Exit Zen
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../../exercises/ex-sharing.rst:66
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In a shared medium, a collision may happen if two hosts transmit at almost the same time as shown in the example below.
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../../exercises/reliability.rst:22
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A version of the Alternating Bit Protocol supporting variable length frames uses a header that contains the following fields :
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../../exercises/network.rst:67
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Routing protocols used in data networks only use positive link weights. What would happen with a distance vector routing protocol in the network below that contains a negative link weight ?
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../../exercises/sockets.rst:102
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A detailed discussion of the socket API is outside the scope of this section and the references cited above provide a detailed discussion of all the details of the socket API. As a starting point, it is interesting to compare the socket API with the service primitives that we have discussed in the previous chapter. Let us first consider the connectionless service that consists of the following two primitives :
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../../exercises/transport.rst:38
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Continue the connection so that `Host B` sends `Hello` as data and `Host A` replies by sending `Pleased to meet you`. After having received the response, `Host B` closes the connection gracefully and `Host A` does the same. Discuss on the state that needs to be maintained inside each host.
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../../principles/naming.rst:19
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The first solution that allowed applications to use names was the :term:`hosts.txt` file. This file is similar to the symbol table found in compiled code. It contains the mapping between the name of each Internet host and its associated address [#fhosts]_. It was maintained by SRI International that coordinated the Network Information Center (NIC). When a new host was connected to the network, the system administrator had to register its name and address at the NIC. The NIC updated the :term:`hosts.txt` file on its server. All Internet hosts regularly retrieved the updated :term:`hosts.txt` file from the SRI_ server. This file was stored at a well-known location on each Internet host (see :rfc:`952`) and networked applications could use it to find the address corresponding to a name.
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../../protocols/dns.rst:26
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The DNS header
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../../principles/security.rst:62
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Threats
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../../exercises/dns.rst:27
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A typical usage of dig is as follows:
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../../exercises/email.rst:13
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Telnet is a protocol that allows to obtain a terminal on a remote server. For this, telnet opens a TCP connection with the remote server on port 23. However, most `telnet` implementations allow the user to specify an alternate port as `telnet hosts port` When used with a port number as parameter, `telnet` opens a TCP connection to the remote host on the specified port. `telnet` can thus be used to test any server using an ASCII-based protocol on top of TCP. Note that if you need to stop a running `telnet` session, ``Ctrl-C`` will not work as it will be sent by `telnet` to the remote host over the TCP connection. On many `telnet` implementations you can type ``Ctrl-]`` to freeze the TCP connection and return to the telnet interface.
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../../exercises/http.rst:22
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Can you explain the different headers placed by curl_ in the request ?
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../../exercises/ipv6.rst:31
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Design questions
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../../exercises/lan.rst:31
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Consider the switched network shown in the figure below. Compute the Spanning Tree of this network.
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../../exercises/routing-policies.rst:59
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from `AS4` to `AS2`
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../../exercises/routing-protocols.rst:83
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We use this mininet_ topology to collect packet traces that show the packets that OSPF routers exchange. For this, we add the following ``post_build`` method that IPMininet_ starts after having constructed the network and before launching the daemons. It simply starts tcpdump_ on each router to collect the first 100 OSPF packets that they send/receive.
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../../exercises/tcp-2.rst:20
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Let us start with a very simple example that uses packetdrill_ to open a TCP connection on a server running on the Linux kernel. A packetdrill_ script is a sequence of lines that are executed one after the other. There are three main types of lines in a packetdrill_ script.
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../../exercises/tcp.rst:52
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With your knowledge of TCP, you should now be able to reorder all the segments exchanged over a TCP connection.
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../../exercises/trace.rst:28
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The ``-6`` parameter passed to curl_ forces the utilization of IPv6. curl_ returns an HTML page that indicates that https must be used instead of http to access this web site.
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../../protocols/bgp.rst:21
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Domains need to be interconnected to allow a host inside a domain to exchange IP packets with hosts located in other domains. From a physical perspective, domains can be interconnected in two different ways. The first solution is to directly connect a router belonging to the first domain with a router inside the second domain. Such links between domains are called private interdomain links or `private peering links`. In practice, for redundancy or performance reasons, distinct physical links are usually established between different routers in the two domains that are interconnected.
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../../protocols/congestion.rst:22
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A key question that must be answered by any congestion control scheme is how congestion is detected. The first implementations of the TCP congestion control scheme opted for a simple and pragmatic approach : packet losses indicate congestion. If the network is congested, router buffers are full and packets are discarded. In wired networks, packet losses are mainly caused by congestion. In wireless networks, packets can be lost due to transmission errors and for other reasons that are independent of congestion. TCP already detects segment losses to ensure a reliable delivery. The TCP congestion control scheme distinguishes between two types of congestion :
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