msgid "" msgstr "" "Project-Id-Version: Czech (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-19 10:01+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: Czech \n" "Language: cs\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=3; plural=(n==1) ? 0 : (n>=2 && n<=4) ? 1 : 2;\n" "X-Generator: Weblate 5.14.3\n" #: ../../exercises/reliability.rst:7 msgid "Reliable transfer" msgstr "" #: ../../exercises/reliability.rst:11 msgid "Open questions" msgstr "" #: ../../exercises/reliability.rst:16 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 "" #: ../../exercises/reliability.rst:19 msgid "" "How would you set the duration of the retransmission timer in the " "alternating bit protocol ?" msgstr "" #: ../../exercises/reliability.rst:22 msgid "" "A version of the Alternating Bit Protocol supporting variable length frames " "uses a header that contains the following fields :" msgstr "" #: ../../exercises/reliability.rst:24 msgid "a `number` (0 or 1)" msgstr "" #: ../../exercises/reliability.rst:25 msgid "a `length` field that indicates the length of the data" msgstr "" #: ../../exercises/reliability.rst:26 msgid "a Cyclic Redundancy Check (`CRC`)" msgstr "" #: ../../exercises/reliability.rst:30 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 "" #: ../../exercises/reliability.rst:32 msgid "" "Each frame contains `D` bytes of data and `c` bytes of control information" msgstr "" #: ../../exercises/reliability.rst:33 msgid "Each acknowledgment contains `c` bytes of control information" msgstr "" #: ../../exercises/reliability.rst:34 msgid "" "The bandwidth of the two directions of the link is set to `B` bits per second" msgstr "" #: ../../exercises/reliability.rst:35 msgid "The delay between the two hosts is `s` seconds in both directions" msgstr "" #: ../../exercises/reliability.rst:36 msgid "there are no transmission errors" msgstr "" #: ../../exercises/reliability.rst:40 msgid "when there are no losses" msgstr "" #: ../../exercises/reliability.rst:42 msgid "" "when every second acknowledgment is discarded due to transmission errors" msgstr "" #: ../../exercises/reliability.rst:44 msgid "" "Same question when using selective repeat instead of go-back-n. Note that " "the answer is not necessarily the same." msgstr "" #: ../../exercises/reliability.rst:50 msgid "Practice" msgstr "" #: ../../exercises/reliability.rst:52 msgid "" "Reliable protocols depend on error detection algorithms to detect " "transmission errors. The following questions will reinforce your " "understanding of these algorithms." msgstr "" #: ../../exercises/reliability.rst:54 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 "" #: ../../exercises/reliability.rst:56 msgid "" "the Internet checksum used by UDP, TCP and other Internet protocols which is " "defined in :rfc:`1071` and implemented in various libraries." msgstr "" #: ../../exercises/reliability.rst:57 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 "" #: ../../exercises/reliability.rst:62 msgid "" "The Cyclic Redundancy Checks (CRCs) are efficient error detection codes that " "are able to detect :" msgstr "" #: ../../exercises/reliability.rst:64 msgid "all errors that affect an odd number of bits" msgstr "" #: ../../exercises/reliability.rst:65 msgid "" "all errors that affect a sequence of bits which is shorter than the length " "of the CRC" msgstr "" #: ../../exercises/reliability.rst:67 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 "" #: ../../exercises/reliability.rst:74 msgid "Discussion questions" msgstr "" #: ../../exercises/reliability.rst:77 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 "" #: ../../exercises/reliability.rst:79 msgid "one frame" msgstr "" #: ../../exercises/reliability.rst:80 msgid "ten frames" msgstr "" #: ../../exercises/reliability.rst:81 msgid "hundred frames" msgstr "" #: ../../exercises/reliability.rst:83 msgid "" "Is it possible for a go-back-n receiver to inter-operate with a selective-" "repeat sender ? Justify your answer." msgstr "" #: ../../exercises/reliability.rst:85 msgid "" "Is it possible for a selective-repeat receiver to inter-operate with a go-" "back-n sender ? Justify your answer." msgstr "" #: ../../exercises/reliability.rst:91 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 ""