A-Z Glossary

Second Level Domain eg, www.yourbusinessname.com.au, the letters after the name and before the .au

A 6to4 gateway adds its IPv4 address to this 2002::/16, creating a unique /48 prefix. As the IPv4 address of the gateway router is used to compose the IPv6 prefix, it is possible to reverse the process and identify the IPv4 address, which can then be looked up in the relevant RIR’s Whois database.

Adjacency attestation (AAO)
An AAO is a digitally signed object that verifies that an AS has made an attestation that it has an inter-domain adjacency with one or more other ASes

See Routing advertisement

African Network Information Centre (AfriNIC) is the Regional Internet Registry for the African Region

Address space allocated by APNIC or NIRs to LIRs for the purpose of subsequent distribution by LIRs to their customers.

The Asia Pacific Internet Development Trust is a fund created to benefit Internet development in the region.

Asia Pacific Network Information Centre (APNIC) is the Regional Internet Registry for the Asia Pacific Region

Application Service Provider
Entity who provides specific application(s) direct to the End User

American Registry for Internet Numbers (ARIN) is the Regional Internet Registry for the North American Region

arpa (or “.arpa”)
The Address and Routing Parameters Area top level domain, used for network infrastructure

Address space assigned for specific use within the Internet infrastructure of a network. Assignments can be made by LIRs to their customer’s network infrastructure or to the LIR’s own infrastructure.

Assignment of a number
The process for providing an international numbering resource to an eligible applicant (when used in the formal sense as defined in Section 5.4 of ITU-T Rec. E.190 (05/97)).

Assignment window
Refers to the amount of IP address space that you can assign or sub-allocate to your customers without the need to send in a second opinion request form for APNIC’s approval

Australian Network Information Centre

Autonomous System (AS)
An AS is a group of IP networks run by one or more network operators with a single clearly defined routing policy

Autonomous System Number (ASN or AS number)
ASNs are globally unique identifiers for Autonomous Systems and are used as identifiers to allow the ASes to exchange dynamic routing information. An Autonomous system (AS) is a group of IP networks having a single clearly defined routing policy run by one or more network operators

These IPv6 addresses are reserved for use in documentation. They should not be used as source or destination addresses.

The Border Gateway Protocol is the routing protocol used to exchange routing information across the Internet. BGP allows ISPs to connect to each other and for end users to connect to more than one ISP. BGP is the only protocol that is designed to deal with a network of the Internet’s size and deal well with having multiple connections to unrelated routing domains

Where false routing advertisements redirect traffic away from its intended destination and instead are directed to a sink point. This results in an effective Denial of Service (DoS), where the target service is taken offline. A side effect may be a rearrangement of traffic flows that could overload some network links

The Recursive Resolver’s cache is its memory where the answers for recent queries are stored. If the answer to a query is on the Recursive Resolver’s cache, the Recursive Resolver will not query any other server, but will give out the stored answer.

E.164 Country Code (as specified in ITU-T Recommendation E.164).

Country Code Top Level Domain

The Cross Community Working Group on Enhancing ICANN Accountability is a group formed by ICANN as part of ICANN’s Enhancing Accountability Process. It was created to examine how ICANN’s accountability mechanisms should be strengthened as part of the IANA Stewardship Transition Process. Also referred to as CCWG-Accountability.

Certificate extensions
To make the original X.509 certificate standard suitable for Resource Certification it needed some minor modifications, or extensions, to provide a place to record the Internet number resources held by the private key holder. See X.509

Computer Emergency Response Teams (CERTs) or Computer Security Incident Response Teams (CSIRTs) are expert groups that respond to cybersecurity incidents, such as malware, DDoS, and ransomware attacks. These groups play a vital role in the maintenance of the networks that comprise the Internet.

Classless Inter Domain Routing is a method of categorizing IP addresses for the purpose of allocating IP addresses to users and for efficiently routing IP packets on the Internet

A method of splitting software functions, for example, a PC-based email client and a network-based email server

A specific country, a group of countries in an integrated numbering plan or a specific geographical area (when used in a formal sense of an ITU-T Rec. E.164 Country Code)

Customer Premises Equipment is any telecommunications equipment sold or leased by the carrier to the customer that is installed at the customer’s location. It is typically installed to originate, route or terminate telecommunication between the customer premises and the carrier or telco’s location from which the service is leased.

