University of British Columbia CICS 515 (Part 1) Internet Computing Lecture 1 - Overview

1
University of British Columbia CICS 515 (Part
1) Internet Computing Lecture 1 - Overview

• Instructor Dr. Son T. Vuong
• Email vuong_at_cs.ubc.ca
• May 8, 2012
• The World Connected

2
Information and Organization

• Instructor Dr. Son Vuong
• Email vuong_at_cs.ubc.ca
• Office Hours T, Th 100-200pm (CS 329)
• TA
• Jonatan Schroeder jonatan_at_cs.ubc.ca
• Shahed Alam malam_at_cs.ubc.ca
• Lectures T, Th 11am-1 pm in DMP 110
• Lab Th 2-4 pm (CS 045/051)

3
Text and Workload

• Text Computer Networking A Top Down Approach
  Featuring the Internet, 6th edition. Jim
  Kurose, Keith Ross. Addison-Wesley, April 2012.
• Course Load
• 2 Projects/Asgmts (20)
• 2 Quizzes (10)
• Midterm (25)
• Final exam (45)
• Bonus for class participation, BlueCT Peerwise
  (4)
• Late penalty 52i , 0lt i lt 3 (i days late)
• Website www.icics.ubc.ca/cics515
• Vista http//www.vista.ubc.ca/ (idpwdCWL)

4
Revised CISC 515 Outline (Tentative)

1. (T - 08/5) Overview (Chapter 1) P1
2. (Th - 10/5) Application Layer (The Web and HTTP)
   (Ch 2)
3. (T - 15/5) WebCache and Transport Layer (Ch 3)
4. (Th - 17/5) Transport Layer (Ch 3)
5. (T - 22/5) Transport Layer (TCP) (Ch 3) Quiz1
6. (Th - 24/5) TCP Congestion (P1) P2
7. (T-29/5) IP (Ch 4) IPv6 (Ch 4) Midterm
8. (Th - 31/6) Other Protocols (ICMP, DHCP, DNS),
   Routing (RIP, OSPF) (Ch 4)
9. (T - 05/6) Routing (RIP, OSPF, BGP) (Ch 4)
10. (Th- 07/6) Data Link protocols (Ethernet) (Ch 5)
    (P2)
11. (T- 12/6) Wireless Networks (WiFi) (Ch 6) Quiz2
12. (Th-14/6) Review 13. (F-15/6) Final Exam

5
Chapter 1 Introduction

• Our goal
• get context, overview, feel of networking
• more depth, detail later in course
• approach
• descriptive
• use Internet as example

• Overview
• whats the Internet
• whats a protocol?
• network edge
• network core
• access net, physical media
• Internet/ISP structure
• performance loss, delay
• protocol layers, service models
• history

6
Chapter 1 roadmap

• 1.1 What is the Internet?
• 1.2 Network edge
• 1.3 Network core
• 1.4 Network access and physical media
• 1.5 Internet structure and ISPs
• 1.6 Protocol layers, service models
• 1.7 Delay loss in packet-switched networks
• 1.8 History

7
Whats the Internet nuts and bolts view

• millions of connected computing devices hosts,
  end-systems
• PCs workstations, servers
• PDAs phones, toasters
• running network apps
• communication links
• fiber, copper, radio, satellite
• transmission rate bandwidth
• routers forward packets (chunks of data)

8
Cool internet appliances
IP picture frame http//www.ceiva.com/
Web-enabled toasterweather forecaster
Worlds smallest web server http//www-ccs.cs.umas
s.edu/shri/iPic.html
9
Whats the Internet nuts and bolts view

• protocols control sending, receiving of msgs
• e.g., TCP, IP, HTTP, FTP, PPP
• Internet network of networks
• loosely hierarchical
• public Internet versus private intranet
• Internet standards
• RFC Request for comments
• IETF Internet Engineering Task Force

router
workstation
server
mobile
local ISP
regional ISP
company network
10
Whats the Internet a service view

• communication infrastructure enables distributed
  applications
• Web, email, games, e-commerce, database., voting,
  file (MP3) sharing
• communication services provided to apps
• connectionless
• connection-oriented

• cyberspace Gibson
• a consensual hallucination experienced daily by
  billions of operators, in every nation, ...."

