The ossification of the Internet protocol stack, due in large part to mangling of packets by middleboxes, has led to a relatively slow rate of change in today's Internet. We have developed the PATHspider active Internet measurement tool which performs onesided measurements of a variety of transport-layer features and extensions, to investigate these impairments to protocol evolution along an Internet path. Data collected with PATHspider can be used both to determine the degree of support for these features, as well as to detect connectivity issues caused by attempting to use them. The wider aim of this effort is to provide quantifiable input to protocol design and deployment choices that can be based on the level of impairment present in the Internet.This paper details PATHspider's design, and applies it to trace the evolution of deployment of two extensions to TCP, Explicit Congestion Notification (ECN) and the newer TCP Fast Open (TFO); as well as the degree of interference with the Differentiated Services Code Point (DSCP) carried in the IP header. Our ECN results, in particular, expand on a long-term study beginning in 2012, and show continued linear adoption of ECN. Automating PATHspider measurements has allowed us to collect far more data than in previous campaigns, allowing us to better distinguish ECN-linked connectivity failures from transient effects. Interestingly, we observe a correlation between ECN-linked connectivity failure in the core of the network with the presence of large-scale, heterogeneous Internet censorship infrastructure.
For over two decades, hierarchical zoning models have dominated operational technology (OT) network design. However, ongoing changes to industrial network technologies and workloads, together with rising threat levels, are now challenging this design pattern. To address these issues, this paper introduces Tableau, a new zoning architecture for OT networks. Tableau increases network flexibility by flattening the zone structure and by allowing the seamless integration of plant, edge, corporate, and cloud networks. Simultaneously, Tableau facilitates modern security practices and is IEC 62443 compatible, ensuring the continued secure operation of OT infrastructure.
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