The Consolidated RIR IANA Stewardship Proposal Team (CRISP) is a group representing the Internet numbering community to produce a proposal for the IANA Stewardship Transition Process.

Critical Internet infrastructure
A collective terms for all hardware and software systems that constitute essential components in the operation of the Internet

The Cross Community Working Group to Develop an IANA Stewardship Transition Proposal on Naming Related Functions (CWG) is a group representing the domain name community to produce a proposal for the IANA Stewardship Transition Process.

Distributed denial-of-service is a DoS attack launched from multiple computers

Digital certificate
A digital certificate is an electronic certificate used to prove your identity or your right to access information or services online. A digital certificate is required in order to access secured services of APNIC. The digital certificates used by APNIC conform to Standard X.509

Digital signature
A digital signature is an electronic signature which authenticates the identity of a message sender, or document signer and possibly to ensure that the original content of the message or document that has arrived unchanged

Domain Name System

Domain Name Security Extensions are extensions to the DNS that provide authentication of the origin of DNS data, integrity of data and authentication of denial of existence.

A set of host names consisting of a single domain name and all the domain names below it

Domain name
As part of the Domain Name System, domain names identify IP resources, such as an Internet website.

Denial-of-service is a type of Internet attack where an attacker attempts to prevent legitimate users from accessing information or services generally by flooding the service provider with bogus requests or traffic

The international public telecommunication numbering plan

E.164 number (for geographical areas)
An E.164 number typically consisting of three fields, CC (country code), NDC (national destination code), and SN (subscriber number)

Principles and responsibilities for the management, assignment and reclamation of E Series international numbering resources

E164 Number
A number from ITU-T Rec E.164 numbering plan that uniquely indicates a public network termination point

In the .arpa domain, the subdomain of ENUM names for E.164 numbers

The APNIC Executive Committee

End site
An end site is defined as an end user (subscriber) who has a business relationship with a service provider that involves that service provider: (i) Assigning address space to the end user (ii) Providing transit service for the end user to other sites (iii) Carrying the end user’s traffic (iv) Advertising an aggregate prefix route that contains the end user’s assignment

Telephone Number Mapping – a protocol and an IETF WG

A system for connecting a number of computer systems to form a local area network

End User

Governmental Advisory Committee, one of ICANN’s stakeholder groups. The GAC provides ICANN with input from governments on issues of public policy.

ICANN’s Global Domains Division, which oversees generic domain operations, domain name industry engagement and web services

Global Service
A service defined by the ITU-T, provisioned on the public switched network, … to enable the provision of that international service between two or more countries … (when used in the formal sense as defined in Section 4.14 of ITU-T Rec. E.164 (05/97)).

Global Unicast
Other than the exceptions documented in this table, the operators of networks using these addresses can be found using the Whois servers of the RIRs listed in the registry at: http://www.iana.org/assignments/ipv6-unicast-address-assignments

Generic Top Level Domain hosting/webhosting – a location (a server somewhere, connected to the internet) which houses your internet address

Packet based multimedia communication systems

The HD-Ratio is a way of measuring the efficiency of address assignment [RFC 3194]. It is an adaption of the HD-Ratio originally defined in [RFC 1715] and is expressed as the number of allocated objects divided by maximum number of allocatable objects. In the case of the “IPv6 Address Allocation and Assignment Policy” document the objects are IPv6 site addresses (/56s) assigned from an IPv6 prefix of a given size

Historical Resource
These are resources delegated to organizations by APNIC prior to the introduction of a membership structure. These resources have always been registered in the APNIC Whois Database but if the resource holder did not become an APNIC member at any time after the introduction of the membership structure, the resources were not made subject to current APNIC policies

Hypertext transfer protocol

Internet Architecture Board

Internet Assigned Numbers Authority

The IANAPlan Working Group is a group representing the Internet protocols and parameters community to produce a proposal for the IANA Stewardship Transition Process.

