A DNS root zone is the top-level DNS zone The DNS namespace is defined by RFC 1034, "Domain Names - Concepts and Facilities" and RFC 1035, "Domain Names - Implementation and Specification". It is divided in hierarchical tree-like fashion into cascading lower-level domains that are ordered as a reverse-prioritized concatenation of names, each level separated by a full in a Domain Name System The Domain Name System is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers (DNS) hierarchy. Most commonly it refers to the root zone of the largest global DNS system deployed for the Internet The Internet is a global system of interconnected computer networks that use the standardized Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by copper wires, fiber-optic. The zone is managed by the Internet Assigned Numbers Authority The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, root zone management for the Domain Name System (DNS), media types, and other Internet Protocol related assignments. It is operated by the Internet Corporation for Assigned Names and Numbers, better known as ICANN (IANA), managed by ICANN ICANN is the Internet Corporation for Assigned Names and Numbers. Headquartered in Marina Del Rey, California, United States, ICANN is a non-profit corporation that was created on September 18, 1998 and incorporated September 30, 1998 in order to oversee a number of Internet-related tasks previously performed directly on behalf of the U.S.

A combination of limits in the DNS and IP protocols, namely the practical size of unfragmented User Datagram Protocol The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission (UDP) packets, resulted in a limited number of root server A root name server is a name server for the Domain Name System's root zone. It directly answers requests for records in the root zone and answers other requests returning a list of the designated authoritative name servers for the appropriate top-level domain . The root name servers are a critical part of the Internet because they are the first addresses that can be accommodated in DNS name query responses. This limit has determined the number of name server installation at currently 13 clusters, serving the needs of the entire public Internet worldwide.

Contents

Initialization of DNS service

There are thirteen root server clusters that are authoritative for queries to the global DNS root zone. The root servers hold the list of addresses for the authoritative servers for the top-level domains A top-level domain is the highest level of a domain name in the root zone of the Domain Name System of the Internet. For all domains in lower levels, it is the last part of the domain name, that is, the label that follows the last dot of a fully qualified domain name. For example, in the domain name www.example.com, the top-level domain is com, or. Every name lookup must either start with an access to a root server, or use information that was once obtained from a root server.

The root servers have the official names a.root-servers.net to m.root-servers.net. However, to look up the IP address of a root server from these names, a DNS resolver must first be able to look up a root server to find the address of an authoritative server for the .net DNS zone. Clearly this creates a paradox, so the address of at least one root server must be known by a host in order to bootstrap In computing, bootstrapping is a technique by which a simple computer program activates a more complicated system of programs. In the start up process of a computer system, a small program such as BIOS, initializes and tests that hardware, peripherals and external memory devices are connected, then loads a program from one of them and passes access to the DNS system. This is usually done by shipping the addresses of all known DNS root servers as a file with the computer operating system: the IP addresses of some root servers will change over the years, but only one correct address is needed for the resolver to obtain the current list of name servers. This file is called named.cache in the BIND nameserver reference implementation and a current version is officially distributed by ICANN ICANN is the Internet Corporation for Assigned Names and Numbers. Headquartered in Marina Del Rey, California, United States, ICANN is a non-profit corporation that was created on September 18, 1998 and incorporated September 30, 1998 in order to oversee a number of Internet-related tasks previously performed directly on behalf of the U.S's InterNIC InterNIC, short for Internet Network Information Center, was the Internet governing body primarily responsible for domain name and IP address allocations until September 18, 1998 when this role was assumed by the Internet Corporation for Assigned Names and Numbers . It was accessed through the website internic.net which was run by Network website.[1]

Once the address of a single functioning root server is known, all other DNS information can be discovered recursively, and the address of any domain name may be looked up.

Redundancy and diversity

The root DNS servers are essential to the function of the Internet, as most Internet services, such as the World-Wide Web and electronic mail, are based on domain names. The DNS servers are potential points of failure for the entire Internet. For this reason, there are multiple root servers worldwide. The number has been limited to 13 in DNS responses because DNS was limited to 512-byte packets until protocol extensions (EDNS EDNS is an extension of the DNS protocol which allows DNS messages larger than 512 bytes over UDP, and expands the number of flags, label types and return codes available to the protocol. The version of EDNS specified by RFC 2671 is known as EDNS0) were designed to lift this restriction. While it is possible to fit more entries into a packet of this size when using "label compression", 13 was chosen as a reliable limit. Since the advent of IPv6 Internet Protocol version 6 is the next-generation Internet Protocol version designated as the successor to IPv4, the first implementation used in the Internet and still in dominant use currently[update]. It is an Internet Layer protocol for packet-switched internetworks. The main driving force for the redesign of Internet Protocol was the, the next generation IP address An Internet Protocol address is a numerical label that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes. An IP address serves two principal functions in networking: host identification and location addressing. The role of the IP address has also been characterized as structure, previous practices are being modified and extra space is filled with IPv6 name servers.

The root name servers are hosted in multiple secure sites with high-bandwidth access to accommodate the traffic load. Initially all of these installations were located in the United States. However, the distribution has shifted and this is no longer the case. Usually each DNS server installation at a given site is physically a cluster of machines with load-balancing routers. A comprehensive list of servers, their locations, and properties is available at http://root-servers.org.

The modern trend is to use anycast Anycast is a network addressing and routing scheme whereby data is routed to the "nearest" or "best" destination as viewed by the routing topology addressing and routing to provide resilience and load balancing across a wide geographic area. For example, the j.root-servers.net root server, maintained by VeriSign VeriSign, Inc. is an American company based in Mountain View, California that operates a diverse array of network infrastructure, including two of the Internet's thirteen root nameservers, the generic top-level domains for .com and .net, one of the largest SS7 signaling networks in North America, and the RFID directory for EPCGlobal. VeriSign also, is represented by 41 (as of July 2008[update]) individual server systems located around the world which can be queried using anycast addressing.[citation needed]

See also

References

  1. ^ http://www.internic.net/zones/named.cache Official named.cache distribution

External links

Categories: Domain name system Categories: Internet governance | Internet standards | Internet architecture | Network addressing | Application layer protocols

 

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