A Framework for Multiaccess Support for Unreliable Internet Traffic using Multipath DCCP

Mobile nodes are typically equipped with multiple radios and can connect to multiple radio access networks (e.g. WiFi, LTE and 5G). Consequently, it is important to design mechanisms that efficiently manage multiple network interfaces for aggregating the capacity, steering of traffic flows or switching flows among multiple interfaces. While such multi-access solutions have the potential to increase the overall traffic throughput and communication reliability, the variable latencies on different access links introduce packet delay variation which has negative effect on the application quality of service and user quality of experience. In this paper, we present a new IP-compatible multipath framework for heterogeneous access networks. The framework uses Multipath Datagram Congestion Control Protocol (MP-DCCP) - a set of extensions to regular DCCP - to enable a transport connection to operate across multiple access networks, simultaneously. We present the design of the new protocol framework and show simulation and experimental testbed results that (1) demonstrate the operation of the new framework, and (2) demonstrate the ability of our solution to manage significant packet delay variation caused by the asymmetry of network paths, by applying pluggable packet scheduling or reordering algorithms

Issues in providing a reliable multicast facility

Issues involved in point-to-multipoint communication are presented and the literature for proposed solutions and approaches surveyed. Particular attention is focused on the ideas and implementations that align with the requirements of the environment of interest. The attributes of multicast receiver groups that might lead to useful classifications, what the functionality of a management scheme should be, and how the group management module can be implemented are examined. The services that multicasting facilities can offer are presented, followed by mechanisms within the communications protocol that implements these services. The metrics of interest when evaluating a reliable multicast facility are identified and applied to four transport layer protocols that incorporate reliable multicast

Digital Signatures for PTP Using Transparent Clocks

Smart grids use synchronous real-time measurements from phasor measurement units (PMU) across portions of a grid to provide grid-wide integrity. Achieving synchronicity requires either accurate GPS clocks at each PMU or a high-resolution clock synchronization protocol, such as the Precision Time Protocol (PTP), specified in IEEE 1588 with the power profile in IEEE C37.238-2011. PTP does not natively include measures to provide authenticity or integrity for timestamps transmitted across an Ethernet network, though there has been recent work in providing end-to-end integrity of transmitted timestamps. However, PTP for use in the smart grid requires a version of the protocol in which network switches update the trusted timestamp in flight, meaning that an end-to-end approach is no longer sufficient. We propose two methods to provide for the integrity of the transmitted and updated timestamps as well as to ensure the authority of all network devices altering the time. In the first, we amend the PTP standard to include signatures as part of the time packet itself at the cost of increased jitter in the system. In the second, we transmit these signatures over a wireless network, reducing congestion on the original network. We test both methods on a simulated PTP switch intended for experimentation only and demonstrate that the use of a second network dedicated to verification-related information is better for current networks, as including signatures in the original packet causes more jitter than is acceptable for synchronizing PMUs in particular

Software systems for operation, control, and monitoring of the EBEX instrument

We present the hardware and software systems implementing autonomous operation, distributed real-time monitoring, and control for the EBEX instrument. EBEX is a NASA-funded balloon-borne microwave polarimeter designed for a 14 day Antarctic flight that circumnavigates the pole. To meet its science goals the EBEX instrument autonomously executes several tasks in parallel: it collects attitude data and maintains pointing control in order to adhere to an observing schedule; tunes and operates up to 1920 TES bolometers and 120 SQUID amplifiers controlled by as many as 30 embedded computers; coordinates and dispatches jobs across an onboard computer network to manage this detector readout system; logs over 3~GiB/hour of science and housekeeping data to an onboard disk storage array; responds to a variety of commands and exogenous events; and downlinks multiple heterogeneous data streams representing a selected subset of the total logged data. Most of the systems implementing these functions have been tested during a recent engineering flight of the payload, and have proven to meet the target requirements. The EBEX ground segment couples uplink and downlink hardware to a client-server software stack, enabling real-time monitoring and command responsibility to be distributed across the public internet or other standard computer networks. Using the emerging dirfile standard as a uniform intermediate data format, a variety of front end programs provide access to different components and views of the downlinked data products. This distributed architecture was demonstrated operating across multiple widely dispersed sites prior to and during the EBEX engineering flight.Comment: 11 pages, to appear in Proceedings of SPIE Astronomical Telescopes and Instrumentation 2010; adjusted metadata for arXiv submissio

Digital Signatures for PTP Using Transparent Clocks

Smart grids use synchronous real-time measurements from phasor measurement units (PMU) across portions of a grid to provide grid-wide integrity. Achieving synchronicity requires either accurate GPS clocks at each PMU or a high-resolution clock synchronization protocol, such as the Precision Time Protocol (PTP), specified in IEEE 1588 with the power profile in IEEE C37.238-2011. PTP does not natively include measures to provide authenticity or integrity for timestamps transmitted across an Ethernet network, though there has been recent work in providing end-to-end integrity of transmitted timestamps. However, PTP for use in the smart grid requires a version of the protocol in which network switches update the trusted timestamp in flight, meaning that an end-to-end approach is no longer sufficient. We propose two methods to provide for the integrity of the transmitted and updated timestamps as well as to ensure the authority of all network devices altering the time. In the first, we amend the PTP standard to include signatures as part of the time packet itself at the cost of increased jitter in the system. In the second, we transmit these signatures over a wireless network, reducing congestion on the original network. We test both methods on a simulated PTP switch intended for experimentation only and demonstrate that the use of a second network dedicated to verification-related information is better for current networks, as including signatures in the original packet causes more jitter than is acceptable for synchronizing PMUs in particular

Enforcement of dynamic HTTP policies on resource-constrained residential gateways

Given that nowadays users access content mostly through mobile apps and web services, both based on HTTP, several filtering applications, such as parental control, malware detection, and corporate policy enforcement, require inspecting Universal Resource Locators (URLs) contained in HTTP requests. Currently, such filtering is most commonly performed in end devices or in middleboxes. Filtering applications running on end devices are less resource intensive because they operate only on traffic from a single user and possibly leverage a hook at the HTTP level to access protocol data, but it is left to the user whether to execute them. On the other hand, middleboxes present the challenge of ensuring that they lay on the path of all the traffic from any relevant device. Residential gateways seem to be the ideal place where to implement traffic filtering because they forward all traffic generated by the hosts on home(-office) networks. However, these devices usually have very limited computation and memory resources, while URL-based filtering is quite demanding. In fact existing approaches rely on a large database of rules coupled with either deep packet inspection or transparent proxying for URL extraction. This paper introduces U-Filter, a URL filtering solution based on a distributed architecture where a lightweight, efficient URL extraction and policy enforcement component runs on residential gateways, delegating to a remote policy server the resource intensive task of verifying policy compliance. Thanks to the lightweight communication between the two components and the very limited resource requirements of the local module, U-Filter (i) can be deployed on resource-limited devices such as residential gateways, and (ii) has almost no impact on the performance of the device, as well as on the users’ browsing experience, as demonstrated by the experiments presented in the paper