11
Uses of Internet

• Business Applications
• Home Applications
• Mobile Users
• Social Issues

12
Business Applications of Networks

• A network with two clients and one server.

13
Business Applications of Networks (2)

• The client-server model involves requests and
  replies.

14
Home Network Applications

• Access to remote information
• Person-to-person communication
• Interactive entertainment
• Electronic commerce

15
Home Network Applications (2)

• In peer-to-peer system there are no fixed
  clients and servers.

16
Home Network Applications (3)

• Some forms of e-commerce.

17
Mobile Network Users

• Combinations of wireless networks and mobile
  computing.

18
Classification of Networks

• Classification of interconnected processors by
  scale.

19
Example Networks

• The Internet
• Connection-Oriented Networks X.25, Frame
  Relay, and ATM
• Ethernet
• Wireless LANs 80211 (WiFi)

20
Network Perspective

• Network users services that their applications
  need, e.g., guarantee that each message it sends
  will be delivered without error within a certain
  amount of time
• Network designers cost-effective design e.g.,
  that network resources are efficiently utilized
  and fairly allocated to different users
• Network providers system that is easy to
  administer and manage e.g., that faults can be
  easily isolated and it is easy to account for
  usage

21
Connectivity

• Building Blocks
• links coax cable, optical fiber...
• nodes general-purpose workstations...
• Direct Links
• point-to-point
• multiple access

22
Switched Networks

• A network can be defined recursively as
• two or more nodes connected
• by a physical link,
• or by two or more networks
• connected by one
• or more nodes
• Internetworks
• Internet vs internet

23
A closer look at network structure

• network edge applications and hosts
• network core
• routers
• network of networks
• access networks, physical media communication
  links

24
Chapter 1 roadmap

• 1.1 What is the Internet?
• 1.2 Network edge
• 1.3 Network core
• 1.4 Network access and physical media
• 1.5 Internet structure and ISPs
• 1.6 Protocol layers, service models
• 1.7 Delay loss in packet-switched networks
• 1.8 History

25
The network edge

• end systems (hosts)
• run application programs
• e.g. Web, email
• at edge of network
• client/server model
• client host requests, receives service from
  always-on server
• e.g. Web browser/server email client/server
• peer-peer model
• minimal (or no) use of dedicated servers
• e.g. Gnutella, KaZaA

26
Network edge connection-oriented service

• Goal data transfer between end systems
• handshaking setup (prepare for) data transfer
  ahead of time
• Hello, hello back human protocol
• set up state in two communicating hosts
• TCP - Transmission Control Protocol
• Internets connection-oriented service

• TCP service RFC 793
• reliable, in-order byte-stream data transfer
• loss acknowledgements and retransmissions
• flow control
• sender wont overwhelm receiver
• congestion control
• senders slow down sending rate when network
  congested

27
Network edge connectionless service

• Goal data transfer between end systems
• same as before!
• UDP - User Datagram Protocol RFC 768
  Internets connectionless service
• unreliable data transfer
• no flow control
• no congestion control

• Apps using TCP
• HTTP (Web), FTP (file transfer), Telnet (remote
  login), SMTP (email)
• Apps using UDP
• streaming media, teleconferencing, DNS, Internet
  telephony

28
Chapter 1 roadmap

• 1.1 What is the Internet?
• 1.2 Network edge
• 1.3 Network core
• 1.4 Network access and physical media
• 1.5 Internet structure and ISPs
• 1.6 Protocol layers, service models
• 1.7 Delay loss in packet-switched networks
• 1.8 History

29
The Network Core

• mesh of interconnected routers
• the fundamental question how is data transferred
  through net?
• circuit switching dedicated circuit per call
  telephone net
• packet-switching data sent thru net in discrete
  chunks

30
Switching Strategies

• Circuit switching dedicated circuit
  send/receive a bit stream
• original telephone network
• Packet switching store-and-forward send/receive
  messages (packets)
• Internet

31
Switching Strategies

• (a) Circuit switching (b) Message switching
  (c) Packet switching

32
Nodal delay

• dproc processing delay
• typically a few microsecs or less
• dqueue queuing delay
• depends on congestion
• dtrans transmission delay
• L/R, significant for low-speed links
• dprop propagation delay
• a few microsecs to hundreds of msecs

33
Packet switching versus circuit switching

• Is packet switching a slam dunk winner?

