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... IP-layer processing of the Quick-Start Request at the sender.) In
approving a Quick-Start Request, a router ...
... only asserting that it is currently underutilized and believes there
is sufficient available bandwidth to accommodate the sender's
requested rate. The Quick-Start mechanism ...
... congestion control mechanisms of that connection. If the Quick-Start
Request is not approved, then the sender would use the default
congestion control mechanisms.
...
... receiver uses reliable, transport-level mechanisms to
inform the sender of the status of the Quick-Start Request. For
example, when TCP ...
... TCP receiver sends feedback to the
sender using a Quick-Start Response option in the TCP header. In
...
... Quick-Start Request packet, and returns this in the Quick-
Start Response. The sender uses the TTL difference to determine if
all the routers ...
... routers along the path, then
the TCP sender combines this allowed rate with the measurement of the
round-trip time, and ends up with an allowed TCP ...
...
Figure 1 shows a successful use of Quick-Start, with the sender's IP
layer and both routers along the path approving the Quick-Start
Request ...
... Quick-Start Response to
return information to the TCP sender. In this example, Quick-Start
is used by TCP ...
... Quick-Start Request. If the
Quick-Start Request is not approved, then the sender uses the default
congestion control mechanisms for that transport protocol ...
... Quick-Start functionality at the IP layer at the
sender.) The QS TTL is used by the sender to detect if all the
...
... sender.) The QS TTL is used by the sender to detect if all the
routers along the path understood and approved the Quick-Start
option ...
...
For a Rate Request, the transport sender MUST calculate and store the
TTL Diff, the difference between the IP TTL ...
... Section 3.4, and a two-bit Reserved field. The sender SHOULD set the
reserved field to zero, and routers ...
... random value.
The sender initializes the Rate Request to the desired sending rate,
including an estimate of the transport ...
... sender, and Section 4.4 discusses the TCP sender's mechanism for
determining if a Quick-Start Request has been approved.
...
... Reserved field.
After an approved Rate Request, the sender MUST report the Approved
Rate, using a Quick-Start Option configured as a Report of Approved
...
... data packet itself. The Report of
Approved Rate does not have to be sent reliably; for example, if the
approved rate is reported in a separate control packet, the sender
does not necessarily know if the control packet has been dropped in
the network ...
... acknowledged, but the acknowledgement packet does not contain a
Quick-Start Response, then the sender MUST assume that the Quick-
Start Request was denied, and set a Report of Approved Rate with a
...
... QS Nonce seen in the original request.
If the Rate Request is denied, the sender MUST send a Report of
Approved Rate with the Rate Report field set to zero.
...
... connection's
current sending rate, then the sender ignores the request, and
reverts to the default congestion control mechanisms of the transport
protocol ...
... link will
continue to be underutilized if this and earlier approved requests
are used by the senders. Otherwise, the router reduces or terminates
the Quick-Start Request ...
... routers to
insert into the QS Nonce field to report back to the sender the
reason that the Quick-Start Request was denied, e.g., that the router ...
... link will remain underutilized if
this and earlier Quick-Start Requests are used by the senders.
In addition, the approval of a Quick-Start Request ...
... required for all routers [RFC1812]. As a result, the sender will be
able to detect that the Quick-Start Request had not been understood
...
... However, the router MAY use the Approved Rate report to check that
the sender is not lying about the approved rate. If the reported
Approved Rate is higher than the rate that the router actually
...
... router MAY decide to deny future Quick-Start Requests from this
sender, including, if desired, deleting Quick-Start Requests from
future packets from this sender ...
... sender, including, if desired, deleting Quick-Start Requests from
future packets from this sender. Section 9.4.1 discusses misbehaving
senders ...
... sender. Section 9.4.1 discusses misbehaving
senders in more detail. From the Report of Approved Rate, the router
can also learn if some of the downstream ...
... is particularly important if the receiver knows the original value of
the Rate Request (e.g., when the sender always requests the same
value, and the receiver has a long history of communication with that
...
... value, and the receiver has a long history of communication with that
sender). Without the QS Nonce, there is nothing to prevent the
receiver ...
