ULTRIX Guide to the Data Link Interface

This document, "ULTRIX Guide to the Data Link Interface" (Order Number: AA-PBKZA-TE), published by Digital Equipment Corporation in June 1990 for ULTRIX Version 4.0 or higher, is a technical manual for application programmers.

Its primary purpose is to instruct users on how to write applications that operate directly at the data link layer on ULTRIX Ethernet nodes using the Data Link Interface (DLI).

Key aspects covered in the guide include:

• DLI Functionality: Explains DLI as network software enabling communication between ULTRIX Ethernet nodes, supporting both standard Ethernet and OSI 8802-3 frame formats, datagram service, and multicast addressing.
• DLI's Scope: Crucially, it clarifies that DLI provides only low-level datagram services. Higher-level network functionalities like packet routing, guaranteed delivery, flow control, error recovery, and data segmentation must be implemented by the application itself.
• Target Audience: It is intended for experienced C programmers with superuser privileges, a thorough knowledge of system/network programming, and familiarity with ULTRIX socket calls and IEEE 8802-2 and 8802-3 protocols.

• Core Programming Concepts:

  • DLI Socket Address Data Structure (sockaddr_dl): Details how to use this structure to specify domain addresses, network devices, and parameters within Ethernet and 8802-3 substructures (e.g., target node physical addresses, protocol types, service classes, and control fields like XID, TEST, and UI commands).
  • ULTRIX System Calls: Describes the use of standard ULTRIX system calls (e.g., socket, bind, setsockopt, read, write, send, recv, sendto, recvfrom, close) with DLI-specific arguments.
  • Programming Procedures: Provides step-by-step instructions for creating, binding, setting options for, transferring data through, and deactivating DLI sockets.

• Hardware Support: Lists specific Digital Ethernet controllers supported by DLI.

• Examples: Includes detailed programming examples for DLI client and server applications using both Ethernet and 8802-3 frame formats, as well as examples for getsockopt and setsockopt calls.