Braden 32 yrs Oct 021 The First 31 Years of the Internet -- An Insider’s View. Bob Braden USC...
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Transcript of Braden 32 yrs Oct 021 The First 31 Years of the Internet -- An Insider’s View. Bob Braden USC...
Braden 32 yrs Oct 02 1
The First 31 Years of the Internet -- An Insider’s View.
Bob Braden
USC Information Sciences Institute Oct 4, 2002
2
Braden 32 yrs Oct 02 2
OutlineA. Historical Overview
o 1961 - 1968: Pre-historyo 1969 - 1973: ARPAnet research periodo 1974 - 1983: Internet Research Periodo 1984 - 1990: Academic Internet Periodo 1990 - ??: Commercial (and Popular) Internet
B. The Internet Architectureo Protocolso Principles
C. Conclusions and Challenges
Braden 32 yrs Oct 02 3
1961 - 1968: Pre-History• Computers:
– Mainframes (mini-computers beginning).– (Discrete) transistors had just replaced tubes.– Data unit was a word of 8, 9, 12, 15, 18, 24, 32, 36, 48, 60 ...
bits. Uniform 8-bit bytes were introduced in 1965.
• Computer communication?– Why? What would my IBM mainframe SAY to your Univac
mainframe???– Too expensive to lease telephone lines.
• The context -- Flower children, JFK & LBJ, the Vietnam War ...
Braden 32 yrs Oct 02 4
1961 - 1968: Pre-History of Computer Communication
MIT:o J. C. R. Licklider: Memos on "Galactic Network", 1962o L. Roberts: Plan to build a computer network, 1967
Rand Corp.o Paul Baran invented packet switching as a concept
NPL (UK):
o Donald Davies & Roger Scantlebury wrote paper on a packet-switching network, 1967
IRIA (France):o Louis Pouzin – Cyclades network
Braden 32 yrs Oct 02 5
1969 - 1973: ARPAnet Research Period
ARPA: Advanced Research Projects Agency A DoD agency formed post-Sputnik to fund long-range
research of ultimate importance to the military.
The ARPAnet: ARPA selected Bolt, Beranek, and Newman (BBN) to
design, build, and operate a prototype packet-switching network, the ARPAnet.
Host Computers: ARPAnet software was developed by university researchers,
funded by ARPA.
Braden 32 yrs Oct 02 6
Packet Switchingo Break data into small packets, each of which carries its
own address. Packets of different users are interlaced (“multiplexed”) on e.g. a leased telephone line.
Address Data
Packet
o Build a network of "packet switches"o Each switch receives, stores, and forwards packets.
o Packets are forwarded hop-by-hop, from any source host computer to any destination host computer.
Braden 32 yrs Oct 02 7
Packet-Switching (cont)o ARPANET packet switches ("IMPs")
o Minicomputers
o High-speed leased lines (56Kbps)
o Distributed adaptive routing algorithm
o The ARPAnet grew from 10 hosts to ~ 200 hosts.
o Mixture of research and DoD production nodes
o Included most major research universities & labs
Braden 32 yrs Oct 02 8
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Braden 32 yrs Oct 02 11
ARPAnet Protocols
IMP-IMP Protocol: Reliably deliver a message (packet) of up to 8000 bits to a
specified destination host.
Bit orientation to handle different word lengths of hosts.
Using this IMP-IMP service, create a:
Host-Host Communication Service: Network Control Protocol or NCP.
Using this host-host service, can create:
User Application Services File transfer, remote terminal login, and email
Braden 32 yrs Oct 02 12
ARPAnet Protocols
Network Control Protocol (NCP) -- why? IMPS only connect computers, but it is really programs that
talk to each other.
NCP can establish multiple logical data streams (“virtual circuits” or “connections”) between a pair of hosts.
NCP opens and closes these connections.
NCP provides flow control on each connection, to prevent overruning receiver application.
NCP establishes an appropriate byte size on each connection.
Braden 32 yrs Oct 02 13
ARPAnet Protocol Stack
NETRJS
Remote Job
Entry
Telnet
VirtualTTY
Terminal
FTP
FileTransfer
SMTP
Host-Host Protocol(“NCP”)
IMP-host Protocol
UserProtocols
Braden 32 yrs Oct 02 14
Legacy of ARPAnet Periodo Demonstrated packet switching technologyo Many new ideas...
