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../../principles/sharing.rst:133
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Besides the link bandwidth, the buffers on the network nodes are the second type of resource that needs to be shared inside the network. The node buffers play an important role in the operation of the network because that can be used to absorb transient traffic peaks. Consider again the example above. Assume that on average host `A` and host `B` send a group of three packets every ten seconds. Their combined transmission rate (0.6 packets per second) is, on average, lower than the network capacity (1 packet per second). However, if they both start to transmit at the same time, node `R1` will have to absorb a burst of packets. This burst of packets is a small `network congestion`. We will say that a network is congested, when the sum of the traffic demand from the hosts is larger than the network capacity :math:`\sum{demand}>capacity`. This `network congestion` problem is one of the most difficult resource sharing problem in computer networks. `Congestion` occurs in almost all networks. Minimizing the amount of congestion is a key objective for many network operators. In most cases, they will have to accept transient congestion, i.e. congestion lasting a few seconds or perhaps minutes, but will want to prevent congestion that lasts days or months. For this, they can rely on a wide range of solutions. We briefly present some of these in the paragraphs below.
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../../protocols/dns.rst:81
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Some DNS resolvers allow any host to send queries. Google operates a `public DNS resolver <https://developers.google.com/speed/public-dns/docs/using>`_ at addresses `2001:4860:4860::8888` and `2001:4860:4860::8844`. Other companies provide similar services.
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../../bibliography.rst:80
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Gettys, J., Nichols, K., `Bufferbloat: dark buffers in the internet <http://queue.acm.org/detail.cfm?id=2063196>`_. Communications of the ACM 55, no. 1 (2012): 57-65.
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../../glossary.rst:26
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a transmission mode where is same information is sent to all nodes in the network
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../../exercises/ex-sharing.rst:560
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If hosts `A` and `B` send to `D` 1000 bits segments and use a sending window of four segments, what is the maximum throughput that they can achieve ?
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../../exercises/reliability.rst:56
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the Internet checksum used by UDP, TCP and other Internet protocols which is defined in :rfc:`1071` and implemented in various libraries.
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../../exercises/sockets.rst:227
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The following program connects a socket to a remote address, sends a message and waits for a reply.
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../../principles/network.rst:102
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With the datagram organization, routers use `hop-by-hop forwarding`. This means that when a router receives a packet that is not destined to itself, it looks up the destination address of the packet in its `forwarding table`. A `forwarding table` is a data structure that maps each destination address (or set of destination addresses) to the outgoing interface over which a packet destined to this address must be forwarded to reach its final destination. The router consults its forwarding table to forward each packet that it handles.
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../../principles/referencemodels.rst:114
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In the remaining chapters of this text, we will often refer to the information exchanged between entities located in different layers. To avoid any confusion, we will stick to the terminology defined earlier, i.e. :
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../../principles/reliability.rst:66
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On the receiver side :
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../../principles/transport.rst:58
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Let us first discuss the syntactical rules. We will later explain how the information flow can be organized by analyzing real networked applications.
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../../bibliography.rst:85
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Garcia-Lunes-Aceves, J., `Loop-Free Routing Using Diffusing Computations <https://dx.doi.org/10.1109/90.222913>`_, IEEE/ACM Transactions on Networking, Vol. 1, No, 1, Feb. 1993
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../../glossary.rst:129
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CIDR
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../../exercises/ex-sharing.rst:561
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Assume now that `R1` is using round-robin scheduling instead of a FIFO buffer. One queue is used to store the packets sent by `A` and another for the packets sent by `B`. `A` sends one 1000 bits packet every second while `B` sends packets at 10 Mbps. What is the round-trip-time measured by each of these two hosts if each of the two queues of `R1` can store 5 packets ?
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../../exercises/network.rst:240
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`R1->R5->R4` and `R3->R2->R4`
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../../exercises/reliability.rst:57
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the 16 bits or the 32 bits Cyclical Redundancy Checks (CRC) that are often used on disks, in zip archives and in datalink layer protocols. See http://rosettacode.org/wiki/CRC-32 for CRC-32 implementations in various languages.
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../../exercises/sockets.rst:259
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Creating a new socket to communicate through a network
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../../principles/naming.rst:127
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if the server process moves to another physical server, all clients must be informed about the new server address
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../../principles/network.rst:104
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The figure illustrates some possible forwarding tables in this network. By inspecting the forwarding tables of the different routers, one can find the path followed by packets sent from a source to a particular destination. In the example above, host `A` sends its packet to router `R1`. `R1` consults its forwarding table and forwards the packet towards `R2`. Based on its own table, `R2` decides to forward the packet to `R5` that can deliver it to its destination. Thus, the path from `A` to `J` is `A -> R1 -> R2 -> R5 -> J`.
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../../principles/referencemodels.rst:116
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physical layer entities exchange bits
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