11 research outputs found
QAware: A Cross-Layer Approach to MPTCP Scheduling
Multipath TCP (MPTCP) allows applications to transparently use all available
network interfaces by creating a TCP subflow per interface. One critical
component of MPTCP is the scheduler that decides which subflow to use for each
packet. Existing schedulers typically use estimates of end-to-end path
properties, such as delay and bandwidth, for making the scheduling decisions.
In this paper, we show that these scheduling decisions can be significantly
improved by incorporating readily available local information from the device
driver queues in the decision-making process. We propose QAware, a novel
cross-layer approach for MPTCP scheduling. QAware combines end-to-end delay
estimates with local queue buffer occupancy information and allows for a better
and faster adaptation to the network conditions. This results in more efficient
use of the available resources and considerable gains in aggregate throughput.
We present the design of QAware and evaluate its performance through
simulations, and also through real experiments, comparing it to existing
schedulers. Our results show that QAware performs significantly better than
other available approaches for various use-cases and applications.Comment: in Proceedings of IFIP Networking 2018, 2018 available at:
https://files.ifi.uzh.ch/stiller/IFIP%20Networking%202018-Proceedings.pd
Through the Lens of Google CrUX: Dissecting Web Browsing Experience Across Devices and Countries
User quality of experience in the context of Web browsing is being researched
widely, with plenty of developments occurring alongside technological advances,
not seldom driven by big industry players. With the huge reach and
infrastructure of Google, the Chrome User Experience Report (CrUX) provides
quantitative real-life measurement data of a vast magnitude. Analysis of this
steadily expanding dataset aggregating different user experience metrics,
yields tangible insights into actual trends and developments. Hence, this paper
is the first to study the CrUX dataset from the viewpoint of relevant metrics
by quantitative evaluation of users Web browsing experience across three device
types and nine European countries. Analysis of data segmented by connection
type in the device dimension shows desktops outperforming other device types
for all metrics. Similar analysis in the country dimension, shows North
European countries (Sweden, Finland) having maximum 4G connections (85.99%,
81.41% respectively) and steadily performing 25%-36% better at the 75th
percentile across all metrics compared to the worst performing country. Such a
high-level longitudinal analysis of real-life Web browsing experience provides
an extensive base for future research.Comment: 7 pages, 4 figures and 1 tabl
From Single Lane to Highways: Analyzing the Adoption of Multipath TCP in the Internet
Multipath TCP (MPTCP) extends traditional TCP to enable simultaneous use of
multiple connection endpoints at the source and destination. MPTCP has been
under active development since its standardization in 2013, and more recently
in February 2020, MPTCP was upstreamed to the Linux kernel.
In this paper, we provide the first broad analysis of MPTCPv0 in the
Internet. We probe the entire IPv4 address space and an IPv6 hitlist to detect
MPTCP-enabled systems operational on port 80 and 443. Our scans reveal a steady
increase in MPTCP-capable IPs, reaching 9k+ on IPv4 and a few dozen on IPv6. We
also discover a significant share of seemingly MPTCP-capable hosts, an artifact
of middleboxes mirroring TCP options. We conduct targeted HTTP(S) measurements
towards select hosts and find that middleboxes can aggressively impact the
perceived quality of applications utilizing MPTCP. Finally, we analyze two
complementary traffic traces from CAIDA and MAWI to shed light on the
real-world usage of MPTCP. We find that while MPTCP usage has increased by a
factor of 20 over the past few years, its traffic share is still quite low.Comment: Proceedings of the 2021 IFIP Networking Conference (Networking '21).