The IANA Stewardship Transition Coordination Group. Formed by ICANN to oversee the IANA Stewardship Transition Process, this group is responsible for collecting and evaluating proposals on the IANA Stewardship Transition Process from the Domain Names Community (CWG), Number Resources Community (CRISP Team), and the Protocol and Parameters Community (IANAPlan WG).

The Internet Engineering Steering Group (IESG) is part of ISOC and is responsible for technical management of IETF activities and the Internet standards process.

Internet Engineering Task Force

Where false routing advertisements redirect traffic away from the intended destination and instead directs traffic to a site that masquerades as the destination service. This form of masquerading is used to gather otherwise confidential information from users of the original service. See Phishing

In the .arpa domain, the subdomain for IP addresses (as names) for host names

Refers to the method of inserting routing information into the routing table. In context, it can also imply the injection of false routing information

Internet Directory
The Internet Directory is a portal that provides data on how Internet number resources are distributed and used in the AP region.

Inspection and alteration
Where false routing advertisements cause traffic to an intended destination to be forwarded to a compromised network segment. Here the traffic may be inspected, or even altered before being passed onward to the actual destination

Internet Exchange Point
Also known as IX or IXP. It is a layer 1 and layer 2 network structure that interconnects three or more Autonomous Systems 9AS) for the purpose of Internet traffic interchange

Internet Exchange Point (IX or IXP)
An Internet Exchange Point is a layer 1 and layer 2 network structure that interconnects three or more Autonomous Systems (AS) for the purpose of Internet traffic interchange.

Internet Registry
An Internet Registry (IR) is an organization that is responsible for distributing IP address space to its members or customers and for registering those distributions. IRs include: (i) APNIC and other Regional Internet Registries (RIRs); (ii) National Internet Registries (NIRs); (iii) Local Internet Registries (LIRs)

Internet resources
APNIC’s refers to IPv4 and IPv6 address blocks and AS numbers as numeric Internet resources.

Internet of Things is a system of interrelated computing devices, mechanical and digital machines provided with unique identifiers and the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction.

Internet Protocol

IPv4 address
An IPv4 address is a binary number consisting of 32 bits that are organized into four bytes. The four bytes are usually portrayed using a dotted decimal notation such as Each decimal number is equivalent of a byte; the dots used between the decimals are used to separate the bytes. For example,

These addresses are used to embed IPv4 addresses in an IPv6 address. One use for this is in a dual stack transition scenario where IPv4 addresses can be mapped into an IPV6 address.

The next generation Internet layer protocol for the Internet. It has a much larger address space than IPv4 with a 128-bit address. This supports 2128 addresses. They are conventionally expressed using hexadecimal strings, for example, 2001:0db8:582:ae33::29

Internet Society

Internet Service Provider

International Telecommunication Union

The Telecommunications standardization sector of the International Telecommunication Union

Latin American & Caribbean Network Information Centre (LACNIC) is the Regional Internet Registry for Latin America and some Caribbean Islands

Local Area Network

Link-Local Addresses
These addresses are used on a single link or a non-routed common access network, such as an Ethernet LAN. They do not need to be unique outside of that link. Link-local addresses may appear as the source or destination of an IPv6

Local Internet Registry (LIR)
A LIR is an Internet Registry (IR) that primarily assigns address space to the users of the network services that it provides. LIRs are generally ISPs, whose customers are primarily end users and possibly other ISPs

This address is used when a host talks to itself over IPv6. This often happens when one program sends data to another.

Memorandum of Understanding

These addresses are used to identify multicast groups. They should only be used as destination addresses, never as source addresses.

Describes a computer host that has multiple IP addresses to connected networks. A multihomed host is physically connected to multiple data links that can be on the same or different networks

Name Server
A DNS component that stores information about one zone (or more) of the DNS name space

Name Space
The structure of the DNS database

Name vs Address vs Route
A name identifies an endpoint, an address tells where it is, and a route tells how to get there

Number Authority Pointer (as used within IETF RFC 2916 to identify possible URLs and numbers that can be returned)

Network Address Translation (NAT) is the process of modifying a network address while in transit for the purpose of remapping a given address space into another

Network function virtualization is a network architecture concept that uses the technologies of IT virtualization to virtualize entire classes of network node function into building blocks that may connect, or chain together, to create communication services.

