The research constrained to Telia’s 13 regional networks consisting of Nokia’s SR, ESS, and SAS series routers and switches. In total, 1139 network elements were measured using fping program run on a Unix server in a separate management network. In order to assess the reliability of the results, additional data gained with traceroute program as well as inventory information such as location and site details was combined with the actual measurement data. The result of the research was a reliability analysis of the measurement statistics and the baseline delivered to designers responsible for planning the regional networks. Despite the fact that ICMP traffic is de-prioritized in network elements, this research proves that a simple measurement method can produce accurate enough information for planning and can reveal issues in the network.Tutkimuksen tavoitteena oli mitata kaksisuuntainen L3-viive Telia Finland Oyj:n MPLS-alueverkossa. Tutkittava aihe oli ajankohtainen, sillä 5G-verkon käyttöönotto vaatii operaattorin runkoverolta huomattavasti pienempää viivettä nykyiseen 4G-standardiin verrattuna. Pääasiallisena tavoitteena oli tuottaa tieto tuotantoverkon viiveistä viiveen vertailuarvojen tuottamiseksi, jolloin vertailuarvoja voidaan hyödyntää alueverkkojen suunnittelussa ja rakentamisessa 5G-verkon käyttöönottoa varten. Tutkimuksessa tarkasteltiin lisäksi kahta eri mittausmenetelmää, jolloin menetelmistä sopivampi voitiin valita tuotantoverkon viivemittauksiin. Lopulliseksi mittausmenetelmäksi valikoitui ICMP-protokollaan perustuva ping ja TWAMP-protokollaa päädyttiin testaamaan ainoastaan Telian laboratorioympäristössä. TWAMP-protokollalla saatuja mittaustuloksia käytettiin kuitenkin tuotantoverkosta mitattujen viiveitten luotattavuuden arviointiin. Mittaus rajoittui Telian 13 alueverkkoon, jotka koostuivat Nokian SR-, ESS- ja SAS-sarjan reitittimistä ja kytkimistä. Mittaukset toteutettiin fping-sovelluksella, jota ajettiin hallintaverkossa sijaitsevalta Unix-palvelimelta, ja mittaukset kohdistuivat yhteensä 1139 verkkolaitteeseen. Tulosten analysoinnin helpottamiseksi mittaustuloksiin yhdistettiin lisäksi laitetietokannan sijainti- ja teletilatietoja sekä traceroute-sovelluksella kerättyä dataa. Työn lopputuloksena oli arvio mittaustulosten luotettavuudesta sekä taulukoitu viivestatistiikka, joka luovutettiin alueverkon suunnittelijoiden käyttöön. Siitä huolimatta että verkkolaitteet käsittelevät ICMP-liikennettä muuta liikennettä alemmalla prioriteetilla, tutkimus osoittaa, että yksinkertainen mittausmenetelmä voi tuottaa riittävän tarkkaa tietoa suunnittelutyöhön sekä paljastaa lisäksi verkon ongelmakohtia