Exit Zen
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../../exercises/http.rst:37
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As for the DNS, besides using software tools that implement the HTTP protocols, it can also be useful to analyze packet traces with wireshark_ . The exercises below contain simple packet traces collected with different versions of the HTTP protocol.
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../../exercises/ipv6.rst:43 • ../../exercises/ipv6.rst:152
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router ``R4`` uses address ``2001:db8:1341:34::4`` on its West interface, address ``2001:db8:1341:24::4`` on its North interface and address ``2001:db8:1341:4::4`` on its East interface
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../../exercises/lan.rst:91
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Fig. 5. Will the link between `S0` and `S1` ever be used?
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../../exercises/routing-policies.rst:151
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Via which provider does `AS456` receive the packets destined to ``2001:db8:caff::bb`` and ``2001:db8:cafe::aa`` ?
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../../exercises/routing-protocols.rst:239
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We can also use the packet traces that were collected by tcpdump_ to observe the packets that the OSPFv3 daemons exchange. OSPFv3 is a more complex protocol that the basic link state protocol that we have described in this book, but you should be able to understand some of these packets. The packet traces are available as :download:`/exercises/traces/ospf6-r1-trace.pcap`, :download:`/exercises/traces/ospf6-r2-trace.pcap` and :download:`/exercises/traces/ospf6-r3-trace.pcap`. Here are a few interesting packets collected on router ``r1``.
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../../exercises/tcp-2.rst:80
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At this point, the socket is ready to accept incoming TCP connections. packetdrill_ needs to inject a TCP segment in the instrumented Linux stack. This can be done with the line below.
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../../exercises/trace.rst:88
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Wireshark : default window
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../../protocols/bgp.rst:55
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To understand the `customer->provider` relationship, let us consider the simple internetwork shown in the figure above. In this internetwork, `AS7` is a stub domain that is connected to one provider : `AS4`. The contract between `AS4` and `AS7` allows a host inside `AS7` to exchange packets with any host in the internetwork. To enable this exchange of packets, `AS7` must know a route towards any domain and all the domains of the internetwork must know a route via `AS4` that allows them to reach hosts inside `AS7`. From a routing perspective, the commercial contract between `AS7` and `AS4` leads to the following routes being exchanged :
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../../protocols/congestion.rst:89
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Furthermore when a TCP connection has been idle for more than its current retransmission timer, it should reset its congestion window to the congestion window size that it uses when the connection begins, as it no longer knows the current congestion state of the network.
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../../protocols/dnssec.rst:161
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the `DNSKEY` record allows storing the public key associated with a zone. This record is encoded as a TLV and includes a `Base64` representation of the key and the identification of the public key algorithm. This allows the `DNSKEY` record to support different public key algorithms.
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../../protocols/email.rst:98
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The email header contains several lines that all begin with a keyword followed by a colon and additional information. The format of email messages and the different types of header lines are defined in :rfc:`5322`. Two of these header lines are mandatory and must appear in all email messages :
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../../protocols/ethernet.rst:92
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What is the Ethernet service ?
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../../protocols/http.rst:58
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The first components of the `world wide web` are the Uniform Resource Identifiers (URI), defined in :rfc:`3986`. A URI is a character string that unambiguously identifies a resource on the world wide web. Here is a subset of the BNF for URIs ::
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../../protocols/ipv6.rst:90
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PIP proposed in :rfc:`1621`
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../../protocols/ppp.rst:35
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`LAPB <http://en.wikipedia.org/wiki/LAPB>`_ and `HDLC <http://en.wikipedia.org/wiki/HDLC>`_ were widely used datalink layer protocols.
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../../protocols/rpc.rst:36
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For basic data types, :rfc:`1832` simply maps their representation into a sequence of bytes. For example a 32 bits integer is transmitted as follows (with the most significant byte first, which corresponds to big-endian encoding).
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../../protocols/ssh.rst:121
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This negotiation of the cryptographic algorithms allows the implementations to evolve when new algorithms are proposed. If a client is upgraded, it can announce a new algorithm as its preferred one even if the server is not yet upgraded.
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../../protocols/tcp.rst:39
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the address of the client
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../../protocols/tls.rst:44
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993
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../../protocols/transport-service.rst:49
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It is sometimes necessary to write IPv6 addresses in text format, e.g. when manually configuring addresses or for documentation purposes. The preferred format for writing IPv6 addresses is `x:x:x:x:x:x:x:x`, where the `x` 's are hexadecimal digits representing the eight 16-bit parts of the address. Here are a few examples of IPv6 addresses :
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