Networking

INFO 253B: Backend Web Architecture

Kay Ashaolu

The Web is built on the internet

We use these phrases

  • "Connects to server"
  • "Sends response to client"
  • "Closes the connection"

  • What do they mean?

Internet Architecture is Composable

  • Emphasize flexibility
  • Allow for growth, incremental adoption
  • Interchangeable parts

Two computers need to communicate

  • String a wire between them
  • Send bits across via voltage changes
  • Wait for response?

Three computers need to communicate

  • Get more wire

Circuit Switching

  • New computer joins network: wire it up
  • Switch the electronic circuit
  • Now we have a network
  • Mostly computer-to-computer
  • How do we communicate between networks?

Circuit Switching

Arpanet :: Network​

  • Circuit Switching -> Packet Switching
  • Relied on Interface Message Processors (IMPs)
  • Government, no commercial traffic

Packet Switching

  • Send small packets of information
  • Addressed to a receiver
  • Can share medium

Internet Protocol

  • Moves responsibility to host software
  • Keeps packet switching and routing
  • Adds concept of ports
  • Packets sent from my house to the iSchool's servers
  • Destination is specified with a number (IP address)
  • Routing is done by forwarding to the next best network

Packets travel over networks

Traceroute

Kays-MacBook-Air:~ Professor$ traceroute ischool.berkeley.edu
traceroute to ischool.berkeley.edu (128.32.78.26), 64 hops max, 52 byte packets
 1  192.168.0.1 (192.168.0.1)  2.527 ms  1.753 ms  1.575 ms
 2  dsldevice.attlocal.net (192.168.1.254)  2.044 ms  2.278 ms  2.338 ms
 3  162-229-188-1.lightspeed.sntcca.sbcglobal.net (162.229.188.1)  22.120 ms  31.756 ms  25.985 ms
 4  71.148.149.108 (71.148.149.108)  19.930 ms  21.653 ms  22.385 ms
 5  * * *
 6  12.83.39.213 (12.83.39.213)  21.868 ms
    12.83.39.209 (12.83.39.209)  25.679 ms  25.866 ms
 7  12.122.114.5 (12.122.114.5)  25.688 ms  26.289 ms  23.622 ms
 8  * * *
 9  * * *
10  cenic.ear1.sanjose1.level3.net (4.15.122.46)  37.818 ms  33.492 ms  32.269 ms
11  oak-agg4--svl-agg4-100ge.cenic.net (137.164.46.41)  34.768 ms
    oak-agg4--svl-agg4-100ge-#2.cenic.net (137.164.46.167)  32.460 ms
    oak-agg4--svl-agg4-100ge.cenic.net (137.164.46.41)  30.218 ms
12  ucb--oak-agg4-10g.cenic.net (137.164.50.31)  34.708 ms  30.780 ms  31.574 ms
13  t2-3.inr-201-sut.berkeley.edu (128.32.0.37)  32.730 ms
    t2-3.inr-202-reccev.berkeley.edu (128.32.0.39)  35.720 ms  33.422 ms
14  e3-48.inr-310-ewdc.berkeley.edu (128.32.0.97)  33.500 ms
    e3-47.inr-310-ewdc.berkeley.edu (128.32.0.99)  33.454 ms
    e3-48.inr-310-ewdc.berkeley.edu (128.32.0.97)  33.181 ms
15  firewall.ischool.berkeley.edu (128.32.16.132)  33.945 ms  42.825 ms  35.531 ms
16  ischool.berkeley.edu (128.32.78.26)  33.876 ms  37.632 ms  34.436 ms

IP Address

  • Numbers, often represented as "dotted decimal" (199.255.189.160)
  • But can also be represented as just a number (3355426208)
  • IPs assigned by Internet Assigned Numbers Authority

Routing

  • Border Gateway Protocol tracks routes to IPs
  • ISPs manually configure peers to share information
  • Routers use BGP to forward packets

Questions?