1,863 research outputs found
Sending multiple RTP streams in a single RTP session
This memo expands and clarifies the behavior of Real-time Transport Protocol (RTP) endpoints that use multiple synchronization sources (SSRCs). This occurs, for example, when an endpoint sends multiple RTP streams in a single RTP session. This memo updates RFC 3550 with regard to handling multiple SSRCs per endpoint in RTP sessions, with a particular focus on RTP Control Protocol (RTCP) behavior. It also updates RFC 4585 to change and clarify the calculation of the timeout of SSRCs and the inclusion of feedback messages
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
Nonparametric Rank Tests for Non-stationary Panels
This study develops new rank tests for panels that include panel unit root tests as a special case. The tests are unusual in that they can accommodate very general forms of both serial and cross-sectional dependence, including cross-unit cointegration, without the need to specify the form of dependence or estimate nuisance parameters associated with the dependence. The tests retain high power in small samples, and in contrast to other tests that accommodate cross-sectional dependence, the limiting distributions are valid for panels with finite cross-sectional dimensions.Nonparametric rank tests, unit roots, cointegration, cross-sectional dependence
The 1980 land cover for the Puget Sound region
Both LANDSAT imagery and the video information communications and retrieval software were used to develop a land cover classifiction of the Puget Sound of Washington. Planning agencies within the region were provided with a highly accurate land cover map registered to the 1980 census tracts which could subsequently be incorporated as one data layer in a multi-layer data base. Many historical activities related to previous land cover mapping studies conducted in the Puget Sound region are summarized. Valuable insight into conducting a project with a large community of users and in establishing user confidence in a multi-purpose land cover map derived from LANDSAT is provided
Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1
This paper presents the first optical variability study of the Westerlund 1
super star cluster in search of massive eclipsing binary systems. A total of
129 new variable stars have been identified, including the discovery of 4
eclipsing binaries that are cluster members, 1 additional candidate, 8 field
binaries, 19 field delta Scuti stars, 3 field W UMa eclipsing binaries, 13
other periodic variables and 81 long period or non-periodic variables. These
include the known luminous blue variable, the B[e] star, 11 Wolf-Rayet stars,
several supergiants, and other reddened stars that are likely members of
Westerlund 1. The bright X-ray source corresponding to the Wolf-Rayet star
WR77o (B) is found to be a 3.51 day eclipsing binary. The discovery of a
reddened detached eclipsing binary system implies the first identification of
main-sequence stars in Westerlund 1.Comment: 28 pages, 9 figures, 3 tables; accepted for publication in The
Astronomical Journal. Full-resolution version and color image of the cluster
are available at http://www.dtm.ciw.edu/bonanos/Westerlund
Determinants of OSS revenue model choices
The open source software movement is traditionally not affiliated to profit-oriented business behaviour. However, commercial activity has become increasingly common, and, business models have institutionalized in the field of open source software. The aim of this research paper is to explore the determinants of profitable revenue models for businesses based on open source software. Therefore, the study focuses on analysing different revenue options of open source software businesses as a part of more comprehensive open source software (OSS) business models. We explore other business model elements as the potential determinants of firm-level revenue model choices. This study draws on a qualitative research approach on the issue through two analytical business cases – MySQL and Red Hat – both of which illustrate the complexity and heterogeneity of solutions and options in the field of OSS. Thus, we analyse the business models of the selected case companies and identify the underlying endogenous elements, i.e. offerings, resources and relationships within them. Finally, we discuss the managerial implications derived from the cases to describe how these business model elements affect the development of successful revenue models in the field of open source software
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