Networking Implementation Notes
4.4BSD Edition

Samuel J. Leffler, William N. Joy, Robert S. Fabry, and Michael J. Karels

Computer Systems Research Group
Computer Science Division
Department of Electrical Engineering and Computer Science
University of California, Berkeley
Berkeley, CA 94720

ABSTRACT

This report describes the internal structure of the networking facilities developed for the 4.4BSD version of the UNIX* operating system for the VAX**. These facilities are based on several central abstractions which structure the external (user) view of network communication as well as the internal (system) implementation.

      The report documents the internal structure of the networking system. The ``Berkeley Software Architecture Manual, 4.4BSD Edition'' (PSD:5) provides a description of the user interface to the networking facilities.

Revised June 10, 1993

TABLE OF CONTENTS

1.  Introduction

2.  Overview

3.  Goals

4.  Internal address representation

5.  Memory management

6.  Internal layering
6.1.    Socket layer
6.1.1.    Socket state
6.1.2.    Socket data queues
6.1.3.    Socket connection queuing
6.2.    Protocol layer(s)
6.3.    Network-interface layer
6.3.1.    UNIBUS interfaces

7.  Socket/protocol interface

8.  Protocol/protocol interface
8.1.     pr_output
8.2.     pr_input
8.3.     pr_ctlinput
8.4.     pr_ctloutput

9.  Protocol/network-interface interface
9.1.     Packet transmission
9.2.     Packet reception

10. Gateways and routing issues
10.1.     Routing tables
10.2.     Routing table interface
10.3.     User level routing policies

11. Raw sockets
11.1.     Control blocks
11.2.     Input processing
11.3.     Output processing

12. Buffering and congestion control
12.1.     Memory management
12.2.     Protocol buffering policies
12.3.     Queue limiting
12.4.     Packet forwarding

13. Out of band data

14. Trailer protocols

Acknowledgements

References

Table of Contents

• 1. Introduction
• 2. Overview
• 3. Goals
• 4. Internal address representation
• 5. Memory management
• 6. Internal layering
  • 6.1. Socket layer
    • 6.1.1. Socket state
    • 6.1.2. Socket data queues
    • 6.1.3. Socket connection queuing
  • 6.2. Protocol layer(s)
  • 6.3. Network-interface layer
    • 6.3.1. UNIBUS interfaces
• 7. Socket/protocol interface
• 8. Protocol/protocol interface
  • 8.1. pr_output
  • 8.2. pr_input
  • 8.3. pr_ctlinput
  • 8.4. pr_ctloutput
• 9. Protocol/network-interface interface
  • 9.1. Packet transmission
  • 9.2. Packet reception
• 10. Gateways and routing issues
  • 10.1. Routing tables
  • 10.2. Routing table interface
  • 10.3. User level routing policies
• 11. Raw sockets
  • 11.1. Control blocks
  • 11.2. Input processing
  • 11.3. Output processing
• 12. Buffering and congestion control
  • 12.1. Memory management
  • 12.2. Protocol buffering policies
  • 12.3. Queue limiting
  • 12.4. Packet forwarding
• 13. Out of band data
• 14. Trailer protocols
• Footnotes