Chaitanya S. K. Vadrevu

Network virtualization over WDM and flexible-grid optical networks☆

Abstract Network virtualization can eradicate the ossification of the Internet and stimulate innovation of new network architectures and applications. Optical networks are ideal substrates for provisioning high-bandwidth virtual-network services. In this study, we investigate the problem of network virtualization over both WDM and flexible-grid optical networks by formulating the problems as mixed integer linear programs (MILP). Two heuristics, namely MaxMapping and MinMapping , are developed for each kind of network to solve the problem quickly but suboptimally. Numerical examples show that MinMapping consumes fewer spectrum resources than MaxMapping and performs very close to the optimal results derived by the MILP in both kinds of optical networks, by exploring the opportunities of traffic grooming. Also, it is verified that flexible-grid optical networks can be more spectrum efficient than WDM networks as the substrate for network virtualization.

Network virtualization over WDM networks

Network virtualization can eradicate the ossification of the Internet and stimulate innovation of new architectures and applications. Optical networks are ideal substrates for provisioning high-bandwidth virtual-network services. We investigate the problem of network virtualization over WDM networks by formulating a mixed integer linear program (MILP). Two heuristics, MaxMapping and MinMapping, are developed to solve the problem quickly but suboptimally. Numerical examples show that MinMapping consumes fewer wavelengths than MaxMapping and performs close to the optimal results of the MILP, by exploring the opportunities of traffic grooming.

Degraded service provisioning in mixed-line-rate WDM backbone networks using multipath routing

Traffic in optical backbone networks is increasing and becoming more heterogeneous with respect to bandwidth and QoS requirements due to the popularity of high-bandwidth services (such as cloud computing, e-science, telemedicine, etc.), which need to coexist with traditional services (HTTP, etc.). Mixed-line-rate (MLR) networks that support lightpaths of different rates such as 10, 40, 100 Gb/s, etc., are being studied to better support the heterogeneous traffic demands. Here, we study the important topic of degraded services in MLR networks, where a service can accept some degradation (i.e., reduction) in bandwidth in case of a failure in exchange for a lower cost, a concept called partial protection. Network operators may wish to support degraded services to optimize network resources and reduce cost. We propose using multipath routing to support degraded services in MLR networks, a problem that has not been studied before and is significantly more challenging than in single-line-rate (SLR) networks. We consider minimum-cost MLR network design (i.e., choosing which transponder rates to use at each node), considering the opportunity to exploit multipath routes to support degraded services. We propose a mixed-integer-linear-program (MILP) solution and a computationally efficient heuristic, and consider two partial-protection models. Our illustrative numerical results show that significant cost savings can be achieved due to partial protection versus full protection and is highly beneficial for network operators. We also note that multipath routing in MLR networks exploits volume discount of higher-line-rate transponders by cost-effectively grooming requests over appropriate line rates to maximize transponder reuse versus SLR.

Integrated Design for Backup Capacity Sharing Between IP and Wavelength Services in IP-Over-WDM Networks

Two-layered IP-over-wavelength-division-multi plexing networks supporting IP and wavelength services are becoming increasingly popular. IP services are traditional data services such as virtual private networks, web browsing, etc., whereas wavelength services are new bandwidth-intensive services with strict quality-of-service (QoS) requirements, such as telemedicine, remote visualization, etc. A generic wavelength service (circuit) may require protection from a dedicated backup circuit to meet strict QoS requirements. With the upcoming huge transmission speeds of 100 Gbps and beyond, these dedicated backup circuits will induce significant underutilization of network capacity and high operational expenditure, which can be minimized by supporting IP traffic over idle backup circuits. However, during failure of backup circuits, the IP topology must always remain connected, and this problem has been preliminarily addressed by means of a suboptimal two-step approach [Opt. Switching Networking, vol. 7, p. 196, 2010]. In this paper, we discuss the opportunities and the challenges of a one-step integrated design, and we propose new methodologies for the integrated design of wavelength and IP services, with backup capacity sharing and ensuring survivability of both the services. We consider two levels of survivability for IP services, i.e., ensuring (a) connectivity of the IP topology and (b) fully reroutable capacity for the IP topology under all single physical link failures. For both the scenarios we propose an integer linear program solution and a computationally efficient heuristic. We observe that integrated provisioning with backup capacity sharing enables much higher resource utilization allowing up to a 60% decrease in wavelength channel usage in supporting IP traffic and up to 35% in the total number of wavelength channels needed to support both IP and wavelength services compared with no backup capacity sharing in our experiments.

