msgid "" msgstr "" "Project-Id-Version: English (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-19 00:32+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: English \n" "Language: en\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=2; plural=n != 1;\n" "X-Generator: Weblate 5.14.3\n" #: ../../exercises/reliability.rst:7 #, read-only msgid "Reliable transfer" msgstr "Reliable transfer" #: ../../exercises/reliability.rst:11 #, read-only msgid "Open questions" msgstr "Open questions" #: ../../exercises/reliability.rst:13 #, read-only msgid "" "Consider a `b` bits per second link between two hosts that has a propagation " "delay of `t` seconds. Derive a formula that computes the time elapsed " "between the transmission of the first bit of a `d` bytes frame from a " "sending host and the reception of the last bit of this frame on the " "receiving host." msgstr "" "Consider a `b` bits per second link between two hosts that has a propagation " "delay of `t` seconds. Derive a formula that computes the time elapsed " "between the transmission of the first bit of a `d` bytes frame from a " "sending host and the reception of the last bit of this frame on the " "receiving host." #: ../../exercises/reliability.rst:15 #, read-only msgid "" "Transmission links have sometimes different upstream and downstream " "bandwidths. A typical example are access networks that use ADSL " "(Asymmetric Digital Subscriber Lines). Consider two hosts connected via an " "ADSL link having an upstream bandwidth of 1 Mbps and a downstream bandwidth " "of 50 Mbps. The propagation delay between the two hosts is 10 milliseconds. " "What is the maximum throughput, expressed in frames/second, that the " "alternating bit protocol can obtain on this link if each data frame has a " "length of 125 bytes and acknowledgments are 25 bytes long. Same question if " "the protocol is modified to support 1500 bytes long data frames." msgstr "" "Transmission links have sometimes different upstream and downstream " "bandwidths. A typical example are access networks that use ADSL " "(Asymmetric Digital Subscriber Lines). Consider two hosts connected via an " "ADSL link having an upstream bandwidth of 1 Mbps and a downstream bandwidth " "of 50 Mbps. The propagation delay between the two hosts is 10 milliseconds. " "What is the maximum throughput, expressed in frames/second, that the " "alternating bit protocol can obtain on this link if each data frame has a " "length of 125 bytes and acknowledgments are 25 bytes long. Same question if " "the protocol is modified to support 1500 bytes long data frames." #: ../../exercises/reliability.rst:17 #, read-only msgid "" "How would you set the duration of the retransmission timer in the " "alternating bit protocol ?" msgstr "" "How would you set the duration of the retransmission timer in the " "alternating bit protocol ?" #: ../../exercises/reliability.rst:19 #, read-only msgid "" "A version of the Alternating Bit Protocol supporting variable length frames " "uses a header that contains the following fields :" msgstr "" "A version of the Alternating Bit Protocol supporting variable length frames " "uses a header that contains the following fields :" #: ../../exercises/reliability.rst:21 #, read-only msgid "a `number` (0 or 1)" msgstr "a `number` (0 or 1)" #: ../../exercises/reliability.rst:22 #, read-only msgid "a `length` field that indicates the length of the data" msgstr "a `length` field that indicates the length of the data" #: ../../exercises/reliability.rst:23 #, read-only msgid "a Cyclic Redundancy Check (`CRC`)" msgstr "a Cyclic Redundancy Check (`CRC`)" #: ../../exercises/reliability.rst:25 #, read-only msgid "" "To speedup the transmission of the frames, a student proposes to compute the " "CRC over the data part of the frame but not over the header. What do you " "think of this proposed solution ?" msgstr "" "To speedup the transmission of the frames, a student proposes to compute the " "CRC over the data part of the frame but not over the header. What do you " "think of this proposed solution ?" #: ../../exercises/reliability.rst:27 #, read-only msgid "" "Derive a mathematical expression that provides the `goodput`, i.e. the " "amount of payload bytes that have been transmitted during a period of time, " "achieved by the Alternating Bit Protocol assuming that :" msgstr "" "Derive a mathematical expression that provides the `goodput`, i.e. the " "amount of payload bytes that have been transmitted during a period of time, " "achieved by the Alternating Bit Protocol assuming that :" #: ../../exercises/reliability.rst:29 #, read-only msgid "" "Each frame contains `D` bytes of data and `c` bytes of control information" msgstr "" "Each frame contains `D` bytes of data and `c` bytes of control information" #: ../../exercises/reliability.rst:30 #, read-only msgid "Each acknowledgment contains `c` bytes of control information" msgstr "Each acknowledgment contains `c` bytes of control information" #: ../../exercises/reliability.rst:31 #, read-only msgid "" "The bandwidth of the two