... QS Nonce, there is nothing to prevent the
receiver from reporting back to the sender a Rate Request of K, when
the received Rate Request was, in fact, less than K.
...
... receiver
MUST report the QS Nonce back to the sender.
If the Rate Request was not decremented in the network ...
...
The requirements for randomization for the sender and routers in
setting `random' values in the QS Nonce ...
... QS Nonce itself, which numbers in the QS Nonce were
generated by the sender, and which were generated by routers along
the path. This makes it harder for the receiver ...
... up to the time when the first Quick-Start packet is acknowledged.
The sender also sends a Report of Approved Rate. In order to use
Quick-Start, the TCP ...
... When sending a Quick-Start Request, the TCP sender SHOULD send the
request on a packet that requires an acknowledgement, such as a SYN,
...
... data packet. In this case, if the packet is acknowledged
but no Quick-Start Response is included, then the sender knows that
the Quick-Start Request has been denied, and can send a Report of
...
... network path, then the current sending
rate may not be appropriate, and the transport sender may use
Quick-Start to probe ...
...
(4) After an application-limited period, when the sender has been
using only a small amount of its appropriate share of the network
...
... case, Quick-Start may be an appropriate mechanism to determine if
the sender can send at a higher rate. For instance, consider an
application that steadily exchanges low- rate control messages
...
...
Of the above, this document recommends that a TCP sender MAY attempt
to use Quick-Start in cases (1) and (2). It is NOT RECOMMENDED that
...
... Quick-Start in cases (1) and (2). It is NOT RECOMMENDED that
a TCP sender use Quick-Start for case (3) at the current time. Case
(3) requires external notifications ...
...
As a general guideline, a TCP sender SHOULD NOT request a sending
rate larger than it is able to use over the next round-trip time of
...
... highest allowable request.
In any circumstances, the sender MUST NOT make a QS request if it has
made a QS ...
... acknowledged, but the acknowledgement does not include a Quick-Start
Response, then the sender MUST send a Report of Approved Rate.
If the checks of the TTL Diff ...
... in bytes (e.g., 40 bytes).
Derivation: the sender is allowed to transmit at R bytes per second
including packet headers ...
... mode, and while in Quick-Start mode, the TCP sender MUST use rate-
based pacing to pace out Quick-Start packets at the approved rate.
...
... If, during Quick-Start mode, the TCP sender receives ACKs for packets
sent before this Quick-Start ...
... Quick-Start Response is received, the TCP
sender's round-trip-time estimate might be longer than for succeeding
round-trip times ...
... round-trip-time estimate could have caused the TCP
sender to translate the approved Quick-Start sending rate in bytes
per second ...
... congestion window that is larger than needed, with
the TCP sender receiving an ACK for the first Quick- Start ...
... congestion window has been used. Thus, when the
TCP sender receives the first ACK for a Quick-Start packet, the
...
... ACK for a Quick-Start packet, the
sender MUST reduce the congestion window to the amount that has
actually been used.
...
...
As an example, a TCP sender with an approved Quick-Start Request of R
KBps, B-byte packets including headers ...
... seconds, would translate the Rate Request of R KBps to a congestion
window of R*T/B packets. The TCP sender would send the Quick-Start
packets rate-paced at R KBps. However, if the actual current round-
...
... Quick-Start
packets rate-paced at R KBps. However, if the actual current round-
trip time was T/2 seconds instead of T seconds, then the sender would
begin to receive acknowledgements for Quick-Start packets after T/2
...
... Quick-Start packets after T/2
seconds. Following the paragraph above, the TCP sender would then
reduce its congestion window from R*T/B to approximately R*T/(B*2)
...
... congestion window adjusted
if necessary, the TCP sender returns to using the default congestion-
control mechanisms, processing further incoming ACK ...
... congestion control mechanisms. For example, if
the TCP sender was in slow-start prior to the Quick-Start Request,
...
... slow-start prior to the Quick-Start Request,
and no packets were lost or marked since that time, then the sender
continues in slow-start after exiting Quick-Start ...
