How the Internet Works

Transcript

1. Noah Kantrowitz Open Source Bridge 2015 How The Internet Works The Life and Times of an HTTP Request
2. It's not a big truck. It's a series of tubes. Ted Stevens
3. We never, ever in the history of mankind have had access to so much information so quickly and so easily. Vint Cerf
5. https:/ /www.google.com/
6. https:/ /www.google.com/
7. DNS
8. DNS • Map names to IP addresses. • gethostbyname() • RFC 1034 & 1035. • "What is the A for www.google.com?"
9. DNS Header ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID QR Opcode Opcode Opcode Opcode AA TC RD RA Z Z Z RCODE RCODE RCODE RCODE QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT
10. DNS Header ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID QR Opcode Opcode Opcode Opcode AA TC RD RA Z Z Z RCODE RCODE RCODE RCODE QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT
11. DNS Header ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID QR Opcode Opcode Opcode Opcode AA TC RD RA Z Z Z RCODE RCODE RCODE RCODE QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT
12. DNS Header ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID QR Opcode Opcode Opcode Opcode AA TC RD RA Z Z Z RCODE RCODE RCODE RCODE QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT
13. DNS Header ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID ID QR Opcode Opcode Opcode Opcode AA TC RD RA Z Z Z RCODE RCODE RCODE RCODE QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT QDCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT ANCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT NSCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT ARCOUNT
14. DNS Question QNAME QTYPE QCLASS
15. DNS Question QNAME QTYPE QCLASS
16. DNS Question QNAME QTYPE QCLASS
17. DNS Question QNAME QTYPE QCLASS
18. DNS Message 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 0 0 0 0 1 1 0 0 1 1 0 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 1 1 0 0 0 1 1 0 0 1 0 1 0 0 0 0 0 0 1 1 0 1 1 0 0 0 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
19. DNS Message 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 0 0 0 0 1 1 0 0 1 1 0 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 1 1 0 0 0 1 1 0 0 1 0 1 0 0 0 0 0 0 1 1 0 1 1 0 0 0 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
20. DNS Message 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 0 0 0 0 0 1 1 0 0 1 1 0 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 1 1 0 0 0 1 1 0 0 1 0 1 0 0 0 0 0 0 1 1 0 1 1 0 0 0 1 1 0 1 1 0 1 1 1 1 0 1 1 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
21. DNS Message 0001010000010000 0000000003777777 06676F6F676C6503 636F6D0000010001
23. IP and UDP
24. IP and UDP • Address and port. • 208.201.224.11:53 • Wrapped in order. • DNS inside UDP inside IP. • RFC 791 & 768.
25. UDP Header Source Port Destination Port Length Checksum Data Data
26. UDP Header Source Port Destination Port Length Checksum Data Data
27. IP Header Version Version Version Version IHL IHL IHL IHL Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Protocol Protocol Protocol Protocol Protocol Protocol Protocol Protocol Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Padding Padding Padding Padding Padding Padding Padding Padding
28. IP Header Version Version Version Version IHL IHL IHL IHL Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Protocol Protocol Protocol Protocol Protocol Protocol Protocol Protocol Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Padding Padding Padding Padding Padding Padding Padding Padding
29. IP Header Version Version Version Version IHL IHL IHL IHL Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Protocol Protocol Protocol Protocol Protocol Protocol Protocol Protocol Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Padding Padding Padding Padding Padding Padding Padding Padding
30. IP Header Version Version Version Version IHL IHL IHL IHL Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Protocol Protocol Protocol Protocol Protocol Protocol Protocol Protocol Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Padding Padding Padding Padding Padding Padding Padding Padding
31. IP Header Version Version Version Version IHL IHL IHL IHL Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Type of Service Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Total Length Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Identification Flags Flags Flags Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Fragment Offset Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Time to Live Protocol Protocol Protocol Protocol Protocol Protocol Protocol Protocol Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Header Checksum Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Source Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Options Padding Padding Padding Padding Padding Padding Padding Padding
32. IP Packet IP Header UDP Header DNS Packet
33. Local Network
34. Local Network • Computer • Switch • Router • Modem
37. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 default 192.168.1.1 eth0
38. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 default 192.168.1.1 eth0
39. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 default 192.168.1.1 eth0
40. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 default 192.168.1.1 eth0
