cnp3-ebook - English @ Weblate

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73 ../../principles/network.rst:423

	English These three solutions have advantages and drawbacks. With the first solution, routers remain simple and do not need to perform any fragmentation operation. This is important when routers are implemented mainly in hardware. However, hosts must be complex since they need to store the packets that they produce if they need to pass through a link that does not support large packets. This increases the buffering required on the hosts. 433/10000 · 433
73 ../../principles/reliability.rst:258

	English `CR` : `0001101` b 18/10000 · 18
73 ../../principles/sharing.rst:475

	English [Abramson1970]_ analyzed the performance of ALOHANet under particular assumptions and found that ALOHANet worked well when the channel was lightly loaded. In this case, the frames are rarely retransmitted and the `channel traffic`, i.e. the total number of (correct and retransmitted) frames transmitted per unit of time is close to the `channel utilization`, i.e. the number of correctly transmitted frames per unit of time. Unfortunately, the analysis also reveals that the `channel utilization` reaches its maximum at :math:`\frac{1}{2 \times e}=0.186` times the channel bandwidth. At higher utilization, ALOHANet becomes unstable and the network collapses due to collided retransmissions. 692/10000 · 692
73 ../../principles/transport.rst:288

	English The example above shows a successful connection establishment. However, in practice not all connections are successfully established. One reason is that the destination user may not agree, for policy or performance reasons, to establish a connection with the initiating user at this time. In this case, the destination user responds to the `Connect.indication` primitive by a `Disconnect.request` primitive that contains a parameter to indicate why the connection has been refused. The service provider will then deliver a `Disconnect.indication` primitive to inform the initiating user. 587/10000 · 587
73 ../../principles/security.rst:860

	English A possible protocol could then be the following. Alice sends :math:`Cert(Alice_{pub},Ted)`. Bob replies with a random nonce. 124/10000 · 124
73 ../../exercises/ipv6.rst:675

	English We can now create the hosts and the routers 43/10000 · 43
73 ../../exercises/routing-protocols.rst:1016

	English When this network is launched, `ping6all` reports connectivity problems. Hosts `h1` and `h4` cannot exchange packets. Can you fix the problem by changing the routing policy used on only one interdomain link ? Justify your answer 228/10000 · 228
73 ../../protocols/bgp.rst:293

	English A frequent practical question about the operation of BGP is how a BGP router decides to originate or advertise a route for the first time. In practice, this occurs in two situations : 183/10000 · 183
73 ../../protocols/email.rst:238 • ../../protocols/email.rst:240

	English 3 1/10000 · 1
73 ../../protocols/ethernet.rst:331

	English The switches exchange `BPDUs` to build the spanning tree. Intuitively, the spanning tree is built by first selecting the switch with the smallest `identifier` as the root of the tree. The branches of the spanning tree are then composed of the shortest paths that allow all of the switches that compose the network to be reached. The `BPDUs` exchanged by the switches contain the following information : 402/10000 · 402
73 ../../protocols/http.rst:385

	English However, in practice, some servers want to provide content tuned for each user. For example, some servers can provide information in several languages. Other servers want to provide advertisements that are targeted to different types of users. To do this, servers need to maintain some information about the preferences of each user and use this information to produce content matching the user's preferences. HTTP contains several mechanisms to solve this problem. We discuss three of them below. 497/10000 · 497
73 ../../protocols/ipv6.rst:261

	English An important consequence of the IPv6 unicast addressing architecture and the utilization of link-local addresses is that each IPv6 host has several IPv6 addresses. This implies that all IPv6 stacks must be able to handle multiple IPv6 addresses. 245/10000 · 245
73 ../../protocols/ethernet.rst:261

	English 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. 1237/10000 · 1237
73 ../../protocols/tcp.rst:235

	English The handling of the TCP options by TCP implementations is one of the many applications of the `robustness principle` which is usually attributed to `Jon Postel`_ and is often quoted as `"Be liberal in what you accept, and conservative in what you send"` :rfc:`1122`. 266/10000 · 266
73 ../../protocols/tls.rst:392

	English Another interesting fact is are the key exchange schemes. In 2012, RSA was the dominant solution, used by more than 80% of the observed connections [KRA2018]_. In 2013, Edward Snowden revealed the surveillance activities of several governments. These revelations had a huge impact on the Internet community. The IETF, which standardizes Internet protocols, considered in :rfc:`7258` that such pervasive monitoring was an attack. Since then, several IETF working groups have developed solutions to counter pervasive monitoring. One of these solutions is to encourage `Perfect Forward Security`. Within TLS, this implies replacing RSA by an authenticated Diffie Hellman key exchange such as ECDHE. Measurements indicate that since summer 2014, ECDHE is more popular than RSA. In 2018, more than 90% of the observed TLS connections used ECDHE. 840/10000 · 840
73 ../../bibliography.rst:96

	English Hogg, S. Vyncke, E., `IPv6 Security <http://www.ciscopress.com/store/ipv6-security-9780133346312>`_, Cisco Press, 2008 118/10000 · 118
74 ../../glossary.rst:69

	English internet 8/10000 · 8
74 ../../principles/network.rst:425

	English Furthermore, a single large packet may potentially need to be retransmitted several times. Consider for example a network similar to the one shown above but with four routers. Assume that the link `R1->R2` supports 1000 bytes packets, link `R2->R3` 800 bytes packets and link `R3->R4` 600 bytes packets. A host attached to `R1` that sends large packet will have to first try 1000 bytes, then 800 bytes and finally 600 bytes. Fortunately, this scenario does not occur very often in practice and this is the reason why this solution is used in real networks. 556/10000 · 556
74 ../../principles/reliability.rst:259

	English `LF` : `0001010` b 18/10000 · 18
74 ../../principles/sharing.rst:478

	English Amateur packet radio 20/10000 · 20

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