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../../protocols/transport.rst:9
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Transport protocols rely on the service provided by the network layer. On the Internet, the network layer provides a connectionless service. The network layer identifies each (interface of a) host by using an IP address. It enables hosts to transmit packets that contain up to 64 KBytes of payload to any destination reachable through the network. The network layer does not guarantee the delivery of information, cannot detect transmission errors and does not preserve sequence integrity.
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../../protocols/udp.rst:11
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The User Datagram Protocol (UDP) is defined in :rfc:`768`. It provides an unreliable connectionless transport service on top of the unreliable network layer connectionless service. The main characteristics of the UDP service are :
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../../protocols/wifi.rst:7
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The radio spectrum is a limited resource that must be shared by everyone. During most of the twentieth century, governments and international organizations have regulated most of the radio spectrum. This regulation controls the utilization of the radio spectrum, in order to prevent interference among different users. A company that wants to use a frequency range in a given region must apply for a license from the regulator. Most regulators charge a fee for the utilization of the radio spectrum and some governments have encouraged competition among companies bidding for the same frequency to increase the license fees.
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../../bibliography.rst:9
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LAN/MAN Standards Committee of the IEEE Computer Society. `IEEE Standard for Information Technology - Telecommunications and information exchange between systems - local and metropolitan area networks - specific requirements - Part 11 : Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications <http://standards.ieee.org/getieee802/802.11.html>`_. IEEE, 1999.
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../../exercises/ex-sharing.rst:15
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Medium Access Control
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../../principles/sharing.rst:16
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A network is designed to support a potentially large number of users that exchange information with each other. These users produce and consume information which is exchanged through the network. To support its users, a network uses several types of resources. It is important to keep in mind the different resources that are shared inside the network.
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../../principles/security.rst:12
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When the first computers were attached to data networks, applications were developed to enable them to access to remote computers through the network. To authenticate the remote users, these applications have also relied on usernames and passwords. When a user connects to a distant computer, she sends her username through the network and then provides her password to confirm her `identity`. This authentication scheme is presented in the time sequence diagram below.
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../../exercises/dns.rst:15
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The DNS
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../../exercises/email.rst:9
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the messages exchanged by the client and the server can be easily understood by a developer or network engineer by simply reading the messages
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../../exercises/http.rst:17
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System administrators who are responsible for web servers often want to monitor these servers and check that they are running correctly. As a HTTP server uses TCP on port 80, the simplest solution is to open a TCP connection on port 80 and check that the TCP connection is accepted by the remote host. However, as HTTP/1.x is an ASCII-based protocol, it is also very easy to write a small script that downloads a web page on the server and compares its content with the expected one. Use `telnet` or `ncat` to verify that a web server is running on host `www.computer-networking.info` [#fhttp]_.
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../../exercises/ipv6.rst:11
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Before starting to determine the paths that packets will follow in an IPv6 network, it is important to remember how to convert IPv6 addresses in binary numbers.
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../../exercises/lan.rst:20
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Consider the switched network shown in Fig. 1. What is the spanning tree that will be computed by 802.1d in this network assuming that all links have a unit cost ? Indicate the state of each port.
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../../exercises/routing-policies.rst:24
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Consider the interdomain topology shown in the figure below.
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../../exercises/routing-protocols.rst:13
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Exploring OSPF
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../../exercises/tcp-2.rst:14
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Injecting segments in the Linux TCP stack
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../../exercises/tcp.rst:25
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Once the connection is established, the client and the server can exchange data and acknowledgments.
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../../exercises/tls.rst:15
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Fortunately, telnet is rarely used without TLS these days and system administrators usually prefer to deploy more secure protocols such as ``ssh``.
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../../exercises/trace.rst:10
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Several packet trace analysis tools are available, either as commercial or open-source tools. These tools are able to capture all the packets exchanged on a link. Of course, capturing packets require administrator privileges. They can also analyze the content of the captured packets and display information about them. The captured packets can be stored in a file for offline analysis.
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../../protocols/bgp.rst:11
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Each domain contains a set of routers. From a routing point of view, these domains can be divided into two classes : the `transit` and the `stub` domains. A `stub` domain sends and receives packets whose source or destination are one of its own hosts. A `transit` domain is a domain that provides a transit service for other domains, i.e. the routers in this domain forward packets whose source and destination do not belong to the transit domain. As of this writing, about 85% of the domains in the Internet are stub domains [#fpotaroo]_. A `stub` domain that is connected to a single transit domain is called a `single-homed stub` (e.g., `S1` in the figure below.). A `multihomed stub` is a `stub` domain connected to two or more transit providers (e.g., `S2`).
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../../protocols/congestion.rst:15
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The TCP congestion control scheme was initially proposed by `Van Jacobson`_ in [Jacobson1988]_. The current specification may be found in :rfc:`5681`. TCP relies on `Additive Increase and Multiplicative Decrease (AIMD)`. To implement :term:`AIMD`, a TCP host must be able to control its transmission rate. A first approach would be to use timers and adjust their expiration times in function of the rate imposed by :term:`AIMD`. Unfortunately, maintaining such timers for a large number of TCP connections can be difficult. Instead, `Van Jacobson`_ noted that the rate of TCP congestion can be artificially controlled by constraining its sending window. A TCP connection cannot send data faster than :math:`\frac{window}{rtt}` where :math:`window` is the maximum between the host's sending window and the window advertised by the receiver.
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