41. Ethernet • Wire framing. • MAC address. • Segments. • IEEE 802.3
42. Segments • Electrical broadcast. • Thicknet. • 10BASE-T and hubs. • Switches.
43. Ethernet Frame Preamble Preamble Preamble Preamble Preamble Preamble Preamble SFD Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Source Address Source Address Source Address Source Address Source Address Source Address Type Type Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding FCS FCS FCS FCS
44. Ethernet Frame Preamble Preamble Preamble Preamble Preamble Preamble Preamble SFD Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Source Address Source Address Source Address Source Address Source Address Source Address Type Type Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding FCS FCS FCS FCS
45. Ethernet Frame Preamble Preamble Preamble Preamble Preamble Preamble Preamble SFD Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Source Address Source Address Source Address Source Address Source Address Source Address Type Type Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding FCS FCS FCS FCS
46. Ethernet Frame Preamble Preamble Preamble Preamble Preamble Preamble Preamble SFD Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Source Address Source Address Source Address Source Address Source Address Source Address Type Type Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding FCS FCS FCS FCS
47. 1000-BASET • Electrical signaling. • IEEE 802.3ab
48. Ethernet Frame Preamble Preamble Preamble Preamble Preamble Preamble Preamble SFD Destination Address Destination Address Destination Address Destination Address Destination Address Destination Address Source Address Source Address Source Address Source Address Source Address Source Address Type Type Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding Data and padding FCS FCS FCS FCS
49. ARP
50. ARP • Bridge between IP and Ethernet. • NDP for IPv6. • "Who has IP address 1.2.3.4?" • In an Ethernet frame. • Broadcast FF:FF:FF:FF:FF:FF.
51. ARP Packet HTYPE PTYPE HLEN PLEN OPER SHA SHA SHA SHA SPA SPA SPA THA THA THA THA TPA TPA TPA
52. ARP Packet HTYPE PTYPE HLEN PLEN OPER SHA SHA SHA SHA SPA SPA SPA THA THA THA THA TPA TPA TPA
53. ARP Packet HTYPE PTYPE HLEN PLEN OPER SHA SHA SHA SHA SPA SPA SPA THA THA THA THA TPA TPA TPA
54. ⌚
55. Sending • Ethernet – 40:4A:3:ED:D2:1C • IP – 208.201.224.11 • UDP – 53 • DNS – www.google.com A
56. Local Router
57. Local Router • Static routing (again). • NAT.
58. Route Table Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 173.228.34.0/24 * eth1 default 173.228.34.1 eth1
59. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 173.228.34.0/24 * eth1 default 173.228.34.1 eth1
60. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 173.228.34.0/24 * eth1 default 173.228.34.1 eth1
61. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 173.228.34.0/24 * eth1 default 173.228.34.1 eth1
62. 208.201.224.11 Destination Gateway Interface 127.0.0.0/8 * lo 192.168.1.0/24 * eth0 173.228.34.0/24 * eth1 default 173.228.34.1 eth1
63. NAT • Rewrite IP and UDP header. • Source address and port. • Share one public address.
64. Sending, Round Two • ARP lookup (or cached). • Ethernet frame. • Send to ISP border router.
65. The Internet
66. A Mesh of Trees • Tree-like at the edges. • Partial mesh in middle. • ~Full mesh in the core.
67. Next Hops • Regional routers. • ISP backbone.
69. BGP
70. Routing Protocol • Distribute routes. • Update over time. • Find optimal paths.
71. BGP • Gossip based. • Prefix based. • Share best routes. • RFC 4271.
72. BGP • Gossip based. • Prefix based. • Share best routes. • RFC 4271.
73. Autonomous Systems • 1-232 (née 216) • ~51000 so far. • AS7065
74. IANA • ICANN department • Internet Assigned Numbers Authority • 5 Regional Internet Registries • AfriNIC, ARIN, APNIC • LACNIC, RIPE NCC
75. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
76. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
77. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
78. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
79. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
80. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
81. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
82. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
83. 1 Weight 5 MED 2 Local Pref 6 Metric 3 AS Path 7 First 4 Origin 8 Tie Breaker BGP Algorithm
