msgid "" msgstr "" "Project-Id-Version: French (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-18 16:43+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" #: ../../exercises/dns.rst:7 msgid "Application layer" msgstr "" #: ../../exercises/dns.rst:11 msgid "" "This is an unpolished draft of the third edition of this e-book. If you find " "any error or have suggestions to improve the text, please create an issue " "via https://github.com/CNP3/ebook/issues?milestone=5 or help us by providing " "pull requests to close the existing issues." msgstr "" #: ../../exercises/dns.rst:15 msgid "The DNS" msgstr "" #: ../../exercises/dns.rst:17 msgid "" "The Domain Name System (DNS) plays a key role in the Internet today as it " "allows applications to use fully qualified domain names (FQDN) instead of " "IPv4 or IPv6 addresses. When using the DNS, it is important to remember the " "role of the different types of DNS records." msgstr "" #: ../../exercises/dns.rst:25 msgid "" "Several software tools can be used to send queries to DNS servers. For this " "exercise, we use dig_ which is installed on most Unix/Linux systems." msgstr "" #: ../../exercises/dns.rst:27 msgid "A typical usage of dig is as follows:" msgstr "" #: ../../exercises/dns.rst:33 msgid "where" msgstr "" #: ../../exercises/dns.rst:35 msgid "`server` is the IP address or the name of a DNS server or resolver" msgstr "" #: ../../exercises/dns.rst:36 msgid "" "`type` is the type of DNS record that is requested by the query such as `NS` " "for a nameserver, `A` for an IPv4 address, `AAAA` for an IPv6 address, `MX` " "for a mail relay, ..." msgstr "" #: ../../exercises/dns.rst:37 msgid "`fqdn` is the fully qualified domain name being queried" msgstr "" #: ../../exercises/dns.rst:39 msgid "" "dig_ also contains some additional parameters and flags that are described " "in the man page. Among these, the `+trace` flag allows to trace all requests " "that are sent when recursively contacting DNS servers." msgstr "" #: ../../exercises/dns.rst:41 msgid "" "What are the IP addresses of the resolvers that the `dig` implementation you " "are using relies on [#fdig]_ ?" msgstr "" #: ../../exercises/dns.rst:43 msgid "" "What are the nameservers that are responsible for the `info` top-level " "domain ? Is it possible to use IPv6 to query them ?" msgstr "" #: ../../exercises/dns.rst:45 msgid "" "What is the IPv6 address that corresponds to `www.computer-networking.info` " "? Which type of DNS query does `dig` send to obtain this information ?" msgstr "" #: ../../exercises/dns.rst:48 msgid "" "When run without any parameter, `dig` queries one of the root DNS servers " "and retrieves the list of the names of all root DNS servers. For technical " "reasons, there are only 13 different root DNS servers. This information is " "also available as a text file from http://www.internic.net/zones/named.root. " "What are the IPv6 addresses of all these servers?" msgstr "" #: ../../exercises/dns.rst:50 msgid "" "Assume now that you are residing in a network where there is no DNS resolver " "and that you need to perform your query manually starting from the DNS root." msgstr "" #: ../../exercises/dns.rst:52 msgid "" "Use `dig` to send a query to one of these root servers to find the IPv6 " "address of the DNS server(s) (NS record) responsible for the `org` top-level " "domain" msgstr "" #: ../../exercises/dns.rst:53 msgid "" "Use `dig` to send a query to one of these DNS servers to find the IP address " "of the DNS server(s) (NS record) responsible for `root-servers.org`" msgstr "" #: ../../exercises/dns.rst:54 msgid "" "Continue until you find the server responsible for `www.root-servers.org`" msgstr "" #: ../../exercises/dns.rst:55 msgid "What is the lifetime associated to this IPv6 address ?" msgstr "" #: ../../exercises/dns.rst:57 msgid "" "Perform the same analysis for a popular website such as `www.google.com`. " "What is the lifetime associated to the corresponding IPv6 address ? If you " "perform the same request several times, do you always receive the same " "answer ? Can you explain why a lifetime is associated to the DNS replies ?" msgstr "" #: ../../exercises/dns.rst:59 msgid "" "Use `dig` to find the mail relays used by the `uclouvain.be` and " "`student.uclouvain.be` domains. What is the `TTL` of these records ? Can you " "explain the preferences used by the `MX` records. You can find more " "information about the MX records in :rfc:`5321`." msgstr "" #: ../../exercises/dns.rst:61 msgid "" "When `dig` is run, the header section in its output indicates the `id` the " "DNS identifier used to send the query. Does your implementation of `dig` " "generates random identifiers ?" msgstr "" #: ../../exercises/dns.rst:73 msgid "" "A DNS implementation such as `dig`, and more importantly a name resolver " "such as bind_ or unbound_, always checks that the received DNS reply " "contains the same identifier as the DNS request that it sent. Why is this so " "important ?" msgstr "" #: ../../exercises/dns.rst:75 msgid "" "Imagine an attacker who is able to send forged DNS replies to, for example, " "associate `www.bigbank.com` to his own IP address. How could he attack a DNS " "implementation that" msgstr "" #: ../../exercises/dns.rst:77 msgid "sends DNS requests containing always the same identifier" msgstr "" #: ../../exercises/dns.rst:78 msgid "" "sends DNS requests containing identifiers that are incremented by one after " "each request" msgstr "" #: ../../exercises/dns.rst:79 msgid "sends DNS requests containing random identifiers" msgstr "" #: ../../exercises/dns.rst:81 msgid "" "The DNS protocol can run over UDP and over TCP. Most DNS servers prefer to " "use UDP because it consumes fewer resources on the server. However, TCP is " "useful when a large answer is expected. Compare `time dig +tcp` and `time " "dig` to query a root DNS server. Is it faster to receive an answer via TCP " "or via UDP ?" msgstr "" #: ../../exercises/dns.rst:84 msgid "" "Besides `dig`, another way to analyze the DNS is to look at packet traces " "with tools such as `wireshark `_ or `tcpdump " "`_ These tools can capture packets in a network and " "also display and analyze their content. `Wireshark " "`_ provides a flexible Graphical User Interface " "that eases the analysis of the captured packets. The three questions below " "should help you to better understand the important fields of DNS messages." msgstr "" #: ../../exercises/dns.rst:93 msgid "" "The next three questions ask you to go one step further by predicting the " "values of specific fields in the DNS messages." msgstr "" #: ../../exercises/dns.rst:101 msgid "" "When a client requests the mapping of a domain name into an IP address to " "its local resolver, the resolver may need to query a large number of " "nameservers starting from the root nameserver. The three exercises below " "show packet traces collected while the resolver was resolving the following " "names: `www.example.com`, `www.google.com` and `www.computer-networking.info`" ". If you understand how the DNS operates, you should be able to correctly " "reorder those packet traces." msgstr "" #: ../../exercises/dns.rst:113 msgid "" "On a Linux machine, the *Description* section of the `dig` man page tells " "you where `dig` finds the list of nameservers to query." msgstr "" #: ../../exercises/dns.rst:115 msgid "" "You may obtain additional information about the root DNS servers from " "http://www.root-servers.org" msgstr ""