Exit Zen
40
../../principles/reliability.rst:180
English
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.
0/12000 · 1200
40
../../principles/sharing.rst:179
English
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 :
0/3470 · 347
40
../../principles/transport.rst:86
English
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 :
0/6130 · 613
41
../../bibliography.rst:127
English
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
0/2050 · 205
41
../../glossary.rst:327
English
The most widely used LAN technology.
0/360 · 36
41
../../exercises/ex-sharing.rst:648
English
the host stops to listen and waits for a random time before sensing again the communication channel to check whether it is free.
0/1280 · 128
41
../../exercises/network.rst:360
English
Routes on C
0/110 · 11
41
../../exercises/sockets.rst:328
English
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 :
0/6130 · 613
41
../../principles/referencemodels.rst:148
English
Compared to the five layers reference model explained above, the :term:`OSI` reference model defined in [X200]_ is divided in seven layers. The four lower layers are similar to the four lower layers described above. The OSI reference model refined the application layer by dividing it in three layers :
0/3020 · 302
41
../../principles/reliability.rst:184
English
Computer networks use a similar approach. Each layer provides a service that is built above the underlying layer and is closer to the needs of the applications. The datalink layer builds upon the service provided by the physical layer. We will see that it also contains several functions.
0/2880 · 288
41
../../principles/transport.rst:88
English
send the most significant byte followed by the least significant byte
0/690 · 69
42
../../bibliography.rst:132
English
Metcalfe R., Boggs, D., `Ethernet: Distributed packet-switching for local computer networks <http://doi.acm.org/10.1145/360248.3602530>`_. Communications of the ACM, 19(7):395--404, 1976.
0/1870 · 187
42
../../glossary.rst:319
English
file transfer
0/130 · 13
42
../../exercises/network.rst:360
English
Routes on D
0/110 · 11
42
../../exercises/reliability.rst:91
English
Same question as above, but assume now that both the sender and the receiver implement selective repeat. Note that the answer can be different from the above question.
0/1670 · 167
42
../../exercises/sockets.rst:330
English
send the most significant byte followed by the least significant byte
0/690 · 69
42
../../principles/network.rst:147
English
The first technique assumes that the underlying network topology is a tree. A tree is the simplest network to be considered when forwarding packets. The main advantage of using a tree is that there is only one path between any pair of nodes inside the network. Since a tree does not contain any cycle, it is impossible to have forwarding loops in a tree-shaped network.
0/3690 · 369
42
../../principles/reliability.rst:188
English
The datalink layer
0/180 · 18
42
../../principles/sharing.rst:182
English
`Which packet(s) should be discarded ?` Once the network node has decided to discard packets, it needs to actually discard real packets.
0/1360 · 136
42
../../principles/transport.rst:89
English
send the least significant byte followed by the most significant byte
0/690 · 69