Exit Zen
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../../principles/reliability.rst:51
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1 Kbps
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../../principles/transport.rst:33
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Alice : `Thank you`
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../../exercises/reliability.rst:34
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The bandwidth of the two directions of the link is set to `B` bits per second
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../../exercises/network.rst:103
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Assume that the routers located in `Denver` and `Kansas City` need to exchange lots of packets. Can you configure the link metrics such that the link between these two routers does not carry any packet sent by another router in the network ?
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../../exercises/sockets.rst:122
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In the following example, a C program is sending the bytes ``'h'``, ``'e'``, ``'l'``, ``'l'`` and ``'o'`` to a remote process located at address ``peer_addr``, using the already created socket ``sock``.
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../../exercises/transport.rst:126
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Practice
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../../principles/naming.rst:77
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The Domain Name System was created at a time when the Internet was mainly used in North America. The initial design assumed that all domain names would be composed of letters and digits :rfc:`1035`. As Internet usage grew in other parts of the world, it became important to support non-ASCII characters. For this, extensions have been proposed to the Domain Name System :rfc:`3490`. In a nutshell, the solution that is used to support Internationalized Domain Names works as follows. First, it is possible to use most of the Unicode characters to encode domain names and hostnames, with a few exceptions (for example, the dot character cannot be part of a name since it is used as a separator). Once a domain name has been encoded as a series of Unicode characters, it is then converted into a string that contains the ``xn--`` prefix and a sequence of ASCII characters. More details on these algorithms can be found in :rfc:`3490` and :rfc:`3492`.
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../../principles/referencemodels.rst:56
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The `Datalink layer` builds on the service provided by the underlying physical layer. The `Datalink layer` allows two hosts that are directly connected through the physical layer to exchange information. The unit of information exchanged between two entities in the `Datalink layer` is a frame. A frame is a finite sequence of bits. Some `Datalink layers` use variable-length frames while others only use fixed-length frames. Some `Datalink layers` provide a connection-oriented service while others provide a connectionless service. Some `Datalink layers` provide reliable delivery while others do not guarantee the correct delivery of the information.
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../../principles/network.rst:74
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To send one byte of information to host `B`, host `A` needs to place this information inside a `packet`. In addition to the data being transmitted, the packet also contains either the addresses of the source and the destination nodes or information that indicates the path that needs to be followed to reach the destination.
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../../principles/reliability.rst:51
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:math:`10^3`
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../../principles/transport.rst:34
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Bob : `You're welcome`
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../../protocols/dns.rst:52
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The `TTL` field indicates the lifetime of the `Resource Record` in seconds. This field is set by the server that returns an answer and indicates for how long a client or a resolver can store the `Resource Record` inside its cache. A long `TTL` indicates a stable `RR`. Some companies use short `TTL` values for mobile hosts and also for popular servers. For example, a web hosting company that wants to spread the load over a pool of hundred servers can configure its nameservers to return different answers to different clients. If each answer has a small `TTL`, the clients will be forced to send DNS queries regularly. The nameserver will reply to these queries by supplying the address of the less loaded server.
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../../protocols/routing.rst:46
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The RIP message format
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../../exercises/reliability.rst:35
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The delay between the two hosts is `s` seconds in both directions
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../../exercises/sockets.rst:135
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As the ``sendto`` function is generic, this function will work correctly independently from the fact that the peer's address is defined as a path on the computer filesystem or a network address.
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../../exercises/transport.rst:128
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Amazon provides the `S3 storage service <https://s3.amazonaws.com/>`_ where companies and researchers can store lots of information and perform computations on the stored information. Amazon allows users to send files through the Internet, but also by sending hard-disks. Assume that a 1 Terabyte hard-disk can be delivered within 24 hours to Amazon by courier service. What is the minimum bandwidth required to match the bandwidth of this courier service ?
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../../principles/referencemodels.rst:58
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An important point to note about the `Datalink layer` is that although the figure below indicates that two entities of the `Datalink layer` exchange frames directly, in reality this is slightly different. When the `Datalink layer` entity on the left needs to transmit a frame, it issues as many `Data.request` primitives to the underlying `physical layer` as there are bits in the frame. The physical layer will then convert the sequence of bits in an electromagnetic or optical signal that will be sent over the physical medium. The `physical layer` on the right hand side of the figure will decode the received signal, recover the bits and issue the corresponding `Data.indication` primitives to its `Datalink layer` entity. If there are no transmission errors, this entity will receive the frame sent earlier.
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../../principles/network.rst:76
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There are two possible organizations for the network layer :
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../../principles/reliability.rst:52
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1 Mbps
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../../protocols/dns.rst:54
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The `RDLength` field is the length of the `RData` field that contains the information of the type specified in the `Type` field.
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