A Framework for Inter-Domain Route Aggregation (RFC2519)
Original Publication Date: 1999-Feb-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
E. Chen: AUTHOR [+1]
This document presents a framework for inter-domain route aggregation and shows an example router configuration which 'implements' this framework. This memo provides information for the Internet community
Network Working Group E. Chen Request for Comments: 2519 Cisco Category: Informational J. Stewart Juniper February 1999
A Framework for Inter-Domain Route Aggregation
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document presents a framework for inter-domain route aggregation and shows an example router configuration which ’implements’ this framework. This framework is flexible and scales well as it emphasizes the philosophy of aggregation by the source, both within routing domains as well as towards upstream providers, and it also strongly encourages the use of the ’no-export’ BGP community to balance the provider-subscriber need for more granular routing information with the Internet’s need for scalable inter-domain routing.
The need for route aggregation has long been recognized. Route aggregation is good as it reduces the size, and slows the growth, of the Internet routing table. Thus, the amount of resources (e.g., CPU and memory) required to process routing information is reduced and route calculation is sped up. Another benefit of route aggregation is that route flaps are limited in number, frequency and scope, which saves resources and makes the global Internet routing system more stable.
Since CIDR (Classless Inter-Domain Routing)  was introduced, significant progress has been made on route aggregation, particularly in the following two areas:
- Formulation and implementation of IP address allocation policies by the top registries that conform to the CIDR principles .
Chen & Stewart Informational [Page 1]
RFC 2519 Inter-Domain Route Aggregation February 1999
This policy work is the cornerstone which makes efficient route aggregation technically possible.
- Route aggregation by large (especially "Tier 1") providers. To date, the largest reductions in the size of the routing table have resulted from efficient aggregation by large providers.
However, the ability of various levels of the global routing system to implement efficient aggregation schemes varies widely. As a result, the size and growth rate of the Internet routing table, as well as the associated route computation required, remain major issues today. To support Internet growth, it is important to maximize the efficiency of aggregation at all levels in the routing system.
Because of the current size of the routing system and its dynamic nature, the first step towards this goal is to establish a clearly defined framework in which scaleable inter-domain route aggregation can be realized. The framework described in this document is based on the predominant and current experience in the Internet. It emphasizes the philosophy of aggregation by the source, both within routing domains as well as towards upstream providers. The framework also...