-- Protocol Layering
-- Packet voice-- Email-- Link state routing protocols-- Connections (“virtual circuits”)
o Reliable, flow-controlled; requires state setup.-- Datagrams [Pouzin, <1974]
o Single packet sent with minimum overheado Unreliable
-- Presentation Layer [Postel & White @ SRI]-- RPC (Remote Procedure Call)
Braden 32 yrs Oct 02 15
Internet Research Period: 1974-1983
o By 1974, other packet-switching technologies had been developed or were planned:o Local Area Networks (LANs): Ethernet
o Packet Radio network (packet switch+radio: now called “ad hoc wireless”)
o Packet-satellite network (SATNET)
o DoD's problem: how to hook them together??
Solution: a network of networks -- an INTERNETWORK.
Braden 32 yrs Oct 02 16
Internet: A Network of (Sub-) Networks
R
R
Host
Hosts
Host
subnet
subnet
subnet
packet
INTERNET
Router [gateway]
RRR
Braden 32 yrs Oct 02 17
Braden 32 yrs Oct 02 18
Internet Research Period: 1974-1983o Seminal paper: "A Protocol for Packet Network
Interconnection", Vinton G. Cerf and Robert E. Kahn, IEEE Trans Comm., com-22, no. 5, May 1974.
o ARPA funded Internet R&D Program 1976 – 198xo Developed Internet protocol suite ("TCP/IP")
o Application layer: TCP/IP versions of ARPAnet application protocols Telnet, FTP, SMTP
o ARPAnet cutover to new Internet protocols TCP/IP:January 1, 1983 (Orchestrated by Jon Postel, ISI)
Braden 32 yrs Oct 02 19
Foundation Internet Technical Documents
IP RFC 791
ICMP RFC 792
TCP RFC 793
Telnet RFC 764
FTP RFC 765
SMTP RFC 788
Name Server IEN 116
Assigned Numbers RFC 790
Although many contributed, these all bear Jon Postel’s name.
Braden 32 yrs Oct 02 20
Braden 32 yrs Oct 02 21
1984 - 1990: Academic Internet
O NSF began to fund Internet growth through NSFnet and CSNET, bringing the Internet to US higher education.
o Higher line speeds: 56 Kbps -> T1 (1.5Mbps) lines
o Exponential growth => repeated growth crises
Braden 32 yrs Oct 02 22
Braden 32 yrs Oct 02 23
Important New Protocol Technology
• Domain Name SystemMap host names => IP addressese.g., "slime.usc.edu" -> 32-bit IP addressLater became the basis for URLs and the Web.
• Two-level routing hierarchy: divide into domains– IGPs (Interior Gateway Protocols) route within domains
[think area codes], plus:– BGP (Border Gateway Protocol) to route among domains
• Solution to congestion collapse: Van Jacobson
• Network management: SNMP
Braden 32 yrs Oct 02 24
1984-1990: Who Ran the Internet?
O US government agencies: NSF, ARPA, DOE, NASA, had an important influence.
(DADDY WAS STILL PAYING...)
o Technical steering committee: a junta of Internet researchers, the Internet Activities Board (IAB).-- Set up by ARPA (Vint Cerf) ~1980 to advise on research
program-- Until 1993, approved all Internet protocol standards.-- Created a set of Task Forces led by IAB members (1983)-- ONE of these task forces grew into the Internet Engineering Task Force
(IETF), which today sets the Internet protocol standards.3 IETF meetings per year, 2500 people, 100 working groups.
Braden 32 yrs Oct 02 25
Who Runs the Internet Today?
At no time has the entire Internet been run by one organization, nor is this likely to ever happen.
– The Internet is not brought to you by the phone company or by a government or by the UN or by Microsoft.
– There is no precedent for a global infrastructure built of thousands of separately controlled/administered pieces.
– It was designed to work that way, more or less; but it’s still a minor miracle.
Braden 32 yrs Oct 02 26
1990 - Now: Commercial Internet
Government funding replaced by commercial enterprises -- ISPs
HTTP and the WWW were invented (~1993) and rapidly became the dominant application.
PCs became the dominant hosts
Exponential growth accelerated!
Huge increase in speed and capacity.
The Internet became part of society.
Braden 32 yrs Oct 02 27
1990 - Now: Stresses on the Protocols
o Growth crisis: 32 bit IP addresses ran low => developed IPv6 with 128-bit host addresses
o Routing problems:scaling, stability
o New protocols and algorithms were developed-- Mobile IP-- Security-- QoS-- Traffic Engineering
Braden 32 yrs Oct 02 28
The Internet Architecture:Outline
Internet Protocol Stack
"Architecture" -- Fundamental design principles -- Guide specific engineering decisions, e.g., protocol design
-- Want them simple and general => elegant
Braden 32 yrs Oct 02 29
Internet Protocol Stack
> Application layer -- same as on ARPAnet
> Internetwork Layer: IP (Internet Protocol)-- Controls end-to-end forwarding of packets by routers.-- Uses globally-unique IP addresses
-- “Best effort” service: packets may be lost, duplicated, reordered.
