Internet and Intranet Protocols and Applications

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Internet and Intranet Protocols and Applications

• Lecture 1 Introduction Review of Networking
• January 18, 2000
• Arthur P. Goldberg
• Computer Science Department
• New York University
• artg_at_cs.nyu.edu

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Tonight

• Introduction
• Growth of the Internet and intranets
• Review networking
• Layered protocol model of computer networks
• Summarize course
• Syllabus
• Textbooks and other readings, such as RFCs and
  papers
• Assignments homework, programming projects, final

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INTRODUCTION Why Study Internet and Intranet
Protocols and Applications?

• Same systems used in the two major types of
  networks, the public Internet and internal
  (corporate) Intranets
• Accessible for study, because protocol standards
  are published and their design is publicly debated

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Systems to study

• Protocols
• Web
• HTTP
• SSL
• Email
• SMTP
• POP3
• IMAP
• Client and server software (and intermediate
  systems, like caching proxies, gateways and
  firewalls)
• Object formats for documents and programs
  (embedded in protocols)

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Challenges

• Heterogeneity
• Client and server system architecture
• Performance (in protocols and applications)
• Interoperability (with existing protocols and
  applications)
• End-user application design
• Applications (Web sites and intranet systems -
  not a topic of this course)

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Highly Heterogeneous Computing Environment
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Other Heterogeneous Dimensions

• OS
• Palm Pilot DOS MVS
• Architecture
• x86 CRAY
• Spoken language
• Legal entity

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Client / Server Internet Application Systems

• Single client single server
• Multiple client single server
• Multiple client multiple server
• Multiple client multiple intermediary multiple
  server
• Intermediaries
• Proxies
• Gateways
• Firewalls
• Load managers

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SPACE TIME DIAGRAMS
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The BSD Socket Interface

• Partly integrated into existing I/O system calls
• Servers
• Wait for a message to arrive
• Clients
• Initiate communications
• Comer fig 5.4

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We wont study

• Networking below the application layer (a
  prerequisite - you should be aware of routing,
  IP, TCP, UDP - but well review today)
• Programming languages (e.g. Java) - covered in
  Amsterdams Programming for the WWW
• Writing HTML, CGI programs (you can learn this
  yourself)
• Cryptographic protocol mathematics (important,
  but covered in Computer Security, Prof. Kedem,
  T 7-9 WWH 101)

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GROWTH OF THE INTERNET AND INTRANETS
Millions 01/96 9,472 07/96
12,881 01/97 16,146 07/97 19,540 01/98
29,670 07/98 36,739 01/99 43,230 07/99
56,218
Source Network Wizards available at
http//www.isc.org/ds/host-count-history.html
8/1999 and Kleinrock, Queueing Systems, Vol 2
Computer Applications, pp. 305-308
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Growth of the Internet
Sampled by PINGing 1 of DNS entries
Survey Adjusted Replied Date Hosts
Count To Ping Jul 99 56,218
Jan 99 43,230 8,426 Jul 98 36,739
6,529 Jan 98 29,670 5,331 Jul
97 19,540 26,053 4,314 Jan 97 16,146 21,819
3,392 Jul 96 12,881 16,729 2,569 Jan 96
9,472 14,352 1,682
Source Network Wizards available at
http//www.nw.com/zone/report-9607.doc, Jan 1997
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Growth of the Web
Source WebCrawler WAS available at
http//webcrawler.com/WebCrawler/Facts/Size.html,
in Jan 1997
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REVIEW NETWORKING Layered protocol model of
computer networks

• Reduce complexity by "layering" protocols
• Solve at most a few challenges in each layer
• E.g.
• Lower layer eliminates all physical noise errors
• Upper layer resends lost messages
• Each layer offers services to the layer above
• Enable improvements to PART of the network

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OSI Layered protocol model

• Application (We focus on activity here)
• Presentation
• Session
• Transport
• Network
• Data
• Physical

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Mnemonics

• Rob Aggrandized Tutition, NYU Declares
  Profitability
• Traditional All People Seem To Need Data
  Processing
• ? A Transvestite Never Dresses (in) Pants!
• Nisha Always Try (to) Date New People

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Layers, protocols and interfaces

