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../../protocols/dns.rst:81
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Some DNS resolvers allow any host to send queries. Google operates a `public DNS resolver <https://developers.google.com/speed/public-dns/docs/using>`_ at addresses `2001:4860:4860::8888` and `2001:4860:4860::8844`. Other companies provide similar services.
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../../exercises/sockets.rst:227
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The following program connects a socket to a remote address, sends a message and waits for a reply.
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../../principles/referencemodels.rst:114
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In the remaining chapters of this text, we will often refer to the information exchanged between entities located in different layers. To avoid any confusion, we will stick to the terminology defined earlier, i.e. :
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../../principles/network.rst:102
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With the datagram organization, routers use `hop-by-hop forwarding`. This means that when a router receives a packet that is not destined to itself, it looks up the destination address of the packet in its `forwarding table`. A `forwarding table` is a data structure that maps each destination address (or set of destination addresses) to the outgoing interface over which a packet destined to this address must be forwarded to reach its final destination. The router consults its forwarding table to forward each packet that it handles.
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../../principles/reliability.rst:66
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On the receiver side :
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../../exercises/network.rst:240
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`R1->R5->R4` and `R3->R2->R4`
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../../exercises/sockets.rst:259
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Creating a new socket to communicate through a network
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../../principles/naming.rst:127
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if the server process moves to another physical server, all clients must be informed about the new server address
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../../principles/referencemodels.rst:116
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physical layer entities exchange bits
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../../principles/network.rst:104
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The figure illustrates some possible forwarding tables in this network. By inspecting the forwarding tables of the different routers, one can find the path followed by packets sent from a source to a particular destination. In the example above, host `A` sends its packet to router `R1`. `R1` consults its forwarding table and forwards the packet towards `R2`. Based on its own table, `R2` decides to forward the packet to `R5` that can deliver it to its destination. Thus, the path from `A` to `J` is `A -> R1 -> R2 -> R5 -> J`.
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../../principles/reliability.rst:66
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every millisecond, record the voltage applied on the electrical wire. If the voltage is set to ``+5V``, record the reception of bit `1`. Otherwise, record the reception of bit `0`
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../../exercises/sockets.rst:261
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Until now, we learned how to use sockets that were already created. When writing a whole program, you will have to create you own sockets and choose the concrete technology that it will use to communicate with others. In this section, we will create new sockets and allow a program to communicate with processes located on another computer using a network. The most recent standardized technology used to communicate through a network is the :term:`IPv6` network protocol. In the IPv6 protocol, hosts are identified using *IPv6 addresses*. Modern operating systems allow IPv6 network communications between programs to be done using the socket API, just as we did in the previous sections.
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../../principles/naming.rst:128
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if there are many concurrent clients, the load of the server will increase without any possibility of adding another server without changing the server addresses used by the clients
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../../principles/referencemodels.rst:117
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datalink layer entities exchange *frames*
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../../principles/reliability.rst:70
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This transmission scheme has been used in some early networks. We use it as a basis to understand how hosts communicate. From a Computer Science viewpoint, dealing with voltages is unusual. Computer scientists frequently rely on models that enable them to reason about the issues that they face without having to consider all implementation details. The physical transmission scheme described above can be represented by using a `time-sequence diagram`.
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../../exercises/network.rst:250
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The network below uses port forwarding tables. It has been running for several hours and all hosts have exchanged packets. What is the content of the port forwarding tables ?
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../../exercises/sockets.rst:264
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A program can use the ``socket`` system call to create a new socket.
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../../principles/referencemodels.rst:118
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network layer entities exchange *packets*
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../../exercises/reliability.rst:62
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The Cyclic Redundancy Checks (CRCs) are efficient error detection codes that are able to detect :
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../../exercises/network.rst:273
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At this point, a new link is added between `R1` and `R3`. What happens for the forwarding of packets ?
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