• Great for bursty data
• resource sharing
• simpler, no call setup
• Excessive congestion packet delay and loss
• protocols needed for reliable data transfer,
  congestion control
• Q How to provide circuit-like behavior?
• bandwidth guarantees needed for audio/video apps
• still an unsolved problem (chapter 6)

34
Packet-switching store-and-forward
L
R
R
R

• Takes L/R seconds to transmit (push out) packet
  of L bits on to link or R bps
• Entire packet must arrive at router before it
  can be transmitted on next link store and
  forward
• delay 3L/R

• Example
• L 7.5 Mbits
• R 1.5 Mbps
• delay 3x 5 sec 15 sec

35
Packet Switching Message Segmenting

• Now break up the message into 5000 packets

• Each packet 1,500 bits
• 1 msec to transmit packet on one link
• pipelining each link works in parallel
• Delay reduced from 15 sec to 5.002 sec

36
Packet Switching Message Segmenting
L
R
R
R
R

• Now assume the message/packets go through 2
  additional switches (over the path of 4 switches)

• What is the total delay to send the message
  without breaking into packets (i.e.
  non-pipelining) ?
• What is the total delay to send the message as
  5000 packets (i.e. pipelining) ?

37
Q 1.1  Peer Instruction packet switching

• Now assume the message/packets go through 2
  additional switches (over the path of 4 switches)
  What is the total delay to send the message as
  5000 packets (i.e. pipelining) ?
• Answer
• (A) 25 s  (B) 15 s  (C) 5.002 s  (D) 5.004 s
• (E) None of the above

38
Q 1.1  Peer Instruction packet switching

• Now assume the message/packets go through 2
  additional switches (over the path of 4 switches)
  What is the total delay to send the message as
  5000 packets (i.e. pipelining) ?
• Answer
• (A) 25 s  (B) 15 s  (C) 5.002 s  (D) 5.004 s
• (E) None of the above

39
Packet-switched networks forwarding

• Goal move packets through routers from source to
  destination
• well study several path selection (i.e.
  routing)algorithms (chapter 4)
• datagram network
• destination address in packet determines next
  hop
• routes may change during session
• analogy driving, asking directions
• virtual circuit network
• each packet carries tag (virtual circuit ID),
  tag determines next hop
• fixed path determined at call setup time, remains
  fixed thru call
• routers maintain per-call state

40
Addressing and Routing

• Address byte-string that identifies a node
• usually unique
• Routing how to forward messages towards the
  destination node based on its address
• Types of addresses
• unicast node-specific
• broadcast all nodes on the network
• multicast some subset of nodes on the network

41
Multiplexing

• Time-Division Multiplexing (TDM)
• Frequency-Division Multiplexing (FDM)

42
Circuit Switching FDMA and TDMA
43
Time Division Multiplexing (T1 Carrier)

• The T1 carrier (1.544 Mbps).

(1 bit 24 slots 8 bits/slot) 8000 frames/s
193 bits/frame 8000 frames/s 1.544 Mbps
44
Peer Instruction 1.1 T1 TDM Question

• How long does it take to send a file of 640,000
  bits from host A to host B over a (sub)channel (a
  circuit) in a T1 TDM based circuit-switched
  network?
• Overall T1 TDM carrier capacity is 1.536 Mbps
• Data transmission uses one of the 24 slots of the
  T1 carrier
• 500 msec to establish end-to-end circuit
• Work it out!
• (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s
• (E) None of the above

