BSD's Role in the Early

Internet

Mike Karels

October 25, 2023

What is BSD?

• BSD: Berkeley Software Distribution
• 2.*BSD: PDP-11 UNIX add-ons (csh, vi), then full systems
• 3BSD, 4.*BSD: VAX UNIX systems with many additions including virtual memory, then networking
• Developed and supported by Computer Systems Research Group (CSRG) at the University of California, Berkeley
• "Berkeley UNIX"

4.2BSD

• 4.2BSD built on 4.1BSD and added:
• First widely-available TCP/IP implementation
• Based on implementation done under contract at BBN
• Integrated and enhanced by Berkeley
• Socket interface to networking
• User-level networking support, e.g. gethostbyname()
• Networking utilities: rlogin/rsh/rcp/telnet/ftp
• Ran on VAX; required UNIX source code license

September 1983

Mike and BSD

• Worked on 2.9BSD for PDP-11 as graduate student in Molecular Biology
• Started as Principal Programmer at CSRG in July, 1983; 4.2BSD released in September
• Replaced Bill Joy, Sam Leffler
• Suddenly was maintainer/developer of most common TCP/IP implementation

BSD and Internet development

• 4.2BSD test release (4.1c) had limited distribution
• 4.2BSD was widely used in Universities, research organizations
• ARPANET, later also MILNET
• Local Ethernet networks
• 4.2BSD was basis for commercial systems (Sun, DEC, many others)
• TCP/IP implementation was basic
• Bug fixes
• New/additional algorithms needed

New Algorithms

• My first algorithm addition: Nagel algorithm
• Goal: collect periodic input (e.g. keystrokes) during round-trip time
• Helpful with slow links (ARPANET was 56 Kbps, John Nagel had slower)
• Implementation: in existing 3-line test, remove middle line

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Q

Nagel Algorithm

Congestion collapse of ARPANET

• ARPANET used 56 Kbps links, packet switching, small computers as IMPs (nodes)
• With increasing use, links and buffers became saturated
• Round trip times highly variable, up to 45 seconds or more
• Typical connections retransmitted frequently, overran the net
• Improvements in round-trip timing, basic retransmission code
• Slow start opened the window gradually, avoiding "blast and lose"
• Congestion avoidance helped to avoid opening window too much
• Published in SIGCOMM 88
• Later: Fast Retransmit, which recovers from lost packets more quickly

Q

New algorithms by Van Jacobson

Other BSD influences on Internet

• Domain Name System (DNS)
• BSD's BIND (Berkeley Internet Name Domain suite)
• Second major DNS implementation, most widely used for some time
• Integrated into base system (named server and C library resolver)
• Internet standards: IETF Host Requirements RFCs
• POSIX API standards: socket interface

BSD and Open Source

• Previous features were in 4.3BSD (1986), 4.3-Tahoe (1988)
• Required UNIX source license
• CSRG received requests for partial releases of networking code
• Net/1 (1989): vertical slice of networking code through system
• Clients, servers, library code, TCP/IP, network drivers
• BSD license, new copyright notice
• Net/2 (1991): nearly complete system; a few kernel files missing
• [small lawsuit intervenes]
• 4.4BSD-Lite(1994), 4.4BSD-Lite2 (1995): final releases from Berkeley

BSD to the present

• Many BSD derivatives continue:
• FreeBSD
• NetBSD
• OpenBSD
• Dragonfly BSD
• Darwin (Apple, in MacOS)

BSDi

• Founded by BSD developers (including me)
• Sold commercial version of BSD for x86 and others (initially BSD/386, then BSD/OS)
• Started with Net/2; filled in missing pieces, added drivers
• Advertised availability; "1-800-ITS-UNIX" phone number
• Lawsuit filed by USL (AT&T) against BSDi, later against UC Berkeley as well
• Lawsuit settled; BSD/386 1.0 is released
• Used in firewalls, routers, web sites

Berkeley Software Design, Inc.

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Questions?

Mike and BSD

• 2BSD (UC Berkeley Molecular Biology)
• Sixth Edition, 2.8BSD, 2.9BSD
• 4BSD, Net/* (UC Berkeley CSRG)
• 4.2BSD, 4.3BSD, 4.3BSD-Tahoe, 4.3BSD-Reno
• Net/1, Net/2
• BSD/386 aka BSD/OS (Berkeley Software Design, BSDi)
• Sidewinder firewall (Secure Computing, McAfee, Intel Security, Intel, Forcepoint)
• FreeBSD