Gateways, architectures, and heffalumps

Abstract

The growth of autonomous intercomputer networks has led to a desire on the part of their respective proprietors to "gateway" from one to the other. Unfortunately, however, the implications and shortcomings of gateways which must translate or map between differing protocol suites are not widely understood. Some protocol sets have such severe functionality mismatches that proper T/MG's cannot be generated for them; all attempts to mesh heterogeneous suites are subject to numerous problems, including the introduction of "singularity points" on logical connections which would otherwise be able to enjoy the advantages of communications subnetwork alternate routing, loss of functionality, difficulty of Flow Control resolution, higher cost than non-translating/mapping Gateways, and the necessity of re-creating T/MG's when a given suite changes. The preferability of a protocol-compatible internet is also touched upon, as is the psychology of those soi-disant architects who posit T/MG's.i

Multiprotocol Interoperability In IPng

“…Despite their known limitations [8], translation or conversion gateways are another technique for handling multiple protocols [11,12]. These gateways perform direct conversion of network traffic from one protocol to another.…”

Perspective on the ARPANET reference model

“…That is, it is an explicit assumption of the ARM that the catenet will be "protocol compatible", in the sense that no attempt will be made to translate or map between dissimilar Host-Host protocols (e.g., TCP and AH-HP) or dissimilar Process-level protocols (e.g., ARPANET FTP and EDN FTP) at the Gateways. The justifications for this position are somewhat complex; the interested reader is encouraged to see Reference [10]. For present purposes, however, it should suffice to note that the case against translating/mapping Gateways is a sound one, and that, as with the ARMS protocols, the great practical virtue of what are sometimes called "IP Gateways" is that they are in place and running.…”