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../../principles/security.rst:469
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Cryptographic protocols
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../../exercises/ipv6.rst:478
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Can you configure the forwarding tables of the six routers to achieve the following network objectives :
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../../exercises/routing-protocols.rst:569
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Note that the path preferred by ``AS3`` to reach ``AS1`` is different.
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../../exercises/tcp-2.rst:644
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the transmission delay for a TCP acknowledgment is negligible
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../../protocols/bgp.rst:143
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From a conceptual point of view, a BGP router connected to `N` BGP peers, can be described as being composed of four parts as shown in the figure below.
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../../protocols/congestion.rst:223
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`NewReno` (:rfc:`3782`), which was proposed as an improvement of the fast recovery mechanism in the `Reno` implementation.
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../../protocols/email.rst:227
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`Base64` divides the sequence of bytes to be encoded into groups of three bytes (with the last group possibly being partially filled). Each group of three bytes is then divided into four six-bit fields and each six bit field is encoded as a character from the table below.
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../../protocols/ethernet.rst:192 • ../../protocols/ethernet.rst:308
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Footnotes
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../../protocols/http.rst:172
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the `Referrer:` header is followed by a URI. It indicates the URI of the document that the client visited before sending this HTTP request. Thanks to this header, the server can know the URI of the document containing the hyperlink followed by the client, if any. This information is very useful to measure the impact of advertisements containing hyperlinks placed on websites.
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../../protocols/ipv6.rst:166
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To preserve the scalability of the routing system, it is important to minimize the number of routes that are stored on each router. A router cannot store and maintain one route for each of the almost 1 billion hosts that are connected to today's Internet. Routers should only maintain routes towards blocks of addresses and not towards individual hosts. For this, hosts are grouped in `subnets` based on their location in the network. A typical subnet groups all the hosts that are part of the same enterprise. An enterprise network is usually composed of several LANs interconnected by routers. A small block of addresses from the Enterprise's block is usually assigned to each LAN.
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../../protocols/ethernet.rst:173
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Two pairs of category 3+ UTP
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../../protocols/routing.rst:150
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A first approach is to select one of the equal cost paths (e.g. the first or the last path found by the SPF computation) and install it in the forwarding table. In this case, only one path is used to reach each destination.
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../../protocols/tcp.rst:151
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A server could, of course, refuse to open a TCP connection upon reception of a `SYN` segment. This refusal may be due to various reasons. There may be no server process that is listening on the destination port of the `SYN` segment. The server could always refuse connection establishments from this particular client (e.g. due to security reasons) or the server may not have enough resources to accept a new TCP connection at that time. In this case, the server would reply with a TCP segment having its `RST` flag set and containing the `sequence number` of the received `SYN` segment incremented by one as its `acknowledgment number`. This is illustrated in the figure below. We discuss the other usages of the TCP `RST` flag later (see :ref:`TCPRelease`).
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../../protocols/tls.rst:225
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``RSA``. This key exchange algorithm uses the encryption capabilities of the RSA public-key algorithm. The client has validated the server's public key thanks to the ``Certificate`` message. It then generates a (48 bytes) random number, encrypts it with the server public key and sends the encrypted number to the server in the ``ClientKeyExchange`` message. The server uses its private key to decrypt the random number. At this point, the client and the server share the same (48 bytes long) secret and use it to derive the secret keys required to encrypt and authenticate data in the second phase. With this key exchange algorithm, the server does not need to send a ``ServerKeyExchange`` message.
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../../protocols/wifi.rst:131
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Despite the utilization of acknowledgments, the 802.11 layer only provides an unreliable connectionless service like Ethernet networks that do not use acknowledgments. The 802.11 acknowledgments are used to minimize the probability of frame duplication. They do not guarantee that all frames will be correctly received by their recipients. Like Ethernet, 802.11 networks provide a high probability of successful delivery of the frames, not a guarantee. Furthermore, it should be noted that 802.11 networks do not use acknowledgments for multicast and broadcast frames. This implies that in practice such frames are more likely to suffer from transmission errors than unicast frames.
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../../bibliography.rst:314
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Russell A., `Rough Consensus and Running Code and the Internet-OSI Standards War <https://dx.doi.org/10.1109/MAHC.2006.42>`_, IEEE Annals of the History of Computing, July-September 2006
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../../glossary.rst:104
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The File Transfer Protocol defined in :rfc:`959` has been the `de facto` protocol to exchange files over the Internet before the widespread adoption of HTTP :rfc:`2616`.
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../../principles/reliability.rst:208
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Bit rate and bandwidth
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../../principles/sharing.rst:197
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In virtual circuit networks, packet marking can be improved if the return packets follow the reverse path of the forward packets. It this case, a network node can detect congestion on the forward path (e.g. due to the size of its buffer), but mark the packets on the return path. Marking the return packets (e.g. the acknowledgments used by reliable protocols) provides a faster feedback to the sending hosts compared to FECN. This technique is usually called `Backward Explicit Congestion Notification (BECN)`.
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../../principles/security.rst:471
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We can now combine the cryptographic operations described in the previous section to build some protocols to securely exchange information. Let us first go back to the problem of authenticating Alice on Bob's computer. We have shown earlier that using a simple password for this purpose is insecure in the presence of attackers.
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