Internet exterior routing protocol development: problems, issues, and misconceptions

Abstract

G l o b a l routing in the Internet continues to have scalability problems which underscore weaknesses in the design and implementation of the various TCP/IP exterior routing protocols. T h i s article explores the historical design a n d development relative to the decision-making process i n the specification and implementation of Internet external routing protocols, in particular discussing problems associated with provider-based address space allocation.his interim solution in no way constrains the selection of the next generation addressing and routing technology. '' -RFC 1367, October 1992 (1J In 1977 published a detailed discussion of hierarchical routing in large internetworks. In their landmark paper, "Hierarchical Routing for Large Networks," they discussed the problems associated with scalability and the length of the route forwarding table in large packet-switched networks. They concluded that hierarchical routing was a requirement €or very large lidworks. Routing tables require less information for destination networks far from the source relative to hop count or another nearness metric. Detailed routing information, one entry per destination, is required for near nodes. The construction of logical sets in the routing hierarchy is not related to geographical distances. Instead, administrative clustering of routing domains becomes the technical basis for designing large scalable internetworks.Problems and issues with scalability in packet-switched networks were well documented prior to 1982, the publication date of Rosen's Internet Request for Comment, "Exterior Gateway Protocol" (EGP) [3]. In this publication, Rosen discussed hierarchical routing and the limitations of EGP clearly and concisely, cautioning the reader that EGP did not "constitute a network routing algorithm." Unable to predict the explosive growth of the Internet, the National Science Foundation (NSF), Internet Engineering Task Force (IEW), Internet Activities Board (IAB), Internet Protocol (IP) service providers, and router vendors embarked on a development track redesigning EGP in favor of the Border Gateway Protocol (BGP). Policy-based routing dominated requirements for global scalability in large packet switched networks.Further inspection confirms that the early IP exterior routing protocol development track by Internet developers and router vendors was dominated by concerns about policy-based routing [4-61. It was not until 1992 that the engineering focus in the IBI'F apparently began to shift from policy-based routing to global network scalability [7-91.A short synopsis of IP exterior routing protocol development is presented in the next section, highlighting EGP, BGP, and policy-based routing in the Internet. The section after that introduces the paradigm shift from a concentration on policy-based routing to an emphasis on global IP scalability. The focus then returns to the BGP-34BGP-4 paradigm shift associated with classless inteidoiiiaiii routing (CIDR). Impoitant quotations in the Internet Requests for Comments (RFCs) ar...

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