msgid "" msgstr "" "Project-Id-Version: Czech (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-18 15:52+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: Czech \n" "Language: cs\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=3; plural=(n==1) ? 0 : (n>=2 && n<=4) ? 1 : 2;\n" "X-Generator: Weblate 5.14.3\n" #: ../../protocols/dns.rst:7 msgid "The Domain Name System" msgstr "" #: ../../protocols/dns.rst:26 msgid "The DNS header" msgstr "" #: ../../protocols/dns.rst:28 msgid "" "The `Transaction ID` (transaction identifier) is a 16-bits random value " "chosen by the client. When a client sends a question to a DNS server, it " "remembers the question and its identifier. When a server returns an answer, " "it returns in the `Transaction ID` field the identifier chosen by the " "client. Thanks to this identifier, the client can match the received answer " "with the question that it sent." msgstr "" #: ../../protocols/dns.rst:40 msgid "" "The `RD` (recursion desired) bit is set by a client when it sends a query to " "a resolver. Such a query is said to be `recursive` because the resolver will " "recursively traverse the DNS hierarchy to retrieve the answer on behalf of " "the client. In the past, all resolvers were configured to perform recursive " "queries on behalf of any Internet host. However, this exposes the resolvers " "to several security risks. The simplest one is that the resolver could " "become overloaded by having too many recursive queries to process. Most " "resolvers [#f8888]_ only allow recursive queries from clients belonging to " "their company or network and discard all other recursive queries. The `RA` " "bit indicates whether the server supports recursion. The `RCODE` is used to " "distinguish between different types of errors. See :rfc:`1035` for " "additional details. The last four fields indicate the size of the `Question`" ", `Answer`, `Authority` and `Additional` sections of the DNS message." msgstr "" #: ../../protocols/dns.rst:42 msgid "" "The last four sections of the DNS message contain `Resource Records` (RR). " "All RRs have the same top level format shown in the figure below." msgstr "" #: ../../protocols/dns.rst:48 msgid "DNS Resource Records" msgstr "" #: ../../protocols/dns.rst:52 msgid "" "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." msgstr "" #: ../../protocols/dns.rst:54 msgid "" "The `RDLength` field is the length of the `RData` field that contains the " "information of the type specified in the `Type` field." msgstr "" #: ../../protocols/dns.rst:61 msgid "Query for the `AAAA` record of `www.ietf.org`" msgstr "" #: ../../protocols/dns.rst:63 msgid "" "This answer contains several pieces of information. First, the name " "`www.ietf.org` is associated to IP address `2001:1890:123a::1:1e`. Second, " "the `ietf.org` domain is managed by six different nameservers. Five of these " "nameservers are reachable via IPv4 and IPv6." msgstr "" #: ../../protocols/dns.rst:65 msgid "" "`CNAME` (or canonical names) are used to define aliases. For example " "`www.example.com` could be a `CNAME` for `pc12.example.com` that is the " "actual name of the server on which the web server for `www.example.com` runs." msgstr "" #: ../../protocols/dns.rst:67 msgid "Reverse DNS" msgstr "" #: ../../protocols/dns.rst:69 msgid "" "The DNS is mainly used to find the address that corresponds to a given name. " "However, it is sometimes useful to obtain the name that corresponds to an IP " "address. This done by using the `PTR` (`pointer`) `RR`. The `RData` part of " "a `PTR` `RR` contains the name while the `Name` part of the `RR` contains " "the IP address encoded in the `in-addr.arpa` domain. IPv4 addresses are " "encoded in the `in-addr.arpa` by reversing the four digits that compose the " "dotted decimal representation of the address. For example, consider IPv4 " "address `192.0.2.11`. The hostname associated to this address can be found " "by requesting the `PTR` `RR` that corresponds to `11.2.0.192.in-addr.arpa`. " "A similar solution is used to support IPv6 addresses :rfc:`3596`, but " "slightly more complex given the length of the IPv6 addresses. For example, " "consider IPv6 address `2001:1890:123a::1:1e`. To obtain the name that " "corresponds to this address, we need first to convert it in a reverse dotted " "decimal notation : " "`e.1.0.0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.a.3.2.1.0.9.8.1.1.0.0.2`. In this " "notation, each character between dots corresponds to one nibble, i.e. four " "bits. The low-order byte (`e`) appears first and the high order (`2`) last. " "To obtain the name that corresponds to this address, one needs to append the " "`ip6.arpa` domain name and query for " "`e.1.0.0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.a.3.2.1.0.9.8.1.1.0.0.2.ip6.arpa`. " "In practice, tools and libraries do the conversion automatically and the " "user does not need to worry about it." msgstr "" #: ../../protocols/dns.rst:80 msgid "Footnotes" msgstr "" #: ../../protocols/dns.rst:81 msgid "" "Some DNS resolvers allow any host to send queries. Google operates a `public " "DNS resolver `_ " "at addresses `2001:4860:4860::8888` and `2001:4860:4860::8844`. Other " "companies provide similar services." msgstr ""