Observations on the use of Components of the Class A Address Space within the Internet
RFC 2036
|
Document |
Type |
|
RFC - Historic
(October 1996; No errata)
|
|
Author |
|
Geoff Huston
|
|
Last updated |
|
2013-03-02
|
|
Stream |
|
Internent Engineering Task Force (IETF)
|
|
Formats |
|
plain text
html
pdf
htmlized (tools)
htmlized
bibtex
|
Stream |
WG state
|
|
(None)
|
|
Document shepherd |
|
No shepherd assigned
|
IESG |
IESG state |
|
RFC 2036 (Historic)
|
|
Consensus Boilerplate |
|
Unknown
|
|
Telechat date |
|
|
|
Responsible AD |
|
(None)
|
|
Send notices to |
|
(None)
|
Network Working Group G. Huston
Request for Comments: 2036 Telstra Internet
Category: Informational October 1996
Observations on the use of Components of the Class A
Address Space within the Internet
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This document is a commentary on the recommendation that IANA
commence allocation of the presently unallocated components of the
Class A address space to registries, for deployment within the
Internet as class-less address blocks.
The document examines the implications for service providers and end
clients within this environment. The document notes the major
conclusion that widespread adoption of class-less routing protocols
is required, within a relatively rapid timeframe for this
recommendation to be effective.
Introduction
The Address Lifetime Expectancy (ALE) Working Group of the IETF has
recorded the allocation of Internet addresses from the unallocated
address pool. ALE has noted that the existing practice of drawing
addresses from the Class C space (192/3 address prefix) will result
in near to medium term exhaustion of this section of the unallocated
address pool. The largest remaining pool is in the Class A space,
where some 25% of Internet addresses (the upper half of the Class A
space) remain, to date, unallocated.
This document is a commentary on the potential recommendation that
the Internet Assigned Numbers Authority (IANA), through delegated
registries, commence allocation of the presently unallocated
components of the Class A address space to registries, for
deployment within the Internet through the mechanism of allocation of
class-less address prefixes.
The deployment of class-less address prefixes from the Class A space
within the Internet will require some changes to the routing
structure within Internet component network domains. The motivation
Huston Informational [Page 1]
RFC 2036 Components of the Class A Address Space October 1996
for, and nature of, such changes as they effect network domains and
network service providers are outlined in this document.
Current Practice with Address Allocations
To date the allocation of class-less network prefixed address blocks
has followed a conservative practice of using address allocations
which are compatible superblocks of Class C addresses, while the
allocation of addresses within the space of Class A and Class B
networks has continued to be aligned with the class-based prefix
structure.
Within this address allocation environment for non-transit network
domains there is accordingly the option to continue to use address
deployment strategies which involve fixed subnet address structures
within contiguous areas, and use Class-full interior routing
protocols. In the situation where variable length subnet masks or
disconnected subnets are deployed within the network domain's routing
structure, interior routing protocols which use subnet-based routing
of Class-full networks can still be successfully deployed and the end
network has the option of using an explicit or implicit sink subnet
default route. Where such non-transit network domains are connected
to the Internet infrastructure the boundary exchange between the
non-transit network and the network service provider (this term is
used as a synonym for a transit network domain, which provides a
traffic transit service to other non-transit and peer transit network
domains) is either a class-full advertisement of routes, or an
aggregated address advertisement where the aggregate is a superblock
of the deployed component class-full networks. At the boundary points
of the non-transit network it is a requirement that the non-transit
network's subnet default route (if used explicitly) not be directed
to the network service provider's domain, to avoid a routing loop at
the domain boundary point.
For network service providers the interior routing protocol can use
either aggregated routing or explicit class-full routing within this
environment. At the network service provider's boundary peering
points the strongly recommended practice is to advertise aggregated
routes to transit peers, which in turn may be further aggregated
across the Internet, within the parameters of permissible policies.
Huston Informational [Page 2]
RFC 2036 Components of the Class A Address Space October 1996
Implications of Address Allocation from the Class A space
Network Service Providers Must Use Class-less Routing
Show full document text