PCH

Routing and Internet Analysis Glossary of Terms

The goal here is to have a definitive glossary of routing and Internet terms which we can all use in communicating about the statistics and analysis we're all doing. With luck, if we do a good job, and publicize our work, we can gain broader adoption of these as standard definitions.

Please "sign off" on each entry with your initials if you agree with it, and remove everyone else's initials from an entry if you make any substantive change.

A

Announcing
Announcement
Anycast

The practice of utilizing the same IP address in multiple distinct places on the Internet, such that the Internet routing protocols will send traffic to the nearest of multiple instances, rather than across the shortest of multiple paths to the same location.

AS (Autonomous System)
AS-Path
ASN (Autonomous System Number)

B

C

Country Code

The ISO 3166-1-Alpha-2 two-letter code identifying a nation, officially listed here or more briefly here. The ISO 3166 list is supplemented by some informal, and soon-to-be-formal values. EU is used for Europe, AP (which is allocated to the African Fisheries consortium) is used for Asia-Pacific, and the ZZ code is increasingly used for international or trans-national entities. GGM BW

Covering Prefix

A covering prefix is one which entirely encloses another. For instance, an organization might have been allocated 10.0.0.0/8, and actually only be using 10.0.1.0/24 and 10.0.8.0/24... rather than announcing two /24 prefixes, or the whole /8, they might choose to announce a covering prefix of 10.0.0.0/20, which is large enough to enclose both of the prefixes which are actually in use, but small enough to allow other prefixes to be announced from other locations. BW

D

Domain Name
Domain Name Registry

E

Enclosed

A prefix which is "enclosed" or "covered" by another is more specific than, and has a longer mask-length than, the enclosing prefix, and falls entirely within it. BW

Enclosing

A prefix which "encloses" or "covers" another is less specific than, and has a shorter mask-length than, the enclosed prefix, which falls entirely within it. BW

F

FIB (Forwarding Information Base)

The OSI Layer-2 forwarding table in a switch or router, which maps the correspondence between MAC addresses (of end stations or next-hop routers) and outbound interfaces. BW

Flat-Rate

G

H

I

in-addr (Inverse Address)

The DNS mapping of IP addresses in "inverse address" format to domain names. For instance, the IP address 10.0.0.1 is rendered as 1.0.0.10.in-addr.arpa in in-addr format, and would appear on the left-hand side of a "PTR" record in the DNS, associated with a hostname on the right-hand side. BW

IPv4
IPv6

J

K

L

M

N

Non-Portable

(see also Portable, Provider-Aggregatable, and Provider-Independent)

95th Percentile

O

Originating AS

P

Peering

Peering is the exchange between the operators of two or more Autonomous Systems of their customer routes. Peering is typically cost-neutral, and is one of the two forms of interconnection between Internet networks; the other being Transit.

Prefix
Portable

(see also Non-Portable, Provider-Aggregatable, and Provider-Independent)

Provider-Aggregatable
Provider-Independent

Q

R

RIB (Routing Information Base)
RIR (Regional Internet Registry)
Registrar
Registry
Route

S

Subnet

subnet : A LAN that is part of a larger logical network.

T

Transit

Transit consists of two bundled services: the advertisement by an Internet Service Provider of routes to a customer's Internet Protocol addresses to the other ISPs who constitute the rest of the Internet, thereby soliciting inbound traffic from them on behalf of the customer; and the advertisement of a default route, or a full set of routes to all of the destinations on the Internet, to the ISP's customer, thereby soliciting outbound traffic from them. Transit is typically a paid or compensated service. Transit is one of the two forms of interconnection between Internet networks, the other being Peering.

Transiting
Transport

U

V

W

Whois

Whois refers, variously, to the very simple ASCII protocol for querying whois databases and receiving their answers, or to the aggregate content of those databases. Contact information for the holders of Internet resources is typically published via whois protocol and databases by Regional Internet Registries and domain name registries. BW

X

Y

Z