University of British Columbia CICS 317 Internet Computing Lecture 1 Overview

1
University of British Columbia CICS 317
Internet Computing Lecture 1 - Overview

• Instructor Dr. Son T. Vuong
• Email vuong_at_cs.ubc.ca
• Jan 06, 2009
• The World Connected

2
Information and Organization

• Instructor Dr. Son Vuong
• Email vuong_at_cs.ubc.ca
• Office Hours T,Th 1100-1200pm (CS 329)
• TAs
• Jonatan Schroeder ltjonatan_at_cs.ubc.cagt
• Kuljeet Singh ltkuljeets_at_cs.ubc.cagt
• Sunjeet Singh ltsstatla_at_cs.ubc.cagt
• Lecture times T, Th 930am-1100am (DMP 110)
• Tutorials A M 900-1000 (ICCS 014) (12)
• B F 1400-1500 (ICCS 014) (32)
• C F 1100-1200 (ICCS 014) (33)

3
Keep the following in Mind

• A course is a learning experience for both the
  instructor, TAs, and students
• Sometimes things might not go quite as expected
• Dont panic
• Be patient, go slow, take a deep breath
• However, no time to slack

4
Text and Workload (tentative)

• Text Computer Networking A Top Down Approach
  Featuring the Internet, 4th edition. Jim Kurose,
  Keith Ross. Addison-Wesley, April 2007.
• Course Load
• 4 Assignments (20)
• 3 Quizzes (10)
• Midterm (20)
• Final exam (50)
• Bonus Peer Instruction Q/A (2), Tutorial (1)
• Late penalty 102i , 0lt i lt N (i days
  late)
• Website www.ugrad.cs.ubc.ca/cs317
• WebCT www.webct.ubc.ca
• http//www.webct.ubc.ca/SCRIPT/cpsc_317_2009w/scri
  pts/serve_home (idpwdCWL)

5
Text and Slides

• This is a new class
• Textbook is required
• These slides adapted from those of Kurose and
  Ross
• Thanks!

Computer Networking A Top Down Approach
Featuring the Internet, 4th edition. Jim
Kurose, Keith RossAddison-Wesley, April 2007.
6
Final Exam

• Do not make any travel arrangements for April
  until after the final exam time has been set. (It
  may be during the last class or during the
  scheduled exam period.)

7
Course Grading Scheme

• Assignments 20
• Quizzes 10
• Midterms 20
• Final Exam 50
• Bonus PeerInstructions (2) Tutorials (1)
• Must pass the final to pass the course
• Must get 50 average overall on assignments
• The lower of the computed grade or 45 will be
  assigned if above conditions are not met

8
Tutorials

• Make sure you have read the latest assignment
• Tutorials will
• Discuss the assignments, key issues and ways to
  think about the assignment
• Review topics relevant to completing the
  assignment, for example
• Needed system calls
• Debugging
• Review concepts/ideas from class
• Peer instructions for group interactions
• Answer your questions come prepared

9
Assignments Exams

• There will be 4 programming assignments
• Programming language is C
• In groups of THREE (or less)
• Recommend - A C reference manual
• The C Programming Language (2nd Edition)
• Authors Brian Kernighan, and Dennis Ritchie
• 3 in class quizzes and a midterm
• Covers material from the previous week(s).
• Final exam
• Comprehensive with more emphasis on material
  after midterm
• See the course web page for all details
• http//www.ugrad.cs.ubc.ca/cs317/

10
Purpose of Assignments

• Help in learning the course concepts
• Develop skills in
• Problem solving
• (Network) Programming
• Debugging
• Communication
• Group interactions

11
Course Grading Scheme

• Assignments 20
• Midterms 30
• Final Exam 50
• Must pass the final to pass the course
• Must get 50 average overall on assignments
• The lower of the computed grade or 45 will be
  assigned if above conditions are not met

12
Marking Disagreements

• You have until the start of the next class after
  a piece of graded work is handed back to inform
  me of any errors in addition etc
• If you believe something was incorrectly marked
  you have until the start of the next class from
  when it was handed back to
• Bring this to my attention along with
• A detailed written response explaining why the
  answer, as written, is correct (no saying things
  like but I meant )

13
Resources

• WebCT grades, midterm solutions
• Lecture slides posted in advance
• Questions at the end of each chapter
• Study Questions
• TAs
• During tutorials
• Via the webct bulletin board
• Office hours

