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../../protocols/tls.rst:518
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A detailed explanation of the TLS 1.3 handshake may be found at https://tls13.ulfheim.net/
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../../principles/network.rst:371
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../../principles/sharing.rst:433
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As shown above, hosts detect collisions when they receive an electrical signal that they cannot decode. In a wired network, a host is able to detect such a collision both while it is listening (e.g. like host C in the figure above) and also while it is sending its own frame. When a host transmits a frame, it can compare the electrical signal that it transmits with the electrical signal that it senses on the wire. At points `(1)` and `(2)` in the figure above, host A senses only its own signal. At point `(3)`, it senses an electrical signal that differs from its own signal and can thus detects the collision. At this point, its frame is corrupted and it can stop its transmission. The ability to detect collisions while transmitting is the starting point for the `Carrier Sense Multiple Access with Collision Detection (CSMA/CD)` Medium Access Control algorithm, which is used in Ethernet networks [Metcalfe1976]_ [IEEE802.3]_ . When an Ethernet host detects a collision while it is transmitting, it immediately stops its transmission. Compared with pure CSMA, CSMA/CD is an important improvement since when collisions occur, they only last until colliding hosts have detected it and stopped their transmission. In practice, when a host detects a collision, it sends a special jamming signal on the cable to ensure that all hosts have detected the collision.
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../../principles/security.rst:976
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Alice chooses a secret integer and sends :math:`A= g^{a} \mod p` to Mallory
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../../exercises/ipv6.rst:873
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A second problem is when there is a forwarding loop inside the network, i.e. packets sent to a specific destination loop through several routers. With the static routes shown below, router ``r2`` forwards the packets towards ``2001:db8:1341:3::b`` via router ``r1``. The entire script is available from :download:`/exercises/ipmininet_scripts/static-1-loop.py`.
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../../exercises/routing-protocols.rst:1375
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We now disable the interdomain link between ``AS3`` and ``AS4``. What are the hosts that ``AS1``, ``AS5`` and ``AS6`` are still able to ping ?
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../../protocols/bgp.rst:368
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insert a medium `local-pref` attribute in the routes learned over a shared-cost peering
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../../protocols/email.rst:242
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../../protocols/ethernet.rst:366
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Otherwise, the switch chooses the best priority vector from its table, `bv = <R,c+cost[q'],T,p,q'>`. The port `q'`, over which this best root priority vector was learned, is the switch port that is closest to the `root` switch. This port becomes the `Root` port of the switch. There is only one `Root` port per switch (except for the `Root` switches whose ports are all `Designated`). The switch can then compute its own `BPDU` as `BPDU = <R,c',S,p>` , where `R` is the `root identifier`, `c'` the cost of the best root priority vector, `S` the identifier of the switch and `p` will be replaced by the number of the port over which the `BPDU` will be sent.
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../../protocols/ipv6.rst:347
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``SCTP`` uses `Next Header` number ``132``
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../../protocols/ethernet.rst:350
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In addition to the `identifier` discussed above, the network administrator can also configure a `cost` to be associated to each switch port. Usually, the `cost` of a port depends on its bandwidth and the [IEEE802.1d]_ standard recommends the values below. Of course, the network administrator may choose other values. We will use the notation `cost[p]` to indicate the cost associated to port `p` in this section.
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../../protocols/tcp.rst:269
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`rcv.wnd` : the current size of the receive window advertised by the remote host
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../../protocols/tls.rst:519
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See https://letsencrypt.org/stats/ for a graph and https://docs.telemetry.mozilla.org/datasets/other/ssl/reference.html for additional information on the dataset
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../../glossary.rst:289
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ISO-3166
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../../principles/network.rst:371
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../../principles/reliability.rst:334
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To solve this problem, a reliable protocol must include a feedback mechanism that allows the receiver to inform the sender that it has processed a frame and that another one can be sent. This feedback is required even though there are no transmission errors. To include such a feedback, our reliable protocol must process two types of frames :
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../../principles/transport.rst:536
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To deal with these issues, the transport layer includes several mechanisms that depend on the service that it provides. It interacts with both the applications and the underlying network layer.
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../../principles/sharing.rst:436
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To better understand these collisions, it is useful to analyze what would be the worst collision on a shared bus network. Let us consider a wire with two hosts attached at both ends, as shown in the figure below. Host A starts to transmit its frame and its electrical signal is propagated on the cable. Its propagation time depends on the physical length of the cable and the speed of the electrical signal. Let us use :math:`\tau` to represent this propagation delay in seconds. Slightly less than :math:`\tau` seconds after the beginning of the transmission of A's frame, B decides to start transmitting its own frame. After :math:`\epsilon` seconds, B senses A's frame, detects the collision and stops transmitting. The beginning of B's frame travels on the cable until it reaches host A. Host A can thus detect the collision at time :math:`\tau-\epsilon+\tau \approx 2\times\tau`. An important point to note is that a collision can only occur during the first :math:`2\times\tau` seconds of its transmission. If a collision did not occur during this period, it cannot occur afterwards since the transmission channel is busy after :math:`\tau` seconds and CSMA/CD hosts sense the transmission channel before transmitting their frame.
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../../principles/security.rst:977
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Mallory generates a secret integer, :math:`m` and sends :math:`M=g^{m} \mod p` to Bob
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../../exercises/ipv6.rst:888
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The ``pingall`` command reveals that there is a problem in this network.
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