Survivable IP topology design with re-use of backup wavelength capacity

In IP-over-WDM networks, wavelength circuits are often protected by dedicated backup circuits. Especially with future deployment of 100G transmission systems, there will be huge under-utilization of backup resources. Network utilization can be boosted by loaning the idle backup circuits to preemptible IP/packet services. In the event of a failure, IP traffic can be pre-empted and wavelength backup can be restored. To reroute the pre-empted IP traffic, the IP topology must remain connected. In this paper, we propose a novel approach for the design of survivable IP topology with re-use of backup wavelength capacity. We observe that borrowing idle backup capacity to preemptible IP traffic enables much higher resource utilization, allowing for relevant decrease of network cost, and that we can still ensure combined survivability of the IP and wavelength services by incurring in a very small additional cost.

Vertical and horizontal circuit/packet integration techniques for the future optical internet

Hybrid circuit/packet networks where circuit and packet networks coexist are becoming attractive to support future Internet applications. They support both packet/ IP services and circuit/wavelength services. Packet services include traditional data services such as VPN, VoIP, and email, while dynamic circuit services include end-to-end bandwidth-intensive applications such as terascale science experiments. In present hybrid networks, such as ESnet, the bandwidth boundary between the circuit and packet sections of the network is fixed. However, a flexible boundary between the circuit and packet sections will enable cost-efficient bandwidth management in the network. Our study investigates two methods to dynamically migrate capacity between the circuit and packet sections, called vertical stacking and horizontal partitioning, and serves as a tutorial. In vertical stacking, the backup capacity of wavelength circuits can be dynamically exchanged between packet and wavelength services while ensuring survivability. The backup capacity can be used to protect wavelength services in the event of a failure and route packet traffic otherwise. In horizontal partitioning, the excess capacity on links in the packet section can be loaned to circuit services. We have conducted experiments using a snapshot of real traffic on ESnet with horizontal partitioning. Control mechanisms for our approaches that can be operational in ESnet are presented.

Survivable IP topology design with re-use of backup wavelength capacity in optical backbone networks

In IP-over-WDM networks, wavelength circuits are often protected by dedicated backup circuits. Especially with future deployment of 100G transmission systems, there will be huge under-utilization of backup resources. Network utilization can be boosted by loaning the idle backup circuits to preemptible IP/packet services. In the event of a failure, IP traffic can be pre-empted and wavelength backup can be restored. To reroute the pre-empted IP traffic, the IP topology must remain connected. In this paper, we propose a novel approach for the design of survivable IP topology with re-use of backup wavelength capacity. We observe that borrowing idle backup capacity to preemptible IP traffic enables much higher resource utilization, allowing for relevant decrease of network cost, and that we can still ensure combined survivability of the IP and wavelength services by incurring in a very small additional cost.

IP restoration vs. optical protection: Which one has the least bandwidth requirements?

Abstract Survivability in IP-over-WDM networks has already been extensively discussed in a series of studies. While many studies assume an IP restoration scheme and focus on network connectivity in order to ensure proper recovery, few studies deal with optical protection. We investigate this question with the objective of estimating the respective bandwidth requirements of both recovery schemes, subject to single or multiple failures. We also design a mixed recovery scenario where the recovery is taken care at a different layer depending on the type of failures. Results shows that optical protection is by far the most economical recovery scheme in terms of bandwidth requirements.

Degraded services in mixed-line-rate networks using multipath routing

Traffic in optical backbone networks is increasing and becoming heterogeneous with respect to bandwidth and QoS requirements due to the popularity of high-bandwidth services such as cloud computing, e-science, telemedicine, etc. which need to coexist with traditional services (HTTP, etc.). Mixed-line-rate (MLR) networks which support lightpaths of different rates are being studied to support the heterogeneous traffic demands. Here, we study the important topic of degraded services in MLR networks, where a service can accept degradation in bandwidth to a certain extent in case of a failure for lower cost, a concept called partial protection. Network operators may wish to support degraded services to optimize network resources and reduce cost. We develop a multipath routing scheme to support degraded services in MLR networks, and our illustrative examples show that significant cost savings can be achieved vs. full protection.

Dimensioning optical WDM backbone networks with mixed line rates

As new Internet applications are emerging, traffic in optical backbone networks is increasing with heterogeneity in bandwidth and QoS requirements. Higher bit-rate wavelength channels of 40 Gbps, 100 Gbps, and beyond are being deployed in WDM backbone networks to meet these growing traffic needs. Mixed-line-rate (MLR) networks that support various line rates on the same fiber are becoming popular to address the heterogeneous traffic growth. We study the important problem of long-term cost-effective dimensioning of WDM backbone networks with MLR. Our study should enable operators to dimension their networks with deployment of MLR transponders and optical cross-connect (OXC) ports over multiple time periods. We study two multi-period dimensioning approaches: all-periods planning and incremental planning. Our approaches predict the network equipment to be deployed at various nodes in the network during each time period while exploiting the cost reduction of network equipment over time to support traffic growth over multiple time periods. We propose mixed-inter-linear-program (MILP) solutions and a computationally-efficient heuristic. Our illustrative examples show that significant cost savings can be achieved by our long-term planning approaches.