Exit Zen
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../../exercises/network.rst:360
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Routes on A
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../../exercises/reliability.rst:83
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Is it possible for a go-back-n receiver to inter-operate with a selective-repeat sender ? Justify your answer.
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../../exercises/sockets.rst:322
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Note that we can reuse our ``send_hello_to_peer`` function without any modification as we wrote it to handle any kind of sockets, including sockets using the IPv6 network protocol.
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../../principles/network.rst:140
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Some networks use the arrival of packets as the trigger to compute the corresponding entries in the forwarding tables. Several technologies have been built upon this principle. When a packet arrives, the router consults its forwarding table to find a path towards the destination. If the destination is present in the forwarding table, the packet is forwarded. Otherwise, the router needs to find a way to forward the packet and update its forwarding table.
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../../principles/referencemodels.rst:141
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Besides this difference in the lower layers, the TCP/IP reference model is very close to the five layers that we use throughout this document.
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../../principles/sharing.rst:175
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When the network load is low, buffer occupancy and link utilization are low. The buffers on the network nodes are mainly used to absorb very short bursts of packets, but on average the traffic demand is lower than the network capacity. If the demand increases, the average buffer occupancy will increase as well. Measurements have shown that the total throughput increases as well. If the buffer occupancy is zero or very low, transmission opportunities on network links can be missed. This is not the case when the buffer occupancy is small but non zero. However, if the buffer occupancy continues to increase, the buffer becomes overloaded and the throughput does not increase anymore. When the buffer occupancy is close to the maximum, the throughput may decrease. This drop in throughput can be caused by excessive retransmissions of reliable protocols that incorrectly assume that previously sent packets have been lost while they are still waiting in the buffer. The network delay on the other hand increases with the buffer occupancy. In practice, a good operating point for a network buffer is a low occupancy to achieve high link utilization and also low delay for interactive applications.
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../../principles/transport.rst:84
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The example above defines several terminals and two commands : `usercommand` and `passwordcommand`. The `ALPHA` terminal contains all letters in upper and lower case. In the `ALPHA` rule, `%x41` corresponds to ASCII character code 41 in hexadecimal, i.e. capital `A`. The `CR` and `LF` terminals correspond to the carriage return and linefeed control characters. The `CRLF` rule concatenates these two terminals to match the standard end of line termination. The `DIGIT` terminal contains all digits. The `SP` terminal corresponds to the white space characters. The `usercommand` is composed of two strings separated by white space. In the ABNF rules that define the messages used by Internet applications, the commands are case-insensitive. The rule `"user"` corresponds to all possible cases of the letters that compose the word between brackets, e.g. `user`, `uSeR`, `USER`, `usER`, ... A `username` contains at least one letter and up to 8 letters. User names are case-sensitive as they are not defined as a string between brackets. The `password` rule indicates that a password starts with a letter and can contain any number of letters or digits. The white space and the control characters cannot appear in a `password` defined by the above rule.
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../../bibliography.rst:126
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McQuillan, J. M., Richer, I., and Rosen, E. C., `An overview of the new routing algorithm for the ARPANET <http://doi.acm.org/10.1145/800092.802981>`_. In Proceedings of the Sixth Symposium on Data Communications (Pacific Grove, California, United States, November 27 - 29, 1979). SIGCOMM '79. ACM, New York, NY, 63-68.
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../../glossary.rst:325
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Ethernet
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../../exercises/ex-sharing.rst:647
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the host continues to listen until the communication channel becomes free. It transmits as soon as the communication channel becomes free.
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../../exercises/network.rst:360
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Routes on B
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../../exercises/reliability.rst:85
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Is it possible for a selective-repeat receiver to inter-operate with a go-back-n sender ? Justify your answer.
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../../exercises/sockets.rst:326
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Endianness: exchanging integers between different computers
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../../principles/network.rst:143
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Computing forwarding tables
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../../principles/referencemodels.rst:146
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The OSI reference model
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../../principles/reliability.rst:180
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All the functions related to the physical transmission or information through a wire (or a wireless link) are usually known as the `physical layer`. The physical layer allows thus two or more entities that are directly attached to the same transmission medium to exchange bits. Being able to exchange bits is important as virtually any information can be encoded as a sequence of bits. Electrical engineers are used to processing streams of bits, but computer scientists usually prefer to deal with higher level concepts. A similar issue arises with file storage. Storage devices such as hard-disks also store streams of bits. There are hardware devices that process the bit stream produced by a hard-disk, but computer scientists have designed filesystems to allow applications to easily access such storage devices. These filesystems are typically divided into several layers as well. Hard-disks store sectors of 512 bytes or more. Unix filesystems group sectors in larger blocks that can contain data or `inodes` representing the structure of the filesystem. Finally, applications manipulate files and directories that are translated in blocks, sectors and eventually bits by the operating system.
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../../principles/sharing.rst:179
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Discarding packets is one of the signals that the network nodes can use to inform the hosts of the current level of congestion. Buffers on network nodes are usually used as FIFO queues to preserve packet ordering. Several `packet discard mechanisms` have been proposed for network nodes. These techniques basically answer two different questions :
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../../principles/transport.rst:86
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Besides character strings, some applications also need to exchange 16 bits and 32 bits fields such as integers. A naive solution would have been to send the 16- or 32-bits field as it is encoded in the host's memory. Unfortunately, there are different methods to store 16- or 32-bits fields in memory. Some CPUs store the most significant byte of a 16-bits field in the first address of the field while others store the least significant byte at this location. When networked applications running on different CPUs exchange 16 bits fields, there are two possibilities to transfer them over the transport service :
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../../bibliography.rst:127
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McQuillan, J.M., Richer, I., Rosen, E., `The New Routing Algorithm for the ARPANET <https://dx.doi.org/10.1109/TCOM.1980.1094721>`_ Communications, IEEE Transactions on , vol.28, no.5, pp.711,719, May 1980
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../../glossary.rst:327
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The most widely used LAN technology.
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