Glossary of Terms

An "A Record" (short for "Address Record") is a DNS record type which translates (or "resolves") a hostname or domain name into an IP address.

The term "account" means your login to the TZO website and does not refer to your domain name. If you have just one domain name with TZO, Support will usually know what you mean when you say "account". Please note the new TZO website allows one account to control more than one domain name.

In the context of DNS, alias usually means CNAME records which resolve to some other hostname. Alternatively "alias" could also mean a group of hostnames which all resolve to an IP address and do not use CNAMES, meaning the group of hostnames are "linked" together in your TZO account (when "domain A" is changed to a new A record, "Domain B" and "Domain C" will automatically inherit the same A record value). Both configurations are possible.

In the context of websites, "alias" will mean "A second hostname that a website folder will respond to or serve content for", for example many web hosting setups will be configured for "example.com" but will also alias to "www.example.com".

An authoritative nameserver (also referred to as "authoritative-only name server") is a server which only returns answers to DNS queries for specific domains which the server has been configured to resolve.

The authoritative nameserver(s) are specified by the Domain Registration account for that domain, and the domain's WHOIS record will state which nameservers are authoritative.

Caching is the process where DNS servers or applications (such as your web browser) will story a copy of DNS records. The cached copy should be identical to what is currently published on the authoritative nameserver, however this is not always the case as the authoritative nameserver could update its records and a caching nameserver will not immediately know about the change. For this reason DNS records set a maximum age on records, known as TTL (time to live). Hostnames which change IP addresses frequently or which need to load-balance via DNS will usually have a very low TTL (30 to 300 seconds).

Client is a generic term meaning any network device or application which connects to a server, for example a web browser or email client. In the context of dynamic DNS or TZO clients, please see Update Client.

CNAME (also: "Canonical Name") is a DNS term for a type of alias. A CNAME record does not provide the final answer (such as an IP address), but instructs applications to conduct an additional query against this other hostname (specified by the CNAME) and use that result as the answer.

CNAMES usually work well for web hostnames, FTP, and other services but should not be used for certain email configurations. You can for example, CNAME "webmail.example.com" to "mail.example.com" and this works because it is well supported by web browsers and servers. On the other hand, a CNAME inside an MX record is invalid and will result in email delivery problems (both sending and receiving).

DDNS is an abbreviation for Dynamic DNS.

The process of specifying which nameservers handle a particular domain zone or hostname.

DHCP (Dynamic Host Configuration Protocol) is a method of assigning IP addresses to devices automatically. DHCP is an easier method that static for assigning IP addresses to devices on a network since it's automatic. This automatic IP assignment also causes problems with hosting or running IP services which dynamic DNS helps overcome.

Short for Domain Name System.

The client-side of the DNS is called a DNS resolver. It is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of the resource sought, e.g., translation of a domain name into an IP address.

DNS Resolvers typically follow local rules for caching of DNS records and may or may not override cache TTLs set in a DNS record. For example, Internet Explorer may cache a DNS record for 10 minutes, even if the cache time is set less than that.

The Domain Name System (DNS) is the address system people use on the Internet. DNS is responsible for resolving hostnames into IP addresses (and in the case of 'reverse DNS', resolving IP addresses back into domain names).

Short for dynamic Domain Name System (or DDNS), which allows a domain name to work with a "dynamic IP address".

Both "TZO Standard DNS" and "TZO Premiere DNS" support dynamic DNS resolution, which in many cases allows you to avoid leasing a "static IP" (which can be $200/month... if your provider even offers the option!). Many TZO customers use our dynamic DNS services to save money, yet still enable easy remote-connections back to their home or office servers and cameras.

A firewall is a device (or software) which is designed to protect networks from unauthorized or outside access. For more background please see the Wikipedia Firewall entry.
Firewalls can deny remote access to a camera or server, even if your TZO is correctly configured. You usually need to manually configure an exception for your firewall, allowing traffic in from outside. Note that most routers will not relax the Firewall rules, even if you specify a router Port Forward (so the port will forward into the firewall, then stop). This means you typically need to set the port twice in your router, once in each area of Administration. Note most PCs will have a software firewall which may also stand in the way, and require a manual exception rule.

Hostname (or "host") is the DNS name (address) of a server or network on the Internet. Hostname sometimes implies the "short host" name, such as "www" in "www.example.com". It is more accurate to refer to systems by their Fully Qualified Domain Name (FQDN) such as "www.example.com".

IP address represents the numeric address of a computer on a given network, most commonly referring to the Internet IP address (or WAN address, provided by your ISP). Less commonly, IP address can also indicate a computer's Local Area Network (LAN) or "private" IP address. If unsure which context of IP address is needed, it is always useful to provide both the WAN IP and the LAN IP.

MX is a DNS record type which indicates a domain's mailserver address(es). MX record values are fully-qualified hostname addresses (for which a hostname must actually exist in DNS). For example, the domain zone "tzo.com" contains an MX record whose value is "mail.tzo.com". When mail is sent to someone @ tzo.com, the sending mailserver will first resolve the MX record, then resolve the host A record for that MX, and direct the mail to that network address.

A Nameserver is a type of server configured to answer DNS queries. Nameservers occur as two different types: Authoritative Nameserver, and Caching Nameserver. To avoid ambiguity between the 2 nameserver contexts, the term "nameserver" is rarely used by itself.

Network Address Translation (NAT) is an IP address rewriting scheme. Most commonly you will head NAT used to describe how many home and small business routers work, where a network of computers on 'private LAN' addresses all share 1 public Internet address. More information can be found at the Wikipedia NAT entry.
Many home/small business Internet providers will provide you with a normal Internet IP address, but then they enable NAT in their modems. This is fine, but you will need to ask the ISP to 'enable Bridge Mode' in your modem, which passes through the true connection IP. An alternative solution to bridge mode is a more complex double-port-forward between your modem and internal router.

A subdomain is a hostname which depends on (belongs with) a domain name. For example, if the Fully Qualified Domain Name (FQDN) is "www.example.com", the domain name really is "example.com", and "www" is the short hostname.

On mailservers, Tarpitting is a service which deliberately attempts to delay incoming connections as long as possible, with the intention that this will slow down and hurt the activities of spammers. In general tarpitting is not that effective. Tarpitting must never be used by email servers which use TZO Store and Forward (SAF) or TZO Spam and Virus Filtering (SVF) services; allowing tarpitting to occur in such circumstances can cause serious problems.

TTL is an acronym for "Time To Live". TTL specifies how long outside DNS servers should cache this DNS record. TTL is sometimes called "cache time".

TXT records are record types which are containers for free-form plain text. TXT record are most commonly used as Sender Policy Framework (SPF) or DomainKeys, which are created using special syntax inside the TXT record.

Wide Area Network IP address, this indicates your "public Internet IP" or routable address. Also known as "shared Internet IP" or "Connection IP". Routers and modems typically display the WAN IP on the device's Status web page. You can also usually determine your WAN IP by opening a web browser to www.MyWanIP.com.

In the context of DNS, wildcards will alias *.example.com to the same IP address as example.com resolves to. The star '*' means "anything", so you can essentially invent subdomains on-the-fly which can be very useful for website management. Wildcards can be overridden, so in the above example if you created a non-wildcard record "go-somewhere-else.example.com" you could configure just this hostname to resolve to another IP address.