45
1.1 Peer Instruction T1 TDM Answer

• How long does it take to send a file of 640,000
  bits from host A to host B over a (sub)channel (a
  circuit) in a T1 TDM based circuit-switched
  network?
• Overall TDM channel capacity is 1.536 Mbps (T1
  1.544 Mbps with 8Kbps framing)
• Data transmission uses one of the 24 slots of the
  TDM channel
• 500 msec 0.5s to establish end-to-end circuit
• Answer Each circuit 1.536Mbps/24 64Kbps
• Tx(file) 640Kb/64Kbps 10s plus Tsetup
• (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s
• (E) None of the above

46
Peer Instruction 1.1 T1 TDM Question

• How long does it take to send a file of 640,000
  bits from host A to host B over 5 (sub)channels
  (circuits) in a T1 TDM based circuit-switched
  network?
• Overall T1 TDM carrier capacity is 1.536 Mbps
• Data transmission uses one of the 24 slots of the
  T1 carrier
• 500 msec to establish end-to-end circuit
• Work it out!
• (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s
• (E) None of the above

47
1.1 Peer Instruction T1 TDM Answer

• How long does it take to send a file of 640,000
  bits from host A to host B over 5 (sub)channel
  (circuits) in a T1 TDM based circuit-switched
  network?
• Overall TDM channel capacity is 1.536 Mbps (T1
  1.544 Mbps with 8Kbps framing)
• Data transmission uses one of the 24 slots of the
  TDM channel
• 500 msec 0.5s to establish end-to-end circuit
• Answer Each circuit 1.536Mbps/24 64Kbps
• Tx(file) 640Kb/(5x64Kbps) 2s plus Tsetup
• (A) 510 ms (B) 1500 ms (C) 2.5 s (D) 10.5 s
• (E) None of the above

48
Statistical Multiplexing (ATDM)

• On-demand time-division, rather than fixed (STDM)
• Schedule link on a per-packet basis
• Packets from different sources interleaved on
  link
• Buffer packets that are contending for the link
• Packet queue may be processed FIFO
• Buffer (queue) overflow is called congestion

ATDM or Concentrator
49
Chapter 1 roadmap

• 1.1 What is the Internet?
• 1.2 Network edge
• 1.3 Network core
• 1.4 Network access and physical media
• 1.5 Internet structure and ISPs
• 1.6 Protocol layers, service models
• 1.7 Delay loss in packet-switched networks
• 1.8 History

50
Protocols

• Building blocks of a network architecture
• Each protocol object has two different
  interfaces
• service operations on this protocol
• peer-to-peer (protocol) messages exchanged with
  peer
• Term protocol is overloaded
• specification of peer-to-peer interface
• module that implements this interface

51
Interfaces (Protocol and Service)
Host 1
Host 2
SERVICE
High-level
High-level
interface
object
object
PROTOCOL
Protocol
Protocol
Peer-to-peer
interface
52
Whats a protocol?

• human protocols
• whats the time?
• I have a question
• introductions
• specific msgs sent
• specific actions taken when msgs received, or
  other events

• network protocols
• machines rather than humans
• all communication activity in Internet governed
  by protocols

protocols define format, order of msgs sent and
received among network entities, and actions
taken on msg transmission, receipt
53
Whats a protocol?

• a human protocol and a computer network protocol

Hi
TCP connection req
Hi
Q Other human protocols?
54
Internet Architecture

• Defined by Internet Engineering Task Force (IETF)
• Hourglass Design
• Application vs Application Protocol (FTP, HTTP)

55
ISO Architecture
56
Reference Models

• The TCP/IP reference model.

