45,476 research outputs found
Is Explicit Congestion Notification usable with UDP?
We present initial measurements to determine if ECN is usable with
UDP traffic in the public Internet. This is interesting because ECN
is part of current IETF proposals for congestion control of UDPbased
interactive multimedia, and due to the increasing use of UDP
as a substrate on which new transport protocols can be deployed.
Using measurements from the author’s homes, their workplace,
and cloud servers in each of the nine EC2 regions worldwide, we
test reachability of 2500 servers from the public NTP server pool,
using ECT(0) and not-ECT marked UDP packets. We show that
an average of 98.97% of the NTP servers that are reachable using
not-ECT marked packets are also reachable using ECT(0) marked
UDP packets, and that ~98% of network hops pass ECT(0) marked
packets without clearing the ECT bits. We compare reachability of
the same hosts using ECN with TCP, finding that 82.0% of those
reachable with TCP can successfully negotiate and use ECN. Our
findings suggest that ECN is broadly usable with UDP traffic, and
that support for use of ECN with TCP has increased
ECN verbose mode: a statistical method for network path congestion estimation
This article introduces a simple and effective methodology to determine the
level of congestion in a network with an ECN-like marking scheme. The purpose
of the ECN bit is to notify TCP sources of an imminent congestion in order to
react before losses occur. However, ECN is a binary indicator which does not
reflect the congestion level (i.e. the percentage of queued packets) of the
bottleneck, thus preventing any adapted reaction. In this study, we use a
counter in place of the traditional ECN marking scheme to assess the number of
times a packet has crossed a congested router. Thanks to this simple counter,
we drive a statistical analysis to accurately estimate the congestion level of
each router on a network path. We detail in this paper an analytical method
validated by some preliminary simulations which demonstrate the feasibility and
the accuracy of the concept proposed. We conclude this paper with possible
applications and expected future work
Critical size of ego communication networks
With the help of information and communication technologies, studies on the
overall social networks have been extensively reported recently. However,
investigations on the directed Ego Communication Networks (ECNs) remain
insufficient, where an ECN stands for a sub network composed of a centralized
individual and his/her direct contacts. In this paper, the directed ECNs are
built on the Call Detail Records (CDRs), which cover more than 7 million people
of a provincial capital city in China for half a year. Results show that there
is a critical size for ECN at about 150, above which the average emotional
closeness between ego and alters drops, the balanced relationship between ego
and network collapses, and the proportion of strong ties decreases. This paper
not only demonstrate the significance of ECN size in affecting its properties,
but also shows accordance with the "Dunbar's Number". These results can be
viewed as a cross-culture supportive evidence to the well-known Social Brain
Hypothesis (SBH).Comment: 6 pages, 4 figures, 1 tabl
ECN with QUIC: Challenges in the Wild
TCP and QUIC can both leverage ECN to avoid congestion loss and its
retransmission overhead. However, both protocols require support of their
remote endpoints and it took two decades since the initial standardization of
ECN for TCP to reach 80% ECN support and more in the wild. In contrast, the
QUIC standard mandates ECN support, but there are notable ambiguities that make
it unclear if and how ECN can actually be used with QUIC on the Internet.
Hence, in this paper, we analyze ECN support with QUIC in the wild: We conduct
repeated measurements on more than 180M domains to identify HTTP/3 websites and
analyze the underlying QUIC connections w.r.t. ECN support. We only find 20% of
QUIC hosts, providing 6% of HTTP/3 websites, to mirror client ECN codepoints.
Yet, mirroring ECN is only half of what is required for ECN with QUIC, as QUIC
validates mirrored ECN codepoints to detect network impairments: We observe
that less than 2% of QUIC hosts, providing less than 0.3% of HTTP/3 websites,
pass this validation. We identify possible root causes in content providers not
supporting ECN via QUIC and network impairments hindering ECN. We thus also
characterize ECN with QUIC distributedly to traverse other paths and discuss
our results w.r.t. QUIC and ECN innovations beyond QUIC.Comment: Accepted at the ACM Internet Measurement Conference 2023 (IMC'23
Measuring ECN++: good news for ++, bad news for ECN over mobile
After ECN was first added to IP in 2001, it was hit by a succession of deployment problems. Studies in recent years have concluded that path traversal of ECN has become close to universal. In this article, we test whether the performance enhancement called ECN++ will face a similar deployment struggle as did base ECN. For this, we assess the feasibility of ECN++ deployment over mobile as well as fixed networks. In the process, we discover bad news for the base ECN protocol: contrary to accepted beliefs, more than half the mobile carriers we tested wipe the ECN field at the first upstream hop. All packets still get through, and congestion control still functions, just without the benefits of ECN. This throws into question whether previous studies used representative vantage points. This article also reports the good news that, wherever ECN gets through, we found no deployment problems for the "++" enhancement to ECN. The article includes the results of other in-depth tests that check whether servers that claim to support ECN actually respond correctly to explicit congestion feedback. Those interested can access the raw measurement data online.The work of Anna Maria Mandalari has been funded by the EU FP7 METRICS (607728) project. The work of Marcelo Bagnulo has been performed in the framework of the H2020-ICT-2014-2 project 5G NORMA and the 5G-City project funded by MINECO. This work was partially supported by the EU H2020 research and innovation program under grant agreement No. 644399 (MONROE) and grant agreement No. 688421 (MAMI)
Connectedness to Nature and Pro-Environmental Behaviour from Early Adolescence to Adulthood: A Comparison of Urban and Rural Canada
Previous research has demonstrated that emotional connectedness to nature (ECN) is one of the strongest predictors of pro-environmental behaviour (PEB). This study investigated the influence of age, gender and living context on ECN and PEB in two Canadian samples.
Study participants completed an environmental survey, which assessed demographic data as well as their levels of ECN and PEB. Project I, which contained 1251 participants, investigated what group factors (age, urban vs. rural living context, male vs. female) contributed to ECN and PEB, as well as whether ECN mediated the relationship between age and PEB. Project II, which contained 84 adolescents, investigated whether participants living in high-accessibility to nature urban settings differed significantly in their levels of ECN or PEB in comparison to those living in a low accessibility to nature urban settings.
Project I’s results revealed that ECN was the strongest predictor of PEB in comparison to the other factors. Results showed that adults displayed significantly higher levels of ECN and PEB in comparison to adolescents, and that females displayed higher levels of both ECN and PEB in comparison to males. Moreover, urban and rural participants significantly differed in their levels of PEB, but not in their levels of ECN. Project II’s results revealed no significant differences between the two urban settings being compared
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