... Slow-Start, the TCP
sender limits the number of packets by which the congestion window is
increased for one window of data during slow-start ...
... value, e.g., to some small multiple of the congestion window. A
possible future research topic is how the sender might modify the
slow-start threshold ...
... When a Quick-Start Request is approved for a TCP sender, the
resulting Quick-Start data traffic ...
... the largest Quick-Start Request of 1.3 Gbps, given a TCP sender with
1500-byte packets and a TCP ...
... receiver should have an understanding of
the packet size the sender will be using. If the receiver does not
have such an understanding or wishes to confirm the negotiated MSS ...
... ACK Ratio K should have a minimum value of two. When the ACK
Ratio is greater than two, and the TCP sender receives
acknowledgements each acknowledging more than two data packets, the
...
... data packets, the
TCP sender may want to use rate-based pacing to control the
burstiness of its outgoing data traffic.
...
... initial window, and a packet from the initial window is lost or
marked, then the TCP sender MUST then slow-start with the default
initial window that would have been used if Quick-Start ...
... used. In addition to reverting to the default congestion control
mechanisms, the sender MUST take into account that the Quick-Start
congestion window ...
... Quick-Start
congestion window was too large. Thus, the sender SHOULD decrease
ssthresh to, at most, half the number of Quick-Start packets that
...
... If a Quick-Start packet is lost or ECN-marked, then the sender SHOULD
NOT make future Quick-Start Requests for this connection ...
... Quick-Start. As is
always the case with ECN, the sender's congestion control response to
an ECN-marked ...
... to which of these two alternatives is best."
If the sender knows the Path MTU when the initial window is sent
(e.g., from a PMTUD ...
... MTU for segments in the initial
window. Unfortunately, the sender doesn't necessarily know the Path
MTU when it sends packets in the initial window. In this case, the
sender ...
... sender doesn't necessarily know the Path
MTU when it sends packets in the initial window. In this case, the
sender should be conservative in the packet size used. Sending a
large number of overly large packets ...
... network can be equally undesirable.
If the sender doesn't know the Path MTU when the initial window is
sent, the sender ...
... sender doesn't know the Path MTU when the initial window is
sent, the sender SHOULD send one large packet in the initial window
with the DF bit ...
... IPv6).
A second possibility would be for the sender to delay sending the
Quick-Start Request for one round-trip time ...
... Path
MTU Discovery.
The sender may be using an iterative approach such as Packetization
Layer Path MTU Discovery (PLPMTUD) [MH06 ...
... MH06] for Path MTU Discovery,
where the sender tests successively larger MTUs. If a probe is
...
... probe. We would note that PLPMTUD does not allow
the sender to determine the Path MTU before sending the initial
window of data.
...
... RFC3360].
RFCs 1122 and 2988 specify that the sender should set the initial RTO
(retransmission timeout ...
... TCP SYN
packet sent with a Quick-Start request, the TCP sender SHOULD use an
initial RTO of three seconds.
...
... in the TCP header negotiating ECN. In this case, the sender could
resend the dropped packet without either the Quick-Start or the ECN ...
... Quick-Start or the ECN
requests. Alternately, the sender could resend the dropped packet
with only the ECN request in the TCP header ...
... congestion event (that
is, a marked or dropped packet), the TCP sender is not restricted
in the rate that it requests. As an example, a server might wait
and send a Quick-Start Request ...
... congestion event, and that has not had a recent
mobility event, the TCP sender can determine the largest
congestion window that the TCP connection ...
...
maximum allowed request rate. If the request is granted, then
the sender essentially restarts with its old congestion window
...
... Quick-Start packets are dropped in the middle of connection,
then the sender MUST revert to half the Quick-Start window, or to
the congestion window ...
... Quick-Start window, or to
the congestion window that the sender would have used if the
Quick-Start request had not been approved, whichever is smaller.
...
... Quick-Start TTL, mod 256. Recall that the
sender considers the Quick-Start Request approved only if the value
of TTL Diff ...
... tunnel allows false positives, where the
TCP sender incorrectly believes that the Quick-Start Request was
approved by all routers ...
