Table of Contents

Glossary

A Domain Name System (DNS) A record maps a host's name to its address. It specifies the Internet Protocol address (in dotted decimal form) of the host. There should be one A record for each host address.

An File Transfer Protocol (FTP) session that uses login name anonymous to access public files. A server that permits anonymous FTP often allows password@, signifying an e-mail address.

A DNS Name server that possesses complete information about a zone.

A collection of bindings or DHCP client options and lease information, managed by the main and backup DHCP servers.

A collection of configuration parameters associated with all DHCP clients. This database holds configuration information about all the datasets.

Involves separating the IP address in the middle of an octet.

A caching name server retains information (cache) learned from other name servers so that it can answer requests quickly, without having to query other servers for each transaction.

Address classes are used to identify networks of varying sizes. The class membership is specified in the first octet of the Internet address. There are five classes: A, B, C, D,
and E.

The category of an IP address. The class of an address determines the location of the boundary between network prefix and host prefix. Internet addresses can be A, B, C, D, or E level addresses. Class D addresses are used for multicast and are not used on hosts. Class E addresses are for experimental use only.

A cluster is a group of DNS or DHCP servers that share the same Network Registrar database.

A CNAME record is used for nicknames or aliases. The name associated with the Resource Record is the nickname. The data portion is the official or canonical name.

A connectionless service treats each packet or datagram as a separate entity that contains the source and destination addresses. The alternative is a connection-based service using a protocol, such as TCP. The IP protocol UDP is often used to implement connectionless services.

The act of assigning responsibility for managing a subdomain to another organization within DNS zones.

DHCP configuration parameters and other control information that are stored in the options field of a DHCP message. DHCP clients determine what options get requested and sent in a DHCP packet.

This interval tells the secondary server how often to check the accuracy of its data by sending an AXFR packet to the primary DNS server.

A top-level or first-level is a child of the root. A second-level domain is a child of the first-level domain.

A domain name that can be of two types: absolute or relative. An absolute name is the fully qualified domain name (FQDN) and is terminated with a period. A relative name is relative to the current domain and does not end with a period.

Domain name aliases are pointers from one domain name to another, the official (or canonical) domain name.

All the nodes within a domain's large inverted tree, beginning at the root (.), are called the domain namespace.

The syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them for a representation of IP addresses. Many TCP/IP application programs accept dotted decimal notation in place of destination machine names.

A point in history chosen as the data from which time is measured. TCP/IP uses
January 1, 1990, Universal Time (formerly called Greenwich Mean Time) as its epoch date. When TCP/IP programs exchange date or time of day they express time as the number of seconds past the epoch date.

A forwarder is a DNS server that has been designated to handle all off-site queries. Using forwarders relieves other DNS servers from having to send packets off-site.

Fully Qualified Domain Name. The absolute domain name that unambiguously specifies a host's location in the DNS hierarchy.

A glue record is the DNS A (address) record that specifies the address of a subdomain's authoritative name server. You only need glue records in the server delegating a domain, not in the domain itself.

DNS Host Info. This resource record provides information about the hardware and software of the host machine.

The DNS address mapping domain that allows you to index host addresses and names. It allows the Internet to convert IP addresses back to host names.

When a DNS query is iterative, the name server returns the closest answer to the querying server.

An RFC standard, Incremental zone transfers allow Network Registrar to update a slave (secondary zone) by transferring only the change data from the primary server.

Lame delegation occurs when DNS servers (CNS resource records) listed in a zone have not been configured to be authoritative for the zone.

The lease grace period is the length of time that the lease is retained in the DHCP server's database after it has expired. This grace period protects a client's lease in cases where the client and server are in different time zones, the computer's clocks are not synchronized, or the client was not on the network when the lease expired.

Leases are used to specify how long a DHCP client (computer) can use an assigned IP address. When the lease expires, the computer has to negotiate a new lease with the DHCP server.

A name server has a zone that enables the server to direct traffic to itself. The host number is almost always 127.0.0.1.

A computer that accepts electronic mail. Some mail exchangers forward the mail to other computers. DNS has a separate resource record type for mail exchangers (MX).

An authoritative name server (primary or secondary) that transfers zone data to secondary servers through zone transfers.