Network Operator Groups are informal forums that bring together network operators, network engineers and other technical professionals to discuss matters relating to routing, network security, peering and interconnection, and other operational Internet issues. While the forums are generally structured around sharing relevant technical information, they also provide training and other skills development opportunities to the region’s operators.

National research and education networks are specialized ISPs dedicated to support the needs of research and education communities within an economy.

National Internet Registry (NIR)
A NIR primarily allocates address space to its members or constituents which are generally LIRs organized at a national level. NIRs mostly exist in the Asia Pacific region

NetOX (Network Operators toolboX) is a set of tools for network operators to get information about their, and other networks to solve routing issues and make better informed decisions like deciding which other networks to connect to.

An international network providing public correspondence services (when used in the formal sense as defined in Section 4.17 of ITU-T Rec. E.164 (05/97))

Nibble boundary
A bit is the smallest unit of data on a binary computer. A nibble is a collection of bits on a four-bit boundary (half-byte), that is, it takes four bits to represent a single binary code decimal (BCD) or hexadecimal digit (0-9, A, B, C, D, E, F in ASCII). When IPv6 addresses are represented in the DNS, the entire binary sequence is listed as hexidecimal characters. When listed in reverse, each hexadecimal character becomes a “nibble boundary”.

Non-portable addresses must be returned if the network changes upstream provider.

Number Portability

Number Resource Organization

The National Telecommunications Information Administration is an agency of the US government’s Department of Commerce, which provides advice on telecommunications and policy issues.

These IPv6 addresses are used for a fixed-term experiment. They should only be visible on an end-to-end basis and routers should not see packets using them as source or destination addresses.

Ownership vs. use of a number
Numbering resources … are not to be considered “owned” by the assignee. Assignment of the numbering resource … confers use of the resources … (in the formal sense of Principle 5 in ITU-T Rec. E.190.)

APNIC Policy Development Process – APNIC’s resource management policies are developed by the Internet community through an open, bottom-up, multi-stakeholder process. The formal process used to develop these policies was itself decided by and is controlled by the community.

Any of several methods designed to illegally acquire sensitive or private information such as bank details, login information or personal details by fraudulently masquerading as a trustworthy entity.

Public Key Infrastructure is a combination of technologies that allow the verification and secure exchange of data through the use of encryption, digitally signed certificates, and public and private keys.

Portable addresses can be retained by the network if the network changes upstream provider.

Portable allocation
APNIC makes portable allocations to organizations. That is, it distributes address space to IRs for the purpose of subsequent distribution by them

The Public Switched Telephone Network

Quality of Service

A protocol interaction between a client and a server

Registration Data Access Protocol is an alternative to whois for accessing Internet resource registration data. It provides standardization of queries and responses; internationalization consideration to cater for languages other than English in data objects; and redirection capabilities to allow seamless referrals to other registries.

Entity which provides direct services to domain name registrants by processing name registrations

Entity which runs the DNS authoritative server for a specific domain

The client-based software that queries a DNS name server and receives the response

Reverse DNS delegation
Reverse DNS delegations allow applications to map to a domain name from an IP address. Reverse delegation is achieved by use of the pseudo-domain names in-addr.arpa (IPv4) and ip6.arpa (IPv6).

Request For Comments – the name for an Internet standards-related specification

Réseaux IP Européens Network Co-ordination Centre (RIPE NCC) is the Regional Internet Registry for Europe, the Middle East and parts of Central Asia.

Regional Internet Registries (RIRs) are established and authorized by respective regional communities and recognized by the IANA to serve and represent large geographical regions. The primary role of RIRs is to manage and distribute public Internet address space within their respective regions

Resource Origin Authorization lists the prefixes that an ASN is authorized to announce. ROAs therefore state which AS is authorized to originate certain IP prefixes. Once validated, a ROA can be used to generate route filters.

Route Origin Validation is the application of RPKI to validate the origin AS. It’s the mechanism by which route advertisements can be authenticated as originating from an expected AS.

