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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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../../exercises/sockets.rst:270
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The ``domain`` parameter specifies the address family that we will use to concretely perform the communication. For an IPv6 socket, the ``domain`` parameter will be set to the value ``AF_INET6``, telling the operating system that we plan to communicate using IPv6 addresses. The ``type`` parameter specifies the communication guarantees that we need. For now, we will use the type ``SOCK_DGRAM`` which allows us to send *unreliable messages*. This means that each data that we send at each call of ``sendto`` will either be completely received or not received at all. The last parameter will be set to ``0``. The following line creates a socket, telling the operating system that we want to communicate using IPv6 addresses and that we want to send unreliable messages.
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../../principles/referencemodels.rst:119
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transport layer entities exchange *segments*
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../../exercises/reliability.rst:64
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all errors that affect an odd number of bits
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../../exercises/network.rst:276
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The network below uses port forwarding tables. What happens if host `A` moves by removing its link with `R1` and replacing it with a link with `R3`? How should networks using port forwarding deal with such mobile hosts ?
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