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../../principles/transport.rst:101
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The message mentioned above will be transmitted starting from the upper 32-bits word in network byte order. The first field is encoded in 16 bits. It is followed by eight one bit flags (`A-H`), a 24 bits field whose high order byte is shown in the first line and the two low order bytes appear in the second line followed by two one byte fields. This ASCII representation is frequently used when defining binary protocols. We will use it for all the binary protocols that are discussed in this book.
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../../bibliography.rst:312
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Roberts, L., `ALOHA packet system with and without slots and capture <http://doi.acm.org/10.1145/1024916.1024920>`_. SIGCOMM Computer Communication Review 5, 2 (Apr. 1975), 28-42.
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../../exercises/network.rst:363 • ../../exercises/network.rst:365
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2 via B
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../../exercises/sockets.rst:343
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The message mentioned above will be transmitted starting from the upper 32-bits word in network byte order. The first field is encoded in 16 bits. It is followed by eight one bit flags (`A-H`), a 24 bits field whose high order byte is shown in the first line and the two low order bytes appear in the second line followed by two one byte fields. This ASCII representation is frequently used when defining binary protocols. We will use it for all the binary protocols that are discussed in this book.
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../../principles/network.rst:187
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By inspecting the source and destination addresses of packets, network nodes can automatically derive their forwarding tables. As we will discuss later, this technique is used in :term:`Ethernet` networks. Despite being widely used, it has two important drawbacks. First, packets sent to unknown destinations are broadcasted in the network even if the destination is not attached to the network. Consider the transmission of ten packets destined to `Z` in the network above. When a node receives a packet towards this destination, it can only broadcast that packet. Since `Z` is not attached to the network, no node will ever receive a packet whose source is `Z` to update its forwarding table. The second and more important problem is that few networks have a tree-shaped topology. It is interesting to analyze what happens when a port-address table is used in a network that contains a cycle. Consider the simple network shown below with a single host.
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../../principles/referencemodels.rst:163
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There is now a rough consensus for the greater use of the Unicode_ character format. Unicode can represent more than 100,000 different characters from the known written languages on Earth. Maybe one day, all computers will only use Unicode to represent all their stored characters and Unicode could become the standard format to exchange characters, but we are not yet at this stage today.
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../../principles/reliability.rst:204
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The `framing` problem can be defined as : "`How does a sender encode frames so that the receiver can efficiently extract them from the stream of bits that it receives from the physical layer`".
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../../principles/sharing.rst:191
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Discarding packets is a frequent reaction to network congestion. Unfortunately, discarding packets is not optimal since a packet which is discarded on a network node has already consumed resources on the upstream nodes. There are other ways for the network to inform the end hosts of the current congestion level. A first solution is to mark the packets when a node is congested. Several networking technologies have relied on this kind of packet marking.
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../../principles/transport.rst:105
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The peer-to-peer model emerged during the last ten years as another possible architecture for networked applications. In the traditional client-server model, hosts act either as servers or as clients and a server serves a large number of clients. In the peer-to-peer model, all hosts act as both servers and clients and they play both roles. The peer-to-peer model has been used to develop various networked applications, ranging from Internet telephony to file sharing or Internet-wide filesystems. A detailed description of peer-to-peer applications may be found in [BYL2008]_. Surveys of peer-to-peer protocols and applications may be found in [AS2004]_ and [LCP2005]_.
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../../bibliography.rst:313
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Ross, F., `An overview of FDDI: The fiber distributed data interface <https://dx.doi.org/10.1109/49.44552>`_, IEEE J. Selected Areas in Comm., vol. 7, no. 7, pp. 1043-1051, Sept. 1989
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../../glossary.rst:102
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ftp
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../../exercises/network.rst:363 • ../../exercises/network.rst:367
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3 via C
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../../exercises/sockets.rst:346
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Exercises
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../../principles/referencemodels.rst:165
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An interesting historical discussion of the OSI-TCP/IP debate may be found in [Russel06]_
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../../principles/reliability.rst:206
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A first solution to this problem is to require the physical layer to remain idle for some time after the transmission of each frame. These idle periods can be detected by the receiver and serve as a marker to delineate frame boundaries. Unfortunately, this solution is not acceptable for two reasons. First, some physical layers cannot remain idle and always need to transmit bits. Second, inserting an idle period between frames decreases the maximum bit rate that can be achieved.
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../../principles/sharing.rst:195
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In datagram networks, `Forward Explicit Congestion Notification` (FECN) can be used. One field of the packet header, typically one bit, is used to indicate congestion. When a host sends a packet, the congestion bit is unset. If the packet passes through a congested node, the congestion bit is set. The destination can then determine the current congestion level by measuring the fraction of the packets that it received with the congestion bit set. It may then return this information to the sending host to allow it to adapt its retransmission rate. Compared to packet discarding, the main advantage of FECN is that hosts can detect congestion explicitly without having to rely on packet losses.
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../../principles/transport.rst:109 • ../../principles/transport.rst:122 • ../../principles/transport.rst:213 • ../../principles/transport.rst:526
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The transport layer
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../../bibliography.rst:314
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Russell A., `Rough Consensus and Running Code and the Internet-OSI Standards War <https://dx.doi.org/10.1109/MAHC.2006.42>`_, IEEE Annals of the History of Computing, July-September 2006
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../../glossary.rst:104
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The File Transfer Protocol defined in :rfc:`959` has been the `de facto` protocol to exchange files over the Internet before the widespread adoption of HTTP :rfc:`2616`.
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../../exercises/network.rst:363
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4 via D
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