Exit Zen
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../../protocols/ssh.rst:81
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In practice, an ``ssh`` implementation supports four types of cryptographic algorithms :
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../../protocols/tcp.rst:20
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non-interactive multimedia applications (flash, ...)
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../../protocols/tls.rst:41
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TLS port
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../../protocols/transport-service.rst:18
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the `port number` on which the application `listens` for SDUs
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../../protocols/udp.rst:43
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UDP uses a single segment format shown in the figure below.
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../../protocols/wifi.rst:19
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Typical throughput
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../../bibliography.rst:28
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Beech, W., Nielsen, D., Taylor, J., `AX.25 Link Access Protocol for Amateur Packet Radio <http://www.tapr.org/pdf/AX25.2.2.pdf>`_, version 2.2, Revision: July 1998
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../../index.rst:149
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Appendices
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../../glossary.rst:119
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Application Programming Interface
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../../exercises/ex-sharing.rst:150
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In ALOHA, the hosts rely on acknowledgments to detect whether their frame has been received correctly by the destination. Consider a network running at 100 Mbps where the host exchange 1000 bits frames and acknowledgments of 100 bits. Draw the frames sent by hosts A and B in the figure below. Assume that a square corresponds to 10 microseconds and that the cable has a length of 2 kilometers.
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../../exercises/reliability.rst:26
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a Cyclic Redundancy Check (`CRC`)
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../../exercises/network.rst:94
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In this network, assume that all the link weights are set to 1. What is the paths followed by a packet sent by the router located in `Los Angeles` to reach :
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../../exercises/sockets.rst:107
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The `DATA` primitives are exchanged through a service access point. In the socket API, the equivalent to the service access point is the `socket`. A `socket` is a data structure which is maintained by the networking stack and is used by the application every time it needs to send or receive data through the networking stack.
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../../exercises/transport.rst:60
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Consider a reliable connection-oriented transport protocol that provides the bytestream service. In this transport protocol, the sequence number that is placed inside each DATA segment reflects the position of the bytes in the bytestream. Considering the connection shown below, provide the DATA segments that are sent by `Host A` in response to the `DATA.request`, assuming that one segment is sent for each `DATA.request`.
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../../principles/naming.rst:25
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Each top-level domain is managed by an organization that decides how sub-domain names can be registered. Most top-level domain names use a first-come first served system, and allow anyone to register domain names, but there are some exceptions. For example, `.gov` is reserved for the US government, `.int` is reserved for international organizations and names in the `.ca` are mainly `reserved <http://en.wikipedia.org/wiki/.ca>`_ for companies or users that are present in Canada.
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../../principles/transport.rst:29
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Alice : `Hello`
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../../principles/sharing.rst:36
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A third organization of a computer network is a star topology. In such networks, hosts have a single physical interface and there is one physical link between each host and the center of the star. The node at the center of the star can be either a piece of equipment that amplifies an electrical signal, or an active device, such as a piece of equipment that understands the format of the messages exchanged through the network. Of course, the failure of the central node implies the failure of the network. However, if one physical link fails (e.g. because the cable has been cut), then only one node is disconnected from the network. In practice, star-shaped networks are easier to operate and maintain than bus-shaped networks. Many network administrators also appreciate the fact that they can control the network from a central point. Administered from a Web interface, or through a console-like connection, the center of the star is a useful point of control (enabling or disabling devices) and an excellent observation point (usage statistics).
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../../principles/security.rst:113
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In the above example, `Eve` can capture all the packets exchanged by Bob and Alice. This implies that Eve can discover Alice's username and Alice's password. With this information, Eve can then authenticate as Alice on Bob's computer and do whatever Alice is authorized to do. This is a major problem from a security point of view. To prevent this attack, Alice should never send her password in clear over a network where someone could eavesdrop the information. In some networks, such as an open wireless network, an attacker can easily collect all the data sent by a particular user. In other networks, this is a bit more complex depending on the network technology used, but various software packages exist to automate this process. As will be described later, the best approach to prevent this type of attack is to rely on cryptographic techniques to ensure that passwords are never sent in clear.
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../../exercises/dns.rst:36
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`type` is the type of DNS record that is requested by the query such as `NS` for a nameserver, `A` for an IPv4 address, `AAAA` for an IPv6 address, `MX` for a mail relay, ...
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../../exercises/email.rst:20
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The Post Office Protocol (POP) is a rather simple protocol described in :rfc:`1939`. POP operates in three phases. The first phase is the authorization phase where the client provides a username and a password. The second phase is the transaction phase where the client can retrieve emails. The last phase is the update phase where the client finalizes the transaction. What are the main POP commands and their parameters ? When a POP server returns an answer, how can you easily determine whether the answer is positive or negative ?
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