... Start, allowing `false positives' where the TCP sender incorrectly
believes that the Quick-Start Request was approved by all routers ...
... Quick-Start
is independent of the TCP sender or a router implementation that
supports Quick-Start ...
... If a tunnel ingress is a separate component from the TCP sender or IP
forwarding, it is possible that a packet with a Quick-Start option is
...
... header, and the value of TTL Diff
echoed to the sender remains unchanged. For example, such a scenario
can occur with a Bump-In-The-Stack (BITS ...
... Start Requests that are traversing these paths will be correctly
understood by the transport sender as having been denied. Any MPLS
paths where the IP TTL ...
... Quick-Start; such paths would
result in false positives, where the TCP sender incorrectly believes
that the Quick-Start Request was approved by all routers ...
... Quick-Start Response
from the receiver to the sender. This response contains the Rate
Request, TTL Diff, and QS Nonce ...
... Quick-Start Response.
* The sender has an estimate of the round-trip time, and translates
the Quick-Start ...
... the Quick-Start Response into an allowed window or allowed sending
rate. The sender sends a Report of the Approved Rate. The sender
starts ...
... Quick-Start Response into an allowed window or allowed sending
rate. The sender sends a Report of the Approved Rate. The sender
starts sending Quick-Start ...
... sending rate.
* After the sender receives the first acknowledgement packet for a
Quick-Start packet, no more Quick-Start ...
... Quick-Start packet, no more Quick-Start packets are sent. The
sender adjusts its current congestion window or sending rate to be
...
...
* When the last Quick-Start packet is acknowledged, the sender
continues using the standard congestion control mechanisms of that
...
...
* If one of the Quick-Start packets is lost, then the sender reverts
to the standard congestion control method ...
... would have been used if the Quick-Start Request had not been
approved. In addition, the sender takes into account the
information that the Quick-Start congestion window ...
...
As discussed in [SAF06], the data sender does not necessarily have
information about the size of the data transfer at connection
initiation ...
... heuristics that end-nodes could use to size their requests
appropriately. For example, the sender might have information about
the bandwidth of the last-mile hop, the size of the local socket ...
... Internet, TCP SYN packets containing unknown IP
options will be dropped. Thus, for the sender one risk in using
Quick-Start is that the packet carrying the Quick-Start Request ...
... Quick-Start Request could
be dropped in the network. It is particularly costly to the sender
when a TCP SYN packet is dropped, because in this case the sender ...
... sender
when a TCP SYN packet is dropped, because in this case the sender
should wait for an RTO of three seconds before re-sending the SYN ...
... Quick-Start data packet dropped:
Another risk for the sender in using Quick-Start lies in the
possibility of suffering from congestion ...
... routers along the path. If a Quick-Start
packet is dropped, then the sender reverts to the congestion control
mechanisms it would have used if the Quick-Start Request ...
... Misbehaving Senders ...
...
A transport sender could try to transmit data at a higher rate than
that approved in the Quick-Start Request. The network ...
... network could use a
traffic policer to protect against misbehaving senders that exceed
the approved rate, for example, by dropping packets that exceed the
allowed transmission rate ...
... The required Approved Rate report also allows traffic policers to
check that the sender's sending rate does not exceed the rate in the
Report of Approved Rate.
...
... larger than the Rate Request in the Quick-Start Request approved for
that sender for that connection in the previous round-trip time, then
...
... Quick-Start Requests from
that sender, e.g., by deleting the Quick-Start Request from future
packets from that sender ...
... sender, e.g., by deleting the Quick-Start Request from future
packets from that sender. We note that routers are not required to
use Approved Rate reports to check if senders ...
... sender. We note that routers are not required to
use Approved Rate reports to check if senders are cheating; this is
at the discretion of the router.
...
... router sees a Report of Approved Rate, and did not see an
earlier Quick-Start Request, then either the sender could be
cheating, or the connection's path could have changed since the
...
... particular, it is reasonable for the router to deny a Quick-Start
request if either the sender is cheating, or if the connection path
suffers from path changes or multipathing.
...
