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../../principles/reliability.rst:59
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To understand some of the principles behind the physical transmission of information, let us consider the simple case of an electrical wire that is used to transmit bits. Assume that the two communicating hosts want to transmit one thousand bits per second. To transmit these bits, the two hosts can agree on the following rules :
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../../principles/sharing.rst:106 • ../../principles/sharing.rst:172
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Network congestion
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../../principles/transport.rst:51
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Bob : `This is not the correct password.`
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../../protocols/dns.rst:69
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The DNS is mainly used to find the address that corresponds to a given name. However, it is sometimes useful to obtain the name that corresponds to an IP address. This done by using the `PTR` (`pointer`) `RR`. The `RData` part of a `PTR` `RR` contains the name while the `Name` part of the `RR` contains the IP address encoded in the `in-addr.arpa` domain. IPv4 addresses are encoded in the `in-addr.arpa` by reversing the four digits that compose the dotted decimal representation of the address. For example, consider IPv4 address `192.0.2.11`. The hostname associated to this address can be found by requesting the `PTR` `RR` that corresponds to `11.2.0.192.in-addr.arpa`. A similar solution is used to support IPv6 addresses :rfc:`3596`, but slightly more complex given the length of the IPv6 addresses. For example, consider IPv6 address `2001:1890:123a::1:1e`. To obtain the name that corresponds to this address, we need first to convert it in a reverse dotted decimal notation : `e.1.0.0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.a.3.2.1.0.9.8.1.1.0.0.2`. In this notation, each character between dots corresponds to one nibble, i.e. four bits. The low-order byte (`e`) appears first and the high order (`2`) last. To obtain the name that corresponds to this address, one needs to append the `ip6.arpa` domain name and query for `e.1.0.0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.a.3.2.1.0.9.8.1.1.0.0.2.ip6.arpa`. In practice, tools and libraries do the conversion automatically and the user does not need to worry about it.
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../../bibliography.rst:68
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Sally Floyd and Van Jacobson. 1993. `Random early detection gateways for congestion avoidance <https://dx.doi.org/10.1109/90.251892>`_. IEEE/ACM Transactions Networking 1, 4 (August 1993), 397-413.
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../../glossary.rst:235
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BNF
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../../exercises/ex-sharing.rst:538 • ../../exercises/ex-sharing.rst:613
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Consider the network depicted in the figure below.
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../../exercises/network.rst:182 • ../../exercises/network.rst:214
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Same question with virtual circuits.
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../../exercises/reliability.rst:50
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Practice
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../../exercises/sockets.rst:216
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``connect``: connecting a socket to a remote address
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../../exercises/transport.rst:146
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Consider a transport protocol that provides the bytestream service and uses 32 bits sequence number to represent the position of the first byte of the payload of DATA segments in the bytestream. How would you modify this protocol so that it can provide a message-mode service ? Consider first short messages that always fit inside a single segment. In a second step, discuss how you could support messages of unlimited size.
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../../principles/naming.rst:117
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To be able to contact the root nameservers, each DNS client must know their addresses. This implies, that DNS clients must maintain an up-to-date list of the addresses of the root nameservers. Without this list, it is impossible to contact the root nameservers. Forcing all Internet hosts to maintain the most recent version of this list would be difficult from an operational point of view. To solve this problem, the designers of the DNS introduced a special type of DNS server : the DNS resolvers. A :term:`resolver` is a server that provides the name resolution service for a set of clients. A network usually contains a few resolvers. Each host in these networks is configured to send all its DNS queries via one of its local resolvers. These queries are called `recursive queries` as the :term:`resolver` must recursively send requests through the hierarchy of nameservers to obtain the `answer`.
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../../principles/network.rst:89
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the information to be sent
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../../principles/reliability.rst:63
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On the sender side :
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../../bibliography.rst:72
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Fortz, B. Rexford, J. ,Thorup, M., `Traffic engineering with traditional IP routing protocols <https://dx.doi.org/10.1109/MCOM.2002.1039866>`_, IEEE Communication Magazine, October 2002
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../../glossary.rst:237
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A Backus-Naur Form (BNF) is a formal way to describe a language by using syntactic and lexical rules. BNFs are frequently used to define programming languages, but also to define the messages exchanged between networked applications. :rfc:`5234` explains how a BNF must be written to specify an Internet protocol.
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../../exercises/ex-sharing.rst:558
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In this network, compute the minimum round-trip-time between `A` (resp. `B`) and `D`. Perform the computation if the hosts send segments containing 1000 bits.
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../../exercises/network.rst:208 • ../../exercises/network.rst:238
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The network operator would like to use the following paths :
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../../exercises/reliability.rst:52
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Reliable protocols depend on error detection algorithms to detect transmission errors. The following questions will reinforce your understanding of these algorithms.
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../../exercises/transport.rst:148
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What is piggybacking and what are the benefits of this technique ?
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