14
Academic Conduct

• Whats allowed
• Use of existing public approaches to problem
  solving
• Discussing with other 317 students existing
  approaches to solving a problem
• Discussion of requirements
• Discussing the merits of a proposed solution with
  the course instructor or TAs

15
Academic Conduct contd

• Whats not allowed
• Submitting someone elses work as your own.
  Examples include
• Having in your possession previous solutions to
  the assignments either someone elses or the
  instructors
• Working with different groups and then handing in
  the work, even a part of it
• Work you have handed in to another course all
  work must be new work

16
Academic Conduct contd

• Making a solution available as an aid to others,
  either now, or in the future
• What to do if you are uncertain?
• Read the departments policy on academic conduct
  at
• http//www.cs.ubc.ca/about/policies/collaboration.
  shtml

Ask the instructor or TAs
17
Possible Penalties

• A failing grade or zero in the course, exam or
  assignment.
• Suspension from the University.
• Reprimand with a letter placed in the students
  file.
• A notation on the students permanent record of
  the penalty imposed.

18
Whats Expected of You

• Do readings the material is examinable
• Think, ask questions
• Do the assignments
• Be prepared for tutorials and class
• Respect your classmates, TAs and instructor

19
Computer Science is not a Spectator Sport!
20
First Programming Assignment

• Introduction to Socket Programming (Web Proxy
  Server)
• Due Date
• Code submission TBA
• No write up for this one
• Goals
• Re-familiarization with socket programming in C
• Understanding of how to perform some basic
  network operations using the UNIX socket API
• Understanding of how a web proxy server works

21
CPSC 317 from 10,000 Metres

• Introduction
• Application Layer
• Web and HTTP, FTP, SMTP and mail, DNS, P2P,
  Sockets
• Transport Layer
• Services, multiplexing and demultiplexing, UDP,
  reliable data transfer, TCP.

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CPSC 317 from 10K Metres

• Network and Lower Layers
• IPv4 (and IPv6)
• Routing, circuit switched vs datagram
• Packet forwarding and addressing
• Link layer moving data from node to node
• Advanced topics (if time permits)
• - e.g. Wireless, P2P video streaming

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CISC 515 Outline (Sypnosis)

• Overview (Chapter 1)
• Application Layer (Intro) (Ch 2)
• Application (HTTP, FTP, SMTP,DNS, P2P) (Ch 2)
• Transport Layer (TCP) (Ch 3)
• Transport (TCP) (Congestion) (Ch 3)
• IP (Ch 4)
• IPv6 (Ch 4)
• Other Protocols (ICMP, DHCP) (Ch 4)
• Routing (RIP, OSPF) (Ch 4)
• Routing (BGP) (Ch 4)
• Data Link protocols (Ethernet) (Ch 5)
• Wireless Networks (WiFi) (Ch 6)

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Chapter 1 Introduction

• Our goal
• get feel of networking and terminology
• more depth, detail later in course
• approach
• 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

25
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

26
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)

27
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
28
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
29
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, ...."

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Uses of Internet

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

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Business Applications of Networks

• A network with two clients and one server.

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Business Applications of Networks (2)

• The client-server model involves requests and
  replies.

33
Home Network Applications

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

34
Home Network Applications (2)

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

35
Home Network Applications (3)

• Some forms of e-commerce.

36
Mobile Network Users

• Combinations of wireless networks and mobile
  computing.

37
Classification of Networks

• Classification of interconnected processors by
  scale.

38
Example Networks

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

39
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

40
Connectivity

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

41
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

42
A closer look at network structure

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

43
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

44
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

45
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

46
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

47
ltDigression/ For A1The Web the http protocol

• http hypertext transfer protocol
• Webs application layer protocol
• client/server model
• client browser that requests, receives,
  displays Web objects
• server Web server sends objects in response to
  requests
• http1.0 RFC 1945
• http1.1 RFC 2068

http request
PC running Explorer
http response
Server running NCSA Web server
http request
http response
Mac running Navigator
48
The http protocol more

• http TCP transport service
• client initiates TCP connection (creates socket)
  to server, port 80
• server accepts TCP connection from client
• http messages (application-layer protocol
  messages) exchanged between browser (http client)
  and Web server (http server)
• TCP connection closed

