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Internet.html
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<title>Internet</title>
<!-- 2014-10-10 Fri 08:08 -->
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<body>
<div id="content">
<h1 class="title">Internet</h1>
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#sec-1">1. The Web Is Built On The Internet</a></li>
<li><a href="#sec-2">2. We Use These Phrases</a></li>
<li><a href="#sec-3">3. Internet Architecture is Composable</a></li>
<li><a href="#sec-4">4. Two Computers Need to Communicate</a>
<ul>
<li><a href="#sec-4-1">4.1. Imagine</a></li>
</ul>
</li>
<li><a href="#sec-5">5. Three Computers Need to Communicate</a>
<ul>
<li><a href="#sec-5-1">5.1. Wires</a></li>
</ul>
</li>
<li><a href="#sec-6">6. Circuit Switching</a>
<ul>
<li><a href="#sec-6-1">6.1. Electronic circuits</a></li>
</ul>
</li>
<li><a href="#sec-7">7. Network</a>
<ul>
<li><a href="#sec-7-1">7.1. Problems</a></li>
</ul>
</li>
<li><a href="#sec-8">8. ARPANET :: Network</a>
<ul>
<li><a href="#sec-8-1">8.1. Details</a></li>
</ul>
</li>
<li><a href="#sec-9">9. Packet Switching</a>
<ul>
<li><a href="#sec-9-1">9.1. Postal</a></li>
</ul>
</li>
<li><a href="#sec-10">10. Trade-offs</a>
<ul>
<li><a href="#sec-10-1">10.1. Communication</a></li>
</ul>
</li>
<li><a href="#sec-11">11. Internet Protocol</a>
<ul>
<li><a href="#sec-11-1">11.1. End-to-end</a></li>
</ul>
</li>
<li><a href="#sec-12">12. Internet Protocol</a>
<ul>
<li><a href="#sec-12-1">12.1. IP</a></li>
</ul>
</li>
<li><a href="#sec-13">13. Packets travel over networks</a>
<ul>
<li><a href="#sec-13-1">13.1. Routing Details</a></li>
<li><a href="#sec-13-2">13.2. <code>traceroute</code></a></li>
</ul>
</li>
<li><a href="#sec-14">14. IP Address</a>
<ul>
<li><a href="#sec-14-1">14.1. IPv4 notation</a></li>
</ul>
</li>
<li><a href="#sec-15">15. Routing</a>
<ul>
<li><a href="#sec-15-1">15.1. More information</a></li>
</ul>
</li>
<li><a href="#sec-16">16. Ethernet</a>
<ul>
<li><a href="#sec-16-1">16.1. Trade-offs</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="outline-container-sec-1" class="outline-2">
<h2 id="sec-1"><span class="section-number-2">1</span> The Web Is Built On The Internet   <span class="tag"><span class="slide">slide</span></span></h2>
</div>
<div id="outline-container-sec-2" class="outline-2">
<h2 id="sec-2"><span class="section-number-2">2</span> We Use These Phrases   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-2">
<ul class="org-ul">
<li>"Connects to server"
</li>
<li>"Sends response to client"
</li>
<li>"Closes the connection"
</li>
</ul>
<p>
What do they mean?
</p>
</div>
</div>
<div id="outline-container-sec-3" class="outline-2">
<h2 id="sec-3"><span class="section-number-2">3</span> Internet Architecture is Composable   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-3">
<div class="figure">
<p><img src="img/composable_inception.jpg" alt="composable_inception.jpg"/></p>
</div>
<ul class="org-ul">
<li>Emphasize flexibility
</li>
<li>Allow for growth, incremental adoption
</li>
<li>Interchangeable parts
</li>
</ul>
</div>
</div>
<div id="outline-container-sec-4" class="outline-2">
<h2 id="sec-4"><span class="section-number-2">4</span> Two Computers Need to Communicate   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-4">
<ul class="org-ul">
<li>String a wire between them
</li>
<li>Send bits across via voltage changes
</li>
<li>Wait for response?
</li>
</ul>
</div>
<div id="outline-container-sec-4-1" class="outline-3">
<h3 id="sec-4-1"><span class="section-number-3">4.1</span> Imagine   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-4-1">
<ul class="org-ul">
<li>A time before the Internet and Web
</li>
<li>Wire could be connected in any way
</li>
<li>Bit could be sent in anyway
</li>
<li>Other computer may respond, may not
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-5" class="outline-2">
<h2 id="sec-5"><span class="section-number-2">5</span> Three Computers Need to Communicate   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-5">
<p>
Get more wire
</p>
<div class="figure">
<p><img src="img/3c-communication.png" alt="3c-communication.png"/></p>
</div>
</div>
<div id="outline-container-sec-5-1" class="outline-3">
<h3 id="sec-5-1"><span class="section-number-3">5.1</span> Wires   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-5-1">
<ul class="org-ul">
<li>Multiple wires between computers?
