msgid "" msgstr "" "Project-Id-Version: French (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-19 12:11+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: French \n" "Language: fr\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=2; plural=n > 1;\n" "X-Generator: Weblate 5.14.3\n" #: ../../protocols/udp.rst:9 msgid "The User Datagram Protocol" msgstr "" #: ../../protocols/udp.rst:11 msgid "" "The User Datagram Protocol (UDP) is defined in :rfc:`768`. It provides an " "unreliable connectionless transport service on top of the unreliable network " "layer connectionless service. The main characteristics of the UDP service " "are :" msgstr "" #: ../../protocols/udp.rst:13 msgid "" "the UDP service cannot deliver SDUs that are larger than 65467 bytes " "[#fmtuudp]_" msgstr "" #: ../../protocols/udp.rst:14 msgid "" "the UDP service does not guarantee the delivery of SDUs " "(losses can occur and SDUs can arrive out-of-sequence)" msgstr "" #: ../../protocols/udp.rst:15 msgid "the UDP service will not deliver a corrupted SDU to the destination" msgstr "" #: ../../protocols/udp.rst:17 msgid "" "Compared to the connectionless network layer service, the main advantage of " "the UDP service is that it allows several applications running on a host to " "exchange SDUs with several other applications running on remote hosts. Let " "us consider two hosts, e.g. a client and a server. The network layer service " "allows the client to send information to the server, but if an application " "running on the client wants to contact a particular application running on " "the server, then an additional addressing mechanism is required other than " "the IP address that identifies a host, in order to differentiate the " "application running on a host. This additional addressing is provided by `" "port numbers`. When a server using UDP is enabled on a host, this server " "registers a `port number`. This `port number` will be used by the clients to " "contact the server process via UDP." msgstr "" #: ../../protocols/udp.rst:19 msgid "" "The figure below shows a typical usage of the UDP port numbers. The client " "process uses port number `1234` while the server process uses port number " "`5678`. When the client sends a request, it is identified as originating " "from port number `1234` on the client host and destined to port number `5678`" " on the server host. When the server process replies to this request, the " "server's UDP implementation will send the reply as originating from port " "`5678` on the server host and destined to port `1234` on the client host." msgstr "" #: ../../protocols/udp.rst:43 msgid "UDP uses a single segment format shown in the figure below." msgstr "" #: ../../protocols/udp.rst:49 msgid "UDP Header Format" msgstr "" #: ../../protocols/udp.rst:51 msgid "The UDP header contains four fields :" msgstr "" #: ../../protocols/udp.rst:53 msgid "a 16 bits source port" msgstr "" #: ../../protocols/udp.rst:54 msgid "a 16 bits destination port" msgstr "" #: ../../protocols/udp.rst:55 msgid "a 16 bits length field" msgstr "" #: ../../protocols/udp.rst:56 msgid "a 16 bits checksum" msgstr "" #: ../../protocols/udp.rst:58 msgid "" "As the port numbers are encoded as a 16 bits field, there can be up to only " "65535 different server processes that are bound to a different UDP port at " "the same time on a given server. In practice, this limit is never reached. " "However, it is worth noticing that most implementations divide the range of " "allowed UDP port numbers into three different ranges :" msgstr "" #: ../../protocols/udp.rst:60 msgid "the privileged port numbers (1 < port < 1024 )" msgstr "" #: ../../protocols/udp.rst:61 msgid "" "the ephemeral port numbers " "( officially [#fephemeral]_ 49152 <= port <= 65535 )" msgstr "" #: ../../protocols/udp.rst:62 msgid "the registered port numbers (officially 1024 <= port < 49152)" msgstr "" #: ../../protocols/udp.rst:64 msgid "" "In most Unix variants, only processes having system administrator privileges " "can be bound to port numbers smaller than `1024`. Well-known servers such as " ":term:`DNS`, :term:`NTP` or :term:`RPC` use privileged port numbers. When a " "client needs to use UDP, it usually does not require a specific port number. " "In this case, the UDP implementation will allocate the first available port " "number in the ephemeral range. The range of registered port numbers should " "be used by servers. In theory, developers of network servers should register " "their port number officially through IANA [#fportnum]_, but few developers " "do this." msgstr "" #: ../../protocols/udp.rst:69 msgid "Computation of the UDP checksum" msgstr "" #: ../../protocols/udp.rst:71 msgid "The checksum of the UDP segment is computed over :" msgstr "" #: ../../protocols/udp.rst:73 msgid "" "a pseudo header :rfc:`2460` containing the source address, the destination " "address, the packet length encoded as a 32 bits number and a 32 bits bit " "field containing the three most significant bytes set to 0 and the low order " "byte set to 17" msgstr "" #: ../../protocols/udp.rst:74 msgid "the entire UDP segment, including its header" msgstr "" #: ../../protocols/udp.rst:83 msgid "" "Several types of applications rely on UDP. As a rule of thumb, UDP is used " "for applications where delay must be minimized or losses can be recovered by " "the application itself. A first class of the UDP-based applications are " "applications where the client sends a short request and expects a quick and " "short answer. The :term:`DNS` is an example of a UDP application that is " "often used in the wide area. However, in local area networks, many " "distributed systems rely on Remote Procedure Call (:term:`RPC`) that is " "often used on top of UDP. In Unix environments, the Network File System " "(:term:`NFS`) is built on top of RPC and runs frequently on top of UDP. A " "second class of UDP-based applications are the interactive computer games " "that need to frequently exchange small messages, such as the player's " "location or their recent actions. Many of these games use UDP to minimize " "the delay and can recover from losses. A third class of applications are " "multimedia applications such as interactive Voice over IP or interactive " "Video over IP. These interactive applications expect a delay shorter than " "about 200 milliseconds between the sender and the receiver and can recover " "from losses directly inside the application." msgstr "" #: ../../protocols/udp.rst:89 msgid "Footnotes" msgstr "" #: ../../protocols/udp.rst:90 msgid "" "This limitation is due to the fact that the network layer cannot transport " "packets that are larger than 64 KBytes. As UDP does not include any " "segmentation/reassembly mechanism, it cannot split a SDU before sending it. " "The UDP header consumes 8 bytes and the IPv6 header 60. With IPv4, the IPv4 " "header only consumes 20 bytes and thus the maximum UDP payload size is 65507 " "bytes." msgstr "" #: ../../protocols/udp.rst:92 msgid "" "A discussion of the ephemeral port ranges used by different TCP/UDP " "implementations may be found in http://www.ncftp.com/ncftpd/doc/misc/" "ephemeral_ports.html" msgstr "" #: ../../protocols/udp.rst:94 msgid "" "The complete list of allocated port numbers is maintained by IANA_ . It may " "be downloaded from http://www.iana.org/assignments/port-numbers" msgstr ""