Exit Zen
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../../exercises/reliability.rst:35
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The delay between the two hosts is `s` seconds in both directions
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../../exercises/sockets.rst:135
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As the ``sendto`` function is generic, this function will work correctly independently from the fact that the peer's address is defined as a path on the computer filesystem or a network address.
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../../exercises/transport.rst:128
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Amazon provides the `S3 storage service <https://s3.amazonaws.com/>`_ where companies and researchers can store lots of information and perform computations on the stored information. Amazon allows users to send files through the Internet, but also by sending hard-disks. Assume that a 1 Terabyte hard-disk can be delivered within 24 hours to Amazon by courier service. What is the minimum bandwidth required to match the bandwidth of this courier service ?
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../../principles/referencemodels.rst:58
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An important point to note about the `Datalink layer` is that although the figure below indicates that two entities of the `Datalink layer` exchange frames directly, in reality this is slightly different. When the `Datalink layer` entity on the left needs to transmit a frame, it issues as many `Data.request` primitives to the underlying `physical layer` as there are bits in the frame. The physical layer will then convert the sequence of bits in an electromagnetic or optical signal that will be sent over the physical medium. The `physical layer` on the right hand side of the figure will decode the received signal, recover the bits and issue the corresponding `Data.indication` primitives to its `Datalink layer` entity. If there are no transmission errors, this entity will receive the frame sent earlier.
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../../principles/network.rst:76
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There are two possible organizations for the network layer :
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../../principles/reliability.rst:52
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1 Mbps
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../../principles/transport.rst:41
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Such a conversation succeeds if both Alice and Bob speak the same language. If Alice meets Tchang who only speaks Chinese, she won't be able to ask him the current time. A conversation between humans can be more complex. For example, assume that Bob is a security guard whose duty is to only allow trusted secret agents to enter a meeting room. If all agents know a secret password, the conversation between Bob and Trudy could be as follows :
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../../principles/sharing.rst:62
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Sharing bandwidth
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../../protocols/dns.rst:54
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The `RDLength` field is the length of the `RData` field that contains the information of the type specified in the `Type` field.
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../../principles/security.rst:198
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In practice, there is a possibility of denial of service attacks as soon as there is a limited resource somewhere in the network. This resource can be the bandwidth of a link, but it could also be the computational power of a server, its memory or even the size of tables used by a given protocol implementation. Defending against real DoS attacks can be difficult, especially if the attacker controls a large number of sources that are used to launch the attacks. In terms of bandwidth, DoS attacks composed of a few Gbps to a few tens of Gbps of traffic are frequent on the Internet. In 2015, `github.com <http://www.github.com>`_ suffered from a distributed DoS that reached a top bandwidth of 400 Gbps according to some `reports <http://www.techworld.com/news/security/worlds-largest-ddos-attack-reached-400gbps-says-arbor-networks-3595715/>`_.
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../../exercises/dns.rst:48
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When run without any parameter, `dig` queries one of the root DNS servers and retrieves the list of the names of all root DNS servers. For technical reasons, there are only 13 different root DNS servers. This information is also available as a text file from http://www.internic.net/zones/named.root. What are the IPv6 addresses of all these servers?
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../../exercises/http.rst:50
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Footnotes
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../../exercises/ipv6.rst:45
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The forwarding paths used in a network depend on the forwarding tables installed in the network nodes. Sometimes, these forwarding tables must be configured manually.
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../../exercises/lan.rst:93
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Most commercial Ethernet switches are able to run the Spanning tree protocol independently on each VLAN. What are the benefits of using per-VLAN spanning trees ?
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../../exercises/routing-policies.rst:153
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How is the reachability of these addresses affected when link `R1`-`R3` fails ?
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../../exercises/routing-protocols.rst:241
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The first packet that this router received his a Hello packet that was sent by router ``r2``. There are several interesting points to note about this packet. First, its source address is the link-local address (``fe80::68bc:b4ff:fe19:42b7``) of router ``r2`` on this interface. The destination address of the packet is reserved IPv6 multicast address for OSPFv3, i.e. ``ff02::5``. The Hop Limit of the packet is set to 1 and OSFPv3 uses a next header of type 89.
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../../exercises/tcp-2.rst:86
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Each line of a packetdrill_ script starts with a `timing` parameter that indicates at what time the event specified on this line should happen. packetdrill_ supports absolute and relative timings. An absolute timing is simply a number that indicates the delay in seconds between the start of the script and the event. A relative timing is indicated by using ``+`` followed by a number. This number is then the delay in seconds between the previous event and the current line. Additional information may be found in [CCB+2013]_.
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../../exercises/trace.rst:94
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The wireshark_ window is divided in three parts. The top part of the window is a summary of the first packets from the trace. By clicking on one of the lines, you can show the detailed content of this packet in the middle part of the window. The middle of the window allows you to inspect all the fields of the captured packet. The bottom part of the window is the hexadecimal representation of the packet, with the field selected in the middle window being highlighted.
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../../protocols/bgp.rst:57
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over a `customer->provider` relationship, the `customer` domain advertises to its `provider` its own prefixes and all the routes that it has learned from its own customers.
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../../protocols/congestion.rst:91
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Initial congestion window
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