LOCAL AREA NETWORK REQUIREMENTS

J. H. Saltzer


List of topics to be discussed

1.   Local network purchase decisions are based on computing application,
          not on communication application. This leads to proliferation,
          diversity, and difficult interconnection problems.

2.   Hardware interconnections are easy to accomplish, software inter-
          change is one or two orders of magnitude harder.

3.   Local network requirements come from two sources:
          - access to equipment that has economy of scale (printers, etc.)
          - information sharing (database, program library, manager).

4.   Typical organization has at least three emerging local nets, in the
          administrative DP area, in engineering, and in word processing.
          But each needs to communicate with some aspect of at least one
          other.

5.   Network protocol design has not gotten sophisticated enough to deal
          with interconnection yet.  Requires high level gateways (protocol
          translation).

6.   Protocol translation problems include: interpretation of the bits,
          order of information, name of target, flow control, packet size,
          error control procedure, and missing functions.

7.   The end-to-end argument is not well understood by protocol designers,
          leading to tremendous arguments about virtual circuits and
          datagrams without much understanding of the application
          requirements.

8.   Inter-enterprise network connection requires some additional functions,
          not yet well understood. (Authentication, preventing unauthorized
          transit, accounting for use, monitoring security, and interface
        to organizational communication policies.)

9.   What is wrong with the question, "Is Ethernet better than SNA?"