Exit Zen
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../../protocols/tcp.rst:510
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This heuristic requires an additional variable in the TCB (`dupacks`). Most implementations set the default number of duplicate acknowledgments that trigger a retransmission to 3. It is now part of the standard TCP specification :rfc:`2581`. The `fast retransmit` heuristic improves the TCP performance provided that isolated segments are lost and the current window is large enough to allow the sender to send three duplicate acknowledgments.
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../../glossary.rst:214
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RPC
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../../principles/reliability.rst:569
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The receiver first waits for `D(0,...)`. If the frame contains a correct `CRC`, it passes the SDU to its user and sends `OK0`. If the frame contains an invalid CRC, it is immediately discarded. Then, the receiver waits for `D(1,...)`. In this state, it may receive a duplicate `D(0,...)` or a data frame with an invalid CRC. In both cases, it returns an `OK0` frame to allow the sender to recover from the possible loss of the previous `OK0` frame.
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../../principles/sharing.rst:740
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Let us first consider the simple problem of a set of :math:`i` hosts that share a single bottleneck link as shown in the example above. In this network, the congestion control scheme must achieve the following objectives [CJ1989]_ :
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../../protocols/email.rst:262
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15
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../../protocols/ipv6.rst:530
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ICMP version 6 packet format
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../../protocols/wifi.rst:26
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802.11n
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../../protocols/tcp.rst:512
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The figure below illustrates the operation of the `fast retransmit` heuristic.
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../../glossary.rst:216
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Several types of remote procedure calls have been defined. The RPC mechanism defined in :rfc:`5531` is used by applications such as NFS
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../../principles/transport.rst:828
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For example, the :manpage:`htonl(3)` (resp. :manpage:`ntohl(3)`) function the standard C library converts a 32-bits unsigned integer from the byte order used by the CPU to the network byte order (resp. from the network byte order to the CPU byte order). Similar functions exist in other programming languages.
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../../principles/sharing.rst:742
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The congestion control scheme must `avoid congestion`. In practice, this means that the bottleneck link cannot be overloaded. If :math:`r_i(t)` is the transmission rate allocated to host :math:`i` at time :math:`t` and :math:`R` the bandwidth of the bottleneck link, then the congestion control scheme should ensure that, on average, :math:`\forall{t} \sum{r_i(t)} \le R`.
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../../protocols/email.rst:262
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P
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../../protocols/ipv6.rst:533
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ICMPv6 specifies two classes of messages : error messages that indicate a problem in handling a packet and informational messages. Four types of error messages are defined in :rfc:`4443` :
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../../protocols/wifi.rst:26
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2.4/5 GHz
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../../protocols/tcp.rst:518
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TCP fast retransmit heuristics
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159
../../glossary.rst:66
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SDU (Service Data Unit)
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../../principles/dv.rst:167
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After having detected the failure, router `B` sends its distance vectors:
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../../principles/reliability.rst:579
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Dealing with corrupted frames
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../../principles/transport.rst:830
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In the application layer, most servers are implemented as processes. The network and transport layer on the other hand are usually implemented inside the operating system and the amount of memory that they can use is limited by the amount of memory allocated to the entire kernel.
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../../principles/sharing.rst:743
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The congestion control scheme must be `efficient`. The bottleneck link is usually both a shared and an expensive resource. Usually, bottleneck links are wide area links that are much more expensive to upgrade than the local area networks. The congestion control scheme should ensure that such links are efficiently used. Mathematically, the control scheme should ensure that :math:`\forall{t} \sum{r_i(t)} \approx R`.
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