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Network connectivity: A response to RFC 603 (RFC0613)

IP.com Disclosure Number: IPCOM000003686D
Original Publication Date: 1974-Jan-21
Included in the Prior Art Database: 2000-Sep-13
Document File: 1 page(s) / 2K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A.M. McKenzie: AUTHOR

Abstract

Network topology is a complicated political and economic question with obvious technical overtones. I shall not attempt, in this note, to cover all the possible arguments which might be made, but merely to respond directly to the points raised in RFC #603.

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Network Working Group Alex McKenzie

RFC # 613 BBN-NET

NIC # 21525 January 21, 1974

Network connectivity: A response to RFC #603

Network topology is a complicated political and economic question with

obvious technical overtones. I shall not attempt, in this note, to

cover all the possible arguments which might be made, but merely to

respond directly to the points raised in RFC #603.

1. The important consideration in deciding whether it is good or

bad to have a node (AMES) be four connected is not how many circuits

are affected by a node failure; rather one should consider how well

the network is still connected after a node failure. For example,

if ALL nodes in the network were four-connected I doubt that anyone

would argue that this was bad for reliability. The weaknesses are

not the three-connected and four-connected nodes but rather the

ONE-connected (Hawaii, London) and two-connected nodes. I must

agree with Burchfiel's implied argument that it is better to have

two adjacent three-connected nodes than to have a four-connected

node adjacent to a two-connected node; unfortunately the realities

of installing interfaces and common carrier services cause the

Network to expand in sub-optimal ways.

2. "Loops" are not good per se, they appear good because the act of

making loops increases the connectivity and thereby reduces the

effect of multiple failures. Adding more circuits costs ARPA money,

both capital cost for IMP interfaces and recurring cost for the

circuits. The network group at BBN has suggested to ARPA several

times that "connectivity should be increased" but it was only late

in December 1973 that we made specific suggestions for the locations

of additional circuits. These recommendations were not based on

building loops (although they may have that effect) but were based

on breaking the long chains of IMPs which have occurred as the

Network has grown. ARPA and NAC are now presumably in the process

of evaluating our suggestions, and perhaps formulating other

possibilities.

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