Internet History

1
Internet History
1961-1972 Early packet-switching principles

• 1961 Kleinrock - queueing theory shows
  effectiveness of packet-switching
• 1964 Baran - packet-switching in military nets
• 1967 ARPAnet conceived by Advanced Reearch
  Projects Agency
• 1969 first ARPAnet node operational

• 1972
• ARPAnet demonstrated publicly
• NCP (Network Control Protocol) first host-host
  protocol
• first e-mail program
• ARPAnet has 15 nodes

2
Internet History
1972-1980 Internetworking, new and proprietary
nets

• 1970 ALOHAnet satellite network in Hawaii
• 1973 Metcalfes PhD thesis proposes Ethernet
• 1974 Cerf and Kahn - architecture for
  interconnecting networks
• late70s proprietary architectures DECnet, SNA,
  XNA
• late 70s switching fixed length packets (ATM
  precursor)
• 1979 ARPAnet has 200 nodes

• Cerf and Kahns internetworking principles
• minimalism, autonomy - no internal changes
  required to interconnect networks
• best effort service model
• stateless routers
• decentralized control
• define todays Internet architecture

3
Internet History
1980-1990 new protocols, a proliferation of
networks

• 1983 deployment of TCP/IP
• 1982 smtp e-mail protocol defined
• 1983 DNS defined for name-to-IP-address
  translation
• 1985 ftp protocol defined
• 1988 TCP congestion control

• new national networks Csnet, BITnet, NSFnet,
  Minitel
• 100,000 hosts connected to confederation of
  networks

4
Internet History
1990s commercialization, the WWW

• Early 1990s ARPAnet decomissioned
• 1991 NSF lifts restrictions on commercial use of
  NSFnet (decommissioned, 1995)
• early 1990s WWW
• hypertext Bush 1945, Nelson 1960s
• HTML, http Berners-Lee
• 1994 Mosaic, later Netscape
• late 1990s commercialization of the WWW

• Late 1990s
• est. 50 million computers on Internet
• est. 100 million users
• backbone links runnning at 1 Gbps

5
ATM Asynchronous Transfer Mode nets

• Internet
• todays de facto standard for global data
  networking
• 1980s
• telcos develop ATM competing network standard
  for carrying high-speed voice/data
• standards bodies
• ATM Forum
• ITU

• ATM principles
• small (48 byte payload, 5 byte header) fixed
  length cells (like packets)
• fast switching
• small size good for voice
• virtual-circuit network switches maintain state
  for each call
• well-defined interface between network and
  user (think of telephone company)

6
ATM layers

• ATM Adaptation Layer (AAL) interface to upper
  layers
• end-system
• segmentation/reassembly
• ATM Layer cell switching
• Physical

7
Summary on Introduction

• Covered a ton of material!
• Internet overview
• whats a protocol?
• network edge, core, access network
• performance loss, delay
• layering and service models
• backbones, NAPs, ISPs
• history
• ATM network

• You now hopefully have
• context, overview, feel of networking
• more depth, detail later in course

8
Application Layer

• Goals
• conceptual implementation aspects of network
  application protocols
• client server paradigm
• service models
• learn about protocols by examining popular
  application-level protocols

• More goals
• specific protocols
• http
• ftp
• smtp
• pop
• dns
• programming network applications
• socket programming

9
Applications and application-layer protocols

• Application communicating, distributed processes
• running in network hosts in user space
• exchange messages to implement app
• e.g., email, file transfer, the Web
• Application-layer protocols
• one piece of an app
• define messages exchanged by apps and actions
  taken
• user services provided by lower layer protocols

10
Client-server paradigm

• Typical network app has two pieces client and
  server

• Client
• initiates contact with server (speaks first)
• typically requests service from server,
• e.g. request WWW page, send email
• Server
• provides requested service to client
• e.g., sends requested WWW page, receives/stores
  received email

11
Application-layer protocols (cont).

• API application programming interface
• defines interface between application and
  transport layer
• socket Internet API
• two processes communicate by sending data into
  socket, reading data out of socket

• Q how does a process identify the other
  process with which it wants to communicate?
• IP address of host running other process
• port number - allows receiving host to
  determine to which local process the message
  should be delivered

lots more on this later.
12
What transport service does an app need?

• Data loss
• some apps (e.g., audio) can tolerate some loss
• other apps (e.g., file transfer, telnet) require
  100 reliable data transfer

• Timing
• some apps (e.g., Internet telephony, interactive
  games) require low delay to be effective

• Bandwidth
• some apps (e.g., multimedia) require minimum
  amount of bandwidth to be effective
• other apps (elastic apps) make use of whatever
  bandwidth they get

13
Transport service requirements of common apps
Time Sensitive no no no yes, 100s msec yes,
few secs yes, 100s msec yes and no
Application file transfer e-mail Web
documents real-time audio/video stored
audio/video interactive games financial apps
Data loss no loss no loss no loss loss-tolerant
loss-tolerant loss-tolerant no loss
Bandwidth elastic elastic elastic audio
5Kb-1Mb video10Kb-5Mb same as above few Kbps
up elastic
14
Internet apps their protocols and transport
protocols
Application layer protocol smtp RFC 821 telnet
RFC 854 http RFC 2068 ftp RFC
959 proprietary (e.g. RealNetworks) NSF proprieta
ry (e.g., Vocaltec)
Underlying transport protocol TCP TCP TCP TCP TCP
or UDP TCP or UDP typically UDP
Application e-mail remote terminal access Web
file transfer streaming multimedia remote file
server Internet telephony