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../../protocols/ethernet.rst:316
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The `Spanning Tree Protocol` (STP), proposed in [Perlman1985]_, is a distributed protocol that is used by switches to reduce the network topology to a spanning tree, so that there are no cycles in the topology. For example, consider the network shown in the figure below. In this figure, each bold line corresponds to an Ethernet to which two Ethernet switches are attached. This network contains several cycles that must be broken to allow Ethernet switches, using the MAC address learning algorithm, to exchange frames.
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../../protocols/tcp.rst:259
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the local IP address
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../../protocols/tls.rst:415
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By supporting only cipher suites that provide Perfect Forward Secrecy in TLS 1.3, the IETF aims at protecting the privacy of users against a wide range of attacks. However, this choice has resulted in intense debates in some enterprises. Some enterprises, notably in financial organizations, have deployed TLS, but wish to be able to decrypt TLS traffic for various security-related activities. These enterprises tried to lobby within the IETF to maintain RSA-based cipher suites that do not provide Perfect Forward Secrecy. Their arguments did not convince the IETF. Eventually, these enterprises moved to ETSI, another standardization body, and convinced them to adopt `entreprise TLS`, a variant of TLS 1.3 that does not provide Perfect Forward Secrecy [eTLS2018]_.
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../../glossary.rst:80
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is the version 4 of the Internet Protocol, the connectionless network layer protocol used in most of the Internet today. IPv4 addresses are encoded as a 32 bits field.
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../../principles/transport.rst:498
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The `request-response service` is a compromise between the `connectionless service` and the `connection-oriented service`. Many applications need to send a small amount of data and receive a small amount of information back. This is similar to procedure calls in programming languages. A call to a procedure takes a few arguments and returns a simple answer. In a network, it is sometimes useful to execute a procedure on a different host and receive the result of the computation. Executing a procedure on another host is often called Remote Procedure Call. It is possible to use the `connectionless service` for this application. However, since this service is usually unreliable, this would force the application to deal with any type of error that could occur. Using the `connection oriented service` is another alternative. This service ensures the reliable delivery of the data, but a connection must be created before the beginning of the data transfer. This overhead can be important for applications that only exchange a small amount of data.
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../../principles/sharing.rst:353
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Carrier Sense Multiple Access
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../../principles/security.rst:937
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From is knowledge of :math:`b` and :math:`A`, Bob can compute :math:`Secret=A^{b} \mod p=(g^{a} \mod p) ^{b} \mod p=g^{a \times b} \mod p`
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../../exercises/ipv6.rst:784
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On its ``a-eth0`` interface, host ``a`` uses IPv6 address ``2001:db8:1341:1::a/64``. The link local address (``fe80::c44e:26ff:fed9:de6d/64``) will be described in another chapter. Finally, we can check the forwarding table of host ``a``.
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../../exercises/routing-protocols.rst:1232
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The network below contains nine ASes with one host per AS. Assuming that ``AS1`` announces prefix `p1` and that ``AS2`` announces prefix `p2`.
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../../protocols/bgp.rst:327
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As BGP routers always prefer the routes with the highest `local-pref` attribute, this policy can be implemented using the following import filter on `R1`
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../../protocols/email.rst:240
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../../protocols/ethernet.rst:356
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100 Mbps
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../../protocols/ipv6.rst:334
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`Traffic class` : this 8 bits field indicates the type of service expected by this packet and contains the ``CE`` and ``ECT`` flags that are used by `Explicit Congestion Notification`
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../../protocols/ethernet.rst:324
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Spanning tree computed in a switched Ethernet network
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../../protocols/tcp.rst:260
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the remote IP address
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../../protocols/tls.rst:417
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The TLS 1.3 handshake differs from the TLS 1.2 handshake in several ways. First, the TLS 1.3 handshake requires a single round-trip-time when the client connects for the first time to a server. To achieve this, the TLS designers look at the TLS 1.2 handshake in details and found that the first round-trip-time is mainly used to select the set of cryptographic algorithms and the cryptographic exchange scheme that will be used over the TLS session. TLS 1.3 drastically simplifies this negotiation by requiring to use the Diffie Hellman exchange with a small set of possible parameters. This means that the client can guess the parameters used by the server (i.e. the modulus, p and the base g) and immediately start the Diffie Hellman exchange. A simplified version of the TLS 1.3 handshake is shown in the figure below.
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../../glossary.rst:81
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IPv6
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../../principles/transport.rst:500
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The `request-response service` allows to efficiently exchange small amounts of information in a request and associate it with the corresponding response. This service can be depicted by using the time-sequence diagram below.
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../../principles/sharing.rst:356
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ALOHA and slotted ALOHA can easily be implemented, but unfortunately, they can only be used in networks that are very lightly loaded. Designing a network for a very low utilization is possible, but it clearly increases the cost of the network. To overcome the problems of ALOHA, many Medium Access Control mechanisms have been proposed which improve channel utilization. Carrier Sense Multiple Access (CSMA) is a significant improvement compared to ALOHA. CSMA requires all nodes to listen to the transmission channel to verify that it is free before transmitting a frame [KT1975]_. When a node senses the channel to be busy, it defers its transmission until the channel becomes free again. The pseudo-code below provides a more detailed description of the operation of CSMA.
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../../principles/security.rst:940
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The security of this protocol relies on the difficulty of computing discrete logarithms, i.e. from the knowledge of :math:`A` (resp. :math:`B`), it is very difficult to extract :math:`\log(A)=\log(g^{a} \mod p)=a` (resp. :math:`\log(B)=\log(g^{b} \mod p)=b`).
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