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../../protocols/bgp.rst:101
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The figure below shows a simple example of the BGP routes that are exchanged between domains. In this example, prefix `2001:db8:cafe::/48` is announced by `AS1`. `AS1` advertises a BGP route towards this prefix to `AS2`. The AS-Path of this route indicates that `AS1` is the originator of the prefix. When `AS4` receives the BGP route from `AS1`, it re-announces it to `AS2` and adds its AS number to the AS-Path. `AS2` has learned two routes towards prefix `2001:db8:cafe::/48`. It compares the two routes and prefers the route learned from `AS4` based on its own ranking algorithm. `AS2` advertises to `AS5` a route towards `2001:db8:cafe::/48` with its AS-Path set to `AS2:AS4:AS1`. Thanks to the AS-Path, `AS5` knows that if it sends a packet towards `2001:db8:cafe::/48` the packet first passes through `AS2`, then through `AS4` before reaching its destination inside `AS1`.
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../../protocols/congestion.rst:180
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Routers that use a single queue measure their buffer occupancy as the number of bytes of packets stored in the queue [#fslot]_. A first method to detect congestion is to measure the instantaneous buffer occupancy and consider the router to be congested as soon as this occupancy is above a threshold. Typical values of the threshold could be 40% of the total buffer. Measuring the instantaneous buffer occupancy is simple since it only requires one counter. However, this value is fragile from a control viewpoint since it changes frequently. A better solution is to measure the *average* buffer occupancy and consider the router to be congested when this average occupancy is too high. Random Early Detection (RED) [FJ1993]_ is an algorithm that was designed to support Explicit Congestion Notification. In addition to measuring the average buffer occupancy, it also uses probabilistic marking. When the router is congested, the arriving packets are marked with a probability that increases with the average buffer occupancy. The main advantage of using probabilistic marking instead of marking all arriving packets is that flows will be marked in proportion of the number of packets that they transmit. If the router marks 10% of the arriving packets when congested, then a large flow that sends hundred packets per second will be marked 10 times while a flow that only sends one packet per second will not be marked. This probabilistic marking allows marking packets in proportion of their usage of the network resources.
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../../protocols/email.rst:174
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The `MIME-Version:` header line indicates the version of the MIME specification that was used to encode the email message. The current version of MIME is 1.0. Other versions of MIME may be defined in the future. Thanks to this header line, the software that processes email messages will be able to adapt to the MIME version used to encode the message. Messages that do not contain this header are supposed to be formatted according to the original :rfc:`822` specification.
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../../protocols/ethernet.rst:172
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Thin coaxial cable, 185m
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../../protocols/http.rst:123
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a `header`, that contains additional information about the response. The response header ends with an empty line.
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../../protocols/http2.rst:228
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By using multiple streams, the server can multiplex different web objects over the same underlying transport connection. However, these objects are only sent in response to requests from clients. There are some situations where the server might know in advance that the client will request a given object. It could speedup the transfer by sending it before having received a client request. This is the `push` feature of HTTP/2.0. A server can independently push web objects to a client without having received any request. This feature can only be used by the server if the client has enabled it by sending `SETTINGS_ENABLE_PUSH` in its `Settings` frame. A classical use case for this `push` feature is to enable a server to automatically send an object which cannot be cached by the client, such as a dynamic javascript code, when another web object that references it is requested. However, measurement studies indicate that very few web servers seem to have adopted this feature [ZWH2018]_.
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../../protocols/ipv6.rst:119
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``2001:db8:0:0:8:800:200c:417a`` is represented as ``2001:db8::8:800:200c:417a``
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../../protocols/ethernet.rst:96
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delivers frames to their destination with a very high probability of successful delivery
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../../protocols/routing.rst:97
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`RC` advertises `2001:db8:5678::/48` at a distance of `2` and `2001:db8:1234::/48` at a distance of `3`
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../../protocols/rpc.rst:116
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`id`: the same identifier as the identifier chosen by the caller
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../../protocols/ssh.rst:228
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``padding`` : random bytes added in each message (at least four) to ensure that the message length is a multiple of the block size used by the negotiated encryption algorithm
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../../protocols/tcp.rst:99
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The rest of this section is organized as follows. We first explain the establishment and the release of a TCP connection, then we discuss the mechanisms that are used by TCP to provide a reliable bytestream service. We end the section with a discussion of network congestion and explain the mechanisms that TCP uses to avoid congestion collapse.
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../../protocols/tls.rst:101
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Securely agree on the keys that will be used to encrypt and authenticate the messages exchanged over the TLS session
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../../protocols/wifi.rst:26
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70/250
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../../exercises/routing-protocols.rst:370
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Later, router ``r2`` will regularly transmit its distance vector inside an unsolicited response message that is sent towards the IPv6 multicast address ``ff02::9``.
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../../bibliography.rst:103
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Karn, P., Price, H., Diersing, R., `Packet radio in amateur service <https://dx.doi.org/10.1109/JSAC.1985.1146214>`_, IEEE Journal on Selected Areas in Communications, 3, May, 1985
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../../exercises/ex-sharing.rst:610
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If host `A` uses a window of two segments and needs to transmit five segments of data. How long does the entire transfer lasts ?
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../../exercises/reliability.rst:67
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Implement a small software that computes the CRC-32 for a text file. Then, modify the contents of the file to change an even number of bits or an odd number of bits inside the file. When modifying the file, remember that an ASCII file is composed of 8 bits characters that are encoded by using the ASCII table that you can find at : http://en.wikipedia.org/wiki/ASCII . You can also write a small program that produces binary files that are a small variation of each other.
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../../principles/network.rst:122
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The `forwarding tables` and the precise format of the packets that are exchanged inside the network are part of the `data plane` of the network. This `data plane` contains all the protocols and algorithms that are used by hosts and routers to create and process the packets that contain user data. On high-end routers, the data plane is often implemented in hardware for performance reasons.
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../../principles/transport.rst:68
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In addition, the :term:`ASCII` table also defines several non-printable or control characters. These characters were designed to allow an application to control a printer or a terminal. These control characters include `CR` and `LF`, that are used to terminate a line, and the `Bell` character which causes the terminal to emit a sound.
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