RFC 1520 (rfc1520) - Page 2 of 9
Exchanging Routing Information Across Provider Boundaries in the CIDR Environment
Alternative Format: Original Text Document
RFC 1520 CIDR Provider Information Exchange September 1993
This document defines a CIDR-capable provider as the provider that
can perform correct IP packet forwarding (both internally and to
other adjacent providers) when the inter-domain routing information
acquired by the provider is expressed solely in terms of IP address
prefixes (with no distinction between A/B/C class of addresses).
This document defines CIDR-capable forwarding as the ability of a
router to maintain its forwarding table and to perform correct
forwarding of IP packets without making any assumptions about the
class of IP addresses.
This document defines CIDR reachability information as reachability
information that may violate any assumptions about the class of IP
addresses. For instance, a contiguous block of class C networks
expressed as a single IP address prefix constitutes CIDR reachability
information.
2. Taxonomy of Service Providers
For the purpose of this document we partition all service providers
into the following categories, based on the type and volume of
inter-domain routing information a provider needs to acquire in order
to meet its service requirements:
- Requirements imposed on a service provider preclude it from
using Default inter-domain route(s) -- we'll refer to such a
pqrovider as a Type 1 provider.
- Requirements imposed on a service provider allow it to rely on
using one or more Default routes for inter-domain routing, but
this information must be supplemented by requiring the provider
to acquire a large percentage of total Internet routing
information -- we'll refer to such a provider as a Type 2
provider.
- Requirements imposed on a service provider allow it to rely on
using one or more Default routes for inter-domain routing;
however, to meet its service requirements the provider must
supplement Default route(s) by acquiring a small percentage of
total Internet routing information -- we'll refer to such a
provider as a Type 3 provider.
- Requirements imposed on a service provider allow it to rely
solely on using one or more Default routes for inter-domain
routing; no other inter-domain routing information need to be
acquired -- we'll refer to such a provider as a Type 4 provider.
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