<ul class="org-ul">
<li>One sending, one receiving?
</li>
</ul>
</li>
<li>Each computer hooked up to every other, no message passing
</li>
<li>Mostly workable
</li>
<li>Disadvantage: what happens when you want to connect another computer?
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-6" class="outline-2">
<h2 id="sec-6"><span class="section-number-2">6</span> Circuit Switching   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-6">
<ul class="org-ul">
<li>New computer joins network: wire it up
</li>
<li>Switch the electronic circuit
</li>
</ul>
<div class="figure">
<p><img src="img/telephone-operators.jpg" alt="telephone-operators.jpg"/></p>
</div>
</div>
<div id="outline-container-sec-6-1" class="outline-3">
<h3 id="sec-6-1"><span class="section-number-3">6.1</span> Electronic circuits   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-6-1">
<ul class="org-ul">
<li>Very similar to phone "networks": wire up the two parties
</li>
<li>Doesn't scale well, but can be fine for small networks
</li>
<li>Computers better when multiple can communicate: conference line
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-7" class="outline-2">
<h2 id="sec-7"><span class="section-number-2">7</span> Network   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-7">
<div class="figure">
<p><img src="img/3c-communication.png" alt="3c-communication.png"/></p>
</div>
<ul class="org-ul">
<li>Now we have a network
</li>
<li>Mostly computer-to-computer
</li>
<li>How to we communicate between networks?
</li>
</ul>
</div>
<div id="outline-container-sec-7-1" class="outline-3">
<h3 id="sec-7-1"><span class="section-number-3">7.1</span> Problems   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-7-1">
<ul class="org-ul">
<li>Can't put whole world on same medium
</li>
<li>Composability: allow different LAN to work independently
</li>
<li>Need some way to address computers that is independent from local network
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-8" class="outline-2">
<h2 id="sec-8"><span class="section-number-2">8</span> ARPANET :: Network   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-8">
<ul class="org-ul">
<li>Circuit Switching -> Packet Switching
</li>
<li>Relied on Interface Message Processors (IMPs)
</li>
<li>Government, no commercial traffic
</li>
</ul>
<div class="figure">
<p><img src="img/Leonard-Kleinrock-and-IMP1.png" alt="Leonard-Kleinrock-and-IMP1.png"/></p>
</div>
</div>
<div id="outline-container-sec-8-1" class="outline-3">
<h3 id="sec-8-1"><span class="section-number-3">8.1</span> Details   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-8-1">
<ul class="org-ul">
<li>First pass: academic inter-network
</li>
<li>Instead of connecting on same medium, use packets that were routed to a
destination with IMPs
</li>
<li>Installation planned at 9 months
</li>
<li>Speed 50 kbit/second (home cable is 245x faster)
<ul class="org-ul">
<li>loading yelp.com would take ~19 seconds
</li>
<li>but wouldn't have fit into memory
</li>
</ul>
</li>
<li>IMPs were early routers, but more complexity: added reliable routing
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-9" class="outline-2">
<h2 id="sec-9"><span class="section-number-2">9</span> Packet Switching   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-9">
<ul class="org-ul">
<li>Send small packets of information
</li>
<li>Addressed to a receiver
</li>
<li>Can share medium
</li>
</ul>
<div class="figure">
<p><img src="img/pony-express.jpg" alt="pony-express.jpg"/></p>
</div>
</div>
<div id="outline-container-sec-9-1" class="outline-3">
<h3 id="sec-9-1"><span class="section-number-3">9.1</span> Postal   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-9-1">
<ul class="org-ul">
<li>More similar to post mail than circuit switched telephones:
</li>
<li>Address a small packet/letter to a person/address
</li>
<li>All mail handled by the same middle layer
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-10" class="outline-2">
<h2 id="sec-10"><span class="section-number-2">10</span> Trade-offs   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-10">
<ul class="org-ul">
<li>Big, expensive IMPs required
</li>
<li>Connection to LAN up to owners
</li>
<li>Couldn't handle multiple connections
</li>
</ul>
</div>
<div id="outline-container-sec-10-1" class="outline-3">
<h3 id="sec-10-1"><span class="section-number-3">10.1</span> Communication   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-10-1">
<ul class="org-ul">
<li>Can't rely on the sophistication of the carrier network
</li>
<li>Can't all be carrying around IMPs
</li>
<li>But we'd still like to send packets of data over some link
</li>
<li>IMPs only expected networks to talk to each other, not applications on
specific hosts
</li>
<li>So next iteration designed to solve these problems
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-11" class="outline-2">
<h2 id="sec-11"><span class="section-number-2">11</span> Internet Protocol   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-11">
<ul class="org-ul">
<li>Moves much responsibility to host software
</li>
<li>Keeps packet switching and routing
</li>
<li>Adds concept of ports*
</li>
</ul>
</div>
<div id="outline-container-sec-11-1" class="outline-3">
<h3 id="sec-11-1"><span class="section-number-3">11.1</span> End-to-end   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-11-1">
<ul class="org-ul">
<li>End-to-end principle: application-specific functionality must reside on
end-hosts, because they know exactly what is required
</li>
<li>Many of the limitations of ARPANET were not able to be composed with new
solution because all of the logic was in the big iron
</li>
<li>Packet switching was a great idea.