84. Security • BGP Hijacking • Ingress Filtering • Rarely used signatures
85. Backbone Router • AS46375 to AS7065
86. DNS Server
87. Receiving • Decode and match IP. • Decode UDP port. • Deliver to process.
88. DNS Server • Decode question. • Check local cache. • Recursion?
89. DNS Recursion
90. Root Servers • 13 DNS servers. • Fixed IP addresses. • Maps TLDs to DNS servers. • [a-m].root-servers.net
91. Recursion Round 1 • DNS query to 198.41.0.4 • com. IN NS a.gtld-servers.net • com. IN NS b.gtld-servers.net. • a.gtld-servers.net. IN A 192.5.6.30 • b.gtld-servers.net. IN A 192.33.14.30
92. Recursion Round 2 • DNS query to 192.5.6.30 • google.com. IN NS ns1.google.com. • google.com. IN NS ns2.google.com. • ns1.google.com. IN A 216.239.32.10 • ns2.google.com. IN A 216.239.34.10
93. Recursion Round 3 • DNS query to 216.239.32.10 • www.google.com. IN A 216.58.192.36
94. DNS Reply • DNS message. • Headers & answer section. • Sent back over the wires. • Un-NAT.
95. TCP
96. TCP • Reliable ACKs. • Three-way handshake. • Congestion control. • RFC 675, 793, ...
97. TCP Headers Source Port Source Port Source Port Source Port Source Port Source Port Source Port Source Port Destination Port Destination Port Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Data Offset Reserved U R G A C K P S H R S T S Y N F I N Window Window Checksum Checksum Checksum Checksum Checksum Checksum Checksum Checksum Urgent Pointer Urgent Pointer Options Options Options Options Options Options Options Options Options Padding
98. TCP Headers Source Port Source Port Source Port Source Port Source Port Source Port Source Port Source Port Destination Port Destination Port Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Data Offset Reserved U R G A C K P S H R S T S Y N F I N Window Window Checksum Checksum Checksum Checksum Checksum Checksum Checksum Checksum Urgent Pointer Urgent Pointer Options Options Options Options Options Options Options Options Options Padding
99. TCP Headers Source Port Source Port Source Port Source Port Source Port Source Port Source Port Source Port Destination Port Destination Port Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Data Offset Reserved U R G A C K P S H R S T S Y N F I N Window Window Checksum Checksum Checksum Checksum Checksum Checksum Checksum Checksum Urgent Pointer Urgent Pointer Options Options Options Options Options Options Options Options Options Padding
100. TCP Headers Source Port Source Port Source Port Source Port Source Port Source Port Source Port Source Port Destination Port Destination Port Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Data Offset Reserved U R G A C K P S H R S T S Y N F I N Window Window Checksum Checksum Checksum Checksum Checksum Checksum Checksum Checksum Urgent Pointer Urgent Pointer Options Options Options Options Options Options Options Options Options Padding
101. TCP Headers Source Port Source Port Source Port Source Port Source Port Source Port Source Port Source Port Destination Port Destination Port Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Acknowledgement Number Data Offset Reserved U R G A C K P S H R S T S Y N F I N Window Window Checksum Checksum Checksum Checksum Checksum Checksum Checksum Checksum Urgent Pointer Urgent Pointer Options Options Options Options Options Options Options Options Options Padding
102. Three Way Handshake • SYN • SYN-ACK • ACK
103. Acknowledgements • Send 1 ... 10. • ACK 10. • Send 11 ... 20. • ACK 15. • Send 15 ... 24.
104. Extras • Slow-start • Avoidance • Fast resend • Karn's • Nagle's • SACK • Scaling • CUBIC
105. TLS
106. TLS (aka SSL) • Stream encryption. • Mutual authentication. • RFC 5246.
107. Crypto
108. TLS Handshake • ClientHello • ServerHello • ChangeCipherSpec • Finished
109. Client Round 1 • ClientHello
110. Server Round 1 • ServerHello • Certificate • ServerKeyExchange • ServerHelloDone
111. Client Round 2 • ClientKeyExchange • ChangeCipherSpec • Finished
112. Server Round 2 • ChangeCipherSpec • Finished
113. Application Data • Data wrapper. • Transparent.
114. HTTP
115. HTTP • Request and response. • Verbs, paths, codes. • RFC 2616.
116. HTTP Request • GET / HTTP/1.1 • Host: www.google.com
117. Sending • TLS • TCP • IP • Ethernet
118. HTTP Response • HTTP/1.1 200 OK • Content-Length: 17914 • \r\n • <!doctype html><html ...
120. ⌚
121. How does the Internet work?
122. Surprisingly well!
123. Questions? @kantrn coderanger.net