57
Layering

• Use abstractions to hide complexity
• Abstraction naturally lead to layering
• Alternative abstractions at each layer

Host-to-host connectivity
58
Layering logical communication

• Each layer
• distributed
• entities implement layer functions at each node
• entities perform actions, exchange messages with
  peers

59
Layering logical communication

• E.g. transport
• take data from app
• add addressing, reliability check info to form
  datagram
• send datagram to peer
• wait for peer to ack receipt
• analogy post office

transport
transport
60
Layering physical communication
61
Protocol layering and data

• Each layer takes data from above
• adds header information to create new data unit
• passes new data unit to layer below

source
destination
message
segment
datagram
frame
62
Chapter 1 roadmap

• 1.1 What is the Internet?
• 1.2 Network edge
• 1.3 Network core
• 1.4 Network access and physical media
• 1.5 Internet structure and ISPs
• 1.6 Protocol layers, service models
• 1.7 Delay loss in packet-switched networks
• 1.8 History

63
How do loss and delay occur?

• packets queue in router buffers
• packet arrival rate to link exceeds output link
  capacity
• packets queue, wait for turn

A
B
64
1.2 Peer Instruction - Packet Error Prob Question

• Let p be the bit error probability.  Assume
  packet of length L bits. What's the packet error
  probability in terms of p and L?
• (A)    (1- p) L
• (B)    1- pL
• (C)    1- p L
• (D)    1- (1-p)L
• (E)    None of the above

65
1.2 Peer Instruction - Packet Error Prob Answer

• Let p be the bit error probability.  Assume
  packet of length L bits. What's the packet error
  probability in terms of p and L?
• (A)    (1- p) L
• (B)    1- pL prob (not all bits in error)
  
• (C)    1- p L
• (D)    1- (1-p)L
• (E)    None of the above
• Answer (D) 
• prob(a bit not in error) 1-p
• prob (L bits not in error) (1-p)L
•    prob(packet error) prob (not all bits not in
  error)
•                                 1- (1-p)L

66
What Goes Wrong in the Network?

• Bit-level errors (electrical interference)
  probp
• Packet-level errors (congestion) 1-(1-p)f
• Link and node failures
• Messages are delayed
• Messages are delivered out-of-order
• Third parties eavesdrop
• The key problem is to fill in the gap between
  what
• applications expect and what the underlying
• technology provides.

67
Four sources of packet delay

• 1. nodal processing
• check bit errors
• determine output link

• 2. queueing
• time waiting at output link for transmission
• depends on congestion level of router

68
Delay in packet-switched networks

• 4. Propagation delay
• d length of physical link
• s propagation speed in medium (2x108 m/sec)
• propagation delay d/s

• 3. Transmission delay
• Rlink bandwidth (bps)
• Lpacket length (bits)
• time to send bits into link L/R

Note s and R are very different quantities!
69
Nodal delay

• dproc processing delay
• typically a few microsecs or less
• dqueue queuing delay
• depends on congestion
• dtrans transmission delay
• L/R, significant for low-speed links
• dprop propagation delay
• a few microsecs to hundreds of msecs

70
Queueing delay (revisited)

• Rlink bandwidth (bps)
• Lpacket length (bits)
• aaverage packet arrival rate

traffic intensity La/R

• La/R 0 average queueing delay small
• La/R -gt 1 delays become large
• La/R gt 1 more work arriving than can be
  serviced, average delay infinite!

71
Digression- Simple Queuing Model

• Queuing system general properties
• Arrival rate ? a msg/s
• Service rate µ R/L msg/s Service time
  Ts L/R ? / a s/msg
• Traffic intensity Utilization factor ? ? /
  µ aL / R
• Little Formula N ? T a T or T N/a
• N Nw Ns and T Tw Ts
• M/M/1 Queue Model (M/M/1 is Kendall notation)
• Can derive
• in system N ? / (1- ?) waiting in
  queue Nw ?2 / (1- ?)
• gt Time in system T N/a Ts / (1- ?)
  (using Little formula)
• Tw Ts N
  Ts Ts (N1) Ts
• Waiting time Tw T Ts Ts / (1- ?) - Ts
  (1/ (1- ?) - 1 )Ts
• ? Ts / (1- ?)
• N Ts

72
Real Internet delays and routes

• What do real Internet delay loss look like?
• Traceroute program provides delay measurement
  from source to router along end-end Internet path
  towards destination. For all i
• sends three packets that will reach router i on
  path towards destination
• router i will return packets to sender
• sender times interval between transmission and
  reply.

