msgid "" msgstr "" "Project-Id-Version: English (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-19 00:33+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: English \n" "Language: en\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" #: ../../principles/naming.rst:9 #, read-only msgid "Naming and addressing" msgstr "Naming and addressing" #: ../../principles/naming.rst:11 #, read-only msgid "" "The network and the transport layers rely on addresses that are encoded as " "fixed size bit strings. A network layer address uniquely identifies a host. " "Several transport layer entities can use the service of the same network " "layer. For example, a reliable transport protocol and a connectionless " "transport protocol can coexist on the same host. In this case, the network " "layer multiplexes the segments produced by these two protocols. This " "multiplexing is usually achieved by placing in the network packet header a " "field that indicates which transport protocol should process the segment. " "Given that there are few different transport protocols, this field does not " "need to be long. The port numbers play a similar role in the transport layer " "since they enable it to multiplex data from several application processes." msgstr "" "The network and the transport layers rely on addresses that are encoded as " "fixed size bit strings. A network layer address uniquely identifies a host. " "Several transport layer entities can use the service of the same network " "layer. For example, a reliable transport protocol and a connectionless " "transport protocol can coexist on the same host. In this case, the network " "layer multiplexes the segments produced by these two protocols. This " "multiplexing is usually achieved by placing in the network packet header a " "field that indicates which transport protocol should process the segment. " "Given that there are few different transport protocols, this field does not " "need to be long. The port numbers play a similar role in the transport layer " "since they enable it to multiplex data from several application processes." #: ../../principles/naming.rst:13 #, read-only msgid "" "While addresses are natural for the network and transport layer entities, " "humans prefer to use names when interacting with network services. Names can " "be encoded as a character string and a mapping services allows applications " "to map a name into the corresponding address. Using names is friendlier for " "humans, but it also provides a level of indirection which is very useful in " "many situations." msgstr "" "While addresses are natural for the network and transport layer entities, " "humans prefer to use names when interacting with network services. Names can " "be encoded as a character string and a mapping services allows applications " "to map a name into the corresponding address. Using names is friendlier for " "humans, but it also provides a level of indirection which is very useful in " "many situations." #: ../../principles/naming.rst:15 #, read-only msgid "" "In the early days of the Internet, only a few hosts (mainly minicomputers) " "were connected to the network. The most popular applications were :term:`" "remote login` and file transfer. By 1983, there were already five hundred " "hosts attached to the Internet [Zakon]_. Each of these hosts were identified " "by a unique address. Forcing human users to remember the addresses of the " "hosts that they wanted to use was not user-friendly. Humans prefer to " "remember names, and use them when needed. Using names as aliases for " "addresses is a common technique in Computer Science. It simplifies the " "development of applications and allows the developer to ignore the low level " "details. For example, by using a programming language instead of writing " "machine code, a developer can write software without knowing whether the " "variables that it uses are stored in memory or inside registers." msgstr "" "In the early days of the Internet, only a few hosts (mainly minicomputers) " "were connected to the network. The most popular applications were :term:`" "remote login` and file transfer. By 1983, there were already five hundred " "hosts attached to the Internet [Zakon]_. Each of these hosts were identified " "by a unique address. Forcing human users to remember the addresses of the " "hosts that they wanted to use was not user-friendly. Humans prefer to " "remember names, and use them when needed. Using names as aliases for " "addresses is a common technique in Computer Science. It simplifies the " "development of applications and allows the developer to ignore the low level " "details. For example, by using a programming language instead of writing " "machine code, a developer can write software without knowing whether the " "variables that it uses are stored in memory or inside registers." #: ../../principles/naming.rst:17 #, read-only msgid "" "Because names are at a higher level than addresses, they allow " "(both in the example of programming above, and on the Internet) to treat " "addresses as mere technical identifiers, which can change at will. Only the " "names are stable." msgstr "" "Because names are at a higher level than addresses, they allow " "(both in the example