The name of the Network Registrar internal database.

Mail Exchange record. Specifies where mail for a domain name should be delivered. You can have multiple MX records for a single domain name, ranked in preference order.

Short for No Acknowledgment.

The portion of the 32-bit IP address that identifies which network a particular system is on. It is determined by performing an AND operation of the subnet mask and the IP address.

An RFC standard that enables DNS master servers to inform their slaves that changes have been made to their zones. The changes are not communicated in the NOTIFY packet, instead the slaves initiate a zone transfer in response.

A group of DHCP attributes or options applied to a single scope or group of scopes.

The server from which secondary servers receive data through a zone transfer request.

Pointer record. Used to enable special names to point to some other location in the domain tree. They are used in the IN-ADDR.ARPA records for translation of addresses to names. PTRs should refer to official names (that is, canonical) and not aliases.

When a DNS query is recursive, the name server asks other DNS server for any non-authoritative data not in its own cache. Recursive queries continue to query all name servers until receiving an answer or an error.

An IP address that is reserved for a specific DHCP client.

Resolvers are the client part of the DNS client/server mechanism. They create queries that are sent across a network to a name server. The resolver queries a name server, interprets responses, and returns information to the requesting programs.

There are many Resource Record types. They include SOA, NS, A, CNAME, HINFO, WKS, MX and PTR. For more information, see the "Resource Records" appendix.

A domain namespace that uses names as addresses in order to support IP address queries. See also IN-ADDR.ARPA.

Root name servers are at the top of the hierarchy for all root name queries. A root name server knows the addresses of the authoritative name servers for all the top-level domains. Resolution of non-authoritative and/or non-cached data must start at the root servers.

The ability of a DNS server to rearrange the order of its multiple same-type records each time it is queried.

An administrative grouping of TCP/IP addresses on a DHCP server.

A secondary name server gets it zone data from another name server authoritative for the zone. When a secondary name server starts up, it contacts the name server from which it receives updates and pulls over the zone data.

A single LAN might have more than one subnet number applicable to the same LAN or network segment in a router. Typically, one subnet is designated as primary, the others as secondary. A site might support addresses on more than one subnet number associated with a single interface. You must configure the DHCP server with the necessary information about your secondary subnets.

Slave forwarders are DNS servers that behave like stub resolvers and pass most queries on to another name server for resolution. See also Stub Resolver.

A Slave Server is a DNS server that always forwards queries it cannot answer from its cache to a fixed list of forwarding servers instead of querying the root name servers for answers.

Start of Authority. This Resource Record designates the start of a zone.

Contains information about IP address bindings so that in the event of server failure information is not lost.

A stub resolver is a server that hands off queries to another server to resolve instead of performing the full resolution itself.

Involves dividing any network class into multiple subnetworks.

A set of IP addresses associated with.a network number and subnet mask, including secondary subnets.

A partition of a domain that has been delegated. It is represented as a child of the parent node. It always ends with the name of its parent, for example, engineering.cisco.com. is a subzone of cisco.com.

An aggregation of IP network addresses advertised as a single classless network address.

The international standard time reference that was formerly called Greenwich Mean Time. It is also called universal coordinated time or UCT.

Any set of IP protocol port numbers preassigned for specific uses by transport level protocols, for example, TCP and UDP. Each server listens at a well-known port so clients can locate it.

Well Known Services. A resource record in a DNS zone that is used to list the services provided by the host. The common protocols are TCP or UDP.

A zone is a delegation point in the DNS tree hierarchy. It contains all the names from a certain point downward except for those names that have been delegated to other zones. A zone defines the contents of a contiguous section of the domain space, usually bounded by administrative boundaries. Each zone has configuration data that are composed of entries called Resource Records. A zone can map exactly to a single domain, but can also include only part of a domain with the remainder delegated to other subzone name servers.

Zone of Authority or zone is a term used in DNS to refer to the group of names for which a given name server is an authority.

This occurs when a secondary DNS server starts up and updates itself from the primary server. A secondary DNS server queries a primary name server with a specific packet type called AXFR or IXFR and initiates a transfer of a copy of the database.

Posted: Thu Nov 18 13:48:44 PST 1999
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