LASTport/Disk

This document, the LASTport/Disk Architecture Specification (EK-LASTD-AS-001, March 1992), defines the architecture and message protocol for accessing named collections of logical blocks, called virtual disks, within a heterogeneous local area network (LAN) client-server model.

Its primary purpose is to provide the detailed LASTport/Disk message protocol necessary for interoperable implementations. The architecture enables client systems to discover, connect to, and manage virtual disk services offered by servers as if they were locally attached devices.

Key elements described in the specification include:

• Disk Service Management: Covers name spaces, load balancing across duplicate media, disk cache policies, and semantics for dynamic virtual disk creation and connection (including data preservation and clear-on-disconnect options).
• Protocol Messages: Defines message types for resource discovery (Solicit), session establishment and termination (Connect/Disconnect), and data/parameter exchange.
• Message Formats and Processing: Specifies the structure of messages, detailing fields for version control, name spaces, service names, server names, and extensible parameter lists. It also outlines rules for message processing, including access modes, service passwords, and policies for server responses to prevent network flooding.
• Revision Control: Explains the protocol's versioning system to ensure backward compatibility and managed evolution.

The document is intended for implementers and programmers porting the architecture, assuming familiarity with LAN concepts and transport protocols.