The root level is the top level of the Domain Name System, a hierarchical tree-like structure that maps domain names to IP addresses. Top level domains include .com, .org, and country-level names such as .ca nd .au

Root Server
A DNS server pointing to all top- level domains

Route Origin Attestation (ROA)
A ROA is a digitally signed object that provides a means of verifying that an IP address block holder has authorized an Autonomous System (AS) to originate routes to one or more prefixes within the address block

Routing advertisements
Each router announces or advertises a list of routes it can process, expressed as ranges of IP addresses for which it can provide routing service. Put simply, a router tells its peers, “If you have traffic intended for IP addresses in the range between and (for example), pass me those packets”.

Resource Public Key Infrastructure (see also PKI) is a structure of digitally signed certificates which contain attestations regarding the right to use numeric Internet resources.

DNS Resource Records

Software Defined Networking technology is an approach to network management that enables the network to be programmed using software applications. This helps operators manage the entire network consistently regardless of the underlying network technology.

Second opinion request
The process that is used to seek APNIC’s approval of assignments or sub-allocation that exceed your assignment window

Service Registrar (for ENUM)
Entity which provides direct services to ENUM registrants and hosts NAPTR records that contain (service-specific) URIs

ITU-T Study Group 2

Special Interest Groups are formed with a focus on a particular subject area. SIGs provide an open public forum to discuss topics of interest to APNIC and the Internet community in the Asia Pacific region. Face-to-face SIG meetings are held at APNIC Meetings, which are held twice per year. SIGs are chaired by members of the community with relevant knowledge and expertise.

Session Initiation Protocol

Simple Mail Transfer Protocol

IP addresses are sub-allocated when they are distributed to an organization that will further assign them to their own end users

Subnet mask
The routing prefix of a designated IP address

This is a mapped address allowing IPv6 tunneling through IPv4 NATs. The address is formed using the Teredo prefix, the server’s unique IPv4 address, flags describing the type of NAT, the obfuscated client port and the client IPv4 address, which is probably a private address. It is possible to reverse the process and identify the IPv4 address of the relay server, which can then be booked up in the relevant RIR’s Whois database. You can do this on the following webpage: http://www.potaroo.net/cgi-bin/ipv6addr

Time to Live (TTL)
One of the fields in the DNS records is the TTL (Time-To-Live) field. This is the number of milliseconds corresponding to the amount of time that the Recursive Resolver should keep the answer in its memory.

Telephone Number

Top-Level Domain (TLD) Server
A Top-Level Domain (TLD) Server is known to the root servers. It is authoritative for TLDs (for example .com, .org, .net).

Test Traffic Measurement- comprehensively measures key parameters regarding the connectivity of the host’s site to other parts of the Internet.

UDP Port
The Recursive Resolver is expecting the answer packet on the same UDP port from where the query was sent.

Unique Local Addresses (ULAs)
These addresses are reserved for local use in home and enterprise environments and are not public address space. These addresses might not be unique and there is no formal address registration. Packets with these addresses in the source or destination fields are not intended to be routed on the public Internet but are intended to be routed within the enterprise or organization.

Uniform Resource Identifier – a URL is a URI

Uniform Resource Locator

United States government


A Variable Length Subnet Mask (VLSM) is a method of allocating IP addresses and other Internet number resources to subnets, according to their individual needs. This serves as an alternative to using a general, network-wide rule.

Voice over IP

Working Group

Working Party 1 of SG 2

X.509 certificate
X.509 is an ITU-T standard for digital certificates that uses PKI digital certificates in a strict hierarchical authentication structure. Sometimes referred to as an RFC3280, or more recently an RFC5280, certificate (RFC3280 defined a form of X.509 called X.509v3, and this has been updated recently by RFC5280. In all important ways this is exactly the same as an X.509 certificate, it just clarifies some forms of information and use). Extensions to the X.509 certificate format allow space for recording IP address and AS numbers (RFC 3779). The extension binds a list of IP address blocks and AS numbers to the subject of a certificate

In DNS, a contiguous portion of a domain consisting of names or delegations. Formally, a domain name belongs to exactly one (authoritative) zone

zone (or “zone”)
A segment of an ENUM domain name (used in the Berlin Liaison Statement (now RFC 3026) solely for convenience)