As a key component of high‐performance switches and routers, the packet forwarding engine (PFE) is mainly responsible for selecting the appropriate output port for tens of thousands of packets within ...an extremely short time frame. However, the performance of PFE is determined by the selected group membership algorithm. This paper puts forth a hybrid strategy–caching scalar‐pair and vectors routing and forwarding (CSVRF), consisting of virtual output port bitmap caching (VOPBC) and fractional‐N SVRF to address major multicast forwarding issues such as scalability by using content addressable memory. In CSVRF, a virtual output port bitmap cache is introduced, which includes the most popular combinations of output port bitmap and divides the big scalar‐pair into N sub‐groups to achieve parallel compute and the reusability of less bit‐length prime. The results demonstrate that the memory space and the forwarding latency are effectively reduced compared with previous work. In space efficiency, it only required 10% memory space compared with the original SVRF/fractional‐N SVRF, decreased 10% memory usage compared with pure VOPBC and nearly improved 1 to 4 orders of magnitude of packet processing time compared with the original SVRF and the fractional‐N SVRF respectively.
We propose a hybrid strategyCaching Scalar‐pair and Vectors Routing and Forwarding (CSVRF) which effectively reduces the processing time by processing each sub‐group in parallel and reducing the memory required after combining with VOPBC.
It is common knowledge that network address translation (NAT) is the most economical means of deployment large-scale users to access the IPv4-based Internet, which could be combined with a few, even ...single public IP addresses. Although the NAT issues do not catch more attention from the research community, it does not mean they are unimportant to modern network deployments, e.g., fifth-generation (5G) and Internet of Things (IoT). This article introduces a structured transparent communications service framework among NATed subdomains, consisting of software-defined networks and an authoritative domain name system. Through addressing via the private fully qualified domain name, the above components coordinate and provide bidirectional interconnect capability among NAT-enabled intranets. In other words, each internal host with a private IP address has a dedicated corresponding PFQDN on the outside. The proposed scheme emphasizes availability: which extends the IPv4 address space from 2 32 to 2 56 or even more; but at the expense of performance: which restricts the concurrent quantity of reverse connections during a time period (depending on the quantity of available public IP addresses). The proposed scheme features a high potential to solve the NAT traversal problems for Internet services and applications that may encounter IPv4 address exhaustion on the current Internet.
This paper introduces a new scalable, efficient and stateless source routing scheme to ensure that unified unicast and multicast packets can be delivered in the Data Center Networks (DCNs). This ...scheme, called Code-Oriented eXplicit multicast (COXcast), is based on unicast and eXplicit multicast (Xcast). It constructs the unicast path and multicast tree by encoding the corresponding output port bitmap of each intermediate node. Using a common identifier and a node-specific key, so packets can be self-routed to multiple receivers without requiring header modification. In addition, intermediate switches/routers on the path/tree can be stateless. Compared to traditional source-based unicasting and explicit-based multicasting schemes, COXcast has lowered the processing cost, protocol overhead and delivery latency, while simplifying the deployment and management of a large number of medium-scale multicast groups, especially when applied to large-scale DCNs.
As a key infrastructure of Industry 4.0, Industrial Internet-of-Things (IIoT) promises the opportunity to build powerful industrial environments by leveraging the growing ubiquity of wired and ...wireless communication technologies. Designing a data delivery scheme in the future IIoT networks is undoubtedly a challenging task, as it should satisfy several conflicting requirements: massive-scale, data-intensive, and mission-critical, the requirements of which have motivated the desired need for feasible IIoT network architecture. In particular, the traffic characteristics of certain IIoT applications feature small-data patterns especially in typical automation control scenarios such as robot control on the downlink. In order to reduce the huge overhead associated with each individual unicast transmission of the small-data message, we propose a novel "multipoint-to-multipoint" and/or "point-to-multipoint with different contents" communication paradigm-Uni-Multi-Unicast (UMUcast), which is based-on traditional 4G technologies such as evolved Multimedia Broadcast Multicast Service (eMBMS) and Group Communication System Enablers (GCSE), and novel 5G technologies such as Multi-Access Edge Computing (MEC). For the downlink, the UMUcast transmitter can jointly encode multiple-sources' small-data messages into a single chunk at MEC equipment in conjoint with a gNB, where chunk can be one-off transmission to multiple receivers simultaneously through an eMBMS frame, whereas the chunk is decoded into multiple small-data by each individual IIoT devices separately and respectively. The simulation results show that UMUcast has remarkable improvements over conventional point-to-point unicasting in handling multi-source, multi-destination, and massive small-data delivery with characteristics of low-overhead, high-throughput, and ultra-low-latency for future 5G-based IIoT networks.
High-performance multicast-enabled packet forwarding engines (PFEs), as an essential component of high-end switches, use a polynomial-time membership query algorithm to determine which port(s) the ...data packet should be forwarded. The currently widely used query algorithm is Bloom Filter (BF), which has been proven to have many fatal flaws. Another error-free membership query algorithm includes Scalar-pair Vectors Routing Forwarding (SVRF), Fractional- N Scalar-pair Vectors Routing Forwarding (Frac- N SVRF), and the Per-Port Prime Filter Array (P 3 FA) also have some shortcomings in space and time efficiencies. In this paper, we proposed a hybrid strategy: Divaricate Heterogeneous SVRF (DH-SVRF) scheme, which based on the P 3 FA and Frac- N SVRF, which randomly divides all member ships into N groups, and each group has the same structure and is independent of each other to obtain higher time efficiency and space utilization. Finally, we also discussed the selection of the optimal egress-diversity threshold. Through mathematical modeling and simulation, we validate that the proposed DH-SVRF scheme is superior to the SVRF/Frac -N SVRF and traditional BF in terms of scalability, space utilization, and time efficiency in specific conditions such as appropriate egress-diversity thresholds.