3 probes
3 probes
3 probes
73
Real Internet delays and routes
traceroute gaia.cs.umass.edu to www.eurecom.fr
Three delay measements from gaia.cs.umass.edu to
cs-gw.cs.umass.edu
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms 2
border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145)
1 ms 1 ms 2 ms 3 cht-vbns.gw.umass.edu
(128.119.3.130) 6 ms 5 ms 5 ms 4
jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16
ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net
(204.147.136.136) 21 ms 18 ms 18 ms 6
abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22
ms 18 ms 22 ms 7 nycm-wash.abilene.ucaid.edu
(198.32.8.46) 22 ms 22 ms 22 ms 8
62.40.103.253 (62.40.103.253) 104 ms 109 ms 106
ms 9 de2-1.de1.de.geant.net (62.40.96.129) 109
ms 102 ms 104 ms 10 de.fr1.fr.geant.net
(62.40.96.50) 113 ms 121 ms 114 ms 11
renater-gw.fr1.fr.geant.net (62.40.103.54) 112
ms 114 ms 112 ms 12 nio-n2.cssi.renater.fr
(193.51.206.13) 111 ms 114 ms 116 ms 13
nice.cssi.renater.fr (195.220.98.102) 123 ms
125 ms 124 ms 14 r3t2-nice.cssi.renater.fr
(195.220.98.110) 126 ms 126 ms 124 ms 15
eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135
ms 128 ms 133 ms 16 194.214.211.25
(194.214.211.25) 126 ms 128 ms 126 ms 17
18 19 fantasia.eurecom.fr
(193.55.113.142) 132 ms 128 ms 136 ms
trans-oceanic link
means no reponse (probe lost, router not
replying)
74
Packet loss

• queue (aka buffer) preceding link in buffer has
  finite capacity
• when packet arrives to full queue, packet is
  dropped (aka lost)
• lost packet may be retransmitted by previous
  node, by source end system, or not retransmitted
  at all

75
Performance Metrics

• Bandwidth (throughput)
• data transmitted per time unit
• link versus end-to-end
• notation
• KB 210 bytes
• Mbps 106 bits per second
• Latency (delay)
• time to send message from point A to point B
• one-way versus round-trip time (RTT)
• components
• Latency Propagation Transmit Queue
• Propagation Distance / c (c3, 2.3, 2x108
  m/s)
• Transmit Size / Bandwidth

76
Bandwidth versus Latency

• Relative importance
• 1-byte 1ms vs 100ms dominates 1Mbps vs 100Mbps
• 25MB 1Mbps vs 100Mbps dominates 1ms vs 100ms
• Infinite bandwidth
• RTT dominates
• Throughput TransferSize / TransferTime
• TransferTime RTT TransferSize / Bandwidth
• 1-GB file to 1-Gbps link as 1-MB packet to 1-Mbps
  link

77
Delay x Bandwidth Product

• Amount of data in flight or in the pipe
• Example 100ms x 45Mbps 560KB

78
ITU

• Main sectors
• Radiocommunications
• Telecommunications Standardization
• Development
• Classes of Members
• National governments
• Sector members
• Associate members
• Regulatory agencies

79
IEEE 802 Standards
The 802 working groups. The important ones are
marked with . The ones marked with ? are
hibernating. The one marked with gave up.
80
Bad Timing

• The apocalypse of the two elephants.

81
Chapter 1 roadmap

• 1.1 What is the Internet?
• 1.2 Network edge
• 1.3 Network core
• 1.4 Network access and physical media
• 1.5 Internet structure and ISPs
• 1.6 Protocol layers, service models
• 1.7 Delay loss in packet-switched networks
• 1.8 History

82
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 Research
  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

83
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

84
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

85
Internet History
1990, 2000s commercialization, the Web, new apps

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

• Late 1990s 2000s
• more killer apps instant messaging, peer2peer
  file sharing (e.g., Naptser)
• network security to forefront
• est. 100 million host, 500 million users
• backbone links running at Gbps