Exit Zen
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../../protocols/tls.rst:23
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A TLS session operates over a TCP connection. TLS is responsible for the encryption and the authentication of the SDUs exchanged by the application layer protocol while TCP provides the reliable delivery of this encrypted and authenticated bytestream. TLS is used by many different application layer protocols. The most frequent ones are HTTP (HTTP over TLS is called HTTPS), SMTP :rfc:`3207` or POP and IMAP :rfc:`2595`, but proprietary application-layer protocols also use TLS [AM2019]_.
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../../protocols/transport-service.rst:11
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the `connection-oriented` or `byte-stream` service
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../../protocols/transport.rst:13
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The Real Time Transport Protocol (RTP), defined in :rfc:`3550` is another important protocol that is used by many multimedia applications. It includes functions that belong to the transport layer, but also functions that are related to the encoding of the information. Due to space limitations, we do not discuss it in this section.
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../../protocols/udp.rst:14
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the UDP service does not guarantee the delivery of SDUs (losses can occur and SDUs can arrive out-of-sequence)
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../../protocols/wifi.rst:13
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While most of the frequency ranges of the radio spectrum are reserved for specific applications and require a special license, there are a few exceptions. These exceptions are known as the `Industrial, Scientific and Medical <http://en.wikipedia.org/wiki/ISM_band>`_ (ISM) radio bands. These bands can be used for industrial, scientific and medical applications without requiring a license from the regulator. For example, some radio-controlled models use the 27 MHz ISM band and some cordless telephones operate in the 915 MHz ISM. In 1985, the 2.400-2.500 GHz band was added to the list of ISM bands. This frequency range corresponds to the frequencies that are emitted by microwave ovens. Sharing this band with licensed applications would have likely caused interference, given the large number of microwave ovens that are used. Despite the risk of interference with microwave ovens, the opening of the 2.400-2.500 GHz allowed the networking industry to develop several wireless network techniques to allow computers to exchange data without using cables. In this section, we discuss in more detail the most popular one, i.e. the WiFi [IEEE802.11]_ family of wireless networks. Other wireless networking techniques such as `BlueTooth <http://en.wikipedia.org/wiki/BlueTooth>`_ or `HiperLAN <http://en.wikipedia.org/wiki/HiperLAN>`_ use the same frequency range.
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../../bibliography.rst:14
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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 5: Token Ring Access Method and Physical Layer Specification. IEEE, 1998. available from http://standards.ieee.org/getieee802
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../../glossary.rst:185
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Additive Increase, Multiplicative Decrease. A rate adaption algorithm used notably by TCP where a host additively increases its transmission rate when the network is not congested and multiplicatively decreases when congested is detected.
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../../exercises/ex-sharing.rst:42
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If the transmitting host is located at another position on the shared medium than one of the edges, then the geometrical pattern that represents the transmission of a frame is slightly different. If the transmitting host is placed in the middle of the cable, then the signal is transmitted in both directions on the cable. The figure below shows the transmission of one 100 bits frame at 100 Mbps by host C on the same cable.
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../../principles/security.rst:48
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Alice and Bob are the first names that are used in examples for security techniques. They first appeared in a seminal paper by Diffie and Hellman [DH1976]_. Since then, Alice and Bob are the most frequently used names to represent the users who interact with a network. Other characters such as Eve or Mallory have been added over the years. We will explain their respective roles later.
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../../exercises/dns.rst:25
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Several software tools can be used to send queries to DNS servers. For this exercise, we use dig_ which is installed on most Unix/Linux systems.
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../../exercises/email.rst:11
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it is possible to test a server manually by using telnet
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../../exercises/http.rst:21
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What is the version of HTTP used by your version of curl_ ?
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../../exercises/ipv6.rst:20
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Now that you master the basics, you can determine the paths followed by IPv6 packets in simple networks.
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../../exercises/lan.rst:28
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Consider the switched network shown in Fig. 1. In this network, assume that the LAN between switches S3 and S12 fails. How should the switches update their port/address tables after the link failure ?
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../../exercises/routing-policies.rst:58
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from `AS1` to `AS4`
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../../exercises/routing-protocols.rst:80
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The code is very simple as by default IPMininet_ enables OSPF on routers. We introduce two specific parameters. First, the interface that connects a router to a host is flagged as a passive interface (``igp_passive=True``). This indicates to the router that there are no other routers attached to this interface and that it should not send or accept OSPF Hello messages on this interface. The second configuration parameter is that we set the IGP cost on each link.
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../../exercises/tcp-2.rst:18
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packetdrill_ is a TCP test suite that was designed to develop unit tests to verify the correct operation of a TCP implementation. A more detailed description of packetdrill_ may be found in [CCB+2013]_. packetdrill_ uses a syntax which is a mix between the C language and the tcpdump_ syntax. To understand the operation of packetdrill_, we first discuss several examples. The TCP implementation in the Linux kernel supports all the recent TCP extensions to improve its performance. For pedagogical reasons, we disable [#fsysctl]_ most of these extensions to use a simple TCP stack. packetdrill_ can be easily installed on recent Linux kernels [#finstall]_.
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../../exercises/tcp.rst:43
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TCP can be extended by using options that are negotiated during the three-way handshake.
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../../exercises/trace.rst:15
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As an illustration, let us use tcpdump_ to analyze the packets exchanged while executing the following command on a Linux host:
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../../protocols/bgp.rst:19
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The stub domains can be further classified by considering whether they mainly send or receive packets. An `access-rich` stub domain is a domain that contains hosts that mainly receive packets. Typical examples include small ADSL- or cable modem-based Internet Service Providers or enterprise networks. On the other hand, a `content-rich` stub domain is a domain that mainly produces packets. Examples of `content-rich` stub domains include google_, yahoo_, microsoft_, facebook_ or content distribution networks such as akamai_ or limelight_. For the last few years, we have seen a rapid growth of these `content-rich` stub domains. Recent measurements [ATLAS2009]_ indicate that a growing fraction of all the packets exchanged on the Internet are produced in the data centers managed by these content providers.
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