> Transport Layer-- Enhances host-host service; e.g., TCP provides reliable full-duplex byte streams.
> Link layer: particular subnet protocol.
Braden 32 yrs Oct 02 30
Internet ("TCP/IP") Protocol Stack
UDPTCP ...
ApplicationLayer
Transport Layer
[Inter]network Layer
Link Layer
IPEthernet ATM PPP SONET ... BBN1822
Telnet FTP SMTP … HTTP POP3 …
IP protocol: > plays a unique role as the universal Internet
protocol -- “common bearer service”. > Very simple, so routers can be very fast > Minimal service assumptions, so Internet can adapt to
new applications and new technologies.
Braden 32 yrs Oct 02 31
Internet Architecture: Deep Assumptions
o Packet switching-- Unit of data is a packet
-- Packets are statistically muxedBecause computers don’t hum to each other, they CHATTER!
I.E., computer communication is fundamentally bursty.
o Strict protocol layering-- Successive layers of functional abstraction-- Headers added/removed in strict LOFO order --
“Stack”model.
o Goal is universal interconnectivity
Braden 32 yrs Oct 02 32
Architectural Requirements
o Generality-- Support ANY set of diverse applications,-- Either datagrams (think video) or VCs (think web).
o Heterogeneity-- Interconnect ANY set of network technologies
o Robustness-- More important than efficiency
o Extensibility-- More important than efficiency
o Scalability(A later discovery. How many ARPAnets could the world support? A few hundred, maybe… ?)
Braden 32 yrs Oct 02 33
The End-to-End Principle
Foundation of the Internet architecture:Dumb network, smart end systems.
(Exact opposite of telephone network!)
o Dumb networks: only least common service-- Datagram service: no connection state in routers
-- Best effort: all packets treated equally.
o Smart hosts:-- Maintain state to enhance service for applications.-- “Fate-sharing”-- If a host crashes and loses comm state,
applications that are communicating share this fate.
Braden 32 yrs Oct 02 34
Fundamental Differences…
o Philosphical gap between Computer Scientists and telecommunication engineers:> Engineers: "The Internet is under-engineered --
it is not optimal or completely predictable orcontrollable.(And we like complexity.)"
> Internet Researchers: "Optimal is NOT the point.The future adaptability of the Internet to new
technologiesand to new services require that we NOT over-engineer
the Internet!Uncertainty and suboptimality: live with it!(And we like generality and simplicity.)"
Braden 32 yrs Oct 02 35
Conclusions
The Internet survived and prospered ... o It survived a series of real (and imaginary) threats
over the years.-- X.25-- FAX (opposing email)-- Many competitors from industry & government --
e.g., XNS, DECNET, BITNET, MFENET, …-- Unimaginative government bureacrats-- ISO Open Systems Interconnect (OSI)
CLNP, TP4, FTAM, …-- ATM
o Exponential growth is a mighty engine, and vendors and ISPs have been running to keep up.
Braden 32 yrs Oct 02 36
Why did the Internet Succeed?
1. Leadership from a handful of visionariesLarry Roberts (ARPA)Vint Cerf (ARPA)Bob Kahn (ARPA)Steve Wolff (NSF)
2. ARPA-funded BSD Unix development used TCP/IP-- Publicly funded OS --> many vendor products-- A generation of students used it and then graduated
3. Triumph of the startups -- Small companies were agile and creative
Braden 32 yrs Oct 02 37
Why ... (cont'd)4. Military concern for "robustness" led to the easily-
deployed IP protocol.
o “Plug-and-play” -- populist model fueled growth
5. Silicon- and Fiber-revolutions were perfectly timed.
6. The Web popularized the Internet.
7. Universal interconnection really is a powerful vision.
8. The Internet architecture provided the generality and extensibility to survive the past and the present.
Braden 32 yrs Oct 02 38
The Future… is fuzzy.
o Economic, business, and political forces are now central The Internet ~ railroads in 1882
Increasingly, large companies rule
o Will ISP mergers lead to monopoly?
o Will the telephone companies rule after all?
o Will Email survive spam?
o Will spam, viruses, hostile attacks fatally threaten the grand vision of universal interconnection?
o Will the Internet fragment into disconnected pieces?Incompatible pieces?
o Will censorship take over the Internet?