... possibilities: (1) the request was denied and/or dropped downstream,
and the sender did not send a Report of Approved Rate; (2) the
request was approved, but the sender did not send a Report of
...
... and the sender did not send a Report of Approved Rate; (2) the
request was approved, but the sender did not send a Report of
Approved Rate; (3) the Approved Rate report was dropped in the
network ...
... (e.g., with multiple paths), and take some corresponding action.
What are the incentives for a sender to cheat by over-sending after a
Quick-Start Request? Assuming that the sender ...
... sender to cheat by over-sending after a
Quick-Start Request? Assuming that the sender's interests are
measured by a performance metric such as the completion time for its
...
... performance metric such as the completion time for its
connections, sometimes it might be in the sender's interests to
cheat, and sometimes it might not; in some cases, it could be
difficult for the sender ...
... sender's interests to
cheat, and sometimes it might not; in some cases, it could be
difficult for the sender to judge whether it would be in its
interests to cheat. The incentives for a sender to cheat by over-
...
... difficult for the sender to judge whether it would be in its
interests to cheat. The incentives for a sender to cheat by over-
sending after a Quick-Start Request are not that different from the
...
... sending after a Quick-Start Request are not that different from the
incentives for a sender to cheat by over-sending even in the absence
of Quick-Start, with one difference: the use of Quick-Start ...
... Quick-Start, with one difference: the use of Quick-Start could
help a sender evade policing actions from policers in the network.
The Report of Approved Rate is designed to address ...
... The Report of Approved Rate is designed to address this and to make
it harder for senders to use Quick-Start to `cover' their cheating.
...
... One form of misbehavior would be for the receiver to lie to the
sender about whether the Quick-Start Request was approved, by falsely
reporting the TTL Diff ...
... successive requests received from the same host. In particular, if
the sender does not act on a Quick-Start Request, then the receiver
...
... TTL Diff, and decrement the QS TTL
by two in the following received request, until the sender acts on
one of the Quick-Start Requests.
...
... receiver misbehavior would be for the receiver to
lie to the sender about the Rate Request for an approved Quick-Start
Request, by increasing the value of the Rate Request field. However,
the receiver ...
... receiver doesn't necessarily know the Rate Request in the
original Quick-Start Request sent by the sender, and a higher Rate
Request reported by the receiver will only be considered valid ...
... receiver will only be considered valid by the
sender if it is no higher than the Rate Request originally requested
by the sender ...
... sender if it is no higher than the Rate Request originally requested
by the sender. For example, if the sender sends a Quick-Start
Request with a Rate Request of X, and the receiver ...
...
by the sender. For example, if the sender sends a Quick-Start
Request with a Rate Request of X, and the receiver reports receiving ...
... receiving
a Quick-Start Request with a Rate Request of Y > X, then the sender
knows that either some router along the path malfunctioned
...
... lying about the Rate Request in the received packet.
If the sender sends a Quick-Start Request with a Rate Request of Z,
the receiver ...
... Request of X, and reports a Rate Request of Y, for X < Y <= Z, then
the receiver only succeeds in lying to the sender about the approved
rate if the receiver successfully reports the rightmost 2Y bits ...
... QS nonce.
If senders often use a configured default value for the Rate Request,
then receivers ...
... the value of the Rate Request field. Similarly, if the receiver
often communicates with a particular sender, and the sender always
uses the same Rate Request for that receiver ...
... receiver
often communicates with a particular sender, and the sender always
uses the same Rate Request for that receiver, then the receiver ...
... receiver might
over time be able to infer the original Rate Request used by the
sender.
There are several possible additional forms of protection against ...
... Request in a Quick-Start Request to report the decrease directly to
the sender. However, this could lead to many reports back to the
sender for a single request, and could also be used in address ...
... the sender. However, this could lead to many reports back to the
sender for a single request, and could also be used in address-
spoofing ...
... attacks.
A second limited form of protection would be for senders to use some
degree of randomization in the requested Rate Request, so that it is
difficult for receivers ...
... receivers to guess the original value for the Rate
Request. However, this is difficult because there is a fairly coarse
granularity in the set of rate requests available to the sender, and
randomizing the initial request only offers limited protection, in
any case.
