Transcript Fox, Armando. Introduction Internet Services CS 241 Internet Services

Introduction
CS 241 Internet Services
© Armando Fox
[email protected]
Today’s Travel Photo: Where Are You?
For extra credit on the diagnostic exam. :) Be specific.
Goals
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What’s an Internet service? Where did they come
from?
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Where is the Internet headed?
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What are the challenges in getting there?
Methodology:
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relevant literature: systems, networks, applications…
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Case studies (specific service examples) & guest speakers
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Systematic characterization of application space
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Build something
Ground Rules
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No whining or spectating, lots of building and reading
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Be on time! Especially for guest speakers!
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This quarter’s featured project topic:
Appliance Computing
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Project is really important

Don’t even think about asking for an extension
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Lots of heavy-duty tools will be made available
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“Best project” judged by panel will receive a prize (probably
an expenses-paid trip to a major Internet conference)
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Referees will include both technical personnel and investors
Short Course Outline
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Overview
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Basics, intro, history, programming & deployment models,
ASP model, proxies and middleware, caching & aggregation
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Appliance computing
The customized Internet
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Mass customization, personalization, privacy/security issues
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Adapting to wireless
Software structure for Internet scale
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software structure of Internet applications, software
techniques for scalability and robustness, application
decomposition, failure management
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Building cluster-based systems
Short Course Outline, cont’d.
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The future and the real world
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Internet infrastructure meets reality, Internet
business/economics
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A research agenda for future work in Internet and related
software infrastructure
Non-topics (except in passing):
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security
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low-level networking
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practicum (“how to build a Web site”)
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“how to do an Internet startup” (but we will talk about
business aspects)
Recommended optional readings will be posted
Features This Quarter
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Guest speakers and Technical Advisory Board (on Web)
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Loose coupling to Internet Infrastructure Lab
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Project themes: ubiquitous and appliance computing
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Why these are very similar to “traditional” (Web-based) services
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Focus on user experience and “end-to-end” application functionality
Administrivia
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Web site always under construction
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Also class mailing lists, cs241-all@lists and cs241-staff@lists
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Also class calendar using Yahoo calendar: username cs444i
password tcseq101…please don’t mess it up!
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We may use this to schedule joint lectures
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No class Monday 1/15 (MLK day)
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HW #1 due by email Wed 1/17
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HW is posted on the Web site already
Diagnostic exam! Woohoo!
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Enrollment results announced by email to cs241-all by
Friday
Outline
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Prehistory and History
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HTTP and HTML as foundations
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Characterizing Services
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Service-Centric View of the Internet
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Engineering Challenges
One-Slide Internet Timeline
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1969: four-node ARPAnet
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1973-75: Internetworking & TCP/IP
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Common standards connect networks of networks
1980: Ethernet, Berkeley UNIX, free TCP/IP
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Computers can communicate
Internetworking becomes real
1990: World Wide Web prototype at CERN
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Anyone can access and publish rich content
(Pre)-History: Early Internet Services
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DNS
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rlogin, rsh, rwho, telnet, ftp
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Archie & Veronica
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gopher
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email & news (non-interactive)
What’s Changed?
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Universal client, least-common-denominator output
format (HTML & friends)
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Universal stackable client-server protocol (HTTP)
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Client extensibility via Java and JavaScript
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Mass deployment: new audience with different
expectations
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Exponential growth
A student’s view of the Internet then...
Long flows, thin pipes, infrequent losses
Internet
(56kbps)
ucbvax.berkeley.edu
Typical late-1980’s
grad students
Thanks: © Stefan Savage, Univ. of Washington
… and the Internet now
Short flows, fat pipes, frequent losses
Internet
(>155Mbps)
www.etrade.com
Typical 1999
grad students
5% drop rate
Thanks: © Stefan Savage, Univ. of Washington
HTTP/1.0 Problems
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Chatty: 1 object request per HTTP “transaction”
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Terrible use of TCP
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Slow start, short connections, terrible congestion behavior
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Background: What was TCP designed for?
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Can’t trust caching
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No standard extensibility mechanisms
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Naming completely broken for things like CGI
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“When all you have is a hammer, everything looks
like a nail”: every protocol on earth has been
tunnelled over HTTP
HTTP/1.1 Fixes Some Problems
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Caching directives standardized
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But will people use them? (cache busting)
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Caching semantics are complicated (cookies)
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Still expiration based
Persistent connections
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Client and server complexity
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Can servers afford to keep connections open?
Request pipelining and partial requests
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Client parsing is much more complicated
Services Emerge From the Ooze
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Conclusion: HTTP is flawed, but it doesn’t matter
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CGI-bin, servlets, etc.: RPC all over again?
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Web front ends (databases, shells, …)
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What are the problems with using the Web
(HTML/HTTP) as a substrate for...
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Ecommerce/transaction services?
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“session oriented” services?
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“Push” services?
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Non-PC clients and slow networks?
Where Do Internet Services Live?
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At the server? (common case)
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At the client? (Java, JavaScript, ActiveX extensions)
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In between? (proxies)
Server-Based Applications
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The common case
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Search engines, e-commerce sites, content, other
“destination” services
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If content servers allow caching, where does the
service live then?
Extending the Client
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Client extension mechanisms
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Java applets
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JavaScript
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ActiveX
When are these useful?
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Latency (& disconnection)
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Common example: input validation
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Are standalone applets Internet services?
Which extension mechanism is “best”?
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Metrics: speed, security, ubiquity…others?
Proxy-based
Client
Svr
ISP
Network
Client
ISP
Client
Proxy
Svr
Svr
Svr
What does the proxy do?
Transducer (compression, filtering, anonymization,
language translation...)
Aggregation from multiple servers (many-to-many
vs. many-to-one)
Possibly caching/firewalling
HCI challenge: orthogonal user interfaces
Server vs. Proxy
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What can you do with one but not the other?
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Groupware
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Web databases (Four11, WhoWhere, search engines)
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Anonymizer
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Character set translation, language translation
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MyCoolNewsFromLotsOfSites.com
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Transformations for weird clients
What about security?
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Other objections to proxies too; we’ll explore them later
Service-Centric vs. Content-Centric
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“Content is king” -> “Services are king”
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Most Yahoo! user loyalty is for Yahoo mail--not content
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Approx. 70% of securities trading in Finland done online
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Approx. 1 in 7 U.S. trades done online (estimate: Bill
Burnham, CS First Boston, April 1999)
Why this is especially important for mobile devices
“Utility Company” Requirements
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Availability 24x7
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Robust fault tolerance--self maintenance
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Replication/redundancy & distribution
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How about exploiting clusters?
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How do we measure availability?
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State management: why not just use a big database?
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Incremental growth
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Rapid deployment
Client Diversity
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The “Post-PC” world
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Moore’s Law has made computing
power smaller, cheaper, faster, lowerpower
•Wireless communication is pervasive
and inexpensive enough for consumers
•The Internet has become a mass
market phenomenon: “Access Is the
Killer App”
•Now includes home appliances!
How do we support all these?
Summary
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Building Internet services today is hard
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Unforgiving novice users demand “perfect” availability
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Enormous traffic loads
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Exponential growth along all axes
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Current user experience is indefensible and problem is about
to worsen
Is this…
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A systems problem?
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A networking problem?
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An application design problem?
…Yes.
Today’s Travel Photo (Wailea Point)