</li>
<li>Ports added in TCP/UDP layer
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-12" class="outline-2">
<h2 id="sec-12"><span class="section-number-2">12</span> Internet Protocol   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-12">
<ul class="org-ul">
<li>Where is the destination? (host addressing)
</li>
<li>How do I get there? (routing)
</li>
<li>Stateless!
</li>
</ul>
</div>
<div id="outline-container-sec-12-1" class="outline-3">
<h3 id="sec-12-1"><span class="section-number-3">12.1</span> IP   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-12-1">
<ul class="org-ul">
<li>Simplify: tease apart central concepts to implement composability
</li>
<li>Best effort delivery: send it off and hope for the best
</li>
<li>Don't even guarantee we got the same data!
</li>
<li>Very simple, but flexible enough to build on top of
</li>
<li>But one of the first things stipulated about the Web was we either
expect the data to show up, or see an error. How does that happen?
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-13" class="outline-2">
<h2 id="sec-13"><span class="section-number-2">13</span> Packets travel over networks   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-13">
<ul class="org-ul">
<li>Packets sent to Yelp from ischool
</li>
<li>Destination is specified with a number (IP address)
</li>
<li>Routing is done by forwarding to the next best network
</li>
</ul>
<div class="figure">
<p><img src="img/ip-communication.png" alt="ip-communication.png"/></p>
</div>
</div>
<div id="outline-container-sec-13-1" class="outline-3">
<h3 id="sec-13-1"><span class="section-number-3">13.1</span> Routing Details   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-13-1">
<ul class="org-ul">
<li>We want to send data to Yelp. But where is Yelp?
</li>
<li>Happens to be in SF, but what if it moves?
</li>
<li>Networks hand off to the next network it thinks is "closer" to Yelp
</li>
<li>That network hands it off… etc.
</li>
<li>Until we get to Yelp
</li>
<li>Lots of problems can happen:
<ul class="org-ul">
<li>No route to host
</li>
<li>It can go different ways
</li>
</ul>
</li>
</ul>
</div>
</div>
<div id="outline-container-sec-13-2" class="outline-3">
<h3 id="sec-13-2"><span class="section-number-3">13.2</span> <code>traceroute</code>   <span class="tag"><span class="slide">slide</span></span></h3>
<div class="outline-text-3" id="text-13-2">
<div class="org-src-container">
<pre class="src src-bash">harbinger:~$ traceroute yelp.com
traceroute to yelp.com (199.255.189.160), 30 hops max, 60 byte packets
1 g3-35.inr-211-srb.Berkeley.EDU (128.32.78.3) 0.960 ms 1.151 ms 1.056 ms
2 t6-1.inr-202-reccev.Berkeley.EDU (128.32.255.126) 0.930 ms 1.068 ms 1.194 ms
3 xe-5-1-0.inr-001-sut.Berkeley.EDU (128.32.0.66) 17.730 ms 17.766 ms 17.687 ms
4 dc-sfo-agg-1--ucb-10ge.cenic.net (137.164.50.16) 1.554 ms 1.596 ms 1.552 ms
5 svl-agg2--sfo-agg1-10g.cenic.net (137.164.22.27) 3.430 ms 3.392 ms 3.291 ms
6 dc-oak-core1--svl-core1-ge-1.cenic.net (137.164.46.213) 4.361 ms 3.971 ms 3.992 ms
7 dc-paix-px1--oak-core1-ge.cenic.net (137.164.47.18) 5.479 ms 5.370 ms 5.189 ms
8 abovenet--paix-px1-ge2.cenic.net (198.32.251.78) 5.613 ms 5.519 ms 5.567 ms
9 xe-3-0-0.cr1.sjc2.us.above.net (64.125.31.66) 7.367 ms 7.501 ms 7.345 ms
10 xe-0-0-0.cr2.sjc2.us.above.net (64.125.30.126) 6.403 ms 6.287 ms 6.261 ms
11 xe-0-1-0.mpr4.sfo7.us.above.net (64.125.26.61) 7.303 ms 7.264 ms 7.240 ms
12 209.66.115.62.t01325-02.above.net (209.66.115.62) 7.326 ms 7.279 ms 7.318 ms
13 www.sfo1.yelp.com (199.255.189.160) 7.356 ms 7.293 ms 7.407 ms