...
... Quick-Start, then the result could be that the Quick-Start Request
falsely appears to the sender to have been approved, and the Quick-
Start ...
... Quick-Start TTL
by the same amount, then the sender's mechanism for determining if
the request was approved by all routers along the path would no
...
... longer be reliable. Rewriting the IP TTL could result in false
positives (with the sender incorrectly believing that the Quick-
Start Request was approved) as well as false negatives (with the
...
... Start Request was approved) as well as false negatives (with the
sender incorrectly believing that the Quick-Start Request was
denied).
...
... Start Requests, and the effectiveness of Quick-Start as a function of
the senders' algorithms for choosing the size of the rate request.
...
... transmission
rate, but they might know the amount of data that can be sent
immediately. Based on this, the sender implementation could decide
whether Quick-Start would be useful, and what rate should be
...
... We note that when Quick-Start is used, the TCP sender is required to
save the QS Nonce and the TTL Diff ...
... Quick-Start. Section 9.4 discusses the potential abuse of Quick-
Start by senders or receivers lying about whether the request was
approved or about the approved rate, and of routers ...
... TTLs in packet headers. All
these problems could result in the sender using a Rate Request that
was inappropriately large, or thinking that a request was approved
when it was in fact denied by at least one router ...
... Quick-Start. In this case, it is possible that a Quick-Start Request
is erroneously considered approved by the sender without the routers
in the tunnel ...
...
One possibility would be for senders to use information from the
packet streams to learn about the available bandwidth ...
... network resources. Based on such estimation and the transfer size,
the TCP sender would determine the optimal initial congestion window
size. The design for TCP ...
... routers is that it
allows the transport sender to reliably learn of available
bandwidth in one round-trip time ...
...
Another possibility that has been suggested [S02] is for the sender
to start with a large initial window without explicit permission from
...
... flows in the network. Such an approach would seem to require some
mechanism for the sender to ensure that the routers along the path
understood the mechanism for marking the first packet of a large
...
... A third question would be the potential role of optimistic
senders in amplifying the damage done by a Distributed Denial of
Service (DDoS) attack ...
... PTP packet that would collect information from routers along
the path from the sender to the receiver [W00]. For example, a
...
... per-packet feedback from XCP can be positive or negative,
and specifies the increase or decrease in the sender's congestion
window when this packet is acknowledged. XCP is a full-fledge
...
... routers could set to indicate that they are underutilized. For each
TCP ACK arriving at the sender indicating that a packet has been
received with the Anti-ECN bit ...
... received with the Anti-ECN bit set, the sender would be able to
increase its congestion window by one packet, as it would during
...
... This document has proposed using an IP Option for the Quick-Start
Request from the sender to the receiver, and using transport
mechanisms for the Quick-Start ...
... Quick-Start Response from the receiver back to the
sender. In this section, we discuss alternate mechanisms, and
consider whether ICMP ([RFC792 ...
... Quick-Start Request, and send an ICMP Reply to the
sender that the request was not approved. If the ICMP Reply was
dropped in the network ...
... dropped in the network, and did not reach the receiver, the sender
would still know that the request was not approved from the absence
of feedback from the receiver ...
... dropped in the network due to congestion, the sender would assume
that the request was not approved. The ICMP message would need the
...
... transport-level or application-level mechanisms to
send a response to the sender, exactly as with the IP Option.
...
... ICMP Reply packet from a router to the
sender is dropped in the network, the sender would still know that
...
... sender is dropped in the network, the sender would still know that
the request was not approved, as stated earlier, so this would not be
as serious of a problem.) In addition, it would be difficult, if not
...
... Quick-Start Requests would be transmitted
downstream from the sender to receiver in the RSVP Path messages ...
... class object would be included in the RSVP Path
message that is sent from the sender to receiver. The object would
contain the rate request field in addition to the common length and
...
... and send an RSVP PathErr message back to the sender. When an RSVP
message with the Quick-Start Request object reaches the receiver ...