directions of the link is set to `B` bits per second" msgstr "" "The bandwidth of the two directions of the link is set to `B` bits per second" #: ../../exercises/reliability.rst:32 #, read-only msgid "The delay between the two hosts is `s` seconds in both directions" msgstr "The delay between the two hosts is `s` seconds in both directions" #: ../../exercises/reliability.rst:33 #, read-only msgid "there are no transmission errors" msgstr "there are no transmission errors" #: ../../exercises/reliability.rst:35 #, read-only msgid "" "Consider a go-back-n sender and a go-back receiver that are directly " "connected with a 10 Mbps link that has a propagation delay of 100 " "milliseconds. Assume that the retransmission timer is set to three seconds. " "If the window has a length of 4 frames, draw a time-sequence diagram showing " "the transmission consisting of 10 data frames " "(each frame contains 10000 bits):" msgstr "" "Consider a go-back-n sender and a go-back receiver that are directly " "connected with a 10 Mbps link that has a propagation delay of 100 " "milliseconds. Assume that the retransmission timer is set to three seconds. " "If the window has a length of 4 frames, draw a time-sequence diagram showing " "the transmission consisting of 10 data frames " "(each frame contains 10000 bits):" #: ../../exercises/reliability.rst:37 #, read-only msgid "when there are no losses" msgstr "when there are no losses" #: ../../exercises/reliability.rst:38 #, read-only msgid "when the third and seventh frames are lost" msgstr "when the third and seventh frames are lost" #: ../../exercises/reliability.rst:39 #, read-only msgid "" "when every second acknowledgment is discarded due to transmission errors" msgstr "" "when every second acknowledgment is discarded due to transmission errors" #: ../../exercises/reliability.rst:41 #, read-only msgid "" "Same question when using selective repeat instead of go-back-n. Note that " "the answer is not necessarily the same." msgstr "" "Same question when using selective repeat instead of go-back-n. Note that " "the answer is not necessarily the same." #: ../../exercises/reliability.rst:45 #, read-only msgid "Practice" msgstr "Practice" #: ../../exercises/reliability.rst:47 #, read-only msgid "" "Reliable protocols depend on error detection algorithms to detect " "transmission errors. The following questions will reinforce your " "understanding of these algorithms." msgstr "" "Reliable protocols depend on error detection algorithms to detect " "transmission errors. The following questions will reinforce your " "understanding of these algorithms." #: ../../exercises/reliability.rst:49 #, read-only msgid "" "Reliable protocols rely on different types of checksums to verify whether " "frames have been affected by transmission errors. The most frequently used " "checksums are :" msgstr "" "Reliable protocols rely on different types of checksums to verify whether " "frames have been affected by transmission errors. The most frequently used " "checksums are :" #: ../../exercises/reliability.rst:51 #, read-only msgid "" "the Internet checksum used by UDP, TCP and other Internet protocols which is " "defined in :rfc:`1071` and implemented in various libraries." msgstr "" "the Internet checksum used by UDP, TCP and other Internet protocols which is " "defined in :rfc:`1071` and implemented in various libraries." #: ../../exercises/reliability.rst:52 #, read-only msgid "" "the 16 bits or the 32 bits Cyclical Redundancy Checks (CRC) that are often " "used on disks, in zip archives and in datalink layer protocols. See http://" "rosettacode.org/wiki/CRC-32 for CRC-32 implementations in various languages." msgstr "" "the 16 bits or the 32 bits Cyclical Redundancy Checks (CRC) that are often " "used on disks, in zip archives and in datalink layer protocols. See http://" "rosettacode.org/wiki/CRC-32 for CRC-32 implementations in various languages." #: ../../exercises/reliability.rst:53 #, read-only msgid "" "the Fletcher checksum [Fletcher1982]_, see https://en.wikipedia.org/wiki/" "Fletcher%27s_checksum for implementation details." msgstr "" "the Fletcher checksum [Fletcher1982]_, see https://en.wikipedia.org/wiki/" "Fletcher%27s_checksum for implementation details." #: ../../exercises/reliability.rst:55 #, read-only msgid "" "By using your knowledge of the Internet checksum, can you find a " "transmission error that will not be detected by these checksums?" msgstr "" "By using your knowledge of the Internet checksum, can you find a " "transmission error that will not be detected by these checksums?" #: ../../exercises/reliability.rst:57 #, read-only msgid "" "The Cyclic Redundancy Checks (CRCs) are efficient error detection codes that " "are able to detect :" msgstr "" "The Cyclic Redundancy Checks (CRCs) are efficient error detection codes that " "are able to detect :" #: ../../exercises/reliability.rst:59 #, read-only msgid "all errors that affect an odd number of bits" msgstr "all errors that affect an odd number of bits" #: ../../exercises/reliability.rst:60 #, read-only