</pre>
</div>
</div>
</div>
</div>
<div id="outline-container-sec-14" class="outline-2">
<h2 id="sec-14"><span class="section-number-2">14</span> IP Address   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-14">
<ul class="org-ul">
<li>Numbers, often represented as "dotted decimal" (199.255.189.160)
</li>
<li>But can also be represented as just a number (3355426208)
</li>
<li>IPs assigned by Internet Assigned Numbers Authority
</li>
</ul>
</div>
<div id="outline-container-sec-14-1" class="outline-3">
<h3 id="sec-14-1"><span class="section-number-3">14.1</span> IPv4 notation   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-14-1">
<ul class="org-ul">
<li>"IP" short for "IP Address"
</li>
<li>"dotted quads"
</li>
<li>IP version 4 : 32 bit, IPv6 : 128 bit
</li>
<li>IANA typically assigns ranges, then delegated out
</li>
<li>ischool gets an IP from a range assigned to Berkeley, which has a range
assigned to UC system (example)
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-15" class="outline-2">
<h2 id="sec-15"><span class="section-number-2">15</span> Routing   <span class="tag"><span class="slide">slide</span></span></h2>
<div class="outline-text-2" id="text-15">
<ul class="org-ul">
<li>Border Gateway Protocol tracks routes to IPs
</li>
<li>ISPs manually configure peers to share information
</li>
<li>Routers use BGP to forward packets
</li>
</ul>
</div>
<div id="outline-container-sec-15-1" class="outline-3">
<h3 id="sec-15-1"><span class="section-number-3">15.1</span> More information   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-15-1">
<ul class="org-ul">
<li>Routing and peering big topics, please follow up with a networking class if
you're interested
</li>
<li>Take-away: networks can communicate with each other even if not directly
connected: packets are forwarded along
</li>
</ul>
</div>
</div>
</div>
<div id="outline-container-sec-16" class="outline-2">
<h2 id="sec-16"><span class="section-number-2">16</span> Ethernet   <span class="tag"><span class="slide">slide</span> <span class="two_col">two_col</span></span></h2>
<div class="outline-text-2" id="text-16">
<ul class="org-ul">
<li>All computers on the same physical medium
</li>
<li>"Frames" addressed to a receiver
</li>
<li>Interruptions happen with re-tries
</li>
</ul>
<div class="figure">
<p><img src="img/http-stack.gif" alt="http-stack.gif"/></p>
</div>
</div>
<div id="outline-container-sec-16-1" class="outline-3">
<h3 id="sec-16-1"><span class="section-number-3">16.1</span> Trade-offs   <span class="tag"><span class="notes">notes</span></span></h3>
<div class="outline-text-3" id="text-16-1">
<ul class="org-ul">
<li>Don't have to wire new computers up with separate cables
</li>
<li>Still have to wire computers on the same physical line
</li>
<li>All computer recieve all messages – just choose to ignore the ones not for
it
</li>
<li>Implications about security, bandwidth
</li>
<li>Ethernet just one type of LAN, now dominate
</li>
</ul>
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</div>
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</div>
</div>
<div id="postamble" class="status">
<p class="author">Author: Jim Blomo</p>
<p class="date">Created: 2014-10-10 Fri 08:08</p>
<p class="creator"><a href="http://www.gnu.org/software/emacs/">Emacs</a> 23.4.1 (<a href="http://orgmode.org">Org</a> mode 8.0.6)</p>
<p class="xhtml-validation"><a href="http://validator.w3.org/check?uri=referer">Validate XHTML 1.0</a></p>
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