Highly effective catalysts are of great importance for artificial nitrogen fixation. Inspired by the natural nitrogenase, we biomimetically designed an inorganic catalyst, Mo(IV)-doped FeS2, for ...electroreduction of dinitrogen to ammonia. The Mo(IV) ions favor the adsorption and activation of N2, while the FeS2 substrate depresses the competitive hydrogen evolution reaction, and the two factors jointly endow the catalyst with a high Faraday efficiency of 14.41% at −0.2 V versus RHE.
ABSTRACT
Investigating how the cut-off energy Ecut varies with X-ray flux and photon index Γ in individual active galactic nuclei (AGNs) opens a new window to probe the yet unclear coronal physics. ...So far Ecut variations have only been detected in several AGNs but different patterns have been reported. Here, we report new detections of Ecut variations in two Seyfert galaxies with multiple Nuclear Spectroscopic Telescope Array (NuSTAR) exposures. While in NGC 3227 Ecut monotonically increases with Γ, the Ecut–Γ relation exhibits a Λ shape in SWIFT J2127.4+5654 (Ecut increasing with Γ at Γ ≲ 2.05, but reversely decreasing at Γ ≳ 2.05), indicating more than a single underlying mechanism is involved. Meanwhile both galaxies show softer spectra while they brighten in X-ray, a common phenomenon in Seyfert galaxies. Plotting all seven AGNs with Ecut variations ever reported with NuSTAR observations in the Ecut–Γ diagram, we find they could be unified with the Λ pattern. Although the sample is small and SWIFT J2127.4+5654 is the only source with Γ varying across the break point thus the only one exhibiting the complete Λ pattern in a single source, the discoveries shed new light on the coronal physics in AGNs. Possible underlying physical mechanisms are discussed.
High-performance multicast packet switching technologies are evolving to meet the growing demand for scalability on the Internet and datacenters, etc. Implementing a high-performance switch/router ...relies on a polynomial-time group membership query algorithm within the Packet Forwarding Engines (PFEs) to determine whether a packet is forwarded through an egress. Among these, Bloom filter (BF)-based and Residue Number System (RNS)-based are being considered as two representatives of the membership query algorithms. However, both approaches suffer from some fatal weaknesses such as false-positive probability and time inefficiencies, especially for a carrier-grade PFE with high port-density features. According to similar properties of the RNS, we propose a simplified forwarding algorithm in this paper, named Per-Port Prime Filter Array (P3FA). The simulation results indicate that the P3FA can significantly improve space efficiencies under specific lower egress-diversities conditions. Under the same space constraints, P3FA improves multicast and unicast time efficiency by 1 to 4 orders of magnitude in the port-density 16-1024 range compared to previous works. Although it comes at the expense of hardware cost, it is still acceptable compared to recently improved previous work.
Due to the variable length and uniqueness of names in NDN, traditional IP address-based routing and forwarding architecture is no longer suitable for NDN networks. It is still a challenge to design a ...high-performance forwarding engine to solve the problem of variable name length and uniqueness in NDN. In this article, Residue Number System (RNS) is applied to the routing and forwarding of NDN for the first time, and a new forwarding engine framework based on the RNS is designed. The simulation results show that this method has a significant performance increase in memory space and system latency. At the core-level node, the RNS-based process requires only about 5 percent of Bloom Filter (BF) in terms of memory space and has a 9.8 percent decrease in system latency compared to applying BF (P=1E-08). This method not only achieves less memory usage and reduces the system latency but also fundamentally solves the false positives and has good scalability due to the superiority of the algorithm itself. The proposed work is admirably suited for realizing large-scale NDNs by hardware implementation of NDN routers.
Software-Defined Networking (SDN) has obtained a lot of attention in the last decade and has played a significant role in the development of next-generation networks (NGN). IP networks can also ...benefit from the SDN evolution to fulfill the data traffic booming. However, the transition of the traditional networking model to SDN architectures poses scalability issues due to the possible flow entry explosion in SDN switches. The limited size of flow-table of SDN switches is not sufficient to handle thousands upon thousands of flows in a large-scale IP network. On the other hand, the interleaved allocation of non-contiguous IP addresses also leads to inefficient routing aggregation and reduces the feasibility of the serious implementation of SDN severely. Therefore, we propose an aggressive flow aggregation scheme—Destination Address Translation and Source-Port Translation on Demand (DATSPToD), which is based on the modified address and port rewriting. DATSPToD enables the aggregation of flow entries in SDNs by translating the destination addresses of multiple same-destination flows with different-source into one flow entry, thus significantly reducing the volume of flow-table occupancy of core-layer SDN switches, even in freely scattered IP address space environments. Simulation results show that DATSPToD outperforms non-aggregation and both wildcard aggregation schemes for a significant reduction of the flow-table occupancy under varied traffic patterns and topologies, especially in large-scale SDNs such as the Internet during the SDN migration period. Compared to the competed schemes under varied traffic patterns and topologies, the simulation results of the DATSPToD could significantly reduce flow-table occupancies by at least1 13%, and by up to 52%. The table-miss rates could be reduced from 11% to 66%.
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