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bandwidth
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... TCP
connection then probes the network for available bandwidth using the
slow-start procedure ([Jac88 ...
... algorithm can be time-consuming --- especially over
networks with large bandwidth or long delays. It may take a number
of RTTs in slow-start ...
... slow-start before the TCP connection begins to fully use
the available bandwidth of the network. For instance, it takes
log_2(N) - 2 round-trip times ...
... round-trip times, where one or two RTTs might have been
sufficient when using the currently available bandwidth along the
path.
...
... router is
only asserting that it is currently underutilized and believes there
is sufficient available bandwidth to accommodate the sender's
...
... [RFC3819] discusses a range of Bandwidth on Demand subnets that
could cause the characteristics of the path to change over time.
...
... Quick-Start Request for a smaller rate or denied the use of Quick-
Start, and adjust its bandwidth allocations accordingly.
...
... transport no longer has a validated
estimate of the available bandwidth for this flow. (An example
could be a persistent-HTTP ...
... TCP receivers to send Quick-Start Requests to request bandwidth
for the acknowledgement traffic on the reverse path. However, in our
...
... appropriately. For example, the sender might have information about
the bandwidth of the last-mile hop, the size of the local socket
buffer ...
... larger than necessary; every Quick-Start Request that is approved but
not used (or not fully used) takes away from the bandwidth pool
available for granting successive Quick-Start Requests.
...
... In order to answer the last question, the router must have some
knowledge of the available bandwidth on the output link and of the
Quick-Start ...
... link and of the
Quick-Start bandwidth that could arrive due to recently approved
Quick-Start Requests. In this way, if an underutilized router ...
...
A simple way for the router to keep track of the potential bandwidth
from recently approved requests is to maintain two counters: one for
...
... intervals for remembering the aggregate approved Quick-Start
bandwidth. A possible router algorithm is given in Appendix E, and
more discussion ...
... aggregate of the Quick-Start Request Rate options granted is low
enough to prevent a near-term bandwidth shortage, then the router
could approve the Quick-Start Request ...
... traffic in one of the routers, a sudden decrease in
available bandwidth on one of the links, or congestion at a non-IP ...
... hosts. The added complexity at the routers is also somewhat
moderate; it involves estimating the unused bandwidth on the output
link over the last several seconds, processing the Quick-Start
request ...
... on the details of the scenario. If some router along the path really
does not have enough available bandwidth to approve the Quick-Start
Request, then Quick-Start packets sent as a result of the falsely
...
... Quick-Start Requests to temporarily
tie up available Quick-Start bandwidth, preventing routers from
approving Quick-Start Requests ...
... attack, to tie up the available Quick-Start
bandwidth, is more difficult to defend against. As discussed in
[SAF06], Quick-Start Requests ...
... downstream, can result in short-term `wasting' of
potential Quick-Start bandwidth, resulting in routers denying
subsequent Quick-Start Requests ...
... connections, in
protecting the availability of Quick-Start bandwidth in the face of
frequent, overly large Quick-Start Requests.
...
... file transfer. The study shows that potential
improvement from Quick-Start is proportional to the delay-bandwidth
product of the path.
...
... router or other network host must be able to determine the
approximate bandwidth of its outbound network interfaces in order to
process incoming Quick-Start ...
... to rely on configuration information to determine link bandwidths;
this has the drawback of not being robust to errors in configuration.
Another possibility would be for network ...
... Another possibility would be for network device drivers to infer the
bandwidth for the interface and to communicate this to the IP layer.
...
... Particular issues will arise for wireless links with variable
bandwidth, where decisions will have to be made about how frequently
the host gets updates of the changing bandwidth ...
... bandwidth, where decisions will have to be made about how frequently
the host gets updates of the changing bandwidth. It seems
appropriate that Quick-Start Requests would be handled particularly
...
... Quick-Start Requests would be handled particularly
conservatively for links with variable bandwidth; to avoid cases
where Quick-Start Requests are approved, the link bandwidth ...
... bandwidth; to avoid cases
where Quick-Start Requests are approved, the link bandwidth is
reduced, and the data packets that are sent end up being dropped.
...
... intranets and other controlled
environments. Quick-Start is most useful on high bandwidth-delay
paths that are significantly underutilized. The primary initial
users of Quick-Start ...
... PABL+05]. Such intranets might
also include high-bandwidth and high-delay paths to remote sites.
In such an environment, Quick-Start would be of benefit to users,
...
... routers. For example, Quick-Start could be quite useful
in high-bandwidth networks used for scientific computing.
...
... GSM Evolution) is expected to
provide wireless bandwidth of up to 384 Kbps (roughly 32 1500-byte
packets per second ...
... satellite
links have one-way propagation delays on the order of 250 ms while
the bandwidth can be measured in megabits per second [RFC2488].
...
... attack on the available Quick-Start
bandwidth by sending bogus Quick-Start Requests for bandwidth that
...
... bandwidth by sending bogus Quick-Start Requests for bandwidth that
will not, in fact, be used. While this impacts the global usability
of Quick-Start ...
... rates, or large initial congestion windows, in over-provisioned,
high-bandwidth environments. We expect there will be an increasing
number of over-provisioned, high-bandwidth environments where the
...
... high-bandwidth environments. We expect there will be an increasing
number of over-provisioned, high-bandwidth environments where the
Quick-Start mechanism, or another mechanism of similar power, could
...
... RFC3649]
or other transport protocols for high-bandwidth transfers, could go a
significant way towards extending the range of performance ...
... congestion control mechanism, and would not help in making more
precise use of the available bandwidth -- that is, of achieving the
goal of high throughput with low delay and low packet-loss rates.
