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


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


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 ...


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


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.


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.


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


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


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.


ARPAnet Protocol Stack

NETRJS

Remote Job

Entry

Telnet

VirtualTTY

Terminal

FTP

FileTransfer

SMTP

Email

Host-Host Protocol(“NCP”)

IMP-host Protocol

UserProtocols


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)


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.


Internet: A Network of (Sub-) Networks

R

R

Host

Hosts

Host

subnet

subnet

subnet

packet

INTERNET

Router [gateway]

RRR


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)


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.


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


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


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.


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.


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.


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


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


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.


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.


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


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… ?)


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.


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.)"


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.


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


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.


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?

braden 32 yrs oct 021 the first 31 years of the internet -- an insider’s view. bob braden usc...

Documents

network of packet

hosthost service

emailbob braden

challengesbob braden

host computers

computer network

arpanet research period1974

destination host computer