Visit https://mptcp.io for up-to-date MPTCP measurement result
Tumor-Shed PGE2 Impairs IL2Rγc-Signaling to Inhibit CD4+ T Cell Survival: Regulation by Theaflavins
BACKGROUND:Many tumors are associated with decreased cellular immunity and elevated levels of prostaglandin E2 (PGE2), a known inhibitor of CD4+ T cell activation and inducer of type-2 cytokine bias. However, the role of this immunomodulator in the survival of T helper cells remained unclear. Since CD4+ T cells play critical roles in cell-mediated immunity, detail knowledge of the effect tumor-derived PGE2 might have on CD4+ T cell survival and the underlying mechanism may, therefore, help to overcome the overall immune deviation in cancer. METHODOLOGY/PRINCIPAL FINDINGS:By culturing purified human peripheral CD4+ T cells or Jurkat cells with spent media of theaflavin- or celecoxib-pre-treated MCF-7 cells, we show that tumor-shed PGE2 severely impairs interleukin 2 receptor gammac (IL2Rgammac)-mediated survival signaling in CD4+ T cells. Indeed, tumor-shed PGE2 down-regulates IL2Rgammac expression, reduces phosphorylation as well as activation of Janus kinase 3 (Jak-3)/signal transducer and activator of transcription 5 (Stat-5) and decreases Bcl-2/Bax ratio thereby leading to activation of intrinsic apoptotic pathway. Constitutively active Stat-5A (Stat-5A1 6) over-expression efficiently elevates Bcl-2 levels in CD4+ T cells and protects them from tumor-induced death while dominant-negative Stat-5A over-expression fails to do so, indicating the importance of Stat-5A-signaling in CD4+ T cell survival. Further support towards the involvement of PGE2 comes from the results that (a) purified synthetic PGE2 induces CD4+ T cell apoptosis, and (b) when knocked out by small interfering RNA, cyclooxygenase-2 (Cox-2)-defective tumor cells fail to initiate death. Interestingly, the entire phenomena could be reverted back by theaflavins that restore cytokine-dependent IL2Rgammac/Jak-3/Stat-5A signaling in CD4+ T cells thereby protecting them from tumor-shed PGE2-induced apoptosis. CONCLUSIONS/SIGNIFICANCE:These data strongly suggest that tumor-shed PGE2 is an important factor leading to CD4+ T cell apoptosis during cancer and raise the possibility that theaflavins may have the potential as an effective immunorestorer in cancer-bearer
A Longitudinal View at the Adoption of Multipath TCP
Multipath TCP (MPTCP) extends traditional TCP to enable simultaneous use of
multiple connection endpoints at the source and destination. MPTCP has been
under active development since its standardization in 2013, and more recently
in February 2020, MPTCP was upstreamed to the Linux kernel. In this paper, we
provide an in-depth analysis of MPTCPv0 in the Internet and the first analysis
of MPTCPv1 to date. We probe the entire IPv4 address space and an IPv6 hitlist
to detect MPTCP-enabled systems operational on port 80 and 443. Our scans
reveal a steady increase in MPTCPv0-capable IPs, reaching 13k+ on IPv4
(2 increase in one year) and 1k on IPv6 (40 increase). MPTCPv1
deployment is comparatively low with 100 supporting hosts in IPv4 and
IPv6, most of which belong to Apple. We also discover a substantial share of
seemingly MPTCP-capable hosts, an artifact of middleboxes mirroring TCP
options. We conduct targeted HTTP(S) measurements towards select hosts and find
that middleboxes can aggressively impact the perceived quality of applications
utilizing MPTCP. Finally, we analyze two complementary traffic traces from
CAIDA and MAWI to shed light on the real-world usage of MPTCP. We find that
while MPTCP usage has increased by a factor of 20 over the past few years, its
traffic share is still quite low.Comment: arXiv admin note: substantial text overlap with arXiv:2106.0735
Perspectives on Negative Research Results in Pervasive Computing
Not all research leads to fruitful results; trying new ways or methods may surpass state of the art, but sometimes the hypothesis is not proven, the improvement is insignificant, or the system fails because of a design error done years ago in previous works. In a systems discipline like pervasive computing, there are many sources of errors, from hardware issues over communication channels to heterogeneous software environments. However, failure to succeed is not a failure to progress. It is essential to create platforms for sharing insights, experiences, and lessons learned when conducting research in pervasive computing so that the same mistakes are not repeated. And sometimes, a problem is a symptom of discovering new research challenges. Based on the collective input of the First International Workshop on Negative Results in Pervasive Computing (PerFail 2022), co-located with the 20th International Conference on Pervasive Computing and Communications (PerCom 2022), this article presents a comprehensive discussion on perspectives on publishing negative results, useful failures, and lessons learned in pervasive computing