of programming above, and on the Internet) to treat " "addresses as mere technical identifiers, which can change at will. Only the " "names are stable." #: ../../principles/naming.rst:21 #, read-only msgid "" "The first solution that allowed applications to use names was the " ":term:`hosts.txt` file. This file is similar to the symbol table found in " "compiled code. It contains the mapping between the name of each Internet " "host and its associated address [#fhosts]_. It was maintained by SRI " "International that coordinated the Network Information Center (NIC). When a " "new host was connected to the network, the system administrator had to " "register its name and address at the NIC. The NIC updated the " ":term:`hosts.txt` file on its server. All Internet hosts regularly retrieved " "the updated :term:`hosts.txt` file from the SRI_ server. This file was " "stored at a well-known location on each Internet host (see :rfc:`952`) and " "networked applications could use it to find the address corresponding to a " "name." msgstr "" "The first solution that allowed applications to use names was the " ":term:`hosts.txt` file. This file is similar to the symbol table found in " "compiled code. It contains the mapping between the name of each Internet " "host and its associated address [#fhosts]_. It was maintained by SRI " "International that coordinated the Network Information Center (NIC). When a " "new host was connected to the network, the system administrator had to " "register its name and address at the NIC. The NIC updated the " ":term:`hosts.txt` file on its server. All Internet hosts regularly retrieved " "the updated :term:`hosts.txt` file from the SRI_ server. This file was " "stored at a well-known location on each Internet host (see :rfc:`952`) and " "networked applications could use it to find the address corresponding to a " "name." #: ../../principles/naming.rst:23 #, read-only msgid "" "A :term:`hosts.txt` file can be used when there are up to a few hundred " "hosts on the network. However, it is clearly not suitable for a network " "containing thousands or millions of hosts. A key issue in a large network is " "to define a suitable naming scheme. The ARPANet initially used a flat naming " "space, i.e. each host was assigned a unique name. To limit collisions " "between names, these names usually contained the name of the institution and " "a suffix to identify the host inside the institution " "(a kind of poor man's hierarchical naming scheme). On the ARPANet few " "institutions had several hosts connected to the network." msgstr "" "A :term:`hosts.txt` file can be used when there are up to a few hundred " "hosts on the network. However, it is clearly not suitable for a network " "containing thousands or millions of hosts. A key issue in a large network is " "to define a suitable naming scheme. The ARPANet initially used a flat naming " "space, i.e. each host was assigned a unique name. To limit collisions " "between names, these names usually contained the name of the institution and " "a suffix to identify the host inside the institution " "(a kind of poor man's hierarchical naming scheme). On the ARPANet few " "institutions had several hosts connected to the network." #: ../../principles/naming.rst:25 #, read-only msgid "" "However, the limitations of a flat naming scheme became clear before the end " "of the ARPANet and :rfc:`819` proposed a hierarchical naming scheme. While " ":rfc:`819` discussed the possibility of organizing the names as a directed " "graph, the Internet opted for a tree structure capable of containing all " "names. In this tree, the top-level domains are those that are directly " "attached to the root. The first top-level domain was `.arpa` [#fdnstimeline]" "_. This top-level name was initially added as a suffix to the names of the " "hosts attached to the ARPANet and listed in the `hosts.txt` file. In 1984, " "the `.gov`, `.edu`, `.com`, `.mil` and `.org` generic top-level domain names " "were added. :rfc:`1032` proposed the utilization of the two letter " ":term:`ISO-3166` country codes as top-level domain names. Since " ":term:`ISO-3166` defines a two letter code for each country recognized by " "the United Nations, this allowed all countries to automatically have a top-" "level domain. These domains include `.be` for Belgium, `.fr` for France, " "`.us` for the USA, `.ie` for Ireland or `.tv` for Tuvalu, a group of small " "islands in the Pacific or `.tm` for Turkmenistan. The set of top-level " "domain-names is managed by the Internet Corporation for Assigned Names and " "Numbers (:term:`ICANN`). :term:`ICANN` adds generic top-level domains that " "are not related to a country and the `.cat` top-level domain has been " "registered for the Catalan language. There are ongoing discussions within " ":term:`ICANN` to increase the number of top-level domains." msgstr "" "However, the limitations of a flat naming scheme became clear before the end " "of the ARPANet and :rfc:`819` proposed a hierarchical naming scheme. While " ":rfc:`819` discussed the possibility of organizing the names as a directed " "graph, the Internet opted for a tree structure capable of containing all " "names. In this tree, the top-level domains are those that are