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../../protocols/routing.rst:67
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Link-state routing protocols are used in IP networks. Open Shortest Path First (OSPF), defined in :rfc:`2328`, is the link state routing protocol that has been standardized by the IETF. The last version of OSPF, which supports IPv6, is defined in :rfc:`5340`. OSPF is frequently used in enterprise networks and in some ISP networks. However, ISP networks often use the IS-IS link-state routing protocol [ISO10589]_ , which was developed for the ISO CLNP protocol but was adapted to be used in IP :rfc:`1195` networks before the finalization of the standardization of OSPF. A detailed analysis of ISIS and OSPF may be found in [BMO2006]_ and [Perlman2000]_. Additional information about OSPF may be found in [Moy1998]_.
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../../protocols/rpc.rst:86
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This object has one field named `Image`. It has five attributes. The first one, `Width`, is an integer set to 800. The third one is a string. The fourth attribute, `Thumbnail` is also an object composed of three different attributes, one string and two integers. JSON can also be used to encode arrays or lists. In this case, square brackets are used as delimiters. The snippet below shows an array which contains the prime integers that are smaller than ten.
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../../protocols/ssh.rst:173
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The second point is that the server authenticates not only the result of the Diffie Hellman exchange but also a hash of all the information sent and received during the exchange. This is important to prevent `downgrade attacks`. A `downgrade attack` is an attack where an active attacker modifies the messages sent by the communicating hosts (typically the client) to request the utilization of weaker encryption algorithms. Consider a client that supports two encryption schemes. The preferred one uses 128 bits secret keys and the second one is an old encryption scheme that uses 48 bits keys. This second algorithm is kept for backward compatibility with older implementations. If an attacker can remove the preferred algorithm from the list of encryption algorithms supported by the client, he can force the server to use a weaker encryption scheme that will be easier to break. Thanks to the hash that covers all the messages exchanged by the server, the downgrade attack cannot occur against ``ssh``. Algorithm agility is a key requirement for security protocols that need to evolve when encryption algorithms are broken by researchers. This agility cannot be used without care and signing a hash of all the messages exchanged is a technique that is frequently used to prevent downgrade attacks.
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../../protocols/tcp.rst:46
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the flags field contains a set of bit flags that indicate how a segment should be interpreted by the TCP entity receiving it :
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../../protocols/tls.rst:46
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443
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../../protocols/transport-service.rst:59
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`ff01:0:0:0:0:0:0:101` is represented as `ff01::101`
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../../protocols/udp.rst:69
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Computation of the UDP checksum
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../../protocols/wifi.rst:23
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35/120
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../../bibliography.rst:67
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Francois, P., Filsfils, C., Evans, J., and Bonaventure, O., `Achieving sub-second IGP convergence in large IP networks <http://doi.acm.org/10.1145/1070873.1070877>`_. SIGCOMM Computer Communication Review 35, 3 (Jul. 2005), 35-44.
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../../glossary.rst:158
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The Border Gateway Protocol is the interdomain routing protocol used in the global Internet.
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../../exercises/ex-sharing.rst:491
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In general, the links have a non-zero delay. This is illustrated in the figure below where a delay has been added on the link between `R` and `C`.
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../../principles/sharing.rst:106 • ../../principles/sharing.rst:172
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Network congestion
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../../principles/security.rst:279
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This principle is important because it remains the basic assumption of all cryptographers. Any system that relies on the secrecy of its algorithm to be considered secure is doomed to fail and be broken one day.
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../../exercises/dns.rst:57
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Perform the same analysis for a popular website such as `www.google.com`. What is the lifetime associated to the corresponding IPv6 address ? If you perform the same request several times, do you always receive the same answer ? Can you explain why a lifetime is associated to the DNS replies ?
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../../exercises/ipv6.rst:154
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Routers ``R2`` and ``R3`` are buggy in this network. Besides the routes for their local interfaces (not shown in the figure), they only have a default route which is shown in the figure below.
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../../exercises/lan.rst:211
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By using :manpage:`brtcl(8)`, we can easily observe the state of the Spanning Tree protocol on the different switches. Let us start with ``s3``, i.e. the root of the Spanning Tree.
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../../exercises/routing-policies.rst:191
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Can you explain why at the eighth, ninth and tenth hopes several IPv6 addresses are reported in the ``traceroute6`` output ?
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../../exercises/routing-protocols.rst:265
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OSPFv3 also includes `LS Acknowledge` packets that acknowledge the correct reception of link state information.
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../../exercises/tcp-2.rst:115
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packetdrill_ can also inject data that will be read by the stack as shown by the lines below.
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../../exercises/trace.rst:111
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the `wireshark wiki <https://wiki.wireshark.org/>` page on `Display filters <https://wiki.wireshark.org/DisplayFilters>`_
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