We study whether the layered encryption and, thus, anonymity of communication can be implemented all-optically, granting ultra-high speed communication and processing. To this end, we evaluate the feasibility of the state-of-the-art all-optical components, including optical linear feedback shift register (oLFSR) and optical XOR (oXOR), for implementing an all-optical stream cipher (oSC). Just like the function of key expansion in today's electronic ciphers, we use pRNGs and oLFSRs to expand short bit sequences of the secret key, thus enabling the transmission and en-/decryption at line rate; oXOR is used for the actual all-optical encryption. Using the principles of information-theoretical entropic security, we evaluate the key uncertainty (entropy and equivocation) and, thus, the computational complexity of various guessing attacks. We also analyze the maximum length of optical key stream and show that oSC can be designed as secure as in today's systems while operating all-optically at higher line rates.

In this paper, we study end-to-end service reliability in Data Center Networks (DCN) with flow and Service Function Chains (SFCs) parallelism. In our approach, we consider large flows to i) be split into multiple parallel smaller sub-flows; ii) SFC along with their VNFs are replicated into at least as many VNF instances as there are sub-flows, resulting in parallel sub-SFCs; and iii) all sub-flows are distributed over multiple shortest paths and processed in parallel by parallel sub-SFCs. We study service reliability as a function of flow and SFC parallelism and placement of parallel active and backup sub-SFCs within DCN. Based on the probability theory and by considering both server and VNF failures, we analytically derive for each studied VNF placement method the probability that all sub-flows can be successfully processed by the parallelized SFC without service interruption. We evaluate the amount of backup VNFs required to protect the parallelized SFC with a certain level of service reliability. The results show that the proposed flow and SFC parallelism in DCN can significantly increase end-to-end service reliability, while reducing the amount of backup VNFs required, as compared to traditional SFCs with serial traffic flows.

Parallelism has become one of the key architectural features in 40-/100-/400-Gb Ethernet multi lane distribution (MLD) standards. The MLD packetizes and distributes traffic adaptively over parallel lanes and maps them to parallel network interfaces for wide area transmission, typically over optical networks. As such, the MLD creates not only new network topology abstractions but also enables modular implementations of various new features to improve the system performance. In this paper, we study the performance of the parallelized Ethernet in combination with erasure coding and more specifically random linear network coding (RLNC). We present a novel theoretical modeling framework, including the derivation of upper and lower bounds of differential delay and the resulting receiver queue size-a critical performance measure in the high-speed Ethernet. The results show benefits of a combined usage of parallelism and RLNC: with a proper set of design parameters, the differential delay and the receiver buffer size can be reduced significantly, while cross-layer design and path computation greatly simplified.

Privacy in form of anonymous communication could be comparably both faster and harder to break in optical routers than in today's anonymous IP networks based on The Onion Routing (Tor). Implementing the practical privacy all-optically, however, is not straightforward, as it requires key generation in each anonymization node to avoid distribution of long keys, and layered encryption, both at the optical line rate. Due to the unavailability of cryptographically strong optical key generation and encryption components, not only a layered encryption is a challenge, but an optical encryption in general. In this paper, we address the challenges of optical anonymous networking for the first time from the system's perspective, and discuss options for practical implementation of all-optical layered encryption. To this end, we propose an optical anonymization component realized with the state-of-the-art optical XOR logic and optical Linear Feedback Shift Registers (oLFSRs). Given that LFSR alone is known for its weak cryptographic security due to its linear properties, we propose an implementation with parallel oLFSRs and analyze the resulting computational security. The results show that proposed optical anonymization component is promising as it can be practically realized to provide a high computational security against deanonymization (privacy) attack.