directly " "attached to the root. The first top-level domain was `.arpa` [#fdnstimeline]" "_. This top-level name was initially added as a suffix to the names of the " "hosts attached to the ARPANet and listed in the `hosts.txt` file. In 1984, " "the `.gov`, `.edu`, `.com`, `.mil` and `.org` generic top-level domain names " "were added. :rfc:`1032` proposed the utilization of the two letter " ":term:`ISO-3166` country codes as top-level domain names. Since " ":term:`ISO-3166` defines a two letter code for each country recognized by " "the United Nations, this allowed all countries to automatically have a top-" "level domain. These domains include `.be` for Belgium, `.fr` for France, " "`.us` for the USA, `.ie` for Ireland or `.tv` for Tuvalu, a group of small " "islands in the Pacific or `.tm` for Turkmenistan. The set of top-level " "domain-names is managed by the Internet Corporation for Assigned Names and " "Numbers (:term:`ICANN`). :term:`ICANN` adds generic top-level domains that " "are not related to a country and the `.cat` top-level domain has been " "registered for the Catalan language. There are ongoing discussions within " ":term:`ICANN` to increase the number of top-level domains." #: ../../principles/naming.rst:27 #, read-only msgid "" "Each top-level domain is managed by an organization that decides how sub-" "domain names can be registered. Most top-level domain names use a first-come " "first served system, and allow anyone to register domain names, but there " "are some exceptions. For example, `.gov` is reserved for the US government, " "`.int` is reserved for international organizations and names in the `.ca` " "are mainly `reserved `_ for companies or " "users that are present in Canada." msgstr "" "Each top-level domain is managed by an organization that decides how sub-" "domain names can be registered. Most top-level domain names use a first-come " "first served system, and allow anyone to register domain names, but there " "are some exceptions. For example, `.gov` is reserved for the US government, " "`.int` is reserved for international organizations and names in the `.ca` " "are mainly `reserved `_ for companies or " "users that are present in Canada." #: ../../principles/naming.rst:56 #, read-only msgid "" "The syntax of the domain names has been defined more precisely in :rfc:`1035`" ". This document recommends the following :term:`BNF` for fully qualified " "domain names (the domain names themselves have a much richer syntax)." msgstr "" "The syntax of the domain names has been defined more precisely in :rfc:`1035`" ". This document recommends the following :term:`BNF` for fully qualified " "domain names (the domain names themselves have a much richer syntax)." #: ../../principles/naming.rst:61 #, read-only msgid "BNF of the fully qualified host names" msgstr "BNF of the fully qualified host names" #: ../../principles/naming.rst:75 #, read-only msgid "" "This grammar specifies that a host name is an ordered list of labels " "separated by the dot (`.`) character. Each label can contain letters, " "numbers and the hyphen character (`-`) [#fidn]_. Fully qualified domain " "names are read from left to right. The first label is a hostname or a domain " "name followed by the hierarchy of domains and ending with the root " "implicitly at the right. The top-level domain name must be one of the " "registered TLDs [#ftld]_. For example, in the above figure, `www.computer-" "networking.info` corresponds to a host named `www` inside the `computer-" "networking` domain that belongs to the `info` top-level domain." msgstr "" "This grammar specifies that a host name is an ordered list of labels " "separated by the dot (`.`) character. Each label can contain letters, " "numbers and the hyphen character (`-`) [#fidn]_. Fully qualified domain " "names are read from left to right. The first label is a hostname or a domain " "name followed by the hierarchy of domains and ending with the root " "implicitly at the right. The top-level domain name must be one of the " "registered TLDs [#ftld]_. For example, in the above figure, `www.computer-" "networking.info` corresponds to a host named `www` inside the `computer-" "networking` domain that belongs to the `info` top-level domain." #: ../../principles/naming.rst:77 #, read-only msgid "Some visually similar characters have different character codes" msgstr "Some visually similar characters have different character codes" #: ../../principles/naming.rst:79 #, read-only msgid "" "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`." msgstr "" "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`." #: ../../principles/naming.rst:81 #, read-only msgid "" "The possibility of using all Unicode characters to create domain names " "opened a new form of attack called the `homograph attack `_. This attack occurs when two " "character strings or domain names are visually similar but do not correspond " "to the same server. A simple example is https://G00GLE.COM and https://" "GOOGLE.COM. These two URLs are visually close but they correspond to " "different names (the first one does not point to a valid server [#fg00gle]_)" ". With other Unicode characters, it is possible to construct domain names " "are visually equivalent to existing