Exit Zen
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../../principles/reliability.rst:51
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1 Kbps
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../../principles/sharing.rst:53
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A fifth physical organization of a network is the tree. Such networks are typically used when a large number of customers must be connected in a very cost-effective manner. Cable TV networks are often organized as trees.
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../../principles/transport.rst:33
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Alice : `Thank you`
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../../bibliography.rst:48
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Clark D., `The Design Philosophy of the DARPA Internet Protocols <https://dx.doi.org/10.1145/205447.205458>`_, Computer Communications Review 18:4, August 1988, pp. 106-114
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../../exercises/ex-sharing.rst:290
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Consider again a network that uses CSMA/CD. This time, the bandwidth is set to 1 Gbps and the cable has a length of two kilometers. When a collision occurs, consider that the hosts B and C retransmit immediately while host A waits for the next slot.
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../../exercises/network.rst:103
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Assume that the routers located in `Denver` and `Kansas City` need to exchange lots of packets. Can you configure the link metrics such that the link between these two routers does not carry any packet sent by another router in the network ?
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../../exercises/reliability.rst:34
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The bandwidth of the two directions of the link is set to `B` bits per second
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../../exercises/sockets.rst:122
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In the following example, a C program is sending the bytes ``'h'``, ``'e'``, ``'l'``, ``'l'`` and ``'o'`` to a remote process located at address ``peer_addr``, using the already created socket ``sock``.
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../../exercises/transport.rst:126
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Practice
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../../principles/naming.rst:77
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The Domain Name System was created at a time when the Internet was mainly used in North America. The initial design assumed that all domain names would be composed of letters and digits :rfc:`1035`. As Internet usage grew in other parts of the world, it became important to support non-ASCII characters. For this, extensions have been proposed to the Domain Name System :rfc:`3490`. In a nutshell, the solution that is used to support Internationalized Domain Names works as follows. First, it is possible to use most of the Unicode characters to encode domain names and hostnames, with a few exceptions (for example, the dot character cannot be part of a name since it is used as a separator). Once a domain name has been encoded as a series of Unicode characters, it is then converted into a string that contains the ``xn--`` prefix and a sequence of ASCII characters. More details on these algorithms can be found in :rfc:`3490` and :rfc:`3492`.
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../../principles/network.rst:74
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To send one byte of information to host `B`, host `A` needs to place this information inside a `packet`. In addition to the data being transmitted, the packet also contains either the addresses of the source and the destination nodes or information that indicates the path that needs to be followed to reach the destination.
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../../principles/referencemodels.rst:56
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The `Datalink layer` builds on the service provided by the underlying physical layer. The `Datalink layer` allows two hosts that are directly connected through the physical layer to exchange information. The unit of information exchanged between two entities in the `Datalink layer` is a frame. A frame is a finite sequence of bits. Some `Datalink layers` use variable-length frames while others only use fixed-length frames. Some `Datalink layers` provide a connection-oriented service while others provide a connectionless service. Some `Datalink layers` provide reliable delivery while others do not guarantee the correct delivery of the information.
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../../principles/reliability.rst:51
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:math:`10^3`
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../../principles/transport.rst:34
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Bob : `You're welcome`
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../../protocols/dns.rst:52
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The `TTL` field indicates the lifetime of the `Resource Record` in seconds. This field is set by the server that returns an answer and indicates for how long a client or a resolver can store the `Resource Record` inside its cache. A long `TTL` indicates a stable `RR`. Some companies use short `TTL` values for mobile hosts and also for popular servers. For example, a web hosting company that wants to spread the load over a pool of hundred servers can configure its nameservers to return different answers to different clients. If each answer has a small `TTL`, the clients will be forced to send DNS queries regularly. The nameserver will reply to these queries by supplying the address of the less loaded server.
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../../bibliography.rst:51
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Cohen, D., `On Holy Wars and a Plea for Peace`, IEN 137, April 1980, http://www.ietf.org/rfc/ien/ien137.txt
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../../glossary.rst:14
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The American Standard Code for Information Interchange (ASCII) is a character-encoding scheme that defines a binary representation for characters. The ASCII table contains both printable characters and control characters. ASCII characters were encoded in 7 bits and only contained the characters required to write text in English. Other character sets such as Unicode have been developed later to support all written languages.
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../../exercises/ex-sharing.rst:316
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An important part of the CSMA/CD algorithm is the exponential backoff. To illustrate the operation of this algorithm, let us consider a cable that has a length of one kilometer. The bandwidth of the network is set to 10 Mbps. Assume that when a collision occurs, host A always selects the highest possible random delay according to the exponential backoff algorithm while host B always selects the shortest one. In this network, the slot time is equal to the time required to transmit 100 bits. We further assume that a host can detect collision immediately (i.e. as soon as the other frame arrives).
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../../exercises/reliability.rst:35
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The delay between the two hosts is `s` seconds in both directions
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../../exercises/sockets.rst:135
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As the ``sendto`` function is generic, this function will work correctly independently from the fact that the peer's address is defined as a path on the computer filesystem or a network address.
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