Exit Zen
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../../protocols/wifi.rst:23
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5 GHz
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../../bibliography.rst:63
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Dijkstra, E., `A Note on Two Problems in Connection with Graphs <https://dx.doi.org/10.1007/BF01386390>`_. Numerische Mathematik, 1:269- 271, 1959
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../../glossary.rst:226
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ATM
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../../exercises/ex-sharing.rst:382
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To understand congestion control algorithms, it can also be useful to represent the exchange of packets by using a graphical representation. As a first example, let us consider a very simple network composed of two hosts interconnected through a switch.
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../../principles/transport.rst:45
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Bob : `This is the correct password, you're welcome`
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../../principles/security.rst:247
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Cryptography techniques have initially been defined and used by spies and armies to exchange secret information in manner that ensures that adversaries cannot decode the information even if they capture the message or the person carrying the message. A wide range of techniques have been defined. The first techniques relied on their secrecy to operate. One of the first encryption schemes is attributed to Julius Caesar. When he sent confidential information to his generals, he would encode each message by replacing each letter with another letter that is :math:`n` positions after this letter in the alphabet. For example, the message `SECRET` becomes `VHFUHW` when encoded using Caesar's cipher. This technique could have puzzled some soldiers during Caesar's wars, but today even young kids can recover the original message from the ciphered one.
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../../exercises/dns.rst:53
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Use `dig` to send a query to one of these DNS servers to find the IP address of the DNS server(s) (NS record) responsible for `root-servers.org`
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../../exercises/http.rst:55
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The list of available language tags can be found at http://www.iana.org/assignments/language-subtag-registry. Versions in other formats are available at http://www.langtag.net/registries.html. Additional information about the support of multiple languages in Internet protocols may be found in rfc5646_.
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../../exercises/ipv6.rst:139
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In this network, select `all` the rules in the shown forwarding tables that ensure that the packets sent from ``A`` to ``B`` follow the reverse path of the packets sent by ``B`` to ``A``.
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../../exercises/lan.rst:140
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This network can be launched with the IPMininet_ script shown below. The entire script is available from :download:`/exercises/ipmininet_scripts/stp.py`.
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../../exercises/routing-policies.rst:163
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A simple network
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../../exercises/routing-protocols.rst:253
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This packet is updated when new information is added in the router's OSPFv3 database. A few seconds router, this router sends another Database description packet that announces more information.
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../../exercises/tcp-2.rst:98
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The third segment of the three-way handshake is sent by packetdrill_ after a delay of 0.1 seconds. The connection is now established and the accept system call will succeed.
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../../exercises/trace.rst:104
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Wireshark : flow graph
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../../protocols/bgp.rst:62
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Coming back to the figure above, `AS4` advertises to its two providers `AS1` and `AS2` its own prefixes and the routes learned from its customer, `AS7`. On the other hand, `AS4` advertises to `AS7` all the routes that it knows.
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../../protocols/congestion.rst:100
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In today's Internet, congestion is controlled by regularly sending packets at a higher rate than the network capacity. These packets fill the buffers of the routers and are eventually discarded. But shortly after, TCP senders retransmit packets containing exactly the same data. This is potentially a waste of resources since these successive retransmissions consume resources upstream of the router that discards the packets. Packet losses are not the only signal to detect congestion inside the network. An alternative is to allow routers to explicitly indicate their current level of congestion when forwarding packets. This approach was proposed in the late 1980s [RJ1995]_ and used in some networks. Unfortunately, it took almost a decade before the Internet community agreed to consider this approach. In the mean time, a large number of TCP implementations and routers were deployed on the Internet.
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../../protocols/dnssec.rst:176
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The simplest way to understand the operation of DNSSEC is to rely on a simple example. Let us consider the `example.org` domain and assume that Alice wants to retrieve the `AAAA` record for `www.example.org` using DNSSEC.
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../../protocols/email.rst:105
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the `To:` header line contains the email addresses of the primary recipients of the message [#fto]_. Several addresses can be separated by using commas.
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../../protocols/ethernet.rst:99
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The first property is a consequence of the utilization of CSMA/CD. The second property is a consequence of the physical organization of the Ethernet network as a shared bus. These two properties are important and all revisions to the Ethernet technology have preserved them.
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../../protocols/http.rst:91
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The first URI corresponds to a document named `rfc3986.html` that is stored on the server named `tools.ietf.org` and can be accessed by using the `http` protocol on its default port. The second URI corresponds to an email message, with subject `current-issue`, that will be sent to user `infobot` in domain `example.com`. The `mailto:` URI scheme is defined in :rfc:`2368`. The third URI references the portion `BaseHTTPServer.BaseHTTPRequestHandler` of the document `basehttpserver.html` that is stored in the `library` directory on the `docs.python.org` server. This document can be retrieved by using the `http` protocol. The query parameter `highlight=http` is associated to this URI. The fourth example is a server that operates the telnet_ protocol, uses IPv6 address `2001:db8:3080:3::2` and is reachable on port 2323. The last URI is somewhat special. Most users will assume that it corresponds to a document stored on the `cnn.example.com` server. However, to parse this URI, it is important to remember that the `@` character is used to separate the user name from the host name in the authorization part of a URI. This implies that the URI points to a document named `top_story.htm` on the host having IPv4 address `10.0.0.1`. The document will be retrieved by using the `ftp` protocol with the user name set to `cnn.example.com&story=breaking_news`.
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