ones. See [Zhe2017]_ for additional " "details on this attack." msgstr "" "The possibility of using all Unicode characters to create domain names " "opened a new form of attack called the `homograph attack `_. This attack occurs when two " "character strings or domain names are visually similar but do not correspond " "to the same server. A simple example is https://G00GLE.COM and https://" "GOOGLE.COM. These two URLs are visually close but they correspond to " "different names (the first one does not point to a valid server [#fg00gle]_)" ". With other Unicode characters, it is possible to construct domain names " "are visually equivalent to existing ones. See [Zhe2017]_ for additional " "details on this attack." #: ../../principles/naming.rst:84 #, read-only msgid "" "This hierarchical naming scheme is a key component of the Domain Name System " "(DNS). The DNS is a distributed database that contains mappings between " "fully qualified domain names and addresses. The DNS uses the client-server " "model. The clients are hosts or applications that need to retrieve the " "mapping for a given name. Each :term:`nameserver` stores part of the " "distributed database and answers the queries sent by clients. There is at " "least one :term:`nameserver` that is responsible for each domain. In the " "figure below, domains are represented by circles and there are three hosts " "inside domain `dom` (`h1`, `h2` and `h3`) and three hosts inside domain " "`a.sdom1.dom`. As shown in the figure below, a sub-domain may contain both " "host names and sub-domains." msgstr "" "This hierarchical naming scheme is a key component of the Domain Name System " "(DNS). The DNS is a distributed database that contains mappings between " "fully qualified domain names and addresses. The DNS uses the client-server " "model. The clients are hosts or applications that need to retrieve the " "mapping for a given name. Each :term:`nameserver` stores part of the " "distributed database and answers the queries sent by clients. There is at " "least one :term:`nameserver` that is responsible for each domain. In the " "figure below, domains are represented by circles and there are three hosts " "inside domain `dom` (`h1`, `h2` and `h3`) and three hosts inside domain " "`a.sdom1.dom`. As shown in the figure below, a sub-domain may contain both " "host names and sub-domains." #: ../../principles/naming.rst:109 #, read-only msgid "" "A :term:`nameserver` that is responsible for domain `dom` can directly " "answer the following queries :" msgstr "" "A :term:`nameserver` that is responsible for domain `dom` can directly " "answer the following queries :" #: ../../principles/naming.rst:111 #, read-only msgid "" "the address of any host residing directly inside domain `dom` " "(e.g. `h2.dom` in the figure above)" msgstr "" "the address of any host residing directly inside domain `dom` " "(e.g. `h2.dom` in the figure above)" #: ../../principles/naming.rst:112 #, read-only msgid "" "the nameserver(s) that are responsible for any direct sub-domain of domain " "`dom` (i.e. `sdom1.dom` and `sdom2.dom` in the figure above, but not " "`z.sdom1.dom`)" msgstr "" "the nameserver(s) that are responsible for any direct sub-domain of domain " "`dom` (i.e. `sdom1.dom` and `sdom2.dom` in the figure above, but not " "`z.sdom1.dom`)" #: ../../principles/naming.rst:114 #, read-only msgid "" "To retrieve the mapping for host `h2.dom`, a client sends its query to the " "name server that is responsible for domain `.dom`. The name server directly " "answers the query. To retrieve a mapping for `h3.a.sdom1.dom` a DNS client " "first sends a query to the name server that is responsible for the `.dom` " "domain. This nameserver returns the nameserver that is responsible for the " "`sdom1.dom` domain. This nameserver can now be contacted to obtain the " "nameserver that is responsible for the `a.sdom1.dom` domain. This nameserver " "can be contacted to retrieve the mapping for the `h3.a.sdom1.dom` name. " "Thanks to this structure, it is possible for a DNS client to obtain the " "mapping of any host inside the `.dom` domain or any of its subdomains. To " "ensure that any DNS client will be able to resolve any fully qualified " "domain name, there are special nameservers that are responsible for the root " "of the domain name hierarchy. These nameservers are called :term:`root " "nameserver`." msgstr "" "To retrieve the mapping for host `h2.dom`, a client sends its query to the " "name server that is responsible for domain `.dom`. The name server directly " "answers the query. To retrieve a mapping for `h3.a.sdom1.dom` a DNS client " "first sends a query to the name server that is responsible for the `.dom` " "domain. This nameserver returns the nameserver that is responsible for the " "`sdom1.dom` domain. This nameserver can now be contacted to obtain the " "nameserver that is responsible for the `a.sdom1.dom` domain. This nameserver " "can be contacted to retrieve the mapping for the `h3.a.sdom1.dom` name. " "Thanks to this structure, it is possible for a DNS client to obtain the " "mapping of any host inside the `.dom` domain or any of its subdomains. To " "ensure that any DNS client will be able to resolve any fully qualified " "domain name, there