In current Data Center Networks (DCNs), Equal- Cost MultiPath (ECMP) is used as the de-facto routing protocol. However, ECMP does not differentiate between short and long flows, the two main categories of flows depending on their duration (lifetime). This issue causes hot-spots in the network, affecting negatively the Flow Completion Time (FCT) and the throughput, the two key performance metrics in data center networks. Previous work on load balancing proposed solutions such as splitting long flows into short flows, using per-packet forwarding approaches, and isolating the paths of short and long flows. We propose DiffFlow, a new load balancing solution which detects long flows and forwards packets using Random Packet Spraying (RPS) with help of SDN, whereas the flows with small duration are forwarded with ECMP by default. The use of ECMP for short flows is reasonable, as it does not create the out-of-order problem; at the same time, RPS for long flows can efficiently help to load balancing the entire network, given that long flows represent most of the traffic in DCNs. The results show that our DiffFlow solution outperforms both the individual usage of either RPS or ECMP, while the overall throughput achieved is maintained at the level comparable to RPS.

Recently, physical layer security in the optical layer has gained significant traction. Security threats in optical networks generally impact the reliability of optical transmission. Linear Network Coding (LNC) can protect from both the security threats in form of eavesdropping and faulty transmission due to jamming. LNC can mix original data to become incomprehensible for an attacker and also extend original data by coding redundancy, thus protecting a data from errors injected via jamming attacks. In this paper, we study the effectiveness of LNC to balance reliable transmission and security in optical networks. To this end, we combine the coding process with data flow parallelization of the source and propose and compare optimal and randomized path selection methods for parallel transmission. The study shows that a combination of flow parallelization, LNC and randomization of path selection increases security and reliability of the transmission. We analyze the so-called catastrophic security threat of the network and show that in case of conventional transmission scheme and in absence of LNC, an attacker could eavesdrop or disrupt a whole secret data by accessing only one edge in a network.

We focus on the problem on security, and to an extent, privacy in optical networks, under the assumption that the wiretap attacker either gains knowledge about secret key and encryption algorithm, or is able to decipher the identity of source and destination, and thus infer the user's privacy of communication. We propose two combined features to address this: (1) to parallelize the transmission between source and destination, i.e., split serial optical flows into multiple flows, and (2) to randomize the traffic forwarding along the parallel paths. To this end, we compare two forwarding methods for parallel transmission: i) explicit forwarding (PAR-EXP), akin to WDM networks with mulitpath routing, ii) random forwarding (PAR-RND), akin to either an optical packet switched network, or a multilayer optical network with Ethernet-based forwarding. The study shows that parallel transmission always increases security compared with serial transmission, whereby random forwarding is potentially more secure than explicit forwarding. We define the \emph{security degree} of the network and show that it depends on various factors, such as the number of wiretap edges, network topology and number of disjoint paths available, and link capacity.

Free Space Optics (FSO) is an attractive high-speed communication technique, with advantages of low power consumption, low cost, easy setup and secure data transmission. On the other hand, the FSO channels are sensitive to atmospheric effects, which can decrease the reliability and capacity of the FSO system. This paper proposes a novel method to achieve a reliable FSO transmission, that combines redundancy of parallel transmission supported by additional radio frequency (RF) or FSO links with the redundancy achievable through the adaptive channel coding. We provide a comparative analysis of three scenarios: serial transmission over one FSO path, parallel transmission over multiple FSO paths, and hybrid transmission with one FSO path and one RF path. For each scenario, we derive analytical expressions of expected code rate as well as the upper bound to evaluate the expected information bit rate. Finally, we show that a reliable transmission is possible in each scenario. The hybrid RF/FSO system shows the most promising performance in terms of reliability and system capacity. The best performance can be achieved in systems where the RF link can offer a variable transmission rate, i.e., able to adapting to the atmospheric effects of the FSO channel.

Load adaptive energy saving (LAES) schemes have been widely considered as a solution to reduce the energy consumption in networks. In LEAS, the time is sliced into time periods according to the daily pattern of traffic loads, such as peak and off-peak traffic, and energy saving operations are typically activated during the off-peak traffic. The effectiveness of LAES depends on the number of time slices precisely. A larger number of small time slices is desirable due to a better adaptiveness to traffic fluctuations. At the same time, energy saving operations should not be too frequent, as they have impact on routing stability and operational procedures. In this paper, we study the effect of nonuniform time quantization on the efficiency of energy saving. We propose a novel time quantization algorithm and show that optimizing time quantization can considerably reduce the number of energy saving operations, while comparably saving the same energy as previously reported.