• TF 1-9
• Solid lines - data flow
• Dashed lines - virtual communications

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Example information flow

• TF 1-11
• Source layer 5 sends M to its layer 5 destination
  peer
• Source layer 4 prepends its header H4
• Source layer 3, facing message size limits,
  fragments into two messages and prepends its
  headers
• Source layer 2 prepends headers and appends
  trailers
• Destination layers reverse the process

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Layered Protocol Models

• Reference models
• OSI
• TF 1-16
• TCP/IP
• TF 1-18
• Hybrid, Tanenbaum
• TF 1-21

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HYBRID reference model, top 3 layers, bottom up

• Network layer
• Route packets from source host to destination
  host
• Routes can be fixed, setup at connection time or
  dynamic
• Congestion control
• Accounting
• Heterogeneous (inter-) networking

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HYBRID reference model, top 3 layers, bottom up,
cont.

• Transport layer
• Maintain persistent connections between processes
• Application
• Programs that use the network

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TCP/IP Model, bottom up

• Internet layer
• Host-to-host communication
• Connectionless
• Packets routed independently
• Internet Protocol (IP)

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TCP/IP Model, bottom up

• Transport layer
• Peer-to-peer communication between source and
  destination processes
• Two protocols TCP and UDP
• Transmission control protocol (TCP)
• Connection-oriented
• Reliable byte stream
• Fragmentation and flow control
• User Datagram Protocol (UDP)
• Connectionless
• Unreliable packets
• Less overhead

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TCP/IP Model - Application layer

• TCP-based
• Virtual terminal (TELNET)
• File transfer (FTP)
• Email (SMTP)
• Web (HTTP)
• Etc.
• UDP - based
• Real Audio
• Network time protocol (NTP)
• TF 1-21

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Contest

• Create your own layered protocol mnemonic
• Eg.
• Polish
• Democracy?
• Never!
• the Soviets
• Prevent it
• Again.
• Email me your mnemonic by next week Ill post
  best few.

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IP Datagram Header Fields

• TF 5-45
• Version
• Now 4, Soon to Be 6
• IHL
• Header Length For Options
• Type Of Service
• Ignored By Routers
• Total Length
• Up To 216 Bytes

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IP Datagram Header Fields, cont.

• Identification, Fragment
• Time To Live
• Decremented At Each Hop Prevents Infinite Loops
• Header Checksum
• Source Address
• Destination Address
• Options

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Instant Buddy Questions

• Prof asks a question
• All students work on answer for about a minute
• Students explain answer to buddy (neighbor) for
  30 seconds
• Prof asks one volunteer to explain answer to class

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IBQ

• What are the services provided by the Network
  layer (to the Transport layer)?
• Eg., list function calls and their arguments.

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Transport layer in the Internet

• TCP (Transmission Control Protocol)
• Uses IP
• Reliable
• Retransmits IP packets that dont arrive
  successfully
• Discards duplicate IP packets
• Transmits byte stream
• Connect before communicate
• Point-to-point
• Significant overhead
• ltmeasure thisgt

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Transport layer in the Internet

• UDP (User Datagram Protocol)
• Uses IP
• Unreliable
• Transmits datagrams
• Connectionless
• Supports broadcast and multi-cast
• Less overhead
• ltmeasure thisgt

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Transport layer addressing

• Communications endpoint addressed by
• IP address (32 bit)
• Port number (16 bit)
• Transport protocol (TCP or UDP)

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IP Addresses

• Network Host
• TF 5-47
• NIC Assigns Network Numbers
• NYU ltupdate thisgt
• Class B
• 128.122. X.Y
• Special Addresses
• TF 5-48

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DNS
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Standard services and port numbers
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Conclusions

• Layering a key concept in computer network design
• Determines design and modularity of network
  software
• Major design decision in building a network
  architecture
• Connection-oriented vs. connectionless
• Both popular
• This course focuses on Application layer software

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Reading for students who forget (or never took)
Networking

• Tanenbaum
• Introduction 1.1 - 1.2.5, 1.3.0 - 1.3.4, 1.4,
  1.5.2 - 1.5.4
• The Physical Layer 2.1 - 2.3
• The Medium Access Sublayer 4.3.0 - 4.3.1, 4.3.3,
  4.5.0 - 4.5.2
• The Network Layer 5.1, 5.2.0 - 5.2.3, 5.3.0 -
  5.3.2, 5.4.0 - 5.4.5, 5.4.7, 5.5.0 - 5.5.3, 5.5.9
  - 5.5.10