A Half Century of Internet: How it works today

1. 00:00Welcome to the third week of our openhpi course "A Half
2. 00:05Century of Internet: How it Works Today".
3. 00:08In this week we want to discuss the idea of internetworking -
4. 00:12the search for the one network.
5. 00:18We have become acquainted with various network types and technologies last week
6. 00:25and each of this network technologies
7. 00:29is fundamentally different from the other one. They are in most
8. 00:34cases incompatible with each other. So the question is how one can organize to
9. 00:41interconnect all these different network technologies and to provide
10. 00:46one homogeneous network.
11. 00:49The network technologies they differ in many characteristics.
12. 00:53They differ in the specific transmission media, they differ in
13. 00:59the performance parameters and control mechanisms,
14. 01:03they differ in the formats such as address schemes and packet formats
15. 01:09and each network technology has its advantages for some special use cases
16. 01:15and has disadvantages when it's used in another use case.
17. 01:21So there is not the network technology that fits all.
18. 01:27For that reason there are different networks and creating the internet
19. 01:33we have to discuss how we can connect this different networks
20. 01:38to together and how we can organize a level and unified level
21. 01:45of the network technology level to provide this homogeneous internet.
22. 01:55We have already discussed the idea of linking different internetworks
23. 02:00when we discussed about wide area networks.
24. 02:06The different networks can be connected bye intermediate systems.
25. 02:12That could be router or another device
26. 02:15which creates a coherent communication system by translating
27. 02:21the different communication protocols between the different networks.
28. 02:27And this technology, this
29. 02:31translation technology of different communication technologies and protocols
30. 02:37this is called internetworking.
31. 02:41Internetworking is a concept for merging heterogenous computer networks
32. 02:46into one uniform communication system and the internet
33. 02:52is the merging of different networks with different network technologies
34. 02:58into one network. It is a virtual network because in fact
35. 03:04it is an interconnection of different networks but for the user
36. 03:09it feels like one homogeneous network.
37. 03:14The idea of linking different networks together is organized
38. 03:20in the following way. We have our network in this case it's the home network
39. 03:26a small home network that is connected by means of a router
40. 03:31via the telephone line with an internet service provider. Internet service provider
41. 03:37who is connected with other internet service providers who
42. 03:42are who help to connect other networks to each other. So in this
43. 03:48way we got a huge network consisting of different networks that are interconnected
44. 03:57by the means of internet server uh service providers and
45. 04:01the important tools here is, important tools for this
46. 04:07interconnection are the routers on each side of each network.
47. 04:15Kind of challenges have to be solved if one wants to provide the one
48. 04:22virtual network in this interconnected tool.
49. 04:27The big question which have to be solved is how do we mediate
50. 04:32between the different network technologies, how this translation is organized?
51. 04:38What do uniform packet formats in address schemes look like
52. 04:43that are understood for all the networks?
53. 04:48Then we have to provide solutions on how data packets find their destination
54. 04:57in such a network of heterogeneous networks.
55. 05:01We have to answer the question how the packet routes are calculated.
56. 05:06How does packet switch the router gets this ability for finding
57. 05:13the pass for a packet?
58. 05:17How error free communication is organised and guaranteed because
59. 05:22each network comes with own each of the internetwork interconnected networks
60. 05:27comes with own technologies? How the transmission errors are avoided or overcome?
61. 05:33How traffic jams and overload situations are avoided? You see there is a
62. 05:38long list of questions that have to be answered.
63. 05:44So the internetworking technology provides such answers
64. 05:50to all those question and we in this week want to have a closer look to it.
65. 05:55So the internet is a network of computer networks.
66. 06:00An internet is a network of computer networks and the internet is the worldwide
67. 06:06connection of diverse computer networks which appear to us,
68. 06:13which appeared to the user as unified communication network
69. 06:17thanks to the network technology.
70. 06:21Network technologies or the core there are so called internet protocol stack
71. 06:28above the
72. 06:29technology layer, the technology layer that comes with different networks
73. 06:34and this internet protocol stack makes the network the connected network appear
74. 06:41as a logically seamless communication system.
75. 06:46So we have to consider internet protocols, we have to consider internet protocol stacks
76. 06:53and the one which is used in practice is a TCP/IP protocol stack.
77. 07:02The internet itself it is an open system architecture.
78. 07:06Everyone knows exactly how the internet is working and how it's composed
79. 07:13and certainly this is a reason for the
80. 07:16explosive growth of the internet. Sixty nine it starts with four computers
81. 07:23at universities and now estimated around twenty billion websites,
82. 07:28one billion internet hosts in the domain name system, four billion internet users.
83. 07:34So meanwhile it's a huge network, it's a basic communication infrastructure
84. 07:41of our modern world.

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