...
... senders to use information from the
packet streams to learn about the available bandwidth, without
explicit information from routers. These techniques would not allow
...
... underutilized environment; one already has to have sent some packets
in order to use the packet stream to learn about available bandwidth.
However, these techniques could allow a start-up considerably faster
...
... JD02] explores the use of periodic packet streams to estimate the
available bandwidth along a path. The idea is that the one-way
delays of a periodic packet stream ...
... packet stream show an increasing trend when the
stream's rate is higher than the available bandwidth (due to an
increasing queue). While [JD02 ...
... JD02]
also gives an overview of some of the earlier work on inferring the
available bandwidth from packet trains.
Swift-Start ...
... congestion window of four
segments is used to estimate the available bandwidth along the path.
This estimate is then used to dramatically increase the congestion
window during the second RTT ...
... TCP and
other transport protocols to learn of available bandwidth without
explicit feedback from the router seems useful, we note that there
...
...
(2) Explicit feedback is more reliable than implicit feedback:
Techniques that attempt to assess the available bandwidth at
connection start-up using implicit techniques are more error-
...
... start with a large initial window without explicit permission from
the routers and without bandwidth estimation techniques and for the
first packet of the initial window to contain information, such as
the size or sending rate ...
... IP option for TCP connections to discover the available bandwidth
along the path. In that proposal, the IP option would query ...
... W00]. For example, a
single PTP packet could be used to determine the bottleneck bandwidth
along a path.
...
... TCP, with the purpose of allowing TCP connections
to use the bandwidth unused by TCP and other traffic in a non-
...
... Quick-Start is intended to be useful for best-effort
traffic that wishes to receive at least as much bandwidth as
competing best-effort connections.
...
... encouraged to use other mechanisms, such as the explicit reservation
of bandwidth. If an upper limit of 1.3 Gbps was not acceptable, then
five or six bits could be used for the Rate Request field.
...
... underutilized. For this, the router could measure the available
bandwidth in bytes per second, or could convert between packets and
bytes by some mechanism.
...
... transport senders
would have the additional complication of estimating the bandwidth
usage added by the packet headers.
...
... fairness is automatic; the router is not granting rate requests for
*additional* bandwidth without knowing the current sending rates of
the different flows.
...
... that the number of Quick-Start packets delivered is a good indication
of the appropriate available bandwidth for that flow, even though
other packets from that window were dropped in the network ...
... link utilization
over the recent past. Second, this utilization needs to be updated
by the potential new bandwidth from recent Quick-Start approvals, and
then compared with the router ...
... algorithm relies
on knowing the bandwidth of the outgoing link (which, in many cases,
can be easily configured), the utilization of the outgoing link ...
... outgoing link (from
an estimation technique such as given above), and an estimate of the
potential bandwidth from recent Quick-Start approvals.
...
... Quick-Start approvals.
Tracking the potential bandwidth from recent Quick-Start approvals is
another case where local policy dictates how it should be done. The
...
... threshold (qs_thresh) that is
the fraction of the outgoing link bandwidth that represents the
router's notion of "significantly underutilized". If the
...
... router's notion of "significantly underutilized". If the
utilization, augmented by the potential bandwidth from recent Quick-
Start approvals, is above this threshold ...
... Quick-Start Rate
Requests will be approved. If the utilization, again augmented by
the potential bandwidth from recent Quick-Start approvals, is less
than the threshold ...
... than the threshold, then Rate Requests can be approved. The Rate
Requests will be reduced such that the bandwidth allocated would not
drive the utilization to more than the given threshold. The
...
... algorithm is:
util_bw = bandwidth * utilization;
util_bw = util_bw + recent_qs_approvals;
if (util_bw < (qs_thresh * bandwidth ...
... bandwidth * utilization;
util_bw = util_bw + recent_qs_approvals;
if (util_bw < (qs_thresh * bandwidth))
{
approved = (qs_thresh * bandwidth ...
... bandwidth))
{
approved = (qs_thresh * bandwidth) - util_bw;
if (rate_request < approved)
approved = rate_request;
...
... Routers that wish to keep close track of the allocated Quick-Start
bandwidth could use Approved Rate reports to learn when rate requests
had been decremented downstream in the network ...
... router approving an Informational Request would not consider this
as an approval for Quick-Start bandwidth to be used, and would not be
under any obligation to approve a similar standard Quick-Start
Request one round-trip time ...
... Start if the original rate request was approved.
Temporary Bandwidth Use: A Temporary codepoint has been proposed to
indicate that a connection ...
... codepoint has been proposed to
indicate that a connection would only use the requested bandwidth for
a single time interval.
...
... Manish Jain, Constantinos Dovrolis, End-to-End Available Bandwidth: Measurement Methodology, Dynamics, and Relation with TCP Throughput, SIGCOMM 2002. ...
... S. Kunniyur, "AntiECN Marking: A Marking Scheme for High Bandwidth Delay Connections", Proceedings, IEEE ICC '03, May 2003. <http://www.seas.upenn.edu/~kunniyur/>. ...
... Dina Katabi, Mark Handley, and Charles Rohrs, Internet Congestion Control for Future High Bandwidth-Delay Product Environments. ACM Sigcomm 2002, August 2002. <http://ana.lcs.mit.edu/dina/XCP/>. ...
... Joon-Sang Park, Bandwidth Discovery of a TCP Connection, report to John Heidemann, 2000, private communication. Citation for acknowledgement purposes only. ...
... Singh, M., Guha, S., and P. Francis, "Utilizing spare network bandwidth to improve TCP performance", ACM SIGCOMM 2005 Work in Progress ...