49
Web caches (proxy server) (A1)
Goal satisfy client request without involving
origin server

• User sets browser Web accesses via cache
• 1. Browser sends all HTTP requests to cache
• 2. Object in cache cache returns object
• 3. Else cache requests object from origin server
  server returns object
• 4. Cache then stores and forward object to client

origin server
1
Proxy server
HTTP request
HTTP request
client
3
HTTP response
HTTP response
2
4
HTTP request
HTTP response
client
origin server
(p. 101)
50
More about Web caching

• Cache acts as both client and server
• Typically cache is installed by ISP (university,
  company, residential ISP)

• Why Web caching?
• Reduce response time for client request.
• Reduce traffic on an institutions access link.
• Internet dense with caches enables poor content
  providers to effectively deliver content (but so
  does P2P file sharing)

A1 /Digressiongt
51
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

52
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

53
Switching Strategies

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

54
Switching Strategies

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

55
Network Core Circuit Switching

• End-end resources reserved for call
• link bandwidth, switch capacity
• dedicated resources no sharing
• circuit-like (guaranteed) performance
• call setup required

56
Network Core Circuit Switching

• network resources (e.g., bandwidth) divided into
  pieces
• pieces allocated to calls
• resource piece idle if not used by owning call
  (no sharing)

• dividing link bandwidth into pieces
• frequency division
• time division

57
Circuit Switching FDM and TDM
58
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
59
Network Core Packet Switching

• each end-end data stream divided into packets
• user A, B packets share network resources
• each packet uses full link bandwidth
• resources used as needed

• resource contention
• aggregate resource demand can exceed amount
  available
• congestion packets queue, wait for link use
• store and forward packets move one hop at a time
• Node receives complete packet before forwarding

60
Packet Switching Statistical Multiplexing
10 Mb/s Ethernet
C
A
statistical multiplexing
1.5 Mb/s
B
queue of packets waiting for output link

• Sequence of A B packets does not have fixed
  pattern ? statistical multiplexing.
• In TDM each host gets same slot in revolving TDM
  frame.

61
Packet switching versus circuit switching

• Packet switching allows more users to use network!

• 1 Mb/s link
• each user
• 100 kb/s when active
• active 10 of time
• circuit-switching
• 10 users
• packet switching
• with 35 users, probability gt 10 active less than
  .0004

N users
1 Mbps link
62
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)

63
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 15 sec

64
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

65
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

66
Network Taxonomy
Telecommunication networks

• Datagram network is not either
  connection-oriented
• or connectionless.
• Internet provides both connection-oriented (TCP)
  and
• connectionless services (UDP) to apps.

67
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

68
Access networks and physical media

• Q How to connect end systems to edge router?
• residential access nets
• institutional access networks (school, company)
• mobile access networks
• Keep in mind
• bandwidth (bits per second) of access to network?
• shared or dedicated?

69
Residential access point to point access

• Dialup via modem
• up to 56Kbps direct access to router (often less)
• Cant surf and phone at same time cant be
  always on

• ADSL asymmetric digital subscriber line
• up to 1 Mbps upstream (today typically lt 256
  kbps)
• up to 10 Mbps downstream (today typically lt 1
  Mbps)
• FDM 50 kHz - 1 MHz band for downstream
• 4 kHz - 50 kHz band for upstream
• 0 kHz - 4 kHz band for ordinary
  two-way telephone

70
Residential access cable modems

• HFC hybrid fiber coax
• asymmetric up to 30Mbps downstream, 2 Mbps
  upstream
• network of cable and fiber - attaches homes to
  ISP router
• homes share access to router
• deployment available via cable TV companies

71
Residential access cable modems
Diagram http//www.cabledatacomnews.com/cmic/diag
ram.html
72
Cable Network Architecture Overview
Typically 500 to 5,000 homes
cable headend
home
cable distribution network (simplified)
73
Cable Network Architecture Overview
cable headend
home
cable distribution network (simplified)
74
Cable Network Architecture Overview
cable headend
home
cable distribution network
75
Cable Network Architecture Overview
FDM
cable headend
home
cable distribution network
76
Company access local area networks

• company/univ local area network (LAN) connects
  end system to edge router
• Ethernet
• shared or dedicated link connects end system and
  router
• 10 Mbs, 100Mbps, Gigabit Ethernet
• LANs chapter 5