are special nameservers that are responsible for the root " "of the domain name hierarchy. These nameservers are called :term:`root " "nameserver`." #: ../../principles/naming.rst:116 #, read-only msgid "" "Each root nameserver maintains the list [#froot]_ of all the nameservers " "that are responsible for each of the top-level domain names and their " "addresses [#frootv6]_. All root nameservers cooperate and provide the same " "answers. By querying any of the root nameservers, a DNS client can obtain " "the nameserver that is responsible for any top-level-domain name. From this " "nameserver, it is possible to resolve any domain name." msgstr "" "Each root nameserver maintains the list [#froot]_ of all the nameservers " "that are responsible for each of the top-level domain names and their " "addresses [#frootv6]_. All root nameservers cooperate and provide the same " "answers. By querying any of the root nameservers, a DNS client can obtain " "the nameserver that is responsible for any top-level-domain name. From this " "nameserver, it is possible to resolve any domain name." #: ../../principles/naming.rst:119 #, read-only msgid "" "To be able to contact the root nameservers, each DNS client must know their " "addresses. This implies, that DNS clients must maintain an up-to-date list " "of the addresses of the root nameservers. Without this list, it is " "impossible to contact the root nameservers. Forcing all Internet hosts to " "maintain the most recent version of this list would be difficult from an " "operational point of view. To solve this problem, the designers of the DNS " "introduced a special type of DNS server : the DNS resolvers. A " ":term:`resolver` is a server that provides the name resolution service for a " "set of clients. A network usually contains a few resolvers. Each host in " "these networks is configured to send all its DNS queries via one of its " "local resolvers. These queries are called `recursive queries` as the " ":term:`resolver` must recursively send requests through the hierarchy of " "nameservers to obtain the `answer`." msgstr "" "To be able to contact the root nameservers, each DNS client must know their " "addresses. This implies, that DNS clients must maintain an up-to-date list " "of the addresses of the root nameservers. Without this list, it is " "impossible to contact the root nameservers. Forcing all Internet hosts to " "maintain the most recent version of this list would be difficult from an " "operational point of view. To solve this problem, the designers of the DNS " "introduced a special type of DNS server : the DNS resolvers. A " ":term:`resolver` is a server that provides the name resolution service for a " "set of clients. A network usually contains a few resolvers. Each host in " "these networks is configured to send all its DNS queries via one of its " "local resolvers. These queries are called `recursive queries` as the " ":term:`resolver` must recursively send requests through the hierarchy of " "nameservers to obtain the `answer`." #: ../../principles/naming.rst:121 #, read-only msgid "" "DNS resolvers have several advantages over letting each Internet host query " "directly nameservers. Firstly, regular Internet hosts do not need to " "maintain the up-to-date list of the addresses of the root servers. Secondly, " "regular Internet hosts do not need to send queries to nameservers all over " "the Internet. Furthermore, as a DNS resolver serves a large number of hosts, " "it can cache the received answers. This allows the resolver to quickly " "return answers for popular DNS queries and reduces the load on all DNS " "servers [JSBM2002]_." msgstr "" "DNS resolvers have several advantages over letting each Internet host query " "directly nameservers. Firstly, regular Internet hosts do not need to " "maintain the up-to-date list of the addresses of the root servers. Secondly, " "regular Internet hosts do not need to send queries to nameservers all over " "the Internet. Furthermore, as a DNS resolver serves a large number of hosts, " "it can cache the received answers. This allows the resolver to quickly " "return answers for popular DNS queries and reduces the load on all DNS " "servers [JSBM2002]_." #: ../../principles/naming.rst:125 #, read-only msgid "Benefits of names" msgstr "Benefits of names" #: ../../principles/naming.rst:127 #, read-only msgid "" "In addition to being more human friendly, using names instead of addresses " "inside applications has several important benefits. To understand them, let " "us consider a popular application that provides information stored on " "servers. This application involves clients and servers. The server provides " "information upon requests from client processes. A first deployment of this " "application would be to rely only on addresses. In this case, the server " "process would be installed on one host and the clients would connect to this " "server to retrieve information. Such a deployment has several drawbacks :" msgstr "" "In addition to being more human friendly, using names instead of addresses " "inside applications has several important benefits. To understand them, let " "us consider a popular application that provides information stored on " "servers. This application