... RSVP message with the Quick-Start
Request object was dropped along the path, the transport sender would
simply proceed with the normal congestion control procedures.
...
... wire. If the Rate Request field was in bytes per second, and the
sender ended up using very small packets, this could translate to a
significantly larger number in terms of bytes per second on the wire.
...
... as the data payload. Of course, this will be, at best, a rough
approximation on the part of the sender; the transport-level sender
...
... approximation on the part of the sender; the transport-level sender
might not know the size of the transport and IP headers ...
... sender expects to receive, not the maximum MSS that the TCP sender
plans to send [RFC793]. However, it is probably often the case that
...
... sender in sending.
We note that the sender does not necessarily know the Path MTU when
the Quick-Start Request ...
... Quick-Start Request in bytes per second, the transport senders
would have the additional complication of estimating the bandwidth
...
... mobility event, or after an application-limited period when the
sender is suddenly ready to send at a much higher rate. In this
case, there can be a significant difference between (1) and (2)
above. In this section, we consider briefly the tradeoffs between
...
... semantics also lends itself to gaming by the
connection, with senders sending frequent Quick-Start Requests in the
hope of gaining a higher rate. If the router ...
... receiver a greater incentive to
lie about the Quick-Start Request. If the sender reverts to slow-
start when a Quick-Start ...
... bit of feedback from routers to indicate
that the sender can increase as fast as slow-starting, in response to
this particular packet acknowledgement. In general, there is
...
... probably considerable power in fine-grained proposals with only two
bits of feedback, indicating that the sender should decrease,
maintain, or increase the sending rate or window when this packet is
...
... for an n-bit field for the QS Nonce, with the sender generating a
random nonce when it generates a Quick-Start Request ...
... SHA1]. The receiver returns the QS nonce to the sender.
Because the sender knows the original value for the nonce ...
... QS nonce to the sender.
Because the sender knows the original value for the nonce, and the
original rate request, the sender ...
... sender knows the original value for the nonce, and the
original rate request, the sender knows the total number of steps s
that the rate has been reduced. The sender then hashes ...
... original rate request, the sender knows the total number of steps s
that the rate has been reduced. The sender then hashes the original
nonce ...
... routers when they reduce a
Quick-Start Request, and from the sender in verifying the nonce
returned by the receiver ...
... Quick-Start Nonce (QS Nonce) that was initialized by the sender to a
non-zero, `random' eight-bit ...
... sending rate, the following questions arise:
(1) How does the sender respond if a Quick-Start packet is dropped?
...
... TCP, if an initial Quick-Start packet is dropped, the CCID
3 sender should revert to the congestion control mechanisms it
would have used if the Quick-Start Request ...
... Quick-Start Request had not been approved.
(2) When does the sender decide there has been no feedback from the
receiver?
...
... CCID 3
receiver sends feedback to the sender roughly once per round-trip
time. In CCID 3, the allowed sending rate ...
... feedback is received from the receiver in at least four round-
trip times (when the sender is sending at least one packet every
two round-trip times). When a Quick-Start Request ...
... Quick-Start Request had been approved.
That is, if a CCID 3 sender uses a Quick-Start Request, special rules
might be required to handle the sender ...
... sender uses a Quick-Start Request, special rules
might be required to handle the sender's response to a period of no
feedback from the receiver regarding the Quick-Start ...
... TCP, there is a straightforward answer to the rate request
that the CCID 3 sender should use in requesting a higher sending
rate after an idle period. The sender ...
... sender should use in requesting a higher sending
rate after an idle period. The sender knows the current loss
event rate, either from its own calculations or from feedback
from the receiver ...
... loss event rate. This is the upper bound on the sending
rate that should be requested by the CCID 3 sender. A Quick-
Start Request is useful with CCID 3 ...
... Start Request is useful with CCID 3 when the sender is coming out
of an idle or underutilized period, because in standard
operation, CCID 3 ...
... of an idle or underutilized period, because in standard
operation, CCID 3 does not allow the sender to send more than
twice as fast as the receiver has reported received in the most
...
... Start had not been requested.
(3) When does the sender decide there has been no feedback from the
receiver?
...