77
Wireless access networks

• shared wireless access network connects end
  system to router
• via base station aka access point
• wireless LANs
• 802.11b/g (WiFi) 11/54 Mbps
• wider-area wireless access
• provided by telco operator
• 3G 384 kbps, 4G ?
• Will it happen??
• WAP (WML)/GPRS in Europe
• i-mode in Japan

78
Home networks

• Typical home network components
• ADSL or cable modem
• router/firewall/NAT
• Ethernet
• wireless access
• point

wireless laptops
to/from cable headend
cable modem
router/ firewall
wireless access point
Ethernet
79
Physical Media

• Twisted Pair (TP)
• two insulated copper wires
• Category 3 traditional phone wires, 10 Mbps
  Ethernet
• Category 5/5e 100Mbps/1Gbps Ethernet
• Unshielded Twisted Pair (UTP)

• Bit propagates betweentransmitter/rcvr pairs
• physical link what lies between transmitter
  receiver
• guided media
• signals propagate in solid media copper, fiber,
  coax
• unguided media
• signals propagate freely, e.g., radio

80
Physical Media coax, fiber

• Fiber optic cable
• glass fiber carrying light pulses, each pulse a
  bit
• high-speed operation
• high-speed point-to-point transmission (e.g., 5
  Gps)
• low error rate repeaters spaced far apart
  immune to electromagnetic noise

• Coaxial cable
• two concentric copper conductors
• bidirectional
• baseband
• single channel on cable
• legacy Ethernet
• broadband
• multiple channel on cable
• HFC

81
Physical media radio

• Radio link types
• terrestrial microwave
• e.g. up to 45 Mbps channels
• LAN (e.g., Wifi)
• 2Mbps, 11Mbps, 54 Mbps
• wide-area (e.g., cellular)
• e.g. 3G hundreds of kbps
• satellite
• up to 50Mbps channel (or multiple smaller
  channels)
• 270 msec end-end delay
• geosynchronous (GEO) versus low altitude (LEO)

• signal carried in electromagnetic spectrum
• no physical wire
• bidirectional
• propagation environment effects
• reflection
• obstruction by objects
• interference

82
Low-Earth Orbit SatellitesIridium

• (a) The Iridium satellites from six necklaces
  around the earth.
• (b) 1628 moving cells cover the earth.

83
TELEDESIC Constellations
84
TELEDESIC Satellite
85
ISS - International Space Station
86
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 Delay loss in packet-switched networks
• 1.7 Protocol layers, service models
• 1.8 History

87
Old Internet
New Internet
88
Internet structure network of networks

• roughly hierarchical
• at center tier-1 ISPs (e.g.,
  MCI-UUNet/WorldCom, BBN/Genuity, Sprint, ATT,
  Qwest),
• national/international coverage
• treat each other as equals

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
89
Tier-1 ISP e.g., Sprint
Sprint US backbone network
90
Internet structure network of networks

• Tier-2 ISPs smaller (often regional) ISPs
• Connect to one or more tier-1 ISPs, possibly
  other tier-2 ISPs

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
91
Internet structure network of networks

• Tier-3 ISPs and local ISPs
• last hop (access) network (closest to end
  systems)

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
92
Internet structure network of networks

• a packet passes through many networks!

Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
93
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

94
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

95
Interfaces (Protocol and Service)
Host 1
Host 2
SERVICE
High-level
High-level
interface
object
object
PROTOCOL
Protocol
Protocol
Peer-to-peer
interface
96
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
97
Whats a protocol?

• a human protocol and a computer network protocol

Hi
TCP connection req
Hi
Q Other human protocols?
98
Internet Architecture

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

99
ISO Architecture
100
Reference Models

• The TCP/IP reference model.

101
Layering

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

Host-to-host connectivity
102
Layering logical communication

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

103
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
104
Layering physical communication
105
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
106
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

107
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
108
What Goes Wrong in the Network?

• Bit-level errors (electrical interference)
  probp
• Packet-level errors (congestion) 1-(1-p)L
• 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.

109
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

110
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!
111
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

112
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!

113
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
114
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 response (probe lost, router not
replying)
115
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

116
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

117
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

118
Delay x Bandwidth Product

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

119
ITU

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

120
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.
121
Bad Timing

• The apocalypse of the two elephants.

122
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

123
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

124
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

125
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

126
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