cnp3-ebook - English @ Weblate

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189 ../../principles/reliability.rst:965

	English The `selective repeat` sender maintains a sending buffer that can store up to `W` unacknowledged frames. These frames are sent as long as the sending buffer is not full. Several implementations of a `selective repeat` sender are possible. A simple implementation associates one retransmission timer to each frame. The timer is started when the frame is sent and canceled upon reception of an acknowledgment that covers this frame. When a retransmission timer expires, the corresponding frame is retransmitted and this retransmission timer is restarted. When an acknowledgment is received, all the frames that are covered by this acknowledgment are removed from the sending buffer and the sliding window is updated. 714/10000 · 714
189 ../../principles/linkstate.rst:159

	English To ensure that all routers receive all LSPs, even when there are transmissions errors, link state routing protocols use `reliable flooding`. With `reliable flooding`, routers use acknowledgments and if necessary retransmissions to ensure that all link state packets are successfully transferred to each neighboring router. Thanks to reliable flooding, all routers store in their LSDB the most recent LSP sent by each router in the network. By combining the received LSPs with its own LSP, each router can build a graph that represents the entire network topology. 563/10000 · 563
189 ../../protocols/email.rst:311

	English F P s \= 22/10000 · 22
189 ../../protocols/ipv6.rst:671

	English Hosts ``A`` and ``B`` are attached to the same datalink layer network. They can thus exchange frames by using the MAC addresses shown in the figure above. To be able to use IPv6 to exchange packets, they need to have an IPv6 address. One possibility would be to manually configure an IPv6 address on each host. However, IPv6 provides a better solution thanks to the `link-local` IPv6 addresses. A `link-local` IPv6 address is an address that is composed by concatenating the ``fe80:://64`` prefix with the MAC address of the device. In the example above, host A would use IPv6 `link-local` address ``fe80::0223:45FF:FE67:89ab`` and host B ``fe80::0234:56FF:FE78:9abc``. With these two IPv6 addresses, the hosts can exchange IPv6 packets. 737/10000 · 737
189 ../../protocols/tcp.rst:636

	English Sending a packet with a different source IP address than the address allocated to the host is called sending a :term:`spoofed packet`. 134/10000 · 134
190 ../../principles/reliability.rst:967

	English The figure below illustrates the operation of `selective repeat` when frames are lost. In this figure, `C(OK,x)` is used to indicate that all frames, up to and including sequence number `x` have been received correctly. 219/10000 · 219
190 ../../principles/linkstate.rst:239

	English Static or dynamic link metrics ? 32/10000 · 32
190 ../../protocols/email.rst:318

	English Now that we have explained the format of the email messages, we can discuss how these messages can be exchanged through the Internet. The figure below illustrates the protocols that are used when `Alice` sends an email message to `Bob`. `Alice` prepares her email with an email client or on a webmail interface. To send her email to `Bob`, `Alice`'s client will use the Simple Mail Transfer Protocol (:term:`SMTP`) to deliver her message to her SMTP server. `Alice`'s email client is configured with the name of the default SMTP server for her domain. There is usually at least one SMTP server per domain. To deliver the message, `Alice`'s SMTP server must find the SMTP server that contains `Bob`'s mailbox. This can be done by using the Mail eXchange (MX) records of the DNS. A set of MX records can be associated to each domain. Each MX record contains a numerical preference and the fully qualified domain name of a SMTP server that is able to deliver email messages destined to all valid email addresses of this domain. The DNS can return several MX records for a given domain. In this case, the server with the lowest numerical preference is used first :rfc:`2821`. If this server is not reachable, the second most preferred server is used etc. `Bob`'s SMTP server will store the message sent by `Alice` until `Bob` retrieves it using a webmail interface or protocols such as the Post Office Protocol (:term:`POP`) or the Internet Message Access Protocol (:term:`IMAP`). 1476/10000 · 1476
190 ../../protocols/ipv6.rst:673

	English Converting MAC addresses in host identifiers 44/10000 · 44
190 ../../protocols/tcp.rst:638

	English The full list of all TCP options may be found at http://www.iana.org/assignments/tcp-parameters/ 96/10000 · 96
190 ../../glossary.rst:277

	English VNC 3/10000 · 3
191 ../../glossary.rst:278

	English vnc 3/10000 · 3
191 ../../principles/reliability.rst:973

	English Selective repeat : example 26/10000 · 26
191 ../../principles/linkstate.rst:241

	English As link state packets are flooded regularly, routers are able to measure the quality (e.g. delay or load) of their links and adjust the metric of each link according to its current quality. Such dynamic adjustments were included in the ARPANET routing protocol [MRR1979]_ . However, experience showed that it was difficult to tune the dynamic adjustments and ensure that no forwarding loops occur in the network [KZ1989]_. Today's link state routing protocols use metrics that are manually configured on the routers and are only changed by the network operators or network management tools [FRT2002]_. 601/10000 · 601
191 ../../protocols/email.rst:342

	English The Simple Mail Transfer Protocol 33/10000 · 33
191 ../../protocols/ipv6.rst:675

	English Appendix A of :rfc:`4291` provides the algorithm used to convert a 48 bits MAC address into a 64 bits host identifier. This algorithm builds upon the structure of the MAC addresses. A MAC address is represented as shown in the figure below. 240/10000 · 240
191 ../../protocols/tcp.rst:640

	English In practice, only the `SYN` segment do not have their `ACK` flag set. 69/10000 · 69
192 ../../glossary.rst:280

	English A networked application that allows to remotely access a computer's Graphical User Interface. See https://en.wikipedia.org/wiki/Virtual_Network_Computing 153/10000 · 153
192 ../../principles/reliability.rst:977

	English Pure cumulative acknowledgments work well with the `go-back-n` strategy. However, with only cumulative acknowledgments a `selective repeat` sender cannot easily determine which frames have been correctly received after a data frame has been lost. For example, in the figure above, the second `C(OK,0)` does not inform explicitly the sender of the reception of `D(2,c)` and the sender could retransmit this frame although it has already been received. A possible solution to improve the performance of `selective repeat` is to provide additional information about the received frames in the acknowledgments that are returned by the receiver. For example, the receiver could add in the returned acknowledgment the list of the sequence numbers of all frames that have already been received. Such acknowledgments are sometimes called `selective acknowledgments`. This is illustrated in the figure above. 899/10000 · 899
192 ../../principles/linkstate.rst:245

	English When a link fails, the two routers attached to the link detect the failure by the absence of HELLO messages received during the last :math:`k \times N` seconds. Once a router has detected the failure of one of its local links, it generates and floods a new LSP that no longer contains the failed link. This new LSP replaces the previous LSP in the network. In practice, the two routers attached to a link do not detect this failure exactly at the same time. During this period, some links may be announced in only one direction. This is illustrated in the figure below. Router `E` has detected the failure of link `E-B` and flooded a new LSP, but router `B` has not yet detected this failure. 692/10000 · 692

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