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../../exercises/ipv6.rst:535
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Let us start our exploration of IPv6 routing with a simple network topology that contains two hosts and three routers and uses static routes.
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../../exercises/routing-protocols.rst:843
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The first of these two routes is preferred as indicated by the `>` character because it has a higher ``local-preference` (150) than the second one (100). For prefix ``2001:cafe:3::/48``, the route learned via ``fe80::3c81:2eff:fe19:465d`` is also preferred for the same reason.
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../../exercises/tcp-2.rst:740
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In question 1, we assumed that the receiver acknowledged every segment received from the sender. In practice, many deployed TCP implementations use delayed acknowledgments. Assuming a delayed acknowledgment timer of 50 milliseconds, modify the time-sequence diagram below to reflect the impact of these delayed acknowledgment. Does their usage decreases or increased the transmission delay ?
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../../protocols/bgp.rst:256
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The bogon filters
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../../protocols/email.rst:234 • ../../protocols/email.rst:236
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1
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../../protocols/ethernet.rst:261
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One of the selling points of Ethernet networks is that, thanks to the utilization of 48 bits MAC addresses, an Ethernet LAN is plug and play at the datalink layer. When two hosts are attached to the same Ethernet segment or hub, they can immediately exchange Ethernet frames without requiring any configuration. It is important to retain this plug and play capability for Ethernet switches as well. This implies that Ethernet switches must be able to build their MAC address table automatically without requiring any manual configuration. This automatic configuration is performed by the `MAC address learning` algorithm that runs on each Ethernet switch. This algorithm extracts the source address of the received frames and remembers the port over which a frame from each source Ethernet address has been received. This information is inserted into the MAC address table that the switch uses to forward frames. This allows the switch to automatically learn the ports that it can use to reach each destination address, provided that this host has previously sent at least one frame. This is not a problem since most upper layer protocols use acknowledgments at some layer and thus even an Ethernet printer sends Ethernet frames as well.
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../../protocols/http.rst:194
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As an illustration of HTTP/1.0, the transcript below shows a HTTP request for `http://www.ietf.org <http://www.ietf.org>`_ and the corresponding HTTP response. The HTTP request was sent using the curl_ command line tool. The `User-Agent:` header line contains more information about this client software. There is no MIME document attached to this HTTP request, and it ends with a blank line.
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../../protocols/ipv6.rst:199
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Now, consider how a router inside ``alpha.com`` would reach a host in the ``UCLouvain`` network. This router has two routes towards ``2001:6a8:3080::1``. The first one, for prefix ``2001:6a8:3080::/48`` is via the direct link between the commercial ISP and UCLouvain. The second one, for prefix ``2001:6a8::/32`` is via the Internet and Belnet. Since :rfc:`1519` when a router knows several routes towards the same destination address, it must forward packets along the route having the longest prefix length. In the case of ``2001:6a8:3080::1``, this is the route ``2001:6a8:3080::/48`` that is used to forward the packet. This forwarding rule is called the `longest prefix match` or the `more specific match`. All IP routers implement this forwarding rule.
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../../protocols/ethernet.rst:179 • ../../protocols/ethernet.rst:358
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10 Gbps
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../../protocols/tcp.rst:203
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the low order bits contain a hash value computed over the local and remote IP addresses and ports and a random secret only known to the server
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../../protocols/tls.rst:315
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The handshake is now finished. The client and the server will exchange authenticated and encrypted records. TLS defines different formats for the records depending on the cryptographic algorithms that have been negotiated for the session. A detailed discussion of these different types of records is outside the scope of this introduction. For illustration, we briefly describe one record format.
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../../bibliography.rst:357
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Zimmermann, H., `OSI Reference Model - The ISO Model of Architecture for Open Systems Interconnection <https://dx.doi.org/10.1109/TCOM.1980.1094702>`_, IEEE Transactions on Communications, vol. 28, no. 4, April 1980, pp. 425 - 432.
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../../glossary.rst:132
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IANA
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../../principles/reliability.rst:224
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0111111001111101001111110
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../../principles/transport.rst:204
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the `connectionless network layer service` may discard SDUs
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../../principles/security.rst:671
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The solution described above works provided that Bob and Alice know their respective public keys before communicating. Otherwise, the protocol is not secure against man-in-the-middle attackers. Consider Mallory sitting in the middle between Alice and Bob and assume that neither Alice nor Bob knows the other's public key.
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../../exercises/ipv6.rst:580
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IPMininet_ simplifies the creation of the network topology by providing a simple API. For this, you simply need to declare a class that extends the ``IPTopo`` class.
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../../exercises/routing-protocols.rst:845
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IPMininet_ also allows to explore the dynamics of BGP by looking at the packets that the routers exchange. For this, we slightly modify the example above and add delays to the interdomain links as follows.
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../../exercises/tcp-2.rst:775
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Let us now explore the impact of congestion on the slow-start and congestion avoidance mechanisms. Consider the scenario below. For graphical reasons, it is not possible anymore to show information about the segments on the graph, but you can easily infer them.
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../../protocols/bgp.rst:258
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Another example of frequently used `import filters` are the filters that Internet Service Providers use to ignore bogon routes. In the ISP community, a bogon route is a route that should not be advertised on the global Internet. Typical examples include the documentation IPv6 prefix (`2001:db8::/32` used for most examples in this book), the loopback address (`::1/128`) or the IPv6 prefixes that have not yet been allocated by IANA. A well managed BGP router should ensure that it never advertises bogons on the global Internet. Detailed information about these bogons may be found in [IMHM2013]_.
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