involves clients and servers. The server provides " "information upon requests from client processes. A first deployment of this " "application would be to rely only on addresses. In this case, the server " "process would be installed on one host and the clients would connect to this " "server to retrieve information. Such a deployment has several drawbacks :" #: ../../principles/naming.rst:129 #, read-only msgid "" "if the server process moves to another physical server, all clients must be " "informed about the new server address" msgstr "" "if the server process moves to another physical server, all clients must be " "informed about the new server address" #: ../../principles/naming.rst:130 #, read-only msgid "" "if there are many concurrent clients, the load of the server will increase " "without any possibility of adding another server without changing the server " "addresses used by the clients" msgstr "" "if there are many concurrent clients, the load of the server will increase " "without any possibility of adding another server without changing the server " "addresses used by the clients" #: ../../principles/naming.rst:133 #, read-only msgid "" "Using names solves these problems and provides additional benefits. If the " "clients are configured with the name of the server, they will query the name " "service before contacting the server. The name service will resolve the name " "into the corresponding address. If a server process needs to move from one " "physical server to another, it suffices to update the name to address " "mapping on the name service to allow all clients to connect to the new " "server. The name service also enables the servers to better sustain the " "load. Assume a very popular server which is accessed by millions of users. " "This service cannot be provided by a single physical server due to " "performance limitations. Thanks to the utilization of names, it is possible " "to scale this service by mapping a given name to a set of addresses. When a " "client queries the name service for the server's name, the name service " "returns one of the addresses in the set. Various strategies can be used to " "select one particular address inside the set of addresses. A first strategy " "is to select a random address in the set. A second strategy is to maintain " "information about the load on the servers and return the address of the less " "loaded server. Note that the list of server addresses does not need to " "remain fixed. It is possible to add and remove addresses from the list to " "cope with load fluctuations. Another strategy is to infer the location of " "the client from the name request and return the address of the closest " "server." msgstr "" "Using names solves these problems and provides additional benefits. If the " "clients are configured with the name of the server, they will query the name " "service before contacting the server. The name service will resolve the name " "into the corresponding address. If a server process needs to move from one " "physical server to another, it suffices to update the name to address " "mapping on the name service to allow all clients to connect to the new " "server. The name service also enables the servers to better sustain the " "load. Assume a very popular server which is accessed by millions of users. " "This service cannot be provided by a single physical server due to " "performance limitations. Thanks to the utilization of names, it is possible " "to scale this service by mapping a given name to a set of addresses. When a " "client queries the name service for the server's name, the name service " "returns one of the addresses in the set. Various strategies can be used to " "select one particular address inside the set of addresses. A first strategy " "is to select a random address in the set. A second strategy is to maintain " "information about the load on the servers and return the address of the less " "loaded server. Note that the list of server addresses does not need to " "remain fixed. It is possible to add and remove addresses from the list to " "cope with load fluctuations. Another strategy is to infer the location of " "the client from the name request and return the address of the closest " "server." #: ../../principles/naming.rst:135 #, read-only msgid "" "Mapping a single name onto a set of addresses allows popular servers to " "dynamically scale. There are also benefits in mapping multiple names, " "possibly a large number of them, onto a single address. Consider the case of " "information servers run by individuals or SMEs. Some of these servers " "attract only a few clients per day. Using a single physical server for each " "of these services would be a waste of resources. A better approach is to use " "a single server for a set of services that are all identified by different " "names. This enables service providers to support a large number of servers " "processes, identified by different names, onto a single physical server. If " "one of these server processes becomes very popular, it will be possible to " "map its name onto a set of addresses to be able to sustain the load. There " "are some deployments where this mapping is done dynamically in function of " "the load." msgstr "" "Mapping a single name onto a set of addresses allows popular servers to " "dynamically scale. There are also benefits in mapping multiple names, " "possibly a large number of them, onto a single address. Consider the case of " "information servers run by individuals or SMEs. Some of these servers " "attract only a few clients per day. Using a single physical server for each " "of these services would be a waste of resources. A better approach is to use " "a single server for a set of services that are all identified by different " "names. This enables service providers to support a large number of servers " "processes, identified by different names, onto a single physical server. If " "one of these server processes becomes very popular, it will be possible to " "map its name onto a set of addresses to be able to sustain the load. There " "are some deployments where this mapping is done dynamically in function of " "the load." #: ../../principles/naming.rst:137 #, read-only msgid "" "Names provide a lot of flexibility compared to addresses. For the network, " "they play a similar role as variables in programming languages. No " "programmer using a high-level programming language would consider using " "hardcoded values instead of variables. For the same reasons, all networked " "applications should depend on names and avoid dealing with addresses as much " "as possible." msgstr "" "Names provide a lot of flexibility compared to addresses. For the network, " "they play a similar role as variables in programming languages. No " "programmer using a high-level programming language would consider using " "hardcoded values instead of variables. For the same reasons, all networked " "applications should depend on names and avoid dealing with addresses as much " "as possible." #: ../../principles/naming.rst:141 #, read-only msgid "Footnotes" msgstr "Footnotes" #: ../../principles/naming.rst:142 #, read-only msgid "" "The :term:`hosts.txt` file is not maintained anymore. A historical snapshot " "from April 1984 is available from http://ftp.univie.ac.at/netinfo/netinfo/" "hosts.txt" msgstr "" "The :term:`hosts.txt` file is not maintained anymore. A historical snapshot " "from April 1984 is available from http://ftp.univie.ac.at/netinfo/netinfo/" "hosts.txt" #: ../../principles/naming.rst:144 #, read-only msgid "" "See http://www.donelan.com/dnstimeline.html for a time line of DNS related " "developments." msgstr "" "See http://www.donelan.com/dnstimeline.html for a time line of DNS related " "developments." #: ../../principles/naming.rst:146 #, read-only msgid "" "This specification evolved later to support domain names written by using " "other character sets than us-ASCII :rfc:`5890`. This extension is important " "to support languages other than English, but a detailed discussion is " "outside the scope of this document." msgstr "" "This specification evolved later to support domain names written by using " "other character sets than us-ASCII :rfc:`5890`. This extension is important " "to support languages other than English, but a detailed discussion is " "outside the scope of this document." #: ../../principles/naming.rst:148 #, read-only msgid "" "The official list of top-level domain names is maintained by :term:`IANA` at " "http://data.iana.org/TLD/tlds-alpha-by-domain.txt Additional information " "about these domains may be found at http://en.wikipedia.org/wiki/" "List_of_Internet_top-level_domains" msgstr "" "The official list of top-level domain names is maintained by :term:`IANA` at " "http://data.iana.org/TLD/tlds-alpha-by-domain.txt Additional information " "about these domains may be found at http://en.wikipedia.org/wiki/" "List_of_Internet_top-level_domains" #: ../../principles/naming.rst:150 #, read-only msgid "" "It is interesting to note that to prevent any homograph attack, Google Inc. " "registered the `g00gle.com` domain name but does not apparently use it." msgstr "" "It is interesting to note that to prevent any homograph attack, Google Inc. " "registered the `g00gle.com` domain name but does not apparently use it." #: ../../principles/naming.rst:152 #, read-only msgid "" "A copy of the information maintained by each root nameserver is available at " "http://www.internic.net/zones/root.zone" msgstr "" "A copy of the information maintained by each root nameserver is available at " "http://www.internic.net/zones/root.zone" #: ../../principles/naming.rst:154 #, read-only msgid "" "Until February 2008, the root DNS servers only had IPv4 addresses. IPv6 " "addresses were slowly added to the root DNS servers to avoid creating " "problems as discussed in http://www.icann.org/en/committees/security/" "sac018.pdf As of February 2021, there remain a few DNS root servers that are " "still not reachable using IPv6. The full list is available at http://" "www.root-servers.org/" msgstr "" "Until February 2008, the root DNS servers only had IPv4 addresses. IPv6 " "addresses were slowly added to the root DNS servers to avoid creating " "problems as discussed in http://www.icann.org/en/committees/security/" "sac018.pdf As of February 2021, there remain a few DNS root servers that are " "still not reachable using IPv6. The full list is available at http://" "www.root-servers.org/"