msgid "" "all errors that affect a sequence of bits which is shorter than the length " "of the CRC" msgstr "" "all errors that affect a sequence of bits which is shorter than the length " "of the CRC" #: ../../exercises/reliability.rst:62 #, read-only msgid "" "Implement a small software that computes the CRC-32 for a text file. Then, " "modify the contents of the file to change an even number of bits or an odd " "number of bits inside the file. When modifying the file, remember that an " "ASCII file is composed of 8 bits characters that are encoded by using the " "ASCII table that you can find at : http://en.wikipedia.org/wiki/ASCII . You " "can also write a small program that produces binary files that are a small " "variation of each other." msgstr "" "Implement a small software that computes the CRC-32 for a text file. Then, " "modify the contents of the file to change an even number of bits or an odd " "number of bits inside the file. When modifying the file, remember that an " "ASCII file is composed of 8 bits characters that are encoded by using the " "ASCII table that you can find at : http://en.wikipedia.org/wiki/ASCII . You " "can also write a small program that produces binary files that are a small " "variation of each other." #: ../../exercises/reliability.rst:64 #, read-only msgid "" "Checksums and CRCs should not be confused with secure hash functions such as " "MD5 defined in :rfc:`1321` or SHA-1 described in :rfc:`4634`. Secure hash " "functions are used to ensure that files or sometimes frames/packets/segments " "have not been modified. Secure hash functions aim at detecting malicious " "changes while checksums and CRCs only detect random transmission errors. Use " "the `shasum `_ or `md5sum `_ programs on Linux to perform the same tests as " "above." msgstr "" "Checksums and CRCs should not be confused with secure hash functions such as " "MD5 defined in :rfc:`1321` or SHA-1 described in :rfc:`4634`. Secure hash " "functions are used to ensure that files or sometimes frames/packets/segments " "have not been modified. Secure hash functions aim at detecting malicious " "changes while checksums and CRCs only detect random transmission errors. Use " "the `shasum `_ or `md5sum `_ programs on Linux to perform the same tests as " "above." #: ../../exercises/reliability.rst:68 #, read-only msgid "Discussion questions" msgstr "Discussion questions" #: ../../exercises/reliability.rst:70 #, read-only msgid "" "Consider two high-end servers connected back-to-back by using a 10 Gbps " "interface. If the delay between the two servers is one millisecond, what is " "the throughput that can be achieved by a reliable protocol that is using " "10,000 bits frames and a window of" msgstr "" "Consider two high-end servers connected back-to-back by using a 10 Gbps " "interface. If the delay between the two servers is one millisecond, what is " "the throughput that can be achieved by a reliable protocol that is using " "10,000 bits frames and a window of" #: ../../exercises/reliability.rst:72 #, read-only msgid "one frame" msgstr "one frame" #: ../../exercises/reliability.rst:73 #, read-only msgid "ten frames" msgstr "ten frames" #: ../../exercises/reliability.rst:74 #, read-only msgid "hundred frames" msgstr "hundred frames" #: ../../exercises/reliability.rst:76 #, read-only msgid "" "Is it possible for a go-back-n receiver to inter-operate with a selective-" "repeat sender ? Justify your answer." msgstr "" "Is it possible for a go-back-n receiver to inter-operate with a selective-" "repeat sender ? Justify your answer." #: ../../exercises/reliability.rst:78 #, read-only msgid "" "Is it possible for a selective-repeat receiver to inter-operate with a go-" "back-n sender ? Justify your answer." msgstr "" "Is it possible for a selective-repeat receiver to inter-operate with a go-" "back-n sender ? Justify your answer." #: ../../exercises/reliability.rst:82 #, read-only msgid "" "A go-back-n sender has sent :math:`2^n` data frames. All the frames have " "been received correctly and in-order by the receiver, but all the returned " "acknowledgments have been lost. Show by using a time sequence diagram " "(e.g. by considering a window of four frames) what happens in this case. Can " "you fix the problem on the go-back-n sender ?" msgstr "" "A go-back-n sender has sent :math:`2^n` data frames. All the frames have " "been received correctly and in-order by the receiver, but all the returned " "acknowledgments have been lost. Show by using a time sequence diagram " "(e.g. by considering a window of four frames) what happens in this case. Can " "you fix the problem on the go-back-n sender ?" #: ../../exercises/reliability.rst:84 #, read-only msgid "" "Same question as above, but assume now that both the sender and the receiver " "implement selective repeat. Note that the answer can be different from the " "above question." msgstr "" "Same question as above, but assume now that both the sender